Source: COLORADO STATE UNIVERSITY submitted to
MINIMIZING THE RISK OF LISTERIA MONOCYTOGENES AND OTHER PATHOGENS IN DRIED FOODS
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
COMPLETE
Funding Source
OTHER GRANTS
Reporting Frequency
Annual
Accession No.
0186460
Grant No.
00-51110-9747
Cumulative Award Amt.
(N/A)
Proposal No.
2000-05329
Multistate No.
(N/A)
Project Start Date
Sep 15, 2000
Project End Date
Sep 14, 2004
Grant Year
2000
Program Code
[(N/A)]- (N/A)
Project Director
Sofos, J. N.
Recipient Organization
COLORADO STATE UNIVERSITY
(N/A)
FORT COLLINS,CO 80523
Performing Department
ANIMAL SCIENCE
Non Technical Summary
Current home-drying methods for meats, fruits and vegetables may fail to control foodborne pathogenic bacteria, as indicated by outbreaks associated with beef and venison jerky. Moreover, cross-contamination of dried foods with bacterial pathogens during packaging may increase food safety risks and this may have been the case with pre-sliced dry and semidry fermented sausages implicated in outbreaks. This project will establish procedures to control pathogenic bacteria in dried foods by developing effective pre-drying treatments and drying processes and by applying antimicrobials without adversely affecting product quality. The results will be used to develop educational material and provide training on safe food drying and storage for Cooperative Extension personnel, processors and consumers.
Animal Health Component
20%
Research Effort Categories
Basic
70%
Applied
20%
Developmental
10%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
7124010110080%
7124010302020%
Knowledge Area
712 - Protect Food from Contamination by Pathogenic Microorganisms, Parasites, and Naturally Occurring Toxins;

Subject Of Investigation
4010 - Bacteria;

Field Of Science
3020 - Education; 1100 - Bacteriology;
Goals / Objectives
Drying is a convenient way of preserving foods for later use. The Cooperative Extension Service has long provided recommendations to consumers on how to dry foods at home. The recent implication of dried/fermented meats, such as beef and venison jerky and fermented sausages, in outbreaks caused by Escherichia coli O157:H7 and other enterohemorrhagic E. coli serotypes and Salmonella of the serovars Enteritidis and Typhimurium indicates that application of current processes, such as drying of meats, may fail to inactivate pathogenic bacteria. Also, the increasing number of foodborne outbreaks associated with fresh produce in recent years suggests that bacterial pathogens may survive in home-dried fruits and vegetables. At present, conflicting data on pathogen destruction in home-dried foods exist, while research has shown that sausage fermentations are insufficient to effect the required 5 log pathogen reduction. Additionally, several drying studies have shown that the initial rapid decline of the target pathogen is followed by survival of a residual population of bacteria in the ready-to-eat product. Furthermore, post-processing contamination of dried foods with enteric pathogens and Listeria monocytogenes may increase food safety risks. The overall goal of the studies is the development and validation of product-specific processes for assuring the safety of home-dried meats, fruits and vegetables, and the development of recommendations for the safe drying and storage of meats and produce. Consumer surveys will be conducted across the United States to understand the range of methods used to dry foods in humid and dry climates and at various elevations. Based on this information, experiments will be designed with the objectives to: 1) Assess the potential for survival of L. monocytogenes, E. coli O157:H7, and Salmonella in foods dried using common home drying methods; 2) Develop effective pre-drying processes and drying procedures for the destruction of the above pathogens in home-dried foods and identify critical control points and critical limits to ensure their safety; 3) Assess the fate of pathogens surviving the drying process or introduced following processing in dried/fermented foods during storage; 4) Apply, when needed, antibacterial agents and/or post-drying processes that have the potential to help control the pathogens during product storage; 5) Conduct consumer taste panels to assess the overall acceptability of uninoculated foods produced by the alternative drying systems that have been validated to destroy the pathogens; 6) Develop product-specific models to predict the risk for pathogen survival in dried foods during processing and storage; 7) Use the information generated to develop extension educational material and training programs to provide food scientists, processors, retailers, Cooperative Extension Agents and Specialists, and consumers with revised recommendations on how to dry, store, distribute and consume dehydrated foods safely. The research will lead to a better understanding of pathogen behavior in foods dried at home or in small-scale operations and will minimize foodborne illness episodes due to such products.
Project Methods
The target of the research is to assess limitations in the effectiveness of drying procedures and practices currently in use, and to find alternative pre-drying, drying or post-drying treatments to minimize any risk of bacterial pathogen survival in dehydrated meats, fruits and vegetables. To accomplish these goals, Cooperative Extension Specialists with food preservation responsibilities will be surveyed nationwide to identify methods recommended for drying foods at home. Foods intended for testing in pre-drying and drying experiments to determine the behavior of bacterial pathogens will include beef and venison meat (whole muscle or ground to make jerky), apples, peaches, tomatoes and parsley. Pathogens to be examined will include L. monocytogenes, E. coli O157:H7 and Salmonella. Use of selected marker bacterial strains, (e.g., resistant to streptomycin or rifampicin), will allow monitoring of pathogens in the presence of natural flora. Fresh meats and produce will be inoculated with single or mixed pathogenic strains at levels that will permit validation of a 5-log reduction during drying. The efficacy of pre-drying treatments (e.g., acids, marinates, heat) to enhance destruction of pathogens when combined with drying will be evaluated with the objective of minimizing survival of bacteria. Developed critical control points and critical limits will be evaluated for the potential to lead to development of stress-resistant bacterial pathogens. Dried experimental or commercial foods with surviving pathogens or inoculated after drying will be stored at refrigeration or ambient temperatures in air or vacuum to evaluate pathogen survival or growth. Antimicrobials (e.g., chemical additives, bacteriocins, protective cultures) and post-processing interventions (e.g., heat) will be used, singly or as multiple hurdles, to enhance inactivation of surviving or post-process contaminating pathogens in dried foods during storage. Consumer panel tests will be conducted to evaluate the overall acceptability of uninoculated foods dried and stored by alternative pre-drying/drying methods validated to destroy the pathogens. Data obtained will be used to develop and validate product-specific models for predicting the fate of pathogens during processing and storage of dried foods. Model design will be based on monitoring of factors that increase the destructive effect of the pre-drying/drying processes or the storage conditions against pathogens (e.g., decrease in D-values, lowering in aw, increase in salt, nitrite or acid concentration). Potential problems might be the ineffectiveness of treatments to deliver the desired pathogen reduction, and the need to identify and test additional treatments, singly or in combinations, while experimental limitations might arise due to operation unreliability of home-style dehydrators. The information generated will be used to revise current fact sheets and bulletins on home drying of foods, which will be distributed through Cooperative Extension and Agricultural Experiment Stations. To enhance adoption of revised methods, train-the-trainer classes will be conducted with Extension Agents and volunteers.

Progress 09/15/00 to 09/14/04

Outputs
The overall aim of the studies was to generate research data and consumer recommendations to enhance the safety of dried meats, fruits and vegetables by controlling through inactivation pathogenic bacteria during processing and storage. The objectives included: (1) survey Cooperative Extension Specialists across the U.S. to identify the range of methods used to dry various foods; (2) assess the potential for survival of Listeria monocytogenes, Escherichia coli O157:H7 and Salmonella in meats, fruits, and vegetables dehydrated using commonly recommended home drying methods; (3) develop effective pre-drying processes and drying procedures for the destruction of the above pathogens in these products; (4) identify critical control points and critical limits to ensure safety when drying products at home or in small-scale operations; (5) assess the fate of pathogens surviving the drying process or introduced following processing in dried/fermented meats, fruits and vegetables during storage; (6) identify and apply, if needed, antibacterial agents and/or post-drying processes that have the potential to help control the pathogens during product storage; (7) conduct consumer taste panels to assess the acceptability of uninoculated foods produced using newly revised or validated alternative drying procedures and systems; (8) develop product-specific models to predict the risk for pathogen survival in dried foods during processing and storage; and, (9) use the information generated to develop, pilot-test and promote extension educational materials and training workshops teaching the new recommendations. All of the objectives have been accomplished. Home food drying recommendations compiled from 27 states showed wide differences among them, including differences in treatments recommended for use before drying. Numerous experiments were conducted with beef, apples, tomatoes, parsley, peaches, carrots and potatoes to assess the effectiveness of various pre- and post-drying treatments. Results generally showed that a blanching or acid-dip pre-treatment enhanced inactivation of L. monocytogenes, E. coli O157:H7, and Salmonella during drying and product storage. Taste panels conducted with consumers showed no differences in acceptance between dried foods produced using traditional methods and those produced using pre-treatments that enhanced inactivation of pathogens. Three CSU Cooperative Extension fact sheets, a 15-page booklet on Drying Foods, and a one-hour training workshop were developed to promote the new recommendations. The workshop was pilot-tested with six groups of consumers and extension educators (n equals 75). Knowledge and attitude scores significantly (P greater than 0.05) improved from pre- to 6-week follow-up evaluation; however, no changes in behavior scores were seen, in part because of the short time between evaluations. The newly developed materials have been made available in electronic and print format. The experimental part of the project involved training of several graduate students and post-doctoral fellows, and resulted in the publication of numerous refereed journal articles and presentations at national scientific meetings.

Impacts
In the past, most home-drying procedures were based on empirical evidence and not evaluated for their influence on bacterial destruction during drying and storage. Such procedures may not be as effective as desired for pathogen inactivation and may lead to sublethal stress and development of resistance of pathogens to food preservation methods. Dried food products such as jerky have been implicated as vehicles of transmission of pathogenic bacteria such as E. coli O157:H7. Data published by USDA have indicated that pathogens such as Salmonella and Listeria monocytogenes are found present in commercial jerky at rates of 0.31 percent and 0.52 percent, respectively. The studies reported here showed that currently used marinade formulations may not be very effective in enhancing destruction of pathogenic bacteria during drying of beef jerky. The modified marinades studied, however, included more antimicrobial hurdles and enhanced death of pathogenic bacteria during drying and storage. Other studies showed that the use of blanching or acidic pre-treatments enhanced inactivation of pathogenic bacteria during drying of fruits and vegetables. Results were used to develop research-based recommendations for home food drying published in electronic and print media forms and promoted through one-hour workshops and the electronic media. Significant improvements in knowledge and attitudes were seen pre- to 6-week follow-up evaluation. Consumers can now dry foods at home with the confidence they are using research-based methods that effectively destroy pathogenic bacteria, if present.

Publications

  • Skandamis, P.N., Yoon, Y., Stopforth, J.D., Kendall, P.A., and Sofos, J.N. 2004. Modeling the effect of aerobic and anaerobic storage on growth/no growth interface of Listeria monocytogenes as a function of temperature, sodium lactate, sodium diacetate and NaCl. 91st Annual Meeting of the International Association for Food Protection, August 8-11, Phoenix, AZ. Abstract No. P118.
  • Samelis, J., and Sofos, J.N. 2003. Strategies to control stress-adapted pathogens and provide safe foods. In: Microbial Adaptation to Stress and Safety of New-Generation Foods. Yousef, A.E., and Juneja, V.K., Editors. CRC Press, Inc. Boca Raton, FL. ISBN 1-56676-912-4, pp. 303-351.
  • Kendall, P. 2003. Bacterial Foodborne Illness. Colorado State University Cooperative Extension Fact Sheet No. 9.300. Colorado State University, Fort Collins, CO. Rev. 3/03.
  • Dipersio, P.A. 2002. Inactivation of Salmonella and Listeria monocytogenes during drying and storage of apple and peach slices treated with acidic or sodium metabisultife solutions. MS Thesis. Colorado State University, Fort Collins, CO.
  • Albright, S.N., Kendall, P.A., Avens, J.A., Sofos, J.N. 2002. Effect of marinade and drying temperature on inactivation of Escherichia coli O157:H7 on Inoculated Home Dried Beef Jerky. J. Food Safety, 22:155-167.
  • Sofos, J.N. 2002. Stress-adapted, cross-protected, resistant: a concern. Food Technol. 56(11):22.
  • Sofos, J.N. 2002. Approaches to pre-harvest food safety assurance. In: Smulders, F.J.M., and Collins, J.D. (Eds.) Food Safety Assurance and Veterinary Public Health; Volume 1, Food Safety Assurance in the Pre-Harvest Phase, Publ. Wageningen Academic Publishers, Wageningen, The Netherlands. ISBN 9076998051, pp. 23-48.
  • Bacon, R.T., and Sofos, J.N. 2002. Biological Food Hazards: Characteristics of Biological Food Hazards. In Current Issues in Food Safety. Willey, NY. pp. 155-193.
  • Sofos, J.N., Yoon, Y., DiPersio, P.A., and Kendall, P.A. 2004. Inactivation of Salmonalla during drying of Nantes carrot slices treated with blanching or immersion in 3.23 pct NaCl before drying, or oven heating after drying. 64th Annual Meeting of the Institute of Food Technologists. July 12-16, Las Vegas, NV. Abstract No. 114C-8.
  • DiPersio, P.A., Kendall, P.A., Yoon, Y., and Sofos, J.N. 2004. Inactivation of Salmonella during drying and storage of nantes carrot slices treated with steam, water or acid blanching before dehydration. 91st Annual Meeting of the International Association for Food Protection, August 8-11, Phoenix, AZ. Abstract No. P217.
  • Skandamis, P.N., Stopforth, J.D., Ashton, L.V., Geornaras, I., Kendall, P.A., and Sofos, J.N. 2004. Effect of drying on survival and acid tolerance of Escherichia coli O157:H7 biofilms formed in beef decontamination runoff fluids. 91st Annual Meeting of the International Association for Food Protection, August 8-11, Phoenix, AZ. Abstract No. P164.
  • Skandamis, P.N., Stopforth, J.D., Yoon, Y., Geornaras, I., Kendall, P.A., and Sofos, J.N. 2004. Heat and acid tolerance response of Listeria monocytogenes as affected by sequential exposure to hurdles during growth. 91st Annual Meeting of the International Association for Food Protection, August 8-11, Phoenix, AZ. Abstract No. P178.
  • Yoon, Y., Skandamis, P.N., Kendall, P.A., Smith, G.C., and Sofos, J.N. 2004. A predictive model to determine the effect of drying temperature and marination in reducing Listeria monocytogenes population during drying of beef jerky. 91st Annual Meeting of the International Association for Food Protection, August 8-11, Phoenix, AZ. Abstract No. P117.
  • Kendall, P.A., DiPersio, P.A., and Sofos, J.N. 2004. Drying vegetables. Colorado State University Cooperative Extension Fact Sheet. No. 9.308. Colorado State University, Fort Collins, CO. Revised 7/04. 4 p.
  • Kendall, P.A., DiPersio, P.A, and Sofos, J.N. 2004. Drying foods: dehydrating fruits, vegetables, leathers and jerkies. Colorado State University Cooperative Extension Bulletin No. 575A. Colorado State University, Fort Collins, CO. 20 p.
  • Yoon, Y., Skandamis, P.N., Kendall, P.A., Smith, G.C., and Sofos, J.N. 2004. Effect of drying temperature and marination in reducing Listeria monocytogenes on beef jerky. Animal Sciences Research Report, Department of Animal Sciences, Colorado State University, Fort Collins, CO. 4 p.
  • Sofos, J.N. 2004. Stress-adapted pathogenic bacteria and strategies for their control. Proceed. Symposium of the Japan Society for Research of food Protection, September 9, Tokyo, Japan. 5 p.
  • Sofos, J.N. 2004. Cleaning, sanitation and biofilms; fresh meat decontamination. Proceed. of the FoodFactory2004 Conference, October 6-8, Laval, France. 6 p.
  • Sofos, J.N. 2004. Recent developments in pre- and post-harvest intervention strategies. 228th American Chemical Society National Meeting, Philadelphia, PA, August 22-26. Abstract AGFD 127.
  • Sofos, J.N. 2004. Food safety issues in the United States. Presented at the Food Safety Commission of Japan, September 10, Tokyo, Japan. Abstract.
  • Sofos, J.N., Geornaras, I., and Stopforth, J.D. 2004. Listeria monocytogenes risk assessment and control. Proceed. Nucleo De Investigacao Formacao Em Segurancae Qualidade Alimentar, Food Protection 2004 International Conference, May 20-22, Monte da Caparica, Lisbon, Portugal, pp. 67-72.
  • Sofos, J.N. 2004. Why is it useful to reduce contamination in unprocessed foods. Proceed. Nucleo De Investigacao Formacao Em Segurancae Qualidade Alimentar, Food Protection 2004 International Conference, May 20-22, Monte da Caparica, Lisbon, Portugal, pp. 94-97.
  • Koutsoumanis, K., Kendall, P.A., and Sofos, J.N. 2003. Development and evaluation of a growth/no growth interface model for Salmonella Typhimurium as a function of temperature, water activity and pH. Presented at the Annual Meeting of the Institute of Food Technologists, Chicago, IL, July 12-16. Abstract 76E-5.
  • Sofos, J.N. 2004. Field data availability and needs for use in microbiological risk management. Proceed. of the European Union Conference on Food Safety and Veterinary Public Health, October 22-23. Rome, Italy. 3 p.
  • Koutsoumanis, K.P., Kendall, P.A., and Sofos, J.N. 2003. Effect of inoculum size on the growth/no growth boundary of Listeria monocytogenes. Presented at the 90th Annual Meeting of the International Association for Food Protection, New Orleans, LA, August 10-13. Abstract T54.
  • Koutsoumanis, K., Kendall, P.A., and Sofos, J.N. 2003. Acid tolerance of Listeria monocytogenes as affected by environmental stresses related to food processing technologies. Presented at the Annual Meeting of the Institute of Food Technologists, Chicago, IL, July 12-16. Abstract 29G-1.
  • Abushelaibi, A.A. 2001. Survival and growth of Listeria monocytogenes and Salmonella in infant cereals hydrated with water, milk or apple juice and stored at different temperatures. M.S. Thesis, Colorado State University, Fort Collins, CO.
  • Kendall, P., Smith, K., Thilmany, D., Hine, S., Melcher, L., and Paul, L. 2001. Value of and satisfaction with food safety training in the intermountain west. Foodservice Res. Intl. 13:1-15.
  • Burnham, J.A., Kendall, P.A., and Sofos, J.N. 2001. Ascorbic acid enhances destruction of Escherichia coli O157:H7 during home-type drying of apple slices. J. Food Prot. 64:1244-1248.
  • Albright, S. N., Sofos, J. N., and Kendall, P. A. 2000. Survival of inoculated Escherichia coli O157:H7 on beef jerky dried at 62.5 C following four preparation treatments. Annual Meeting of the International Association for Food Protection, August 6-9, Atlanta, GA. Abstract P025, page 45.
  • Derrickson-Tharington, E.L. 2001. Evaluation of common acidulants for enhancement of destruction of Escherichia coli O157:H7 during drying of gala apple slices and whole muscle beef jerky. M.S. Thesis, Colorado State University, Fort Collins, CO.
  • Sofos, J.N., Samelis, J., Calicioglu, M., and Kendall, P.A. 2002. Pathogen control with chemical additives in muscle foods. IFT Annual Meeting, Anaheim, CA, June 15-19. Abstract 4-3.
  • Sofos, J.N. 2002. Riesgos Microbiologicos de las Carnes y productos Carnicos; Programas nacionales de reduccion de patogenos. In Seguridad Alimentaria de la Carne y los Productos Carnicos. II Seminario Internacional Fundisa, Madrid, 2 y 3 de Octubre. Obra Colectiva Dirigida y Coordinada por: Jesus Lizaso y Almuneda Anton Boix, Madrid Spain. Pages 53-100.
  • Ikeda, J., Stopforth, J.D., Kendall, P.K., and Sofos, J.N. 2002. Survival of acid-adapted or nonadapted Escherichia coli O157:H7 in apple wounds following chemical treatments and storage of samples. IAFP Annual Meeting. San Diego, CA, June 30-July 3. Abstract P167.
  • Hillers, V.N., Medeiros, L.C., Kendall, P.A., Chen, G., and DiMascola, S. 2002. Identification of consumer food handling behaviors associated with prevention of specific foodborne illnesses. IFT Annual Meeting, Anaheim, CA, June 15-19. Abstract 46B-9.
  • Kendall, P.A., Medeiros, L.C., Hillers, V.N., Chen, G., and DiMascola, S. 2002. Identification of food handling behaviors of special importance for the very young, elderly, pregnant and immunocompromised. IFT Annual Meeting, Anaheim, CA, June 15-19. Abstract.
  • Ikeda, J., Stopforth, J.D., Kendall, P.A., and Sofos, J.N. 2002. Survival of acid-adapted or nonadapted Escherichia coli O157:H7 in apple wounds following chemical treatments and storage of samples. IAFP Annual Meeting. San Diego, CA, June 30-July 3. Abstract P167.
  • Calicioglu, M., Sofos, J.N., Samelis, J., Kendall, P.A., and Smith, G.C. 2002. Destruction of acid-adapted and non-adapted Salmonella during drying and storage of beef jerky treated with marinades. Animal Sciences Research Report, Colorado State University, Fort Collins. pp. 49-51.
  • Calicioglu, M., Sofos, J.N., Samelis, J., Kendall, P.A., and Smith, G.C. 2002. Effect of acid adaptation and marinades on destruction of Escherichia coli O157:H7 during drying and storage of beef jerky. Animal Sciences Research Report, Colorado State University, Fort Collins. pp. 57-59.
  • Sofos, J.N. 2001. Control of foodborne pathogens in meat products by sanitation, drying and antimicrobials. United States Department of Agriculture, Food Safety and Inspection Service, Technical Conference on Performance Standards for the Production of Processed Meat and Poultry Products, Washington, DC, May 8.
  • Kendall, P., Smith, K., Thilmany, D., Hine, S., Melcher, L., and Paul, P. 2001. Value of and satisfaction with food safety training in the intermountain west. Society for Nutrition Education Annual Meeting, Oakland, CA, July 21-24. Oral presentation.
  • Derrickson, E.L., Kendall, P.A., and Sofos, J.N. 2001. Destruction of Escherichia coli O157:H7 in beef jerky exposed to acidified marinades before drying. IFT Annual Meeting, New Orleans, Louisiana, June 23-26. Abstract 59E-7.
  • Lakkakula, S., Kendall, P.A., Samelis, J., and Sofos, J.N. 2001. Destruction of Escherichia coli O157:H7 on apples of different varieties treated with citric acid before drying. IAFP Annual Meeting, Minneapolis, Minnesota, August 5-8. Abstract PO32.
  • Derrickson, E.L., Kendall, P.A., and Sofos, J.N. 2001. Destruction of Escherichia coli O157:H7 during drying of apple slices pre-treated with acidic solutions after inoculation. IAFP Annual Meeting, Minneapolis, Minnesota, August 5-8. IAFP Annual Meeting, Minneapolis, Minnesota, August 5-8. Abstract PO33.
  • Medeiros, L.C, Hillers, V.N., Kendall, P.A., and Mason, A. 2001. Food safety education: what should we be teaching to consumers. J. Nutrition Educ. 33:108-115.
  • Koutsoumanis, K.P., Kendall, P.A., and Sofos, J.N. 2004. Modeling the boundaries of growth of Salmonella Typhimurium in broth as a function of temperature, water activity, and pH. J. Food Prot. 67:53-59.
  • Samelis, J., Kendall, P.A., Smith, G.C., and Sofos, J.N. 2004. Acid tolerance of acid- and non-adapted Escherichia coli O157:H7 following habituation (10 C) in fresh beef decontamination runoff fluids of different pH values. J. Food Prot. 67:638-645.
  • DiPersio, P.A., Kendall, P.A., and Sofos, J.N. 2004. Inactivation of Listeria monocytogenes during drying and storage of peach slices treated with acidic or sodium metabisulfite solutions. J. Food Microbiol. 21:641-648.
  • Yoon, Y., Stopforth, J.D., Kendall, P.A., and Sofos, J.N. 2004. Inactivation of Salmonella during drying of Roma tomatoes exposed to pre-drying treatments including peeling, blanching, and dipping in organic acid solutions. J. Food Prot. 67:1344-1352.
  • Nummer, B.A., Harrison, J.A., Harrison, M.A., Kendall, P.A., Sofos, J.N., and Andress, E.L. 2004. Effects of preparation methods on the microbiological safety of home-dried meat jerky. J. Food Prot. 67:2337-2341.
  • Stopforth, J.D., Ikeda, J.S., Kendall, P.A., and Sofos, J.N. 2004. Survival of acid-adapted or nonadapted Escherichia coli O157:H7 in apple wounds and surrounding tissue following chemical treatments and storage. Int. J. Food Microbiol. 90:51-61.
  • Koutsoumanis, K.P., Kendall, P.A., and Sofos, J.N. 2004. A comparative study on growth limits of Listeria monocytogenes as affected by temperature, pH and water activity when grown in suspension or on a solid surface. Food Microbiol. 21:415-422.
  • Skandamis, P.N., Stopforth, J.D., Sofos, J.N., and Kendall, P.A. 2004. Modeling of the effect of inoculum size and acid adaptation on growth/no growth interface of Escherichia coli O157:H7. 64th Annual Meeting of the Institute of Food Technologists. July 12-16, Las Vegas, NV. Abstract No. 114D-6.
  • Skandamis, P.N., Yoon, Y., Stopforth, J.D., Sofos, J.N., and Kendall, P.A. 2004. Heat and acid tolerance of Listeria monocytogenes after exposure to sequential or simultaneous sublethal stresses. 64th Annual Meeting of the Institute of Food Technologists. July 12-16, Las Vegas, NV. Abstract No. 99D-7.
  • Skandamis, P.N., Yoon, Y., Smith, G.C., Sofos, J.N., and Kendall, P.A. 2004. Modeling the effect of marination and temperature on inactivation of Escherichia coli O157:H7 during drying of beef jerky. 64th Annual Meeting of the Institute of Food Technologists. July 12-16, Las Vegas, NV. Abstract No. 67E-13.


Progress 01/01/03 to 12/31/03

Outputs
Dried foods are stored at room temperature and generally consumed without further cooking. Bacterial growth in these products is inhibited by low water activity and other hurdles such as low pH and preservatives. Jerky is a nutritious dried meat product produced by consumers at home as well as by the industry. Consequently, numerous recipes for making jerky are available and are based on using meat from several species, variable preparation procedures, different marination techniques, and variations in drying processes and temperature. Diversity in process parameters may affect the effectiveness of drying for inactivating pathogenic bacteria. In response to Salmonella and Escherichia coli O157 H7 outbreaks linked to jerky consumption as well as Listeria monocytogenes outbreaks from post-processing contaminated ready-to-eat meat and poultry products, new food preservation methods/technologies to inactivate bacteria while avoiding severe treatments that may change desired characteristics of the food are needed. Although growth of pathogens such as Escherichia coli O157 H7, Listeria monocytogenes and Salmonella is not expected in beef jerky, extent of destruction and duration of survival of these bacteria may vary depending on a number of factors including the severity and variety of antimicrobial hurdles and history of bacterial contaminant. For example, acid-adaptation of pathogens may enhance survival in acidic foods and increase cross-protection to sublethal stresses associated with other food processing treatments. Also, there is a concern that stressed pathogens may exhibit lower infectious doses and be of increased virulence. Studies were conducted to evaluate the influence of pre-drying marinade treatments on inactivation of acid-adapted or nonadapted Salmonella and Listeria monocytogenes on beef jerky during preparation, drying and storage. Inoculated beef slices were subjected to various pre-drying treatments based on modified marinades that included multiple hurdles for pathogen inactivation. After inoculation and marination (24 h, 4 degrees C) the slices were dried (60 degrees C for 10 h) and stored aerobically (25 degrees C for 60 d). Bacterial survivors were determined on tryptic soy agar with 0.1 percent pyruvate, xylose-lysine-tergitol 4 (XLT4) agar (Salmonella), and PALCAM agar (Listeria). Nonadapted Salmonella cultures were more (P less than 0.05) resistant to inactivation during drying than acid-adapted Salmonella in all treatments. Bacterial populations decreased below the detection limit (-0.4 log CFU cm2) as early as 7 h during drying or remained detectable even after 60 d of storage, depending on acid-adaptation, pre-drying treatment, and agar media. The results also revealed that using food grade chemicals as pre-drying treatments (sodium lactate, acetic acid, soy sauce with ethanol, acetic acid and Tween 20) improved the effectiveness of the meat-drying process for inactivating pathogens compared to the process used in traditional jerky making. In addition, the modified marinades enhanced inactivation of post-processing inoculated Salmonella and Listeria monocytogenes during storage of the dried products.

Impacts
Dried products are considered as one of the safest food groups because of antimicrobial hurdles such as drying temperature, low water activity, and preservatives. However, in recent years, jerky consumption has been associated with foodborne illness outbreaks involving pathogens such as Salmonella, Escherichia coli O157 H7 and Staphylococcus aureus, while pathogens such Listeria monocytogenes have also been isolated from commercially available jerky. Data published by the United States Department of Agriculture have confirmed the presence of pathogenic bacteria in commercial jerky, while it is estimated by the Centers for Disease and Prevention (CDC) that numbers of illnesses, hospitalizations and deaths caused annually in the United States by Listeria monocytogenes and Escherichia coli O157 H7 are approximately 2,500, 2,300 and 500, and 62,000, 1,800 and 52, respectively. Thus, there is increased interest for development of new recommendations for appropriate procedures to produce safe dried foods such as jerky. The results of the studies reported here demonstrated that currently used marinades may not be effective in enhancing destruction of pathogenic bacteria during drying of beef jerky. The modified marinades studied, however, included more antimicrobial hurdles and enhanced death of pathogens such as Salmonella and Listeria monocytogenes introduced on the product before or after drying as post-processing contaminants. The results of the studies should be useful in developing drying recommendations for use by the industry and consumers preparing jerky.

Publications

  • Ashton, L.V., K.P. Koutsoumanis, I. Geornaras, P.A. Kendall and J.N. Sofos. 2003. Acid tolerance of Escherichia coli O157 H7 during aerobic storage at 4 degrees C, 10 degrees C and 25 degrees C of beef treated with hot water and lactic acid. Presented at the 90th Annual Meeting of the International Association for Food Protection, New Orleans, LA, August 10-13. Abstract P027.
  • Samelis, J. and Sofos, J.N. 2003. Yeasts in meat and meat products. In Yeasts in Foods, Beneficial and Detrimental Aspects. T. Boekhourt and V. Robert, Editors. Behrs Verlag, Hamburg, Germany. ISBN 3-86022-961-3, pp. 239-265.
  • Ashton, L.V., Koutsoumanis, K.P., Geornaras, I., P.A. Kendall, P.A., and Sofos, J.N. 2003. Changes in Escherichia coli O157 H7 populations during storage of beef decontaminated with hot water and lactic acid. pp. 5-8. Animal Sciences Research Report, Department of Animal Sciences, Colorado State University, Fort Collins, CO.
  • Yoon, Y., Kendall, P.A., Smith, G.C., and Sofos, J.N. 2003. Effect of contamination level on death of Escherichia coli O157 H7 during drying of beef jerky. pp. 15-18. Animal Sciences Research Report, Department of Animal Sciences, Colorado State University, Fort Collins, CO.
  • Geornaras, I., Koutsoumanis, K.P., Ashton, L.V., Kendall, P.A., and Sofos, J.N. 2003. Influence of decontamination treatments on survival and growth of Salmonella during storage of fresh beef. pp. 23-25. Animal Sciences Research Report, Department of Animal Sciences, Colorado State University, Fort Collins, CO.
  • Stopforth, J.D., Samelis, J., Sofos, J.N., Kendall, P.A., and Smith, G.C. 2003. Inactivation of acid-adapted Escherichia coli O157 H7 biofilms formed in fresh beef decontamination fluids. pp. 19-22. Animal Sciences Research Report, Department of Animal Sciences, Colorado State University, Fort Collins, CO.
  • Kendall, P., and Sofos, J. 2003. Drying Fruits. Colorado State University Cooperative Extension Fact Sheet. No. 9.309. Colorado State University, Fort Collins, CO. Revised 3/03.
  • Kendall, P. and Sofos, J. 2003. Leathers and Jerkies. Colorado State University Cooperative Extension Fact Sheet. No. 9.309. Colorado State University, Fort Collins, CO. Revised 3/03.
  • Calicioglu, M., Sofos, J.N., Kendall, P.A., and Smith, G.C. 2003. Effects of acid adaptation and modified marinades on survival of postdrying Salmonella contamination on beef jerky during storage. J. Food Prot. 66:396-402.
  • Calicioglu, M., Sofos, J.N., and Kendall, P.A. 2003. Influence of marinades on survival during storage of acid-adapted and nonadapted Listeria monocytogenes inoculated post-processing on beef jerky. Int. J. Food Microbiol. 86:283-292.
  • Calicioglu, M., Sofos, J.N., Samelis, J., Kendall, P.A., and Smith, G.C. . 2003. Effect of acid adaptation on inactivation of Salmonella during drying and storage of beef jerky treated with marinades. Int. J. Food Microbiol. 89:51-65.
  • Yoon, Y., Kendall, P.A., Smith, G.C., and Sofos, J.N. 2003. Influence of inoculum level and acidic marination on inactivation of Escherichia coli O157 H7 during drying and storage of beef jerky. Presented at the 90th Annual Meeting of the International Association for Food Protection, New Orleans, LA, August 10-13. Abstract P155.
  • Dipersio, P.A., Kendall, P.A., and Sofos, J.N. 2003. Consumer acceptance of peach quarters and slices treated with antimicrobial solutions before home-type dehydration. Presented at the Annual Meeting of the Institute of Food Technologists, Chicago, IL, July 12-16. Abstract 104D-5.
  • Ashton, L.V., Samelis, J., Kendall, P.A., and Sofos, J.N. 2003. Changes in the acid tolerance of Escherichia coli O157 H7 as affected by acid adaptation procedures. Presented at the 90th Annual Meeting of the International Association for Food Protection, New Orleans, LA, August 10-13. Abstract P023.
  • Koutsoumanis, K.P., L.V. Ashton, I. Geornaras, P.A. Kendall and J.N. Sofos. 2003. Survival and growth of Escherichia coli O157 H7 on fresh beef inoculated before and after decontamination with hot water and lactic acid in different sequences. Presented at the 90th Annual Meeting of the International Association for Food Protection, New Orleans, LA, August 10-13. Abstract P026.
  • Geornaras, I., Koutsoumanis, K., Ashton, L. Kendall, P.A., and Sofos, J.N. 2003. Effect of decontamination treatments, storage temperature and storage time on the acid tolerance response of Salmonella inoculated on fresh beef. Presented at the Annual Meeting of the Institute of Food Technologists, Chicago, IL, July 12-16. Abstract 60C-4.
  • Yoon, Y. 2003. Inactivating pathogens in tomatoes and beef jerky. Master of Science Thesis, Department of Animal Sciences, Colorado State University, Fort Collins, CO.
  • Calicioglu, M., Sofos, J.N., and Kendall, P.A. 2003. Fate of acid-adapted and non-adapted Escherichia coli O157 H7 inoculated post-drying on beef jerky treated with marinades before drying. Food Microbiol. 20:169-177.


Progress 01/01/02 to 12/31/02

Outputs
Jerky is a meat product common in North America for centuries. Native Americans have been preparing it by smoking and sun drying meat strips. Numerous recommendations for making jerky are available to the industry and consumers drying meat. Such recommendations vary by type of meat (e.g., beef, poultry, game), the form or state of meat (e.g., thin or thick slices or ground), type and method of applying marinades (e.g., ingredients, amount, temperature, time), and drying procedure (e.g., oven, food dehydrator, smokehouse, temperature). Recent association of consumption of jerky products with bacterial disease outbreaks has raised concern related to the safety of these products, even though they may involve multiple antimicrobial hurdles such as low water activity, heat of drying and chemical preservatives. The inactivation of both acid-adapted and unadapted populations of the pathogenic bacterium Escherichia coli O157:H7 during processing and storage of beef jerky was studied. Following inoculation with the pathogen, beef slices were subjected to different pre-drying treatments, dried at 60 degrees Celsius (C) for 10 h and stored at 25 C for 60 days. The pre-drying treatments evaluated included: 1) no treatment control, 2) a commonly used traditional marinade, 3) double-strength traditional marinade, modified with added 1.2 percent sodium lactate, 9 percent acetic acid and 68 percent soy sauce with 5 percent ethanol, 4) dipping in 5 percent acetic acid for 10 min followed by application of traditional marinade, and 5) dipping in 1 percent Tween 20 for 15 min and then in 5 percent acetic acid for 10 min followed by traditional marinade. Surviving bacteria were enumerated during drying and storage with tryptic soy agar plus 0.1 percent pyruvate, modified eosin methylene blue agar, and sorbitol MacConkey agar. Results indicated that bacterial populations decreased during drying in the order of: pre-drying treatment 5 (4.9 to 6.7 log) more than treatment 4, more than treatment 3, more than the control treatment 1, more than treatment 2 (2.8 to 4.9 logs). Populations of acid-adapted Escherichia coli O157:H7 decreased faster (p greater than 0.05) in treatments 4 and 5 than nonadapted populations, whereas no significant difference was found in inactivation of acid-adapted and nonadapted inocula in treatments 1 and 2. Treatment 3 was more effective in inactivating the nonadapted than the acid-adapted inoculum. Bacterial populations continued to decline during storage and dropped below the detection limit (-0.4 log colony-forming-units - CFU/square centimeter) as early as day-0 (after drying) or as late as day-60, depending on acid adaptation, pre-drying treatment and agar medium used for bacterial enumeration. The results indicated that acid adaptation may cause only minor changes in resistance to hurdles involved in jerky processing and that use of additional antimicrobial chemicals or preservatives in jerky marination may improve the effectiveness of drying in activating Escherichia coli O157:H7. Another study indicated that the same treatments were also effective against Listeria monocytogenes during drying and storage of beef jerky.

Impacts
Dried food products such as jerky have been implicated as vehicles of transmission of pathogenic bacteria such as Escherichia coli O157:H7 causing illness in humans. Data published by the United States Department of Agriculture have indicated that pathogens such as Salmonella and Listeria monocytogenes are found present in commercial jerky at rates of 0.31 percent and 0.52 percent, respectively. It is estimated by the Centers for Disease and Prevention (CDC) that numbers of illnesses, hospitalizations and deaths caused annually in the United States by Listeria monocytogenes and Escherichia coli O157:H7 are approximately 2,500, 2,300 and 500, and 62,000, 1,800 and 52, respectively. The results of the studies reported here demonstrated that currently used marinade formulations may not be very effective in enhancing destruction of pathogenic bacteria during drying of beef jerky. The modified marinades studied, however, included more antimicrobial hurdles and enhanced death of the pathogenic bacteria during jerky drying and storage. The results of the studies should be useful in developing drying recommendations for use by the industry and consumers preparing jerky.

Publications

  • Calicioglu, M., Sofos, J.N., Samelis, J., P.A. Kendall, P.A., and Smith, G.C. 2002. Inactivation of acid-adapted and nonadapted Escherichia coli O157:H7 during drying and storage of beef jerky treated with different marinades. J. Food Prot. 65:1394-1405.
  • Calicioglu, M. Sofos, J.N., Samelis, J., Kendall, P.A., and Smith, G.C. 2002. Destruction of acid- and non-adapted Listeria monocytogenes during drying and storage of beef jerky. Food Microbiol. 19:545-559.
  • Calicioglu, M., Sofos, J.N., Samelis, J., and Kendall, P.A. 2002. Influence of marinades on survival during storage at 25 degrees C of acid-adapted and nonadapted Escherichia coli O157:H7 inoculated post-drying on beef jerky. IFT Annual Meeting, Anaheim, CA, June 15-19 (Abstrast 76B-8).
  • DiPersio, P., Kendall, P.A., Calicioglu, M., and Sofos, J.N. 2002. Destruction of Listeria monocytogenes during drying and storage of peaches treated with acid or sodium metabisulfite solutions. IFT Annual Meeting, Anaheim, CA, June 15-19 (Abstrast 15D-13).
  • Yoon, Y., Kendall P.A., and Sofos, J.N. 2002. Inactivation of Salmonella during drying of Roma tomatoes treated with organic acids. IAFP Annual Meeting. San Diego, CA, June 30-July 3 (Abstract P95).
  • DiPersio, P., Kendall, P.A., Calicioglu, M., and J.N. Sofos, J.N. 2002. Inactivation of Salmonella during drying and storage of Gala apples treated with acid or sodium metabisulfite solutions. IAFP Annual Meeting. San Diego, CA, June 30-July 3 (Abstract P103).
  • Lakkakula, S.P., Kendall, P.A., Samelis, J., and Sofos, J.N. 2002. Effect of acid adaptation on inactivation of Escherichia coli O157:H7 during drying of apple slices. IAFP Annual Meeting. San Diego, CA, June 30-July 3 (Abstract P108).
  • Calicioglu, M., Sofos, J.N., Samelis, J., and Kendall, P.A. 2002. Effect of acid adaptation on destruction of Salmonella during drying (60C) and storage (25C) of beef jerky treated with marinades. IAFP Annual Meeting. San Diego, CA, June 30-July 3 (Abstract P180).
  • Calicioglu, M., Sofos, J.N., Samelis, J., and Kendall, P.A. 2002. Influence of marinades on survival during storage at 25C of acid-adapted and nonadapted Listeria monocytogenes and Salmonella inoculated post-drying on beef jerky. IAFP Annual Meeting. San Diego, CA, June 30-July 3 (Abstract P181).
  • Calicioglu, M, Sofos, J.N., Samelis, J., and Kendall, P.A. 2002. Inactivation of acid-adapted and nonadapted Escherichia coli O157:H7 during drying (60 degrees C) and storage (25 degrees C) of beef jerky strips previously treated with various marinades. ASM General Meeting. Salt Lake City, Utah, May 19-23. (Abstrast P-23).
  • Calicioglu, M. Sofos, J.N., Samelis, J., Kendall, P.A., and Smith, G.C. 2002. Effect of marinades on survival of acid-adapted and nonadapted Listeria monocytogenes on beef jerky. 48th Int. Congress of Meat Science and Technology. Rome, Italy, August 25-30.
  • Calicioglu, M., Sofos, J.N., Samelis, J., Kendall, P.A., and Smith, G.C. 2002. Destruction of acid-adapted and non-adapted Salmonella during drying and storage of beef jerky treated with marinades. Animal Sciences Research Report, Colorado State University, Fort Collins. pp. 49-51.
  • Lakkakula, Suman Priya. 2002. Inactivation of Escherichia coli O157:H7 during drying of apple slices previously treated with citric acid. M. S. Thesis, Colorado State University, Fort Collins, Colorado.
  • Calicioglu, M., Sofos, J.N., Samelis, J., Kendall, P.A., and Smith, G.C. 2002. Effect of acid adaptation and marinades on destruction of Escherichia coli O157:H7 during drying and storage of beef jerky. Animal Sciences Research Report, Colorado State University, Fort Collins. pp. 57-59.
  • Yoon, Y., Kendall, P.A., and Sofos, J.N. 2002. Inactivation of Salmonella during dehydration of Roma tomatoes treated with organic acids. Animal Sciences Research Report, Colorado State University, Fort Collins. pp. 77-80.
  • Calicioglu, M., Sofos, J.N., Samelis, J., Kendall, P.A., and Smith, G.C. 2002. Listeria monocytogenes destruction during drying and storage of beef jerky treated with marinades. Animal Sciences Research Report, Colorado State University, Fort Collins. pp. 85-87.


Progress 01/01/01 to 12/31/01

Outputs
Dried and fermented foods, such as beef and venison jerky and fermented sausages, have been implicated in foodborne illness in recent years. These events have raised questions about the microbial safety of dried foods which are traditionally considered as microbiologically stable products. Studies were conducted to: 1) evaluate inactivation of acid-adapted and non-adapted Salmonella inoculated on beef jerky exposed to various marination treatments, dried (60 degrees C, 10h) and stored at 25 degree C temperature; 2) assess bacterial survival on Gala apple slices inoculated with a five-strain acid adapted or non-adapted culture of Escherichia coli O157:H7 and pre-treated with water or a citric acid solution (1.7 percent) for 10 min or 18h (4 degrees C), followed by drying at 57.2 degrees for 6h. Inoculated (6.0 log10 CFU/cm2) beef slices were subjected to the following marinades: 1) control (C), 2) traditional marinade (TM), 3) double amount of TM modified with added 1.2 percent sodium lactate, 9 percent acetic acid and 6 percent soy sauce containing 5 percent ethanol (MM), 4) dipping into a 5 percent acetic acid solution and then exposed to TM (AATM), and 5) dipping into 1 percent Tween 20 and then into 5 percent acetic acid, followed by exposure to TM (TWTM). Results indicated that drying reduced bacterial populations in the order of pre-drying treatments TWTM (4.8-6.0 log10 CFU/cm2), greater than AATM, greater than MM, greater than TM, greater than C (2.6-5.0 log 10 CFU/cm2). Nonadapted Salmonella were significantly (P less than 0.05) more resistant to destruction during drying than acid-adapted in all treatments. Bacterial populations decreased below the detection limit as early as 7 h during drying or remained detectable even after 60 d of storage depending on acid-adaptation of the inoculum or pre-drying treatment. The results indicated that culture acid-adaption may not cause increased resistance of Salmonella to the hurdles involved in drying of jerky and that use of modified marinades in jerky preparation may improve the effectiveness of drying in inactivating Salmonella. Gala apple slices were inoculated with acid-adapted or nonadapted cultures of E. coli O157:H7 and not pre-treated, or pre-treated with sterile water or 1.7 percent citric acid solution for 10 min or 18h (4 degrees C) followed by drying at 57.2 degrees C for 6h. Bacterial changes following pre-treatment (10 min or 18h) were plus 0.2 to negative 0.6 log CFU/g and negative 0.8 to negative 1.5 log CFU/g for inoculated slices pre-treated in sterile water and citric acid, respectively. After 6h of dehydration, bacterial populations on control and sterile water treated apple slices were reduced by 1.7-3.3 log CFU/g when inoculated with nonadapted cultures, and by 2.4-4.3 log CFU/g when inoculated with acid-adapted cultures. In comparison, bacterial reductions on citric acid treated apple slices following 6h dehydration were 5.1-5.4 log CFU/g for both acid-adapted and nonadapted cultures. Results suggest that pre-treating apple slices with citric acid enhances inactivation, while acid adaptation does not affect inactivation of E. coli O157:H7 during drying.

Impacts
Home-drying procedures for meat and plant food products need to be evaluated for their influence on bacterial destruction during drying and for pathogen survival during product storage. Procedures that are based on empirical development and use may not be as effective as desired for pathogen inactivation and may lead to sublethal stress and development of resistance of pathogens to food preservation methods. Results of these studies will be used to develop training materials and drying guidelines for Cooperative Extension personnel, processors and consumers.

Publications

  • Derrickson, E.L., Kendall, P.A., and Sofos, J.N. 2001. Survival of Escherichia coli O157:H7 on apple slices treated with acidic solutions. IFT Annual Meeting, New Orleans, Louisiana, June 23-(Abstract 59E-6).
  • Samelis, J., Sofos, J.N., Ikeda, J.S., Kendall, P.A., and Smith, G.C. 2001. Effect of glucose supplementation on growth and acid tolerance of Escherichia coli O157:H7 in pure and mixed cultures with a Pseudomonas spp. at 10 degrees C. IAFP Annual Meeting, Minneapolis, Minnesota, August 5-8. (Abstract PO99).
  • Juneja, V. K. and Sofos, J.N. (editors). 2001. Control of Foodborne Microorganisms. Marcel Dekker, Inc., New York, NY. 535 p.
  • Sofos, J. N. 2001. Microbial Control in Foods: Needs and Concerns. In Control of Foodborne Microorganisms, V. K. Juneja, and J. N. Sofos, Editors. Marcel Dekker, Inc., New York, NY. Pp. 1-11.


Progress 01/01/00 to 12/31/00

Outputs
The implication of dried/fermented meats, such as beef and venison jerky and fermented sausages, in outbreaks of illness caused by Escherichia coli O157:H7, other enterohemorrhagic E. coli serotypes and Salmonella indicates that application of current processes, such as drying of meats, may fail to inactive pathogens. Also, the increasing number of outbreaks associated with fresh produce in recent years suggests that bacterial pathogens may survive in home-dried fruits and vegetables. At present, conflicting data on pathogen destruction in home-dried foods exist, while research has shown that sausage fermentations are insufficient to effect the required 5 log pathogen reduction. Additionally, several drying studies have shown that the initial rapid decline of the target pathogen is followed by survival of a residual population of bacteria in the ready-to-eat product. Furthermore, post-processing contamination of dried foods with enteric pathogens and Listeria monocytogenes may increase food safety risks. The overall goal of the studies is the development and validation of processes for assuring the safety of home-dried meats, fruits and vegetables. The project was approved and initiated on 15 September 2000. Previous work showed that heat and acid work together to destroy E. coli O157:H7 during drying of apples. Thus, acid treatment of fruit products needs to be evaluated to determine its potential effect on pathogen survival. The preliminary studies to date evaluated the effect of acid treatments on survival and growth of E. coli O157:H7 on apple slices stored for 6 hours after treatment at room temperature. Half-ring slices (0.6 cm thick) of peeled and cored Gala apples were immersed for 30 min in a 3-strain composite inoculum of E. coli O157:H7. Inoculated slices received: 1) no treatment; or a 10-min immersion in 2) sterile water, 3) 2.9% ascorbic acid, 4) 1.7% citric acid, 5) 50% commercial lemon juice, or, 6) 50% commercial lemon juice with preservatives. Slices were then placed in sterile bags and stored for up to 6 hours at room temperature. Samples were plated on each of five types of agar media to determine populations of bacteria during storage. Immersion in water reduced bacterial populations by 0.9-1.1 log colony forming units per g (log CFU/g), while reductions following immersion in acid solutions were 0.9-1.5 log CFU/g, depending on agar medium. During the 6 hour storage period, populations of bacteria increased by 1.0-1.6 log CFU/g in control and water immersed slices, while in acid immersed samples, populations decreased by 0.3 or increased by 0.6 log CFU/g. Differences in cell recovery achieved by the five agar media tested were minor. The results showed that acidic treatment before apple drying does not have a major effect on survival or growth of E. coli O157:H7. Acidulants seemed to slow growth of the organism but did not destroy the cells. Combining acidic treatments with some other form of preservation, such as drying, may be an effective way of inactivating E. coli O157:H7 on fruit. However, increased development of acid tolerance by the acid resistant E. coli O157:H7 and other pathogens needs further study.

Impacts
Current home-drying methods for meats, fruits and vegetables may fail to control foodborne pathogenic bacteria, as indicated by outbreaks with beef and venison jerky. Moreover, cross-contamination of dried foods with bacterial pathogens during packaging may also increase food safety risks. The results of this project (initiated on September 15, 2000) will be used to develop educational material and provide training on safe food drying and storage for Cooperative Extension personnel, processors and consumers.

Publications

  • No publications reported this period