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Publication #FSHN12-07

Growth, Reduction, and Survival of Bacteria on Melon Types1

Thao P. Nguyen, Michelle D. Danyluk, and Keith R. Schneider2

From 1990 to 2000, over 700 cases of foodborne illness were associated with outbreaks due to melon consumption in the United States and Canada (FDA, 2001). Although there has been an increase in effort to educate industry and consumers of safe handling practices of fresh produce (via Good Agricultural Practices [GAPs] and Good Manufacturing Practices [GMPs]), in the last decade there were still over 1,100 documented illnesses associated with melon consumption (CDC, 2011a). Of 24 outbreaks implicating melon consumption, eight involved watermelon, seven involved cantaloupe, and three involved honeydew. Three cases were due to consuming cantaloupe and/or honeydew, two cases due to consuming cantaloupe and/or watermelon, and one case due to melon consumption of unknown type. Cantaloupes, responsible for at least 11 of the 24 cases, are the source for the majority of the outbreaks (CDC, 2011a). Foodborne pathogens such as Norovirus, Campylobacter, Shigella, and Escherichia coli O157:H7 are of concern in all of these outbreaks; however, Salmonella is reportedly the most prevalent pathogen of concern for melons (CDC, 2011a). As of October 2011, Listeria monocytogenes was added to the list of pathogens that could be of concern for melons; a multi-state outbreak of listeriosis involving cantaloupes from a farm in Colorado caused 123 illnesses, 118 hospitalizations, and 25 deaths (CDC, 2011b). These numbers are overwhelming and have proven the significance of melons as a potential vehicle for foodborne pathogens.

Figure 1. 

Skin, Flesh, Seeds


Credit:

Photo by Amanda Rudkin, CC BY-NC-ND 2.0, http://flic.kr/p/xr6pv


[Click thumbnail to enlarge.]

A variety of factors contribute to the susceptibility of melons becoming contaminated during harvest, packing, and shipping; most of the research currently available focuses on cantaloupes. During growth and development, melons can have direct contact with the soil, which can be a potential source of contamination with human pathogens that may be present in the soil (Richards and Beuchat, 2005b). Rind characteristics also play a role in susceptibility of contamination given that melons may have netted surfaces (cantaloupes), a characteristic that would make it more difficult to remove the pathogen just by washing alone, if contaminated.

Mechanical damage can also be a problem since melons are quite heavy, and wounds incurred (e.g., punctures, cracks, bruising) make an excellent entry point for pathogens (Fleming et al., 2005). These physical damages, as well as disease, can compromise the outer protection layer of the melon and can allow for contamination of the mesocarp tissue, or flesh (Richards and Beuchat, 2005b). Infiltration and adherence of pathogen at the stem scar tissue is also a possibility that is believed to heighten survival of pathogens in cantaloupe, due to the availability of nutrients and almost neutral pH of the inner flesh (Richards and Beuchat, 2004). Maturity of the melon can also play a role in susceptibility in that ripe melons may allow for better growth and survival of pathogens on their surface (Suslow, 1997). Furthermore, the increased consumption of ready-to-eat commodities such as fresh-cut fruits introduces a new route of microbial contamination: transfer from rind to flesh during cutting. Due to the many factors that may contribute to melon contamination, as well as the numbers of illnesses associated with melons, studies to eliminate bacterial growth on melons have been done to further understand the effectiveness of different sanitizers and food processing techniques.

This document, therefore, is intended to highlight the research that has been done to provide insight on possible sanitation methods and their efficacy in decontaminating melon types of foodborne pathogens as well as natural microflora. Given that melons with netted surfaces such as cantaloupes were implicated in the majority of the outbreaks mentioned above, it follows that cantaloupe was the main concern in a number of the studies reviewed in this table. Bacterial studies included in this table use a variety of sanitizer treatments including chlorine, chlorine dioxide (ClO2), gaseous ozone, hydrogen peroxide (H2O2), nisin, nisin in combination with chelating agents, sodium lactate (NaL), citric acid, acetic acid, and bacteriophages. The studies also use a variety of food processing techniques including different time and temperature combinations and the vacuum-steam-vacuum (VSV) process. (The VSV process, developed and patented by USDA's Agricultural Research Service, entails a short exposure to vacuum to remove insulating fluids, followed by a quick burst of steam intended to transfer energy directly to contaminated sample, then a second exposure to vacuum in order to cool product via evaporation [Ukuku et al., 2006].) Also included are studies with simulation components that mimic commercial distribution and home preparation as well as transfer studies that focus specifically on bacterial transfer from rind to flesh.

The table is organized as follows:

  • By melon type, including cantaloupe, honeydew, watermelon, and mixed melons

  • By portion of melon used in study, including whole melons, rinds, fresh-cuts, mesocarp tissue (inner tissue, variable distances from the rind), and stem scar tissue

  • By bacteria, including E. coli, Listeria spp., natural microflora, and Salmonella spp.

The intended audience for this document includes melon handlers and processors, researchers, and government officials interested in melon safety:

  • During evaluation of current processing and sanitation techniques, melon processors can use the table as a reference as they seek alternative or adaptable technologies.

  • Researchers can gain insight as to which direction to take when deciding on new research and technology development for melon safety.

  • Government officials can reference this table as current food safety policies and regulations are evaluated and updated.

Information on storage conditions and the efficacy of certain rinsing and scrubbing scenarios are also featured here for the benefit of consumers and educators of consumers. Overall, this review serves as a reference for everyone concerned in the safety of melon consumption.

Table 1. 

Fruit, Type

Pathogen

Method of Inoculation

Treatment / Storage Conditions

Temp (°C)

Initial Counts

(log CFU)

Incubation time

Treatment Specifications

Final Counts (log10 CFU)

Unit

Comments

Reference

Cantaloupe, Whole

E. coli ATCC 25922

Submerged in 4 l of inoculum for 5 min

Air-dried for 1 h on absorbent paper on each side in biosafety cabinet, then stored in plastic tubs lined with absorbent paper at 4°C or 19°C for up to 72 h

4 or 19

5.07, 5.07

24 h

Heat Treatments:

  1. 24 h control

  2. 76°C for 2 min

  3. 76°C for 3 min

  1. 4.84, 5.14

  2. 0.27, 0.10

  3. ND, ND

Results shown are counts for samples stored at 4°C and 19°C, respectively

CFU/cm2

Initial counts shown for 4°C and 19°C, respectively

Annous et al., 2004

Cantaloupe, Whole

E. coli O157:H7 (C7927, EDL933, and 204P)

100 µl spot inoculated on 5 cm2 of surface, air dried @ 22°C for 1 h (concentration of bacterial culture: 108–9 CFU/ml)

90–95% RH; melons treated with different levels of ClO2 gas for up to 10 min

 

7–8 log CFU/ml

 

mg/l of ClO2 gas:

0.5 (2 and 10 min)

1.0 (2 and 10 min)

1.5 (2 and 10 min)

3.0 (2 and 10 min)

5.0 (2 and 10 min)

Reductions:

0.6, 2.7

1.1, 2.7

1.1, 2.8

2.2, 3.4

2.2, 4.6

CFU/5 cm2

 

Mahmoud et al., 2008

Cantaloupe, Whole

E. coli O157:H7 (SEA 13B88 and Oklahoma)

Melon was submerged in 3 l of inoculum, rotated with a glove-covered hand for 10 min

Dried in biosafety cabinet for 1 h, then stored at 5°C for up to 7 days before antimicrobial treatments

5

5.27

0 or 7 days

Wash Treatments:

  1. Sterile tap water

  2. 2.5% H2O2

  3. Solution of 1% H2O2, 25 µg/ml nisin, 1% sodium lactate (NaL), and 0.5% citric acid (HPLNC)

Results shown for Day 0:

  1. No significant reduction (data not shown)

  2. 3 log reduction

  3. 4 log reduction

Treatment with HPLNC after Day 7 yielded better results than H202 in reduction of bacterial population.

Population of E. coli slightly decreased during storage for 7 days.

CFU/cm2

pH of both wash solutions adjusted to 6.7 by adding 2N NaOH; melons were washed similar to method of inoculation, but only rotated for 5 min

Ukuku et al., 2005

Cantaloupe, Whole

E. coli NCTC 10418

Submerged in inoculum (2 concentrations: 103 and 106) solution for 5 min, dried for 1 h at 20°C ± 2°C

Stored for 7 d at 8°C (stored to simulate commercial distribution in Australia); placed in an open bag to allow for high RH

8

2.26

7 d

n/a

1.04

Results shown for the high inoculum concentration

CFU/cm2

 

Behrsing et al., 2003

Cantaloupe, Whole

Listeria innocua 2305

Submerged in inoculum (2 concentrations: 103 and 106) solution for 5 min, dried for 1 h at 20°C ± 2°C

Stored for 7 d at 8°C (stored to simulate commercial distribution in Australia); placed in an open bag to allow for high RH

8

3.53

7 d

n/a

5.46

Results shown for the high inoculum concentration

CFU/cm2

 

Behrsing et al., 2003

Cantaloupe, Whole

Listeria monocytogenes (Scott A, F5069, and LCDC 81-861)

100 µl spot inoculated on 5 cm2 of surface, air dried at 22°C for 1 h (concentration of bacterial culture: 108–9 CFU/ml)

90–95% RH; melons treated with different levels of ClO2 gas for up to 10 min

 

7–8 log CFU/ml

 

mg/l of ClO2 gas:

0.5 (2 and 10 min)

1.0 (2 and 10 min)

1.5 (2 and 10 min)

3.0 (2 and 10 min)

5.0 (2 and 10 min)

Reductions:

1.2, 3.3

1.8, 3.2

2.1, 3.7

2.1, 3.8

2.2, 4.3

CFU/5 cm2

 

Mahmoud et al., 2008

Cantaloupe, Whole

Listeria monocytogenes (Scott A and CCR1-L-G)

Submerged in 3 l of inoculum, rotated with a glove-covered hand for 10 min

Dried in biosafety cabinet for 1 h, then stored at 5°C for up to 7 days before treatments

5

4.07

0 or 7 days

Wash Treatments:

  1. Sterile tap water

  2. 2.5% H2O2

  3. Solution of 1% H2O2, 25 µg/ml nisin, 1% sodium lactate (NaL), and 0.5% citric acid (HPLNC)

Results shown for Day 0:

  1. No significant reduction (data not shown)

  2. 3 log reduction

  3. None detected

Treatment with HPLNC after Day 7 yielded better results than H202 in reduction of bacterial population.

Population of L. mono remained the same during storage for 7 days.

CFU/cm2

pH of both wash solutions adjusted to 6.7 by adding 2N NaOH melons were washed similar to method of inoculation, but only rotated for 5 min

Ukuku et al., 2005

Cantaloupe, Whole

Listeria monocytogenes (Scott A, ATCC 15313, H7778, and CCR1-L-G)

Submerged in 3 l of inoculum (108 CFU/ml), w/ agitation by glove-covered hand for 10 min, dried for 1 h

Whole cantaloupes were divided into 2 groups: ½ was untreated and other ½ was treated with 70% ETOH, (treated by submerging melon into ETOH solution for 1 min)

5

 

24 h

Wash Treatments:

  1. Sterile tap water

  2. 1000 ppm chlorine

  3. 5% H2O2

ETOH treated cantaloupes with Treatment (2) and (3) reduced L. mono below detection limit (2 CFU/cm2), (3- or 4-log reduction).

CFU/cm2

 

Ukuku and Fett, 2002

Cantaloupe, Whole

Natural microflora

n/a

Immersed in 5 l of either water or dilute acetic acid for 1 min

 

6.7

 
  1. Water (25°C)

  2. Water (95°C)

  3. Acetic Acid (25°C)

  4. Acetic Acid (95°C)

  1. 6.3

  2. 3.7

  3. 6.0

  4. 3.3

CFU/cm2of surface rind

Final counts shown reflect an average of APC counts from 4 different sampling sites

Fouladkhah and Avens, 2010

Cantaloupe, Whole

Natural microflora (total coliforms)

n/a

Treated with gaseous ozone and submerged in hot water (75°C)

 

2.3

 
  1. 10,000 ppm O3/30 min

  2. 10,000 ppm O3/ 30 min + CO2

  3. Hot H20 (75°C/1 min)

  4. Hot H20 (75°C/1 min) + 10,000 ppm O3/30 min

  1. 1.0

  2. 1.2

  3. 0.0

  4. 0.0

CFU/g of rind

 

Selma et al., 2008a

Cantaloupe, Whole

Natural microflora (mesophilic bacteria)

n/a

Air-dried, treated with chlorine dioxide gas, packaged in plastic clamshell containers, wrapped in PVC film

22

4.2

6.3

7.3

7.5

8.2

0 days

3 days

6 days

9 days

12 days

5.0 mg/l (2 and 10 min)

3.0, 2.3

4.9, 3.8

5.3, 4.0

5.6, 4.8

6.0, 5.8

CFU/cm2

 

Mahmoud et al., 2008

Cantaloupe, Whole

Natural microflora (mesophilic bacteria)

n/a

Treated with gaseous ozone and submerged in hot water (75°C)

 

5.9

 
  1. 10,000 ppm O3/30 min

  2. 10,000 ppm O3/30 min+ CO2

  3. Hot H20 (75°C/1 min)

  4. Hot H20 (75°C/1 min) + 10,000 ppm O3/30 min

  1. 4.8

  2. 4.4

  3. 3.3

  4. 2.1

CFU/g of rind

 

Selma et al., 2008a

Cantaloupe, Whole

Natural microflora (molds)

n/a

Treated with gaseous ozone and submerged in hot water (75°C)

 

2.2

 
  1. 10,000 ppm O3/30 min

  2. 10,000 ppm O3/30 min+ CO2

  3. Hot H20 (75°C/1 min)

  4. Hot H20 (75°C/1 min) + 10,000 ppm O3/30 min

  1. 0.7

  2. 0.5

  3. 0.3

  4. 0.0

CFU/g of rind

 

Selma et al., 2008a

Cantaloupe, Whole

Natural microflora (psychrotrophic bacteria)

n/a

Air-dried, treated with chlorine dioxide gas, packaged in plastic clamshell containers, wrapped in PVC film

22

3.6

3.9

4.9

5.8

6.4

0 days

3 days

6 days

9 days

12 days

5.0 mg/l (2 and 10 min)

ND, ND

2.8, ND

3.2, ND

4.0, ND

4.5, 2.3

CFU/cm2

 

Mahmoud et al., 2008

Cantaloupe, Whole

Natural microflora (psychrotrophic bacteria)

n/a

Treated with gaseous ozone and submerged in hot water (75°C)

 

5.6

 
  1. 10,000 ppm O3/30 min

  2. 10,000 ppm O3/ 30 min + CO2

  3. Hot H20 (75°C/1 min)

  4. Hot H20 (75°C/1 min) + 10,000 ppm O3/30 min

  1. 4.3

  2. 4.4

  3. 1.3

  4. 0.5

CFU/g of rind

 

Selma et al., 2008a

Cantaloupe, Whole

Natural microflora (mesophilic aerobes, YM, and Pseudomonas spp.)

n/a

Cantaloupes individually placed in Vacuum-Steamed-Vacuum (VSV) processor with 138°C saturated steam for 0.1 s

 

6.39

3.09

2.89

 

VSV treatment – 2 and 3 cycles

Reductions:

~1 log

~2 log

~1 log

Results shown for mesophilic aerobes, YM, and Pseudomonas spp., respectively

CFU/cm2

Initial Counts for mesophilic aerobes, YM, and Pseudomonas spp., respectively

Ukuku et al., 2006

Cantaloupe, Whole

Natural microflora

n/a

Stored at 4°C prior to surface pasteurization treatment at indicated temp. and time

4

6.18

 

Heat Treatments:

  1. 96°C for 2 min

  2. 86°C for 2 min

  3. 76°C for 2 min

  4. 76°C for 3 min

  1. 3.88

  2. 4.24

  3. 3.88

  4. 4.00

CFU/cm2

 

Annous et al., 2004

Cantaloupe, Whole

Natural microflora (aerobic mesophilic bacteria, YM, Pseudomonas spp.)

n/a

n/a

n/a

n/a

n/a

n/a

6.6, 2.8, 2.9

Results for mesophiles, YM, and Pseudomonas spp., respectively

CFU/cm2

 

Ukuku and Sapers, 2007

Cantaloupe, Whole

Salmonella Poona

100 µl spot inoculated on 5 cm2 of surface, air dried at 22°C for 1 h (concentration of bacterial culture: 108–9 CFU/ml)

90%–95% RH; melons treated with different levels of ClO2 gas for up to 10 min

 

7–8 log CFU/ml

 

mg/l of ClO2 gas:

0.5 (2 and 10 min)

1.0 (2 and 10 min)

1.5 (2 and 10 min)

3.0 (2 and 10 min)

5.0 (2 and 10 min)

Reductions:

0.9, 3.2

1.2, 3.5

1.5, 4.7

3.2, >5

3.2, >5

CFU/5 cm2

 

Mahmoud et al., 2008

Cantaloupe, Whole

Salmonella Poona RM 2350

Submerged in 4 l of inoculum for 5 min

Air-dried for 1 h on absorbent paper on each side in biosafety cabinet, then stored in plastic tubs lined with absorbent paper at 4°C or 19°C for up to 72 h

4 or 19

3.66, 3.66

24 h

Heat Treatments:

  1. 24-hr control

  2. 76°C for 3 min

  3. RT wash for 3 min

  1. 3.31, 5.54

  2. 0.10, 0.16

  3. 4.23, 5.08

Results shown are counts for samples stored at 4°C and 19°C, respectively.

CFU/cm2

Initial count for 4 and 19°C, respectively

Annous et al., 2004

Cantaloupe, Whole

Salmonella Poona RM 2350

Submerged in 4 l of inoculum for 5 min

Air-dried at either 4°C or 19°C for up to 72 h

4 or 19

 

2 h

24 h

48 h

72 h

Effect of storage temperature on survival

4.26, 4.26

6.72, 3.40

6.95, 3.08

7.02, 3.37

Results shown are for storage temperature of 4°C and 19°C (2 h, 24 h, 48 h, 72 h).

CFU/cm2

 

Annous et al., 2004

Cantaloupe, Whole

Salmonella Salford IMB 1710

Submerged in inoculum (2 concentrations: 103 and 106) solution for 5 min, dried for 1 h at 20 ± 2°C

Stored for 7 d at 8°C (stored to simulate commercial distribution in Australia); placed in an open bag to allow for high RH

8

2.08

7 d

n/a

1.78

Results shown for the high inoculum concentration

CFU/cm2

 

Behrsing et al., 2003

Cantaloupe, Whole

Salmonella Stanley H0558

Submerged in 3 l of inoculum (108 CFU/ml), w/ agitation by glove-covered hand for 10 min, dried for 1 h

Washed melons were submerged in wash solution with manual rotation for 5 min, dried on crystallizing dish for 1 h

4 and 20

3.8

0 h

24 h

72 h

120 h

144 h

Wash Treatments:

  1. Sterile tap water

  2. 1000 ppm chlorine

  3. 5% H2O2

  1. No significant reduction at either temp.

  2. (4°C) – 3.4 log reduction at 0 and 24 h, less reduction at all times thereafter; (20°C) – 3 log reduction at 0 h, declined at all times thereafter

  3. (4°C) – 3.2 and 1.6 log reductions at 0 h and 24 h, respectively, 0.8–0.9 log reduction at all times thereafter; (20°C) – 3 log reduction @ 0 h, declined at all times thereafter

CFU/cm2

 

Ukuku and Sapers, 2001

Cantaloupe, Whole

Salmonella (Stanley H0558, Newport H1275, Anatum F4317, Infantis F4319, and Poona RM2350)

Submerged in 3 l of inoculum cocktail (108 CFU/ml), rotated with a glove-covered hand for 10 min

Air-dried, melons were dipped into 3 l of sanitizer solutions with manual rotating for 5 min

5

4.76

0, 3, or 7 days

Wash Treatments:

  1. Sterile tap water

  2. nisin-EDTA

  3. nisin-NaL

  4. NaL-KS

  5. nisin-NaL-KS

4.54, 4.44, 4.36*

1.66, 2.59, 2.66

1.50, 2.52, 2.46

1.40, 2.40, 2.36

1.70, 2.66, 2.70

1.32, 2.22, 2.26

Results shown for Days 0, 3, and 7, respectively

CFU/cm2

*Day 0: all combination treatments reducedSalmonella by 3 logs; no significant reductions for melons stored for 3 or 7 days

Ukuku and Fett, 2004

Cantaloupe, Whole

Salmonella (Poona RM2350, Stanley H0558, Newport H1275, Anatum F4317, Infantis F4319)

Submerged in 3 l of inoculum (8.3 x 108 CFU/ml) for 10 min w/out agitation

Cantaloupes placed on a crystallizing dish to air dry for 1 h, stored at 5 or 20°C for up to 5 days

5 or 20

4.7

Data shown for 8 h post-inoculation

Wash Treatments:

  1. Water (70°C)

  2. 5% H2O2 (70°C)

  3. Water (97°C)

  1. 2.6

  2. 0.9

  3. 1.1

Salmonella population (on rind surface) declined slightly at 5°C and increased slightly at 20°C during the 5-day storage (data not shown in paper).

CFU/cm2

Treatment was carried out ~8 h after inoculation and applied for 60 s

Ukuku et al., 2004

Cantaloupe, Whole

Salmonella (Poona RM2350, Stanley H0558, Newport H1275, Anatum F4317, Infantis F4319)

Submerged in 3 l of inoculum (~20°C) of 3 concentrations (103, 106, 108 CFU/ml) for 10 min w/out agitation

Cantaloupes placed on a crystallizing dish to air dry for 1 h

20

  1. 4.7

  2. 3.5

  3. 1.9

3 days

3 different inoculum levels (CFU/ml):

  1. 108

  2. 106

  3. 103

  1. 2.7, 0.8, 1.3

  2. 1.1, +, +

  3. +, - , -

Results shown are for H2O (70°C), H2O2 (70°C), and H2O (97°C), respectively,for each level (see comments).

CFU/cm2

(+) Means positive after enrichment

(-) Means negative after enrichment

Ukuku et al., 2004

Cantaloupe, Fresh-cut

E. coli O157:H7 LJH537

200 µl of 104, 105, 106, 107, 108, 109 CFU/ml on surface of rind of whole melon

(Transference of pathogen during cutting)

Melons cut through point of inoculation and rind removed, transference determined by TSA-Kan plates, visualization of green fluorescence on flesh melon cubes under UV-light and PCR analysis

       

Fresh-cut pieces inoculated with 4.3 to 8.3 log were all positive for E. coli; pieces inoculated with 3.3 log were negative for E. coli.

CFU/rind

Results for fresh-cut pieces were consistently positive or negative by all methods.

Selma et al., 2008a

Cantaloupe, Fresh-cut

E. coli O157:H7 (SEA 13B88 and Oklahoma)

Whole melon submerged in 3 l of inoculum, rotated with a glove-covered hand for 10 min (Transference of pathogen during cutting)

Inoculated whole melons cut into 4 sections, rinds removed, and interior flesh cut into ~3 cm cubes

5

 

0 or 7 days

Wash Treatments:

  1. Sterile tap water

  2. 2.5% H2O2

  3. Solution of 1% H2O2, 25 µg/ml nisin, 1% sodium lactate (NaL), and 0.5% citric acid (HPLNC)

  1. 6, 6

  2. 1 (2), 3 (3)

  3. 0 (0), 1 (1)

Numbers listed represent # of melons (rinds) out of 6 that were positive for pathogen at Days 0 and 7, respectively.

See comments for #’s in parentheses.

 

#’s enclosed in parentheses represent fresh-cut pieces that were negative by direct plating but positive after enrichment

Ukuku et al., 2005

Cantaloupe, Fresh-cut

E. coli O157:H7 (204P, 301C, 505B, 45753-35)

Pieces placed in stomacher bags and inoculated 1.0 ml of 104 cocktail (method not specified)

Rinds sanitized before cutting, flesh cut into 2-cm cubes

5 or 25

Not specified

up to 34 h

Cubes held at 5°C or 25°C for up to 34 h

Watermelon cubes incubated at 25°C supported growth better than cantaloupe. Significant (p<0.05) increases in population occurred b/t 4 and 6 h. Population reached 6.81 log after 28 h incubation at 25°C. No significant change in population on cubes held at 5°C.

CFU/g of melon

Watermelon pH 5.56; Cantaloupe pH 7.01

Article has hand-drawn graph of growth at various time intervals up to 34 h

Delrosario and Beuchat, 1995

Cantaloupe, Fresh-cut

E. coli O157:H7 (B6914 gfp 86)

25 µl of inoculum (6.15 log CFU/ml was added to each melon well

Rind of whole melons sprayed with 80% ETOH, melon was cut in ½ and seeds removed by gloved hand, 1 cm thick slices were cut with a deli-slicer, each slice cut into ~25 mm wedges by knife, metal cork borer (0.5 cm diam.) used to make a well in each wedge

4

 

0, 2, 5, 7 days

ECP-100 is a bacteriophage cocktail composed of 3 E. coli O157:H7-specific lytic bacteriophages (ECML-4, ECML-117, and ECML-134). Phages were mixed in phosphate-buffered saline (pH 7.4); final concentration was 8.3 log PFU/ml in PBS; 25 µl of ECP-100 was applied via pipette.

Control:

3.74, 3.34, 3.23, 3.46

Treated with ECP-100:

3.53, 0.77, 1.28, 0.96

Results shown in each group represent Days 0, 2, 5, and 7.

CFU/ml

Samples were placed in commercial, 530 ml domed plastic fruit bowls

Sharma et al., 2009

Cantaloupe, Fresh-cut

E. coli O157:H7 (B6914 gfp 86)

25 µl of inoculum (6.15 log CFU/ml was added to each melon well

Rind of whole melons sprayed with 80% ETOH, melon was cut in ½ and seeds removed by gloved hand, 1-cm thick slices were cut with a deli-slicer, each slice cut into ~25 mm wedges by knife, metal cork borer (0.5 cm diam.) used to make a well in each wedge

20

 

0, 2, 5, 7 days

ECP-100 is a bacteriophage cocktail composed of 3 E. coli O157:H7-specific lytic bacteriophages (ECML-4, ECML-117, and ECML-134). Phages were mixed in phosphate-buffered saline (pH 7.4); final concentration was 8.3 log PFU/ml in PBS; 25 µL of ECP-100 was applied by pipette.

Control:

3.74, 7.53, 7.83, 8.36

Treated with ECP-100:

3.53, 6.17, 6.59, 6.99

Results shown in each group represent Days 0, 2, 5, and 7.

CFU/ml

Samples were placed in commercial, 530 ml domed plastic fruit bowls

Sharma et al., 2009

Cantaloupe, Fresh-cut

Listeria monocytogenes (Scott A and CCR1-L-G)

Whole melon submerged in 3 l of inoculum, rotated with a glove-covered hand for 10 min (Transference of pathogen during cutting)

Inoculated whole melons cut into 4 sections, rinds removed, and interior flesh cut into ~3 cm cubes

5

 

0 or 7 days

Wash Treatments:

  1. Sterile tap water

  2. 2.5% H2O2

  3. Solution of 1% H2O2, 25 µg/ml nisin, 1% sodium lactate (NaL), and 0.5% citric acid (HPLNC)

  1. 6, 6

  2. 1 (1), 1 (3)

  3. 0 (0), 0 (0)

Numbers listed represent # of melons (rinds) out of 6 that were positive for pathogen at Day 0 and Day 7, respectively.

See comments for #’s in parentheses.

 

#’s in parentheses represent fresh-cut pieces that were negative by direct plating but positive after enrichment

Ukuku et al., 2005

Cantaloupe, Fresh-cut

Listeria monocytogenes (Scott A, ATCC 15313, H7778, and CCR1-L-G)

Fresh-cut pieces were immersed in 3 l of inoculum (106 CFU/ml) for 30 s

Melon flesh was surface sanitized by dipping in Cl or H2O2 solution for 5 min and cut into 3-cm cubes prior to inoculation

4, 8, 20

3.5

Up to 15 days

 

4°C: L. monocytogenes survived but did not grow for up to 15 days

8°C and 20°C: Population reached 4.86 logs at 15 days

CFU/g

Growth evident at 8 and 20°C but there was an observed lag time for both: 6 h and 4 h, respectively

Ukuku and Fett, 2002

Cantaloupe, Fresh-cut

Listeria monocytogenes (Scott A, ATCC 15313, H7778, and CCR1-L-G)

Whole melon submerged in 3 l of inoculum (108 CFU/ml), w/ agitation by glove-covered hand for 10 min,(Transference of pathogen during cutting)

Melons were cut into 4 sections. Each section was further cut, rinds removed, then ~100g of interior flesh placed into stomacher bag.

4

3.5 (on rind)

0, 1, 5, 10, 15 days

Wash Treatments:

  1. Sterile tap water

  2. 1000 ppm chlorine

  3. 5% H2O2

Water-washed samples had growth of L. monocytogenes at 0, 1, and 5 days (after enrichment), but not on Days 10 and 15. Chlorine- and H2O2- washed samples did not have growth at any measured interval.

CFU/cm2

Control sample also did not have growth of L. monocytogenes on Days 10 and 15

Ukuku and Fett, 2002

Cantaloupe, Fresh-cut

Natural microflora (mesophilic bacteria)

Transference of pathogen during cutting

Cubes placed in a 3-pocket tub tall plastic bowl

5 and 10

 

3 days

6 days

9 days

VSV treatment – 2 and 3 cycles

No significant reductions

CFU/g

 

Ukuku et al., 2006

Cantaloupe, Fresh-cut

Natural microflora (YM)

Transference of pathogen during cutting

Cubes placed in a 3-pocket tub tall plastic bowl

5 and 10

 

3 days

6 days

9 days

VSV treatment – 2 and 3 cycles

Reduced to below levels of detections (<1 CFU/g); not recovered for up to 3 days at 5°C, but showed up at Day 6 and Day 9

CFU/g

 

Ukuku et al., 2006

Cantaloupe, Fresh-cut

Natural microflora (Pseudomonas spp.)

Transference of pathogen during cutting

Cubes placed in a 3-pocket tub tall plastic bowl

5 and 10

 

3 days

6 days

9 days

VSV treatment – 2 and 3 cycles

No significant reductions

CFU/g

 

Ukuku et al., 2006

Cantaloupe, Fresh-cut

Natural microflora (total plate count [TPC])

Transference of pathogen during cutting

Whole cantaloupes sanitized by submerging into water under 3 different conditions; melons then peeled (w/ mechanical peelers) and cubed

4

n/a

Up to 20 days

Submersion Conditions:

  1. 10°C for 20 min

  2. 20 ppm chlorine solution at 10°C for 20 min (pH 6.5)

  3. 76°C for 3 min

Total plate count plated on TSA (tryptic soy agar).

Final counts for each condition under each trial are for Days 1, 6, 8, 10, 13, 16, and 20, respectively.

Trial 1:

  1. 2.9, 3.3, 3.1, 3.4, 3.3, 3.5, 4.2

  2. 3.2, 3.4, 3.3, 3.1, 3.0, 3.5, 3.6

  3. 3.9, 3.4, 3.4, 3.4, 3.8, 3.6, 3.8

Trial 2:

  1. 3.1, 3.8, 4.2, 4.9, 6.3, 6.9, 7.9

  2. 2.9, 3.5, 4.3, 4.8, 5.6, 6.9, 7.8

  3. 2.9, 2.3, 3.9, 2.9, 3.6, 2.8, 5.0

Trial 3:

  1. 2.8, 4.3, 4.8, 5.8, 7.3, 7.4, 8.0

  2. 2.6, 3.9, 4.9, 6.0, 6.5, 7.4, 7.3

  3. 3.2, 2.4, 3.0, 2.7, 3.2, 3.8, 4.6

CFU/g

Samples also analyzed for appearance, aroma, firmness, color, soluble solids content, fluid loss, ascorbic acid content, and headspace O2 and CO2 w/in the packages

Fan et al., 2008

Cantaloupe, Fresh-cut

Natural microflora (Yeast and Molds [YM])

Transference of pathogen during cutting

Whole cantaloupes sanitized by submerging into water under 3 different conditions; melons then peeled (w/ mechanical peelers) and cubed

4

n/a

Up to 20 days

Submersion Conditions:

  1. 10°C for 20 min

  2. 20 ppm chlorine solution at 10°C for 20 min (pH 6.5)

  3. 76°C for 3 min

YM plated on Yeast and Mold Petrifilm.

Final counts for each condition under each trial are for Days 1, 6, 8, 10, 13, 16, and 20, respectively.

Trial 1:

  1. 2.2, 2.0, 2.3, 2.7, 2.0, 2.2, 3.2

  2. 2.1, 2.5, 2.6, 2.5, 2.0, 2.6, 2.4

  3. 2.5, 1.9, 1.7, 2.3, 2.2, 2.7, 2.3

Trial 2:

  1. 2.3, 2.8, 2.6, 2.7, 2.9, 3.2, 3.4

  2. 1.9, 2.0, 2.3, 2.2, 1.4, 1.8, 2.2

  3. 2.2, 0.9, 1.7, 1.1, 1.3, 1.7, 1.9

Trial 3:

  1. 2.0, 3.0, 2.7, 3.5, 3.3, 3.0, 3.6

  2. 1.9, 2.7, 2.9, 4.0, 3.6, 3.2, 3.8

  3. 1.5, 2.1, 1.9, 2.2, 1.5, 1.7, 1.1

CFU/g

Samples also analyzed for appearance, aroma, firmness, color, soluble solids content, fluid loss, ascorbic acid content, and headspace O2 and CO2 w/in the packages

Fan et al., 2008

Cantaloupe, Fresh-cut (ripe)

Natural microflora (coliforms, LAB, P. fluorescens, and yeasts)

 

After cutting, cubes stored at 5°C for 30 min, then treated (or left untreated) with gaseous ozone and packaged in polypropylene (PP) containers with passive MAP

5

2.7, 2.9, 4.4, 3.9

4 days

7 days

Gaseous Ozone Conditions:

  1. 5000 ppm/30 min

  2. 20,000 ppm/30 min

  1. 1.6, 2.4, 4.0, 3.4

  2. – ,1.0, – , –

Initial and final counts shown for coliforms, LAB, P. fluorescens, and yeasts, respectively

CFU/cube

 

Selma et al., 2008b

Cantaloupe, Fresh-cut (non-ripe)

Natural microflora (coliforms, LAB,P. fluorescens, and yeasts)

 

After cutting, cubes stored at 5°C for 30 min, then treated (or left untreated) with gaseous ozone and packaged in polypropylene (PP) containers with passive MAP

5

0.5–0.7 log lower than ripe melons except for LAB

4 days

7 days

Gaseous Ozone Conditions:

20,000 ppm/30 min

On Day 7, with the 20,000 ppm/30 min of ozone treatments, counts were lowered by 1.6, 1.6, 0.7, and 1.1 logs from the initial counts.

CFU/cube

 

Selma et al., 2008b

Cantaloupe, Fresh-cut

Natural microflora (aerobic mesophilic bacteria, YM, Pseudomonas spp.)

n/a

n/a

n/a

n/a

n/a

n/a

3.2, 0.6, 0.8

Results for mesophiles, YM, and Pseudomonas spp., respectively

CFU/g

 

Ukuku and Sapers, 2007

Cantaloupe, Fresh-cut

Natural microflora (aerobic mesophilic bacteria, YM, Pseudomonas spp.)

Transference of pathogen during cutting

Whole melon cut into 4 sections, rinds removed, flesh cut into 3-cm cubes; pieces were then left out at 22°C for 5 h, then refrigerated at 5°C for 3 h

n/a

n/a

n/a

n/a

Mesophiles increased ~1 log; Yeast and mold increased from 0.6 to 1.3 logs; Pseudomonas spp. increased ~1 log

CFU/g

 

Ukuku and Sapers, 2007

Cantaloupe, Fresh-cut

Salmonella Stanley H0558

Whole melon submerged in 3 l of inoculum (108 CFU/ml), w/ agitation by glove-covered hand for 10 min, dried for 1 h

(Transference of pathogen during cutting)

Pieces treated w/ chlorine and hydrogen peroxide were analyzed for presence of Salmonella through pre-enrichment steps

4

0.21, 0.23, 0.22, 0.22

0, 1, 3, 5 days

Wash Treatments:

  1. Sterile tap water

  2. 1000 ppm chlorine

  3. 5% H2O2

Pieces treated with chlorine and H2O2 were done so within 24 h of inoculation.

  1. 0.21, 0.20, 0.20, 0.23

  2. BD, BD, 0.12, 0.18

  3. BD, BD, 0.16, 0.20

Results shown for Days 0, 1, 3, 5, respectively, for each wash treatment

CFU/g

Initial counts are shown for Days 0, 1, 3, 5, respectively

BD – below detectable limits (<0.1 CFU/g)

Ukuku and Sapers, 2001

Cantaloupe, Fresh-cut

Salmonella Stanley H0558

Whole melon submerged in 3 l of inoculum (108 CFU/ml), w/ agitation by glove-covered hand for 10 min, dried for 1 h

(Transference of pathogen during cutting)

Pieces treated w/ chlorine and hydrogen peroxide were analyzed for presence of Salmonella through pre-enrichment steps

20

0.22, 0.21, 0.24, 0.20

0, 1, 3, 5 days

Wash Treatments:

  1. Sterile tap water

  2. 1000 ppm chlorine

  3. 5% H2O2

Pieces treated with chlorine and H2O2 were done so within 24 h of inoculation.

  1. 0.20, 0.20, 0.21, 0.22

  2. BD, BD, 0.14, 0.18

  3. BD, BD, 0.18, 0.14

Results shown for Days 0, 1, 3, 5, respectively, for each wash treatment

CFU/g

Initial counts shown for Days 0, 1, 3, 5, respectively.

BD – below detectable limits (<0.1 CFU/g)

Ukuku and Sapers, 2001

Cantaloupe, Fresh-cut

Salmonella Stanley H0558

Fresh-cut cubes were dipped in inoculum, concentration of 104or 106 CFU/ml for 1 min

Melon flesh was surface-sanitized by dipping in Cl or H2O2 solution for 5 min and cut into 3-cm cubes prior to inoculation.

4, 8 or 20

102to 103

up to 14 days (examined every 2 days)

Wash Treatments:

  1. Sterile tap water

  2. 1000 ppm chlorine

  3. 5% H2O2

4°C: all pieces positive on Day 8 and thereafter

8°C: all pieces positive on Day 4 and thereafter

20°C: all pieces positive at Day 2 and Day 4*

*For 20°C, study terminated after Day 4 due to presence of slime, odor, and mold

CFU/g

Below detectable limits for non-specified days

Ukuku and Sapers, 2001

Cantaloupe, Fresh-cut

Salmonella (Stanley H0558, Newport H1275, Anatum F4317, Infantis F4319, and Poona RM2350)

Whole melon submerged in 3 l of inoculum cocktail (108 CFU/ml), rotated with a glove-covered hand for 10 min

(Transference of pathogen during cutting)

Air-dried

5

1.96, 2.31, 2.66

0, 3, or 7 days

Wash Treatments:

  1. nisin-EDTA

  2. nisin-NaL

  3. nisin-KS

  4. NaL-KS

  5. nisin-NaL-KS

Only detectable on Day 7:

  1. .48

  2. .35

  3. .51

  4. .23

  5. ND

CFU/g

Initial counts shown for Days 0, 3, and 7, respectively

Ukuku and Fett, 2004

Cantaloupe, Fresh-cut

Salmonella (Stanley H0558, Newport H1275, Anatum F4317, Infantis F4319, and Poona RM2350)

Fresh-cut pieces dipped in inoculum cocktail (106 CFU/ml) for 2 min

Cut from uninoculated whole melons; inoculated pieces placed in a basket to dry for 3 h before sanitizing, then washed for 1 min with sanitizing solutions; stored in bags after sanitized

5

3.42, 3.91, 4.46

0, 3, or 7 days

Wash Treatments:

  1. Sterile tap water

  2. nisin-EDTA

  3. nisin-NaL

  4. nisin-KS

  5. NaL-KS

  6. nisin-NaL-KS

Pieces washed for 1 min with respective solutions

  1. 3.02, 3.85, 4.58

  2. 3.07, 3.15, 3.18

  3. 2.62, 2.69, 2.58

  4. 2.82, 2.88, 2.78

  5. 2.40, 2.49, 2.52

  6. 2.02, 2.25, 2.18

Results shown for Days 0, 3, and 7, respectively

CFU/g

Initial counts shown for Days 0, 3, 7, respectively

Nisin-NaL-KS was most effective for reducing Salmonella, and had significant differences in reduction from all other sanitizing solutions

Ukuku and Fett, 2004

Cantaloupe, Fresh-cut

Salmonella (Poona RM2350, Stanley H0558, Newport H1275, Anatum F4317, and Infantis F4319)

Whole melon submerged in 3 l of inoculum (8.3 × 108 CFU/ml) for 10 min w/out agitation

Wash treatments carried out 3 days post-inoculation; fresh-cut pieces prepared and sampled immediately after wash treatments

5

4.7, 2.9

3 days

Wash Treatments:

  1. Water (70°C)

  2. 5% H2O2 (70°C)

  3. Water (97°C)

Treatments applied for 60 s

  1. 2.6, 0.7

  2. 0.9, +

  3. 1.1, +

Results shown for whole and fresh-cut, respectively

CFU/cm2

Initial counts shown for whole and fresh-cut, respectively

(+) Means positive after enrichment

Ukuku et al., 2004

Cantaloupe, Fresh-cut

Salmonella (Newport 02-216, Poona 418, Hidalgo 02-517-2, Typhimurium 45, St. Paul FSIS 039)

Pieces submerged in inoculum (105 CFU/ml) for 30 s

Whole melon cut into 4 sections, rinds removed, flesh cut into 3-cm cubes; after inoculation, pieces dried for 1 h, then placed inside a 9.75-inch diameter, 3-pocket, plastic bowl

5, 10, and 22

2.2

Up to 12 days

 

5°C: No significant decline after 12 d

10°C: Increased to 3.6 log by Day 12

22°C: Plateaued at Day 2 and declined to below initial populations thereafter

 

Whole melons were individually washed under running tap water (19°C) for 5 min to mimic home preparation before cut

Ukuku and Sapers, 2007

Cantaloupe, Fresh-cut

Salmonella (Newport 02-216, Poona 418, Hidalgo 02-517-2, Typhimurium 45, St. Paul FSIS 039)

Pieces submerged in inoculum (105 CFU/ml) for 30 s

Whole melon cut into 4 sections, rinds removed, flesh cut into 3-cm cubes; after inoculation, pieces dried for 1 h, then placed inside a 9.75-inch diameter, 3-pocket, plastic bowl

5 and/ or 22

   
  1. Stored at 5°C immediately after preparation

  2. Held at 22°C for 3 h before storage at 5°C

  3. Held at 22°C for 5 h before storage at 5°C

  4. Held at 5°C for 3 h, after preparation

  1. 2.2

  2. 2.5

  3. 3.5

  4. 1.9

CFU/g

 

Ukuku and Sapers, 2007

Cantaloupe, Rind

E. coli O157:H7 (204P, 301C, 505B, 45753-35)

7 areas (2–3 cm in diameter) delineated on rind

0.1 ml of inoculum (102 log CFU/ml) pipetted in each of the 7 areas on rind, melons held in covered plastic boxes until enumeration; RH 93% ± 5%

5 or 25

Not specified

Up to 21 days

 

25°C: Significant (p<0.05) increases in population w/in 4 days, then remained constant thereafter

Growth more prolific on cantaloupe than watermelon rind

5°C: Significant decreases w/in 4 days

<101 recovered after 8 days

CFU/cm2 of rind surface

Inoculated areas remained wet throughout incubation due to high RH

Delrosario and Beuchat, 1995

Cantaloupe, Rind

Natural microflora (total plate count [TPC]; yeast and molds [YM])

n/a

Whole cantaloupes sanitized by submerging into water under 3 different conditions

10 or 76

Trial 1:

  1. 5.3

  2. 4.2

Trial 2:

  1. 5.4

  2. 4.4

Trial 3:

  1. 4.6

  2. 4.9

TPC (1) and YM (2)

n/a

Submersion Cond.:

  1. 10°C for 20 min

  2. 20 ppm chlorine solution at 10°C for 20 min (pH 6.5)

  3. 76°C for 3 min

Total plate count plated on TSA (tryptic soy agar)

Yeast and molds plated on Yeast and Mold Petrifilm

Trial 1 (TPC and YM):

  1. 5.1, 3.9

  2. 4.5, 3.1

  3. 3.9, 1.9

Trial 2 (TPC and YM):

  1. 5.0, 4.1

  2. 5.0, 3.7

  3. 4.3, 1.3

Trial 3 (TPC and YM):

  1. 4.6, 4.9

  2. 4.8, 4.3

  3. 3.6, 1.3

CFU/cm2

 

Fan et al., 2008

Cantaloupe, Rind tissue – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242), NA resistant

Whole melons immersed in inoculum suspensionand constantly agitated with gloved hands for 5 min

Melon stored at 4°C or 30°C for 24 h and dipped into inoculum with initial temp. of 4°C or 30°C. Melons placed on elevated mesh screens for 2 min, then placed into a biosafety hood to dry for 1 h at 22°C.CFU

4 or 30

~7 log CFU/ml (Cocktail concentration)

 

Melon Temp. and Inoculum Temp.:

  1. 4°C and 4°C

  2. 4°C and 30°C

  3. 30°C and 4°C

  4. 30°C and 30°C

  1. 5.00

  2. 5.00

  3. 4.56

  4. 4.74

Adherence to or infiltration to rind is enhanced when cantaloupe is at 4°C compared with 30°C, regardless of immersion temperature.

CFU/cm2

Inoculum (12 l at 4 or 30°C) was poured into PE bags and placed in a 34 l plastic container

Richards and Beuchat, 2004

Cantaloupe, Rind tissue – Western (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242), NA resistant

Whole melons immersed in suspension and constantly agitated with gloved hands for 5 min

Melon stored at 4°C or 30°C for 24 h and dipped into inoculum with initial temp. of 4°C or 30°C. Melons placed on elevated mesh screens for 2 min, then placed into a biosafety hood to dry for 1 h at 22°C.

4 or 30

~7 log CFU/ml (Cocktail concentration)

 

Melon Temp. and Inoculum Temp.:

  1. 4°C and 4°C

  2. 4°C and 30°C

  3. 30°C and 4°C

  4. 30°C and 30°C

  1. 5.25

  2. 4.66

  3. 5.32

  4. 4.68

Melons at 30°C immersed in 30°C inoculum had significantly lower counts than melons at 4 or 30°C immersed in 4°C inoculum (indicates adherence of pathogen diminishes when warm fruits are immersed in warm inoculum)

CFU/cm2

Inoculum (12 l at 4 or 30°C) was poured into PE bags and placed in a 34 l plastic container

Richards and Beuchat, 2004

Cantaloupe, Rind and mesocarp tissue – Western (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242), NA resistant

10 µl of S. Poona suspension (~5.9 log CFU/ml) pipetted directly in wounded rind tissue on Day 0

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of inoculation site – 4 inoculation sites/melon

20

3.90 log CFU/10 µl of inoculum

Day 3 (D3)

Day 5 (D5)

Day 7 (D7)

Day 10 (D10)

Distance from site of inoculation to inwards towards edible tissue:

  1. 0–1 cm

  2. 1–2 cm

  3. 2–3 cm

  4. 3–4 cm

D3: 5.58, BD (0/8), BD (0/8), BD (0/8)

D5: 6.28, 0.21 (1/7), BD (1/8), BD (0/8)

D7: 6.75, 2.30 (0/2), 1.70 (2/4),1.09(2/5)

D10: 5.36, BD (0/8), BD (0/8), BD (0/8)

Results for each day are the distances of #'s 1–4 in treatment column

BD – below limit of detection (1.30 log CFU/sample)

Parentheses indicate # of melons positive for S. Poona after enrichment

CFU/tissue

Melons adjusted to 22°C over a 16- to 20-h period before experiments. Inoculated melons dried for 2 h at 22°C

Richards and Beuchat, 2005a

Cantaloupe, Rind and mesocarp tissue – Western (shipper)

Salmonella Poona(00A3207, 01A3923, 02A3275, 00A3279, 01A242), NA resistant; and C. cladosporioides

10 µl of S. Poona suspension (~5.9 log CFU/ml) and 10 µl of mold suspension (~4-5 log CFU/ml) pipetted directly in wounded rind tissue on Day 0

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of inoculation site – 4 inoculation sites/melon

20

3.90 log CFU/10 µl of inoculum

Day 3 (D3)

Day 5 (D5)

Day 7 (D7)

Day 10 (D10)

Distance from site of inoculation to inwards towards edible tissue:

  1. 0–1 cm

  2. 1–2 cm

  3. 2–3 cm

  4. 3–4 cm

D3: 5.36, BD (1/8), BD (2/8), BD (2/8)

D5: 5.74, BD (2/8), BD (1/8), BD (0/8)

D7: 5.70, BD (5/8), BD (2/8), BD (2/8)

D10: 5.98, BD (3/8), BD (1/8), BD (3/8)

Results for each day are the distances of #'s 1–4 in the treatment specifications column

BD – below limit of detection (1.30 log CFU/sample)

Parentheses indicate # of melons positive for S. Poona after enrichment

CFU/tissue

Melons adjusted to 22°C over a 16- to 20-h period before experiments. Inoculated melons dried for 2 h at 22°.

Richards and Beuchat, 2005a

Cantaloupe, Rind and mesocarp tissue – Western (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242), NA resistant; and P. expansum

10 µl of S. Poona suspension (~5.9 log CFU/ml) and 10 µl of mold suspension (~4-5 log CFU/ml) pipetted directly in wounded rind tissue on Day 0

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of inoculation site – 4 inoculation sites/melon

20

3.90 log CFU/10 µl of inoculum

Day 3 (D3)

Day 5 (D5)

Day 7 (D7)

Day 10 (D10)

Distance from site of inoculation to inwards towards edible tissue:

  1. 0–1 cm

  2. 1–2 cm

  3. 2–3 cm

  4. 3–4 cm

D3: 5.97, 0.47 (3/7), BD (0/8), BD (1/8)

D5: 4.94, BD (3/8), BD (3/8), BD (2/8)

D7: 2.61 (0/4), BD (0/8), BD (2/8), BD (0/8)

D10: 2.71 (1/4), 0.75 (1/3), 0.52 (4/5), 0.24 (4/6)

Results for each day are the distances of #'s 1–4 in the treatment specifications column

BD – below limit of detection (1.30 log CFU/sample)

Parentheses indicate # of melons positive for S. Poona after enrichment

CFU/tissue

Melons adjusted to 22°C over a 16- to 20-h period before experiments Inoculated melons dried for 2 h at 22°C

Richards and Beuchat, 2005a

Cantaloupe, Rind and mesocarp tissue – Western (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242), NA resistant; and C. cladosporioides

10 µl of mold suspension (~4-5 log CFU/ml) pipetted on wounded rind tissue on Day 0, followed by inoculation of 10 µl of S. Poona suspension (~5.9 log CFU/ml) 3 days later

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of inoculation site – 4 inoculation sites/melon; analysis done respective days after inoculation with S. Poona

20

3.20 log CFU/10 µl of inoculum

Day 3 (D3)

Day 5 (D5)

Day 7 (D7)

Day 10 (D10)

Distance from site of inoculation to inwards towards edible tissue:

  1. 0–1 cm

  2. 1–2 cm

  3. 2–3 cm

  4. 3–4 cm

D3: 3.77 (1/1), BD (0/8), BD (5/8), BD (4/8)

D5: 6.33, 1.16 (0/6), BD (2/8), BD (1/8)

D7: 5.11 (0/1), 0.96 (2/6), BD (3/8), BD (4/8)

D10: 4.74 (1/1), BD (2/8), BD (2/8), BD (1/8)

Results for each day are the distances of #'s 1–4 in the treatment specifications column

BD – below limit of detection (1.30 log CFU/sample)

Parentheses indicate # of melons positive for S. Poona after enrichment

CFU/tissue

Melons adjusted to 22°C over a 16- to 20-h period before experiments Inoculated melons dried for 2 h at 22°C

Richards and Beuchat, 2005a

Cantaloupe, Rind and mesocarp tissue – Western (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242), NA resistant; and P. expansum

10 µl of mold suspension (~4-5 log CFU/ml) pipetted on wounded rind tissue on Day 0, followed by inoculation of 10 µl of S. Poona suspension (~5.9 log CFU/ml) 3 days later

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of inoculation site – 4 inoculation sites/melon; analysis done respective days after inoculation with S. Poona

20

3.20 log CFU/10 µl of inoculum

Day 3 (D3)

Day 5 (D5)

Day 7 (D7)

Day 10 (D10)

Distance from site of inoculation to inwards towards edible tissue:

  1. 0–1 cm

  2. 1–2 cm

  3. 2–3 cm

  4. 3–4 cm

D3: 0.66 (0/6), BD (0/8), BD (0/8), BD (0/8)

D5: 0.60 (0/6), BD (0/8), BD (0/8), BD (0/8)

D7: 0.30 (1/7), BD (1/8), BD (0/8), BD (0/8)

D10: 1.11 (0/5), BD (0/8), BD (0/8), BD (0/8)

Results for each day are the distances of #'s 1–4 in the treatment specifications column

BD – below limit of detection (1.30 log CFU/sample)

Parentheses indicate # of melons positive for S. Poona after enrichment

CFU/tissue

Melons adjusted to 22°C over a 16- to 20-h period before experiments

Inoculated melons dried for 2 h at 22°C

Richards and Beuchat, 2005a

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto rind – 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.64 log CFU/20 µl of inoculum for both incubation temp.

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. 2.13 (1/1)

  2. 9.03 (ND)

  3. 2.01 (1/1)

  4. 9.38 (ND)

  5. 1.04 (2/2)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant

20 µl ofS. Poona suspension (5 log CFU of each strain/ml) inoculated onto rind - 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.64 log CFU/20 µl of inoculum for both incubation temp.

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. < 1.60 (0/3)

  2. 1.46 (2/2)

  3. < 1.60 (2/3)

  4. 6.53 (ND)

  5. < 1.60 (2/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and A. alternata

10 µl of conidia suspension (4 log CFU/ml) and 10 µl ofS. Poona suspension (5 log CFU of each strain/ml) inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.34 log CFU/10 µl of inoculum for both incubation temp.

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. < 1.60 (1/3)

  2. 1.38 (0/2)

  3. < 1.60 (1/3)

  4. 5.89 (ND)

  5. < 1.60 (0/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and A. alternata

10 µl of conidia suspension (4 log CFU/ml) and 10 µl ofS. Poona suspension (5 log CFU of each strain/ml) inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.64 log CFU/10 µl of inoculum for both incubation temp.

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. 3.45 (ND)

  2. 8.66 (ND)

  3. 3.24 (ND)

  4. 9.21 (ND)

  5. 1.84 (1/1)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and A. alternata

20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 0, then 20 µl of S. Poona suspension inoculated on Day 3 (5 log CFU of each strain/ml) Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

20

3.48 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 1.42 (0/2)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and A. alternata

20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 0, then 20 µl of S. Poona suspension inoculated on Day 3 (5 log CFU of each strain/ml) Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

20

3.48 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 7.75 (ND)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and A. alternata

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated on Day 0, then 20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 3 Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

Analysis done on respective days 2 d after inoculation with S. Poona

20

3.64 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for intactsites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 0.69 (1/0)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and A. alternata

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated on Day 0, then 20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 3 Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

Analysis done on respective days 2 d after inoculation with S. Poona

20

3.64 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 8.27 (ND)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto rind - 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.64 log CFU/20 µl of inoculum for both incubation temp.

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. < 1.60 (0/3)

  2. 1.46 (2/2)

  3. < 1.60 (2/3)

  4. 6.53 (ND

  5. < 1.60 (2/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation.

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and C. cladosporioides

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto rind - 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.64 log CFU/20 µl of inoculum for both incubation temp.

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. 2.13 (1/1)

  2. 9.03 (ND)

  3. 2.01 (1/1)

  4. 9.38 (ND)

  5. 1.04 (2/2)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and C. cladosporioides

10 µl of conidia suspension (4 log CFU/ml) and 10 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.34 log CFU/10 µl of inoculum for both incubation temp.

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. < 1.60 (0/3)

  2. 1.46 (2/2)

  3. < 1.60 (0/3)

  4. 6.53 (ND)

  5. < 1.60 (1/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation.

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and C. cladosporioides

10 µl of conidia suspension (4 log CFU/ml) and 10 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.34 log CFU/10 µl of inoculum for both incubation temp.

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. 4.13 (ND)

  2. 8.57 (ND)

  3. 3.69 (ND)

  4. 9.32 (ND)

  5. 2.05 (ND)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and C. cladosporioides

20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 0, then 20 µl of S. Poona suspension inoculated on Day 3 (5 log CFU of each strain/ml) Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

20

3.48 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 1.61 (1/1)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and C. cladosporioides

20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 0, then 20 µl of S. Poona suspension inoculated on Day 3 (5 log CFU of each strain/ml) Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

20

3.48 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 8.92 (ND)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and C. cladosporioides

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated on Day 0, then 20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 3 Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

Analysis done on respective days 2 d after inoculation with S. Poona

20

3.64 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 1.83 (ND)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and C. cladosporioides

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated on Day 0, then 20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 3 Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

Analysis done on respective days 2 d after inoculation with S. Poona

20

3.64 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 9.53 (ND)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto rind - 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.11 log CFU/20 µl of inoculum for both incubation temp.

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. < 1.60 (1/3)

  2. 1.25 (0/2)

  3. < 1.60 (2/3)

  4. 7.78 (ND)

  5. < 1.60 (2/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and E. nigrum

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto rind - 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.11 log CFU/20 µl of inoculum for both incubation temp.

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. 2.44 (ND)

  2. 7.88 (ND)

  3. 1.76 (1/1)

  4. 9.41 (ND)

  5. < 1.60 (3/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and E. nigrum

10 µl of conidia suspension (4 log CFU/ml) and 10 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

2.81 log CFU/10 µl of inoculum for both incubation temp.

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. < 1.60 (1/3)

  2. < 1.60 (3/3)

  3. < 1.60 (1/3)

  4. < 1.60 (2/3)

  5. < 1.60 (0/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and E. nigrum

10 µl of conidia suspension (4 log CFU/ml) and 10 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

2.81 log CFU/10 µl of inoculum for both incubation temp.

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. 3.41 (ND)

  2. 4.72 (0/1)

  3. < 1.60 (3/3)

  4. 9.44 (ND)

  5. < 1.60 (2/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and E. nigrum

20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 0, then 20 µl of S. Poona suspension inoculated on Day 3 (5 log CFU of each strain/ml) Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

20

3.42 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. < 1.60 (3/3)

  2. 5.20 (0/1)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and E. nigrum

20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 0, then 20 µl of S. Poona suspension inoculated on Day 3 (5 log CFU of each strain/ml) Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon.

20

3.42 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 7.80 (ND)

  2. 9.20 (ND)

  3. ND (ND)

ND – Enrichment steps Initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and E. nigrum

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated on Day 0, then 20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 3 Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

Analysis done on respective days 2 d after inoculation with S. Poona

20

3.11 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 0.88 (2/2)

  2. 2.84 (0/1)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and E. nigrum

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated on Day 0, then 20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 3 Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

Analysis done on respective days 2 d after inoculation with S. Poona

20

3.11 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 8.87 (ND)

  2. 9.48 (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto rind - 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.51 and 3.64 log CFU/20 µl of inoculum for 4 and 20°C, respectively

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. < 1.60 (0/3)

  2. 1.46 (2/2)

  3. < 1.60 (2/3)

  4. 6.53 (ND)

  5. < 1.60 (0/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and G. candidum

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto rind - 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.51 and 3.64 log CFU/20 µl of inoculum for 4 and 20°C, respectively

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. 2.13 (1/1)

  2. 9.03 (ND)

  3. 2.01 (1/1)

  4. 9.38 (ND)

  5. 1.04 (2/2)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and G. candidum

10 µl of conidia suspension (4 log CFU/ml) and 10 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.21 and 3.34 log CFU/10 µl of inoculum for 4 and 20°C, respectively

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. < 1.60 (3/3)

  2. 0.76 (1/2)

  3. < 1.60 (1/3)

  4. 5.72 (ND)

  5. < 1.60 (1/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation.

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and G. candidum

10 µl of conidia suspension (4 log CFU/ml) and 10 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.21 and 3.34 log CFU/10 µl of inoculum for 4 and 20°C, respectively

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. 4.89 (ND)

  2. 7.84 (0/1)

  3. 4.91 (ND)

  4. 8.91 (ND)

  5. 4.74 (ND)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation.

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and G. candidum

20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 0, then 20 µl of S. Poona suspension inoculated on Day 3 (5 log CFU of each strain/ml) Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

20

3.48 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 2.80 (1/1)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and G. candidum

20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 0, then 20 µl of S. Poona suspension inoculated on Day 3 (5 log CFU of each strain/ml) Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

20

3.48 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 8.18 (ND)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and G. candidum

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated on Day 0, then 20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 3 Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

Analysis done on respective days 2 d after inoculation with S. Poona

20

3.64 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 3.70 (ND)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and G. candidum

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated on Day 0, then 20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 3 Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

Analysis done on respective days 2 d after inoculation with S. Poona

20

3.64 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 8.58 (ND)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto rind - 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.64 log CFU/20 µl of inoculum for both temp.

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. < 1.60 (0/3)

  2. 1.46 (2/2)

  3. < 1.60 (2/3)

  4. 6.53 (ND)

  5. < 1.60 (2/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and P. expansum

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto rind - 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.64 log CFU/20 µl of inoculum for both temp.

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. 2.13 (1/1)

  2. 9.03 (ND)

  3. 2.01 (1/1)

  4. 9.38 (ND)

  5. 1.04 (2/2)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and P. expansum

10 µl of conidia suspension (4 log CFU/ml) and 10 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.34 log CFU/10 µl of inoculum for both temp.

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. < 1.60 (2/3)

  2. < 1.60 (1/3)

  3. < 1.60 (1/3)

  4. 6.29 (ND)

  5. < 1.60 (0/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation.

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and P. expansum

10 µl of conidia suspension (4 log CFU/ml) and 10 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

4 or 20

3.34 log CFU/10 µl of inoculum for both temp

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (4°C)

  2. Day 7 (20°C)

  3. Day 14 (4°C)

  4. Day 14 (20°C)

  5. Day 21 (4°C)

  6. Day 21 (20°C)

  1. < 1.60 (2/3)

  2. 8.87 (ND)

  3. < 1.60 (2/3)

  4. 7.47 (ND)

  5. < 1.60 (0/3)

  6. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and P. expansum

20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 0, then 20 µl of S. Poona suspension inoculated on Day 3 (5 log CFU of each strain/ml) Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

20

3.48 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 4.88 (1/1)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and P. expansum

20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 0, then 20 µl of S. Poona suspension inoculated on Day 3 (5 log CFU of each strain/ml) Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

20

3.48 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 6.74 (ND)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and P. expansum

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated on Day 0, then 20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 3 Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

Analysis done on respective days 2 d after inoculation with S. Poona

20

3.64 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for intact sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. < 1.60 (2/3)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant; and P. expansum

20 µl of S. Poona suspension (5 log CFU of each strain/ml) inoculated on Day 0, then 20 µl of conidia suspension (4 log CFU/ml) inoculated on Day 3 Inoculated onto 6 sites (3 intact, 3 wounded)

End (8-mm wide) of stainless steel spatula used to create a 4-mm deep wound in center of 3 inoculation sites – 6 inoculation sites/melon

Analysis done on respective days 2 d after inoculation with S. Poona

20

3.64 log CFU/20 µl of inoculum

7, 14, 21 days

Final counts for wounded sites on rind:

  1. Day 7 (20°C)

  2. Day 14 (20°C)

  3. Day 21 (20°C)

  1. 8.72 (ND)

  2. ND (ND)

  3. ND (ND)

ND – Enrichment steps initiated but not completed because counts obtained by direct plating or samples too decayed to analyze.

Parentheses indicate # of samples + for S. Poona out of number enriched

CFU/rind

Inoculated melons dried under laminar flow hood for 2h at 22°C before placing in PE containers and incubation

Richards and Beuchat, 2005b

Cantaloupe, Rind

Salmonella Typhimurium LT2 (NA resistant)

20 µl of inoculum (108 CFU/ml) was spot inoculated onto a 2.5 cm2 section of the rind of intact whole melon

After 1h dry, whole melons were soaked or scrubbed for 60s in water

Rind squares were excised for recovery of bacteria

n/a

  1. 5.2

  2. <1.7

Counts for inoculated site (1) and adjacent site (2)

n/a

Sites adjacent to or on side opposite (remote site) of inoculated site were also examined for spread of bacteria throughout washing

Scrub brush also examined for bacterial residue counts

Soak 60s:

  1. 4.5 (inoculated site)

  2. <1.7 (adjacent site)

  3. <1.7 (remote site)

Scrubbed 60s:

  1. 3.6 (inoculated site)

  2. <1.7 (adjacent site)

  3. <1.7 (remote site)

  4. ND (scrub brush)

LOD (<5 CFU/sample)

CFU/sample

 

Parnell et al., 2004

Cantaloupe, Rind

Salmonella Typhimurium LT2 (NA resistant)

20 µl of inoculum (108 CFU/ml) was spot inoculated onto a 2.5 cm2 section of the rind of intact whole melon

After 1h dry, whole melons were soaked or scrubbed for 60s in 200 ppm total chlorine

Rind squares were excised for recovery of bacteria

n/a

  1. 5.3

  2. <1.7

Counts for inoculated site (1) and adjacent site (2)

n/a

Sites adjacent to or on side opposite (remote site) of inoculated site were also examined for spread of bacteria throughout washing. Scrub brush also examined for bacterial residue counts

Soak 60s:

  1. 3.5 (inoculated site)

  2. <1.7 (adjacent site)

  3. <1.7 (remote site)

Scrubbed 60s:

  1. 2.6 (inoculated site)

  2. <1.7 (adjacent site)

  3. <1.7 (remote site)

  4. <2.4 (scrub brush)

LOD (<5 CFU/sample)

CFU/sample

 

Parnell et al., 2004

Cantaloupe, Rind

Salmonella Typhimurium LT2 (NA resistant)

20 µl of inoculum (108 CFU/ml) was spot inoculated onto a 2.5 cm2 section of the rind of intact whole melon

After 1h dry, whole melons were soaked or scrubbed in water

Rind squares were excised for recovery of bacteria

n/a

  1. 5.5

  2. <1.7

Counts for inoculated site (1) and adjacent site (2)

 

Sites adjacent to or on side opposite (remote site) of inoculated site were also examined for spread of bacteria throughout washing. Scrub brush also examined for bacterial residue counts

Scrubbed 5s and 10s:

  1. 3.8, 3.9 (inoculated site)

  2. 2.2, <1.7 (adjacent site)

  3. <1.7, <1.7 (remote site)

  4. 3.4, 3.7 (scrub brush)

Immersed 30s:

  1. 5.1 (inoculated site)

  2. <1.7 (adjacent site)

  3. ) <1.7 (remote site)

CFU/sample

LOD (<5 CFU/sample)

Parnell et al., 2004

Cantaloupe, Stem scar tissue – Eastern (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant

Whole melons immersed in suspension and constantly agitated with gloved hands for 5 min

Melon stored at 4°C or 30°C for 24 h and dipped into inoculum with initial temp. of 4°C or 30°C

Melons placed on elevated mesh screens for 2 min, then placed into a biosafety hood to dry for 1 h at 22°C

4 or 30

~7 log CFU/ml (Cocktail concentration)

 

Melon Temp. and Inoculum Temp.:

  1. 4°C and 4°C

  2. 4°C and 30°C

  3. 30°C and 4°C

  4. 30°C and 30°C

  1. 5.83

  2. 6.01

  3. 6.00

  4. 5.79

Populations recovered were not significantly different, regardless of cantaloupe and inoculum temperature combination

CFU/cm2

Inoculum (12 l at 4 or 30°C) was poured into PE bags and placed in a 34 l plastic container

Richards and Beuchat, 2004

Cantaloupe, Stem scar tissue – Western (shipper)

Salmonella Poona (00A3207, 01A3923, 02A3275, 00A3279, 01A242) NA resistant

Whole melons immersed in suspension and constantly agitated with gloved hands for 5 min

Melon stored at 4°C or 30°C for 24 h and dipped into inoculum with initial temp. of 4°C or 30°C

Melons placed on elevated mesh screens for 2 min, then placed into a biosafety hood to dry for 1 h at 22°C

4 or 30

~7 log CFU/ml (Cocktail concentration)

 

Melon Temp. and Inoculum Temp.:

  1. 4°C and 4°C

  2. 4°C and 30°C

  3. 30°C and 4°C

  4. 30°C and 30°C

  1. 5.56

  2. 5.42

  3. 6.78

  4. 5.37

Populations recovered were not significantly different, regardless of cantaloupe and inoculum temperature combination

CFU/cm2

Inoculum (12 l at 4 or 30°C) was poured into PE bags and placed in a 34 l plastic container

Richards andBeuchat, 2004

Honeydew, Whole

E. coli NCTC 10418

Submerged in inoculum (2 concentrations: 104 and 106) solution for 5 min, dried for 1 h at 20 ± 2°C

Stored for 1 d at 12°C, then 5 days at 8°C (stored to simulate commercial distribution in Australia); placed in an open bag to allow for high RH

12 and 8

3.12

6 d

n/a

Detected on 1 out of 4 samples after enrichment

Results shown for the high inoculum concentration

CFU/cm2

 

Behrsing et al., 2003

Honeydew, Whole

E. coli O157:H7 (SEA 13B88 and Oklahoma)

Submerged in 3 l of inoculum, rotated with a glove-covered hand for 10 min

Dried in biosafety cabinet for 1 h, then stored at 5°C for up to 7 days before treatments

5

3.45

0 or 7 days

Wash Treatments:

  1. sterile tap water

  2. 5% H2O2

  3. solution of 1% H2O2, 25 µg/ml nisin, 1% sodium lactate (NaL), and 0.5% citric acid (HPLNC)

Results shown for Day 0:

  1. No significant reduction (data not shown)

  2. 3 log reduction

  3. none detected

Treatment with HPLNC after Day 7 was more significant at reducing bacterial population than H202

Population of E. coli slightly decreased during storage for 7 days

CFU/cm2

pH of both wash solutions adjusted to 6.7 by adding 2N NaOH, melons were washed similar to method of inoculation,however, only rotated for 5 min

Ukuku et al., 2005

Honeydew, Whole

Listeria innocua 2305

Submerged in inoculum (2 concentrations: 103 and 105) solution for 5 min, dried for 1 h at 20 ± 2°C

Stored for 1 d at 12°C, then 5 days at 8°C (simulating commercial distribution in Australia); placed in an open bag to allow for high RH

12 and 8

2.28

6 days

n/a

0.97

Results shown for the high inoculum concentration

CFU/cm2

 

Behrsing et al., 2003

Honeydew, Whole

Listeria monocytogenes (Scott A and CCR1-L-G)

Submerged in 3 l of inoculum, rotated with a glove-covered hand for 10 min

Dried in biosafety cabinet for 1 h, then stored at 5°C for up to 7 days before treatments

5

3.05

0 or 7 days

Wash Treatments:

  1. Sterile tap water

  2. 2.5% H2O2

  3. Solution of 1% H2O2, 25 µg/ml nisin, 1% sodium lactate (NaL), 0.5% citric acid (HPLNC)

Results shown for Day 0:

  1. No significant reduction (data not shown)

  2. 3 log reduction

  3. none detected

Treatment with HPLNC after Day 7 was more significant at reducing bacterial population than H202

Population of L. mono remained the same during storage for 7 days

CFU/cm2

pH of both wash solutions adjusted to 6.7 by adding 2N NaOH, melons were washed similar to method of inoculation,however, only rotated for 5 min

Ukuku et al., 2005

Honeydew, Whole

Natural microflora (aerobic mesophilic bacteria, YM, Pseudomonas spp.)

n/a

n/a

n/a

n/a

n/a

n/a

2.8, 0.8, 0.3

Results for mesophiles, YM, and Pseudomonas spp., respectively

CFU/cm2

 

Ukuku and Sapers, 2007

Honeydew, Whole

Salmonella Salford IMB 1710

Submerged in inoculum (2 concentrations: 103 and 106) solution for 5 min, dried for 1 h at 20 ± 2°C

Stored for 1 d at 12°C, then 5 days at 8°C (stored to simulate commercial distribution in Australia); placed in an open bag to allow for high RH

12 and 8

1.92

6 days

n/a

Detected on 4 out of 4 samples after enrichment

Results shown for the high inoculum concentration

CFU/cm2

 

Behrsing et al., 2003

Honeydew, Fresh-cut

E. coli O157:H7 (SEA 13B88 and Oklahoma)

Whole melon was submerged in 3 l of inoculum, rotated with a glove-covered hand for 10 min (Transference of pathogen by cutting)

Inoculated whole melons cut into 4 sections, rinds removed, and interior flesh cut into ~3 cm cubes

5

 

0 or 7 days

Wash Treatments:

  1. Sterile tap water

  2. 2.5% H2O2

  3. Solution of 1% H2O2, 25 µg/ml nisin, 1% sodium lactate (NaL), and 0.5% citric acid (HPLNC)

  1. 6, 6

  2. 0 (0), 2 (2)

  3. 0 (0), 0 (0)

Final counts are # of melons (rinds) out of 6 that were positive for pathogen at Days 0 and 7, respectively

See comments for number in parentheses

 

#’s in parentheses represent fresh-cut pieces that were negative by direct plating but positive after enrichment

Ukuku et al., 2005

Honeydew, Fresh-cut

Natural microflora (aerobic mesophilic bacteria, YM, Pseudomonas spp.)

n/a

n/a

n/a

n/a

n/a

n/a

0.9, BD, BD

Results for mesophiles, YM, and Pseudomonas spp., respectively

CFU/g

BD = below limit of detection (1 CFU/g)

Ukuku and Sapers, 2007

Honeydew, Fresh-cut

Natural microflora (aerobic mesophilic bacteria, YM, Pseudomonas spp.)

Transference of pathogen during cutting

Whole melon cut into 4 sections, rinds removed, flesh cut into 3-cm cubes; pieces were then left out at 22°C for 5 h, then refrigerated at 5°C for 3 h

n/a

n/a

n/a

n/a

Mesophiles increased ~1 log

Yeast and mold BD (<1 CFU/g) for up to 2 h

Pseudomonas spp. increased ~1 log

CFU/g

 

Ukuku and Sapers, 2007

Honeydew, Fresh-cut

Listeria monocytogenes strain LCDC 81-861

Pipette inoculated w/ 25 µl of pathogen suspension (placed in commercial 530-ml dome fruit plastic bowls before inoculated)

Inoculated pieces sprayed with 25 µl of various concentrations (104, 105, 106, 107, 108) of phage mixture (2 pieces/treatment placed in each bowl)

10

  1. 1.5

  2. 1.3

  3. 1.2

  4. 0.7

  5. 1.1

  6. 0.0

0 d

2 d

5 d

7 d

Phage Concentration:

  1. 0

  2. 104

  3. 105

  4. 106

  5. 107

  6. 108

  1. 2.7, 5.3, 6.1

  2. 2.7, 5.2, 6.1

  3. 2.6, 5.0, 6.3

  4. 2.2, 4.4, 5.3

  5. 1.1, 3.1, 4.0

  6. 0.0, 0.4, 1.8

Results shown for Days 2, 5, and 7, respectively

CFU/sample

Phage concentration in units of PFU/mL

Leverentz et al., 2004

Honeydew, Fresh-cut

Listeria monocytogenes strain LCDC 81-861

Pipette inoculated w/ 25 µl of pathogen suspension (placed in commercial 530-ml dome fruit plastic bowls before inoculated)

25 µl of phage cocktail pipetted onto a depression on the fruit pieces at each specified time

10

1 h: 0.9

0.5 h: 0

0 d

2 d

5 d

7 d

These pieces treated 1 h and 0.5 h BEFORE inoculated

Day 2: (0.3, 0)

Day 5: (0.8, 0.8)

Day 7: (2.3, 0.4)

Results shown for 1h and 0.5 h each day

CFU/sample

Phage concentration in units of PFU/mL

Leverentz et al., 2004

Honeydew, Fresh-cut

Listeria monocytogenes strain LCDC 81-861

Pipette inoculated w/ 25 µl of pathogen suspension (placed in commercial 530-ml dome fruit plastic bowls before inoculated)

25 µl of phage cocktail pipetted onto a depression on the fruit pieces at each specified time

10

  1. 0.8

  2. 1.4

  3. 1.0

  4. 1.6

  5. 1.6

0 d

2 d

5 d

7 d

Pieces sprayed:

  1. 0 h after contam.

  2. 0.5 h after contam.

  3. 1 h after contam.

  4. 2 h after contam.

  5. 4 h after contam.

  1. 0, 2.9, 5.7, 7.2

  2. 0, 0, 3.2, 4.6

  3. 1.3, 0.3, 2.7, 3.1

  4. 1.3, 0.7, 3.7, 4.1

  5. 0.3, 1.7, 4.0, 5.6

Results shown for specified treatment at Day 0, 2, 5, and 7, respectively

CFU/sample

Phage concentrations in units of PFU/mL

Leverentz et al., 2004

Honeydew, Fresh-cut

Listeria monocytogenes (Scott A and CCR1-L-G)

Whole melon was submerged in 3 l of inoculum, rotated with a glove-covered hand for 10 min (Transference of pathogen by cutting)

Inoculated whole melons cut into 4 sections, rinds removed, and interior flesh cut into ~3 cm cubes

5

 

0 or 7 days

3 Wash Solutions:

  1. Sterile tap water

  2. 2.5% H2O2

  3. Solution of 1% H2O2, 25 µg/ml nisin, 1% sodium lactate (NaL), and 0.5% citric acid (HPLNC)

  1. 6, 6

  2. 0 (0), 0 (0)

  3. 0 (0), 0 (0)

Final Counts are # out of 6 melons (rinds) that were positive for pathogen at Day 0 and Day 7, respectively

See comments for #’s in parentheses

 

#’s in parentheses represent fresh-cut pieces that were negative by direct plating, but positive after enrichment

Ukuku et al., 2005

Honeydew, Fresh-cut

Salmonella (Newport 02-216, Poona 418, Hidalgo 02-517-2, Typhimurium 45, St. Paul FSIS 039)

Pieces submerged in inoculum (105 CFU/ml) for 30 s

Whole melon cut into 4 sections, rinds removed, flesh cut into 3-cm cubes; after inoculation, pieces dried for 1 h, then placed inside a 9.75-inch diameter, 3-pocket, plastic bowl

5, 10, and 22

1.9

Up to 12 days

 

5°C: Decreased by 1 log over 10 days

10°C: Increased to 3.0 log by Day 12

22°C: Increased to 6.0 log by Day 12

CFU/g

Whole melons were individually washed under running tap water (19°C) for 5 min to mimic home preparation before cut.

Ukuku and Sapers, 2007

Honeydew, Fresh-cut

Salmonella (Newport 02-216, Poona 418, Hidalgo 02-517-2, Typhimurium 45, St. Paul FSIS 039)

Pieces submerged in inoculum (105 CFU/ml) for 30 s

Whole melon cut into 4 sections, rinds removed, flesh cut into 3-cm cubes; after inoculation, pieces dried for 1 h, then placed in a 9.75-inch diameter, 3-pocket, plastic bowl

5 and/ or 22

   
  1. Stored at 5°C immediately after preparation

  2. Held at 22°C for 3 h before storage at 5°C

  3. Held at 22°C for 5 h before storage at 5°C

  4. Held at 5°C for 3 h after preparation

  1. 1.9

  2. 2.0

  3. 2.6

  4. 1.5

CFU/g

 

Ukuku and Sapers, 2007

Honeydew, Rind

Salmonella Typhimurium LT2 (NA resistant)

20 µl of inoculum (108 CFU/ml) was spot inoculated onto a 2.5 cm2 section of the rind of intact whole melon

After 1h, dry, whole melons were soaked or scrubbed for 60s in water

Rind squares were excised for recovery of bacteria

n/a

  1. 5.8

  2. ND

Counts for inoculated site (1) and adjacent site (2).

ND – not done

n/a

Sites adjacent to or on side opposite (remote site) of inoculated site were also examined for spread of bacteria throughout washing; Scrub brush also examined for bacterial residue counts; Recovered using BSAN (bismuth sulfite agar supplemented with 50 µg/ml nalidixic acid

Soak 60s:

  1. 3.0 (inoculated site)

  2. <1.7 (adjacent site)

  3. <1.7 (remote site)

Scrubbed 60s:

  1. <1.7 (inoculated site)

  2. <1.7 (adjacent site)

  3. <1.7 (remote site)

  4. <2.6 (scrub brush)

LOD (<5 CFU/sample)

CFU/sample

 

Parnell et al., 2004

Watermelon, Whole

Natural microflora (aerobic mesophilic bacteria, YM, Pseudomonas spp.)

n/a

n/a

n/a

n/a

n/a

n/a

4.1, 0.8, 0.4

Results for mesophiles, YM, and Pseudomonas spp., respectively

CFU/cm2

 

Ukuku and Sapers, 2007

Watermelon, Fresh-cut

E. coli O157:H7 (204P, 301C, 505B, 45753-35)

Pieces placed in stomacher bags and inoculated 1.0 ml of 104 cocktail (method not specified)

Rinds sanitized before cutting, flesh cut into 2-cm cubes

5 or 25

Not specified

Up to 34 h

Cubes held at 5°C or 25°C for up to 34 h

Watermelon cubes incubated at 25°C supported growth better than cantaloupe

Significant (p<0.05) increases in population occurred b/t 4 and 6 h

Population reached 8.51 log after 28 h incubation at 25°C

No significant change in population on cubes held at 5°C

CFU/g of melon

Watermelon (pH 5.56), cantaloupe (pH 7.01)

Article has hand-drawn graph of growth at various time intervals up to 34 h

Delrosario and Beuchat, 1995

Watermelon, Fresh-cut

Natural microflora (aerobic mesophilic bacteria, YM, Pseudomonas spp.)

n/a

n/a

n/a

n/a

n/a

n/a

0.8, BD, BD

Results for mesophiles, YM, and Pseudomonas spp., respectively

CFU/g

BD = below limit of detection (1 CFU/g)

Ukuku and Sapers, 2007

Watermelon, Fresh-cut

Natural microflora (aerobic mesophilic bacteria, YM, Pseudomonas spp.)

Transference of pathogen during cutting

Whole melon cut into 4 sections, rinds removed, flesh cut into 3-cm cubes; pieces were then left out at 22°C for 5 h, then refrigerated at 5°C for 3 h

n/a

n/a

n/a

n/a

Mesophiles increased ~1 log

Yeast and mold BD (<1 CFU/g) for up to 2 h

Pseudomonas spp. increased ~1 log

CFU/g

 

Ukuku and Sapers, 2007

Watermelon, Fresh-cut

Salmonella (Newport 02-216, Poona 418, Hidalgo 02-517-2, Typhimurium 45, St. Paul FSIS 039)

Pieces submerged in inoculum (105 CFU/ml) for 30 s

Whole melon cut into 4 sections, rinds removed, flesh cut into 3-cm cubes; after inoculation, pieces dried for 1 h, then placed inside a 9.75-inch diameter, 3-pocket, plastic bowl

5, 10, and 22

2.0

Up to 12 days

 

5°C: Decreased by 1 log over 10 days

10°C: Increased to 3.0 log by Day 12

22°C: Increased to 3.8 log by Day 12

CFU/g

Whole melons were individually washed under running tap water (19°C) for 5 min to mimic home preparation before cut.

Ukuku and Sapers, 2007

Watermelon, Fresh-cut

Salmonella (Newport 02-216, Poona 418, Hidalgo 02-517-2, Typhimurium 45, St. Paul FSIS 039)

Pieces submerged in inoculum (105 CFU/ml) for 30 s

Whole melon cut into 4 sections, rinds removed, flesh cut into 3-cm cubes; after inoculation, pieces dried for 1 h, then placed inside a 9.75-inch diameter, 3-pocket, plastic bowl

5 and/ or 22

   
  1. Stored at 5°C immediately after preparation

  2. Held at 22°C for 3 h before storage at 5°C

  3. Held at 22°C for 5 h before storage at 5°C

  4. Held at 5°C for 3 h, after preparation

  1. 2.1

  2. 2.0

  3. 2.2

  4. 1.6

CFU/g

 

Ukuku and Sapers, 2007

Watermelon, Rind

E. coli O157:H7 (204P, 301C, 505B, 45753-35)

7 areas (2–3 cm in diameter) delineated on rind

0.2 ml of inoculum (102 log CFU/ml) pipetted in each of the 7 areas on rind, melons held in covered plastic boxes until enumeration; RH 93 ± 5%

5 or 25

Not specified

up to 21 days

 

25°C: Significant (p<0.05) increases in population w/in 4 days, then remained constant thereafter

Growth more prolific on cantaloupe than watermelon rind

5°C: Significant decreases w/in 4 days, <101 recovered after 14 days

CFU/cm2 of rind surface

Inoculated areas remained wet throughout incubation due to high RH.

Delrosario and Beuchat, 1995

Mixed Melons, Fresh-cut (cantaloupe, honeydew, watermelon)

Natural microflora (aerobic mesophilic bacteria, YM, Pseudomonas spp.)

Transference of pathogen during cutting

Whole melon cut into 4 sections, rinds removed, flesh cut into 3-cm cubes; pieces were then left out at 22°C for 5 h, then refrigerated at 5°C for 3 h

n/a

n/a

n/a

n/a

Mesophiles increased ~1 log

Yeast and mold increased from 0.9 to 1.7 log

Pseudomonas spp. increased ~1 log

CFU/g

 

Ukuku and Sapers, 2007

Mixed Melons, Fresh-cut (cantaloupe, honeydew, watermelon)

Salmonella (Newport 02-216, Poona 418, Hidalgo 02-517-2, Typhimurium 45, St. Paul FSIS 039)

Pieces submerged in inoculum (105 CFU/ml) for 30 s

Whole melon cut into 4 sections, rinds removed, flesh cut into 3-cm cubes; after inoculation, pieces dried for 1 h, then placed inside a 9.75-inch diameter, 3-pocket, plastic bowl

5, 10, and 22

2.2

Up to 12 days

 

5°C: No significant decline after 12 d

10°C: Data not specified

22°C: Plateaued at Day 2 and declined to below initial populations thereafter

CFU/g

Whole melons were individually washed under running tap water (19°C) for 5 min to mimic home preparation before cut.

Ukuku and Sapers, 2007

Mixed Melons, Fresh-cut (cantaloupe, honeydew, watermelon)

Salmonella (Newport 02-216, Poona 418, Hidalgo 02-517-2, Typhimurium 45, St. Paul FSIS 039)

Pieces submerged in inoculum (105 CFU/ml) for 30 s

Whole melon cut into 4 sections, rinds removed, flesh cut into 3-cm cubes; after inoculation, pieces dried for 1 h, then placed inside a 9.75-inch diameter, 3-pocket, plastic bowl

5 and/ or 22

   
  1. Stored at 5°C immediately after preparation

  2. Held at 22°C for 3 h before storage at 5°C

  3. Held at 22°C for 5 h before storage at 5°C

  4. Held at 5°C for 3 h, after preparation

  1. 2.5

  2. 2.8

  3. 3.6

  4. 2.0

CFU/g

 

Ukuku and Sapers, 2007

References

Annous, B. A., A. Burke, and J. E. Sites. 2004. Surface pasteurization of whole fresh cantaloupes inoculated with Salmonella Poona or Escherichia coli. Journal of Food Protection 67 (9): 1876–1885.

Behrsing J., J. Jaeger, F. Horlock, N. Kita, P. Franz, and R. Premier. 2003. Survival of Listeria innocua, Salmonella Salford, and Escherichia coli on the surface of fruit with inedible skins. Postharvest Biology and Technology 29 (3): 249–256.

CDC (Centers for Disease Control and Prevention, U.S. Department of Health and Human Services). 2011a. Foodborne Outbreak Online Database (FOOD). Available at http://wwwn.cdc.gov/foodborneoutbreaks/. Accessed 25 Oct 2011.

CDC. 2011b. Investigation Update: Multistate Outbreak of Listeriosis Linked to Whole Cantaloupes from Jensen Farms, Colorado. Available at http://www.cdc.gov/listeria/outbreaks/cantaloupes-jensen-farms/101811/index.html. Accessed 25 Oct 2011.

Delrosario, B. A., and L. R. Beuchat. 1995. Survival and growth of enterohemorrhagic Escherichia coli O157:H7 in cantaloupe and watermelon. Journal of Food Protection 58 (1): 105–107.

Fan, X., B. A. Annous, J. C. Beaulieu, and J. E. Sites. 2008. Effect of hot water surface pasteurization of whole fruit on shelf life and quality of fresh-cut cantaloupe. Journal of Food Science 73 (3): M91–M98.

FDA. 2001. Retail Food Safety Program Information Manual: Safe Handling Practices for Melons. Available at http://www.fda.gov/Safety/Recalls/ucm267667.htm. Accessed on 25 Oct 2011.

Fouladkhah, A. and J. S. Avens. 2010. Effects of combined heat and acetic acid on natural microflora reduction on cantaloupe melons. Journal of Food Protection 73 (5): 981–984.

Fleming, P., W. Pool, and J. Gorny, eds. 2005. Commodity Specific Food Safety Guidelines for the Melon Supply Chain, 1st ed. Produce Marketing Association and United Fresh Produce Association. Available at http://www.fda.gov/downloads/Food/FoodSafety/Product-SpecificInformation/FruitsVegetablesJuices/GuidanceComplianceRegulatoryInformation/UCM168625.pdf. Accessed on 25 Oct 2011.

Leverentz, B., W. S. Conway, W. Janisiewicz, and M. J. Camp. 2004. Optimizing concentration and timing of a phage spray application to reduce Listeria monocytogenes on honeydew melon tissue. Journal of Food Protection 67 (8): 1682–1686.

Mahmoud, B. S. M., N. A. Vaidya, C. M. Corvalan, and R. H. Linton (2008) Inactivation kinetics of inoculated Escherichia coli O157: H7, Listeria monocytogenes, and Salmonella Poona on whole cantaloupe by chlorine dioxide gas. Food Microbiology 25: 857–865.

Parnell, T. L., L. J. Harris, and T. V. Suslow. 2005. Reducing Salmonella on cantaloupes and honeydew melons using wash practices applicable to postharvest handling, foodservice, and consumer preparation. International Journal of Food Microbiology 99 (1): 59–70.

Richards, G. M., and L. R. Beuchat. 2004. Attachment of Salmonelia Poona to cantaloupe rind and stem scar tissues as affected by temperature of fruit and inoculum. Journal of Food Protection 67 (7): 1359–1364.

Richards, G. M. and L. R. Beuchat. 2005a. Infection of cantaloupe rind with Cladosporium cladosporioides and Penicillium expansum, and associated migration of Salmonella Poona into edible tissues. International Journal of Food Microbiology 103 (1): 1–10.

Richards, G. M., and L. R. Beuchat. 2005b. Metabiotic associations of molds and Salmonella Poona on intact and wounded cantaloupe rind. International Journal of Food Microbiology 97 (3): 327–339.

Selma, M. V., A. M. Ibanez, A. Allende, M. Cantwell, and T. Suslow. 2008a. Effect of gaseous ozone and hot water on microbial and sensory quality of cantaloupe and potential transference of Escherichia coli O157:H7 during cutting. Food Microbiology 25 (1): 162–168.

Selma, M. V., A. M. Ibáñez, M. Cantwell, and T. Suslow. 2008b. Reduction by gaseous ozone of Salmonella and microbial flora associated with fresh-cut cantaloupe. Food Microbiology 25 (4): 558–565.

Sharma, M., J. R. Patel, W. S. Conway, S. Ferguson, and A. Sulakvelidze. 2009. Effectiveness of bacteriophages in reducing Escherichia coli O157:H7 on fresh-cut cantaloupes and lettuce. Journal of Food Protection 72 (7): 1481–1485.

Suslow, T. V. Postharvest chlorination: Basic properties and key points for effective disinfection, 1997, University of California, DANR, cited in FDA, Guidance for Industry: Guide to Minimize Microbial Food Safety Hazards of Melons; Draft Guidance (U.S. Department of Health and Human Services, 2009). Available at http://www.fda.gov/Food/GuidanceRegulation/GuidanceDocumentsRegulatory Information/ProducePlantProducts/ucm174171.htm [3 April 2013].

Ukuku, D. O., M. L. Bari, S. Kawamoto, and K. Isshiki. 2005. Use of hydrogen peroxide in combination with nisin, sodium lactate, and citric acid for reducing transfer of bacterial pathogens from whole melon surfaces to fresh-cut pieces. International Journal of Food Microbiology 104 (2): 225–233.

Ukuku, D. O., X. Fan, and M. F. Kozempel. 2006. Effect of vacuum-steam-vacuum treatment on microbial quality of whole and fresh-cut cantaloupe. Journal of Food Protection 69 (7): 1623–1629.

Ukuku, D. O., andW. F. Fett. 2002. Behavior of Listeria monocytogenes inoculated on cantaloupe surfaces and efficacy of washing treatments to reduce transfer from rind to fresh-cut pieces. Journal of Food Protection 65 (6): 924–930.

Ukuku, D. O., and W. F. Fett. 2004. Effect of nisin in combination with EDTA, sodium lactate, and potassium sorbate for reducing Salmonella on whole and fresh-cut cantaloupe. Journal of Food Protection 67 (10): 2143–2150.

Ukuku, D. O., V. Pilizota, and G. M. Sapers. 2004. Effect of hot water and hydrogen peroxide treatments on survival of Salmonella and microbial quality of whole and fresh-cut cantaloupe. Journal of Food Protection 67 (3): 432–437.

Ukuku, D. O., and G. M. Sapers. 2001. Effect of sanitizer treatments on Salmonella Stanley attached to the surface of cantaloupe and cell transfer to fresh-cut tissues during cutting practices. Journal of Food Protection 64 (9): 1286–1291.

Ukuku, D. O., and G. M. Sapers. 2007. Effect of time before storage and storage temperature on survival of Salmonella inoculated on fresh-cut melons. Food Microbiology 24 (3): 288–295.

Footnotes

1.

This document is FSHN12-07, one of a series of the Food Science and Human Nutrition Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Published May 2012. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

Thao P. Nguyen, graduate research assistant, CREC (Citrus Research and Education Center, Lake Alfred, FL); Michelle D. Danyluk (contact author), assistant professor, CREC; Keith R. Schneider, associate professor, FSHN (Food Science and Human Nutrition Department, UF Main Campus); Institute of Food and Agricultural Sciences; University of Florida; Gainesville, FL 32611.


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U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.