Gerald M. Sapers

Effect of Sanitizer Treatments on Salmonella Stanley Attached to the Surface of Cantaloupe and Cell Transfer to Fresh-Cut Tissues during Cutting Practices

The ability of Salmonella Stanley to attach and survive on cantaloupe surfaces, its in vivo response to chlorine or hydrogen peroxide treatments, and subsequent transfer to the interior tissue during cutting was investigated. Cantaloupes were immersed in an inoculum containing Salmonella Stanley (10(8) CFU/ml) for 10 min and then stored at 4 or 20 degrees C for up to 5 days. Periodically, the inoculated melons were washed with chlorine (1,000 ppm) or hydrogen peroxide (5%), and fresh-cut tissues were prepared. The incidence of Salmonella Stanley transfer from the rinds to the fresh-cut tissues during cutting practices was determined. A population of 3.8 log10 CFU/cm2 of Salmonella Stanley was recovered from the inoculated rinds. No significant (P < 0.05) reduction of the attached Salmonella population was observed on cantaloupe surfaces stored at 4 or 20 degrees C for up to 5 days, and the population was not reduced after washing with water. Salmonella Stanley was recovered in fresh-cut pieces prepared from inoculated whole cantaloupes with no sanitizer treatment. Washing with chlorine or hydrogen peroxide solutions was most effective immediately after inoculation, resulting in an approximate 3.0-log10 CFU/cm2 reduction, and the level of recovered Salmonella population transferred to fresh-cut samples was reduced to below detection. The effectiveness of both treatments diminished when inoculated cantaloupes stored at 4 or 20 degrees C for more than 3 days were analyzed, and the fresh-cut pieces prepared from such melons were Salmonella positive. Salmonella outgrowth occurred on inoculated fresh-cut cubes stored above 4 degrees C.

Attachment and Growth of Salmonella Chester on Apple Fruits and In Vivo Response of Attached Bacteria to Sanitizer Treatments

Attachment and growth of Salmonella Chester on fresh-cut apple disks and in vivo response of attached bacteria to sanitizer treatments were investigated. Apple disks (14 mm in diameter and 3 to 4 mm in thickness) were immersed in a bacterial suspension that contained 8.17 log CFU/ml of Salmonella Chester and air dried at room temperature for 10 min. After two rinses, the population of Salmonella Chester retained on apple disks that contained no skin was 13 to 19% higher than that retained on disks that contained skin, indicating that Salmonella Chester attached more firmly to the surfaces of injured tissue than to the unbroken skin. The number of bacteria attached to the disk was not affected by the immersion time but was directly proportional to the concentration of bacteria in the suspension. The distribution of artificially inoculated Salmonella Chester on the surfaces of three different parts of whole fruit was determined; 94% of attached bacteria was found on the stem and calyx cavity areas and 6% on the skin of the remaining area of the fruit. Despite their acidic pH (4.1), apple disks supported the growth of Salmonella Chester at 20 degrees C but not at 8 degrees C. All four sanitizers tested in the study, including 6% hydrogen peroxide, 2% trisodium phosphate, 0.36% calcium hypochlorite, and 1.76% sodium hypochlorite, were effective in reducing the population of Salmonella Chester on apple disks by 1 to 2 logs. However, 5 to 13% of bacteria survived the sanitizer treatments. Hydrogen peroxide, which reduced the population of Salmonella Chester on skin by 3 to 4 logs and the population of bacteria on stem or calyx by 1 to 2 logs, was the most effective among the four sanitizers tested. Firm attachment of bacteria on calyx, stem, and injured tissue and partial resistance of attached bacteria to sanitizer treatments are two major obstacles to be considered when developing methods for cleaning and decontaminating apple fruits destined for juice production and fresh consumption.

Microbiology of fruits and vegetables.

Microbial Contamination of Fresh Fruits and Vegetables, James R. Gorny Attachment of Microorganisms to Fresh Produce, Robert E. Mandrell, Lisa Gorski, and Maria Brandl Internalization and Infiltration, Jerry A. Bartz Stress adaptation, Luis A. Rodriguez-Romo and Ahmed E. Yousef Bacterial soft rot, Ching-Hsing Liao Microbial Spoilage of Fresh Mushrooms, Naveen Chikthimmah and Robert B. Beelman Spoilage of Juices and Beverages by Alicyclobacillus Species, Mickey E. Parish Interventions to Ensure the Microbiological Safety of Sprouts, William F. Fett Microbiological Safety of Fresh Citrus and Apple Juices, Susanne E. Keller and Arthur J. Miller Microbiological Safety Issues of Fresh Melons, Dike Ukuku and Gerald M. Sapers Fresh-cut Vegetables, Pascal Delaquis Outbreaks Associated with Cyclospora and Cryptosporidium, Ynes Ortega and Charles Sterling Patulin, Lauren S. Jackson, and Mary Ann Dombrink-Kurtzman Safety of Minimally Processed, Acidified and Fermented Vegetable Products, Fred Breidt, Jr. HACCP: A Process Control Approach for Fruit and Vegetable Safety, William C. Hurst The Effect of Quality Sorting and Culling on the Microbiological Quality of Fresh Produce, Susanne E. Keller Washing and Sanitizing Treatments for Fruits and Vegetables, Gerald M. Sapers Gas/Vapor-phase Sanitation (Decontamination) Treatments, Richard H. Linton, Yingchan Han, Travis L. Selby and Philip E. Nelson Modified Atmosphere Packaging, Brenda G. Werner and Joseph H. Hotchkiss, Hot Water Treatments for Control of Fungal Decay on Fresh Produce, Elazar Fallik Surface Pasteurization with Hot Water and Steam, Bassam A. Annous and Michael Kozempel Novel Non-thermal Treatments, Dongsheng Guan and Dallas G. Hoover Biological control of Microbial Spoilage of Fresh Produce, Julien Mercier and Pamela G. Marrone Sampling, Detection and Enumeration of Pathogenic and Spoilage Microorganisms, Larry R. Beuchat Rapid detection of Microbial Contaminants, Daniel Y.C. Fung Methods in Microscopy for the Visualization of Bacteria and Their Behavior on Plants, Maria Brandl and Jean-Michel Monier

Biofilm formation, cellulose production, and curli biosynthesis by Salmonella originating from produce, animal, and clinical sources.

The ability of 71 strains of Salmonella enterica originating from produce, meat, or clinical sources to form biofilms was investigated. A crystal violet binding assay demonstrated no significant differences in biofilm formation by isolates from any source when tested in any of the following three media: Luria-Bertani broth supplemented with 2% glucose, tryptic soy broth (TSB), or 1/20th-strength TSB. Incubation was overnight at 30 degrees C under static conditions. Curli production and cellulose production were monitored by assessing morphotypes on Luria-Bertani agar without salt containing Congo red and by assessing fluorescence on Luria-Bertani agar containing calcofluor, respectively. One hundred percent of the clinical isolates exhibited curli biosynthesis, and 73% demonstrated cellulose production. All meat-related isolates formed curli, and 84% produced cellulose. A total of 80% of produce-related isolates produced curli, but only 52% produced cellulose. Crystal violet binding was not statistically different between isolates representing the three morphotypes when grown in TSB; however, significant differences were observed when strains were cultured in the two other media tested. These data demonstrate that the ability to form biofilms is not dependent on the source of the test isolate and suggest a relationship between crystal violet binding and morphotype, with curli- and cellulose-deficient isolates being least effective in biofilm formation.

Efficacy of Washing with a Commercial Flatbed Brush Washer, Using Conventional and Experimental Washing Agents, in Reducing Populations of Escherichia coli on Artificially Inoculated Apples

Conventional and experimental washing formulations were applied with a commercial flatbed brush washer under conditions representative of commercial practice to determine their efficacy in decontaminating apples inoculated with a nonpathogenic Escherichia coli strain. Golden Delicious apples (18 kg) inoculated with E. coli were mixed with approximately 109 kg of uninoculated Fuji apples (distinctly different in appearance) in a wet dump tank containing 1,325 liters of water at 20 degrees C for 15 min. The combined apples were washed in a flatbed brush washer with the following washing solutions: water at 20 degrees C, water at 50 degrees C, 200 ppm of chlorine (pH 6.4) at 20 degrees C, 8% trisodium phosphate at 20 degrees C, 8% trisodium phosphate at 50 degrees C, 5% hydrogen peroxide at 20 degrees C, 5% hydrogen peroxide at 50 degrees C, 1% APL Kleen 245 at 50 degrees C, and two-stage washing treatments using the combination of 1% APL Kleen 245 at 20 or 50 degrees C followed by 5% hydrogen peroxide at 35 or 50 degrees C. None of the washing treatments tested under the conditions of this experiment significantly reduced the E. coli populations on the inoculated apples or in cider made from these apples, probably as a consequence of the inability of this washing system to inactivate or remove the bacterial cells in inaccessible calyx and stem areas of apples. These results are important because they demonstrate the need for new fruit washing technology that can overcome this limitation. Also, there was no significant cross-contamination of the Fuji apples in the dump tank. Significant cross-contamination of cider, made with uninoculated apples, occurred in the hammer mill and/or the press cloth when these units were not sanitized following a trial with inoculated apples.

Effect of hot water and hydrogen peroxide treatments on survival of salmonella and microbial quality of whole and fresh-cut cantaloupe.

Cantaloupe melon has been associated with outbreaks of salmonellosis. Contamination might be introduced into the flesh from the rind by cutting or by contact of cut pieces with contaminated rinds. Our objectives were to investigate the efficacy of hot water or hot 5% hydrogen peroxide treatments in reducing the population of native microflora and inoculated Salmonella on cantaloupe rind and transfer to fresh-cut tissue during cutting. Whole cantaloupes, inoculated with a cocktail of Salmonella serovars to give 4.6 log CFU/cm2 and stored at 5 or 20 degrees C for up to 5 days, were treated with hot water (70 or 97 degrees C) or 5% hydrogen peroxide (70 degrees C) for 1 min at 0, 1, 3, or 5 days postinoculation. Aerobic mesophilic bacteria and yeast and mold on treated whole melon and fresh-cut pieces were significantly (P < 0.05) reduced by all three treatments. Treatments with hot water (70 and 97 degrees C) caused a 2.0- and 3.4-log CFU/cm2 reduction of Salmonella on whole cantaloupe surfaces irrespective of days of postinoculation storage prior to treatment up to 5 days at 5 or 20 degrees C, respectively. Treatment with 5% hydrogen peroxide (70 degrees C) caused a 3.8-log CFU/cm2 reduction of Salmonella. Fresh-cut pieces prepared from untreated inoculated melons and those treated with 70 degrees C hot water were positive for Salmonella. However, fresh-cut pieces prepared from inoculated whole melon dipped in water (97 degrees C) or hydrogen peroxide (70 degrees C) for 60 s were negative for Salmonella, as determined by dilution plating onto agar medium, but were positive after enrichment at days 3 and 5 of storage at 5 degrees C. The ability to detect Salmonella in fresh-cut pieces was dependent on the initial level of inoculation. The results of this study indicate that the use of hot water (97 degrees C) or heated hydrogen peroxide to reduce the population of Salmonella on contaminated whole cantaloupes will enhance the microbial safety of the fresh-cut product.

Microbial safety of minimally processed foods.

VARIABLE FOOD ENVIRONMENTS Microbial Safety of Bakery Products, James P. Smith, Daphne Phillips Daifas, Wassim El-Khoury, and John W. Austin Concerns with Minimal Processing in Apple, Citrus, and Vegetable Products, Kathleen T. Rajkowski and Elizabeth A. Baldwin The Microbial Safety of Minimally Processed Seafood with Respect to Listeria Monocytogenes, Adam D. Hoffman, Kenneth L. Gall, and Martin Wiedmann, Fate of Clostridium Perfringens in Cook-Chill Foods, John S. Novak Sous-Vide Processed Foods: Safety Hazards and Control of Microbial Risks, Vijay K. Juneja PATHOGEN DETECTION AND ASSESSMENT HACCP and Regulations Applied to Minimally Processed Foods, O. Peter Snyder, Jr. Rapid Methods for Microbial Detection in Minimally Processed Foods, Karl R. Matthews Quantitative Risk Assessment of Minimally Processed Foods, Siobain Duffy, Yuhuan Chen, and Donald W. Schaffner CURRENT AND FUTURE INNOVATIONS Microbial Safety during Nonthermal Preservation of Foods, Gaurav Tewari Modified Atmosphere Packaging for Shelf-Life Extension, James T. C. Yuan Washing and Sanitizing Raw Materials for Minimally Processed Fruit and Vegetable Products, Gerald M. Sapers Microbial Safety, Quality, Extended Shelf-Life, and Sensory Aspects of Fresh-Cut Fruits and Vegetables, Hong Zhuang, M. Margaret Barth, and Thomas R. Hankinson Irradiation of Fresh and Minimally Processed Fruits, Vegetables, and Juices, Brendan A. Niemira Irradiation of Minimally Processed Meats, Christopher H. Sommers Biological Control on Minimally Processed Fruits and Vegetables, Britta Leverentz, Wojciech Janisiewicz, and William S. Conway INDEX

The Survival of Escherichia coli O157:H7 in the Presence of Penicillium expansum and Glomerella cingulata in Wounds on Apple Surfaces†

The survival of Escherichia coli O157:H7 in the presence of one of two plant pathogens, Penicillium expansum and Glomerella cingulata, in wounds on apples was observed during 14 days storage at room temperature (RT) and at 4 degrees C. The aim of this work was to determine if changes in apple physiology caused by the proliferation of fungal decay organisms would foster the survival of E. coli O157:H7. Trials were performed where (A) plant pathogens (4 log10 spores) were added to apple wounds 4 days before the wounds were inoculated with E. coli O157:H7 (3 log10 CFU g(-1) apple) (both RT and 4 degrees C storage), (B) plant pathogens and E. coli O157:H7 were added on the same day (both RT and 4 degrees C storage), and (C) E. coli O157:H7 was added 2 days (RT storage) and 4 days (4 degrees C storage) before plant pathogens. In all trials E. coli O157:H7 levels generally declined to <1 log10 at 4 degrees C storage, and in the presence of P. expansum at 4 degrees C or RT. However, in the presence of G. cingulata at RT E. coli O157:H7 numbers increased from 3.18 to 4.03 log10 CFU g(-1) in the apple wound during trial A, from 3.26 to 6.31 log10 CFU g(-1) during trial B, and from 3.22 to 6.81 log10 CFU g(-1) during trial C. This effect is probably a consequence of the attendant rise in pH from 4.1 to approximately 6.8, observed with the proliferation of G. cingulata rot. Control apples (inoculated with E. coli O157:H7 only) were contaminated with opportunistic decay organisms at RT during trials A and B, leading to E. coli O157:H7 death. However, E. coli O157:H7 in control apples in trial C, where no contamination occurred, increased from 3.22 to 5.97 log10 CFU g(-1). The fact that E. coli O157:H7 can proliferate in areas of decay and/or injury on fruit highlights the hazards associated with the use of such fruit in the production of unpasteurized juice.

Studies to select appropriate nonpathogenic surrogate Escherichia coli strains for potential use in place of escherichia coli O157:H7 and Salmonella in pilot plant studies

The response of a potential nonpathogenic surrogate organism to a particular treatment should closely mimic the response of the target pathogenic organism. In this study, growth characteristics (generation time, lag phase duration, and maximum population), pH at stationary phase, and survival characteristics (level of attachment and survival on apple surfaces, resistance to hydrogen peroxide decontamination treatments, and thermal resistance at 60 degrees C) of 15 nonpathogenic generic Escherichia coli strains and one nonpathogenic E. coli O157:H43 strain were compared with those of two E. coli O157:H7 strains and two Salmonella strains. Few differences in growth characteristics or pH at stationary phase were evident between nonpathogenic and pathogenic strains tested. However, considerably more separation among strains was seen following investigation of survival characteristics. E. coli ECRC 97.0152, which does not contain genes encoding for known virulence factors associated with E. coli O157:H7, appears to be a good surrogate candidate, with growth and survival characteristics similar to those of E. coli O157:H7 strains. The less heat-resistant surrogate strains E. coli NRRL B-766 and NRRL B-3054 and E. coli ATCC 11775, ATCC 25253, and ATCC 25922 may be used when attempting to model the heat resistance of Salmonella Montevideo G4639 and Salmonella Poona RM 2350, respectively. These surrogate strains may be useful for evaluating the efficacy of intervention steps in reducing populations of selected strains of E. coli O157:H7 and Salmonella in processing environments where these pathogens cannot be introduced.

Determination of ascorbic acid, dehydroascorbic acid and ascorbic acid-2-phosphate in infiltrated apple and potato tissue by high-performance liquid chromatography

Abstract A high-performance liquid chromatography procedure for the determination of ascorbic acid-2-phosphate (AAP), ascorbic acid (AA), and dehydroascorbic acid (DHAA) in raw apple and potato, treated with AAP and AA to prevent browning, was developed. These compounds were extracted with a mixture of mobile phase and 2.5% metaphosphoric acid and separated on an aminopropyl bonded-phase silica column. DHAA was determined as AA following reduction with dithiothreitol. The method was evaluated with spiked samples and found to be accurate and reproducible at concentrations as high as 0.9 m M AA or AAP.