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United States Department of Agriculture

Agricultural Research Service


Location: Residue Chemistry and Predictive Microbiology Research

2012 Annual Report

1a. Objectives (from AD-416):
To determine sensory, nutritional and/or product quality impacts of efficacious food processing interventions and combinations of interventions. To develop antimicrobial packaging-based treatments for controlling pathogens. To identify compounds of potential concern formed by novel non-thermal food processing interventions. To develop/optimize treatment processes and combinations to control pathogens and to minimize loss of product quality and value.

1b. Approach (from AD-416):
An integrated approach to enhance microbial safety while maintaining product quality will be adopted by combining efficacious treatments and processes with antimicrobial packaging. Current antimicrobial treatments, processes, and intervention technologies that have been demonstrated to be effective in inactivating human pathogens will be modified and evaluated to confirm their effectiveness in obtaining a minimum 3 log CFU/g reduction of E. coli O157:H7 and Salmonella spp. on fresh and fresh-cut produce (mainly leafy green vegetables and tomatoes). Novel intervention technologies with higher efficacy of pathogen reduction will be developed and optimized. The impact of efficacious chemical and physical intervention technologies on sensory properties, nutrients, and shelf-life will be determined using the intensity (time, concentration, dose, etc.) that achieves a 3-log CFU/g reduction of the pathogens. In addition, new antibrowning/antimicrobial formulas will be developed to minimize risk of L. monocytogenes contamination during processing of cut fruit while inhibiting tissue browning. Furthermore, accumulation of chemical by-products as a result of chemical sanitizers and physical interventions will be investigated. Antimicrobial packaging as the final defense against human pathogens will be developed for a variety of food products (fresh-cut produce, meats, etc.) to reduce or control the re-growth of surviving pathogens during storage. Finally, combinations of efficacious intervention technologies with antimicrobial packaging will be evaluated for additive or synergistic inhibition of pathogens and preservation of product quality. Strategies and treatments will be developed to minimize adverse effects of intervention technologies and antimicrobial packaging on product quality. By combining efficacious intervention technologies and treatments with antimicrobial packaging, a 5-log reduction of common pathogens may be achieved. Intervention technologies either alone or in combination with antimicrobial packaging will be transferred to industry to enhance microbial safety of commercial food products.

3. Progress Report:
Organic acids are generally recognized as safe. Effects of common organic acids and electrolyzed water have been investigated as alternatives to chemical sanitizers for decontamination of fresh fruits and vegetables. Results indicate that organic acids such as acetic, lactic, malic, and citric acid can reduce the population of Salmonella spp. inoculated onto tomatoes by 96.8-99.9%. Some soft fruits such as tree-ripe apricots cannot be washed without damaging quality. Studies were conducted to evaluate the efficacy of ultraviolet light (UV-C) for inactivation of Salmonella and E. coli O157:H7 on tomato and apricot. Both Salmonella and E. coli O157:H7 populations decreased with increased doses of UV. Results suggest that a 10-second UV-C treatment can reduce 99% of Salmonella spp. and E. coli O157:H7 inoculated onto tomatoes or apricot. Salmonella exhibited slightly higher resistance to UV-C compared with E. coli O157:H7. In addition, UV light in combination with liquid phase ozone (1.4 parts per million) reduced 99.99% of Salmonella in an agitated system with surging bubbles. Antimicrobial coatings with edible and non-edible polymers and natural antimicrobials were developed for inactivating pathogens on shell eggs. Results show that the antimicrobial coatings were able to reduce up to 99.9999% of Salmonella cells on eggs. There was no re-growth of the pathogen on eggs after coating treatments and during the 28 days’ storage at 7 Degrees C. Results also indicated that the coatings were able to reduce the weight loss of eggs during storage at 7 or 4 Degrees C. Furan is a potential human carcinogen. The formation of furan was studied in model food systems as affected by heating, ultraviolet, and gamma radiation. Fatty acids and sugars as possible procurers of the compound were further investigated. Results suggest that changes in food composition would influence furan formation as a result of thermal and non-thermal processing. Based on one survey, one eighth of shrimp samples in the U.S. market is contaminated with L. monocytogenes, a pathogen causing listeriosis. The antimicrobial effects of ozone, antimicrobial coating, and cryogenic freezing, used alone or in combination, on survival of Listeria innocua (a surrogate of L. monocytogenes) on shrimp were investigated. Results indicated that antimicrobial coating in combination with cryogenic freezing reduced more than 99.999% of L. innocua and natural bacteria. The antimicrobial activity of three essential oils and their major components were evaluated as a gaseous treatment to reduce Salmonella Typhimurium on tomatoes. Texture, color, vitamin C, and lycopene contents of tomatoes were also analyzed after treatments. Results showed that treatment with gaseous cinnamon and oregano essential oils reduced Salmonella on tomatoes by 99.99% and maintained quality of the fruit.

4. Accomplishments
1. Antimicrobial coatings effectively inactivate foodborne pathogens. Pathogenic contamination of food usually starts from food surfaces. The presence and potential growth of pathogens in food during storage and transportation is a safety concern. ARS researchers at Wyndmoor, Pennsylvania, used antimicrobial coatings to kill pathogens on food surfaces and to prevent further cross-contaminations during transportation, storage, and store display. The coating treatments were capable of reducing Salmonella by more than 99.9999% on cantaloupe, tomato stem scar, and shell eggs, and no re-growth during 14 days storage at 10 Degrees C. Results from this study will provide food processors with viable options for designing antimicrobial coatings to improve the microbiological safety and quality of produce.

2. In-package pasteurization for fresh and fresh-cut produce. Fresh fruits and vegetables are usually consumed by consumers directly without a cooking step to kill foodborne pathogens. Any pathogenic contamination in fresh fruits and vegetables can potentially cause severe illnesses or even deaths. ARS researchers at Wyndmoor, Pennsylvania, developed an in-package chlorine dioxide releasing film that can kill pathogens on packaged foods. Results indicated antimicrobial films in a food container can inactivate 99.9% of Salmonella inoculated onto fresh grape tomatoes and some other types of produce. The in-package pasteurization provides a single, simple, inexpensive technique to enhance the microbial safety and extend the shelf-life of packaged fresh and fresh-cut produce.

3. Integrated approach to enhance microbial safety of tomato fruits. Fresh tomatoes have been implicated in recent outbreaks of foodborne diseases. ARS researchers at Wyndmoor, Pennsylvania integrated ultraviolet C (UV-C) light with low dose gamma radiation to control human pathogens on tomato fruits. Results indicated greater than 99.999% of E. coli O157:H7 and Salmonella enterica strains inoculated onto tomato fruits was inactivated by a combined treatment of low dose UV-C and gamma radiation. Furthermore, this treatment significantly reduced the population of native microbes during 3 weeks of storage at 10 Degrees C, without causing substantial quality changes in tomatoes. This approach may be used by the produce industry to decontaminate fresh tomatoes.

Review Publications
Jin, Z.T., He, Y. 2012. Antibacterial activities of magnesium oxide (MgO) nanoparticles against foodborne pathogens. Journal of Nanoparticle Research. 13:6877-6885.

Chen, W., Jin, Z.T., Gurtler, J., Geveke, D.J., Fan, X. 2012. Inactivation of Salmonella on whole cantaloupe by application of an antimicrobial coating containing chitosan and allyl isothiocyanate. International Journal of Food Microbiology. 155:165-170.

Fan, X., Lee, E.J., Ahn, D. 2011. Volatile sulfur compounds in foods as a result of ionizing radiation. In: Qiang, M., Fan, X., Mahattanatawee, K., editors. American Chemistry Society Book Chapter. Book chapter for ACS Publications. Washingnton, DC: American Chemical Society. p. 243-258.

Dong, X., Dong, M., Lu, Y., Turley, A., Jin, Z.T., Wu, C. 2011. Antimicrobial and antioxidant activities of lignin from residue of corn stover to ethanol production. Industrial Crops and Products. 34(3):1629-1634.

Li, W., Li, X., Fan, X., Tang, Y., Yun, J. 2012. Response of antioxidant activity and sensory quality in fresh-cut pear as affected by high O2,active packaging compared with low O2 packaging. Food Science and Technology International. 18:197-205.

Fan, X., Guan, W., Sokorai, K.J. 2012. Quality of fresh-cut iceberg lettuce and spinach irradiated at doses up to 4kGy. Journal of Radiation Physics and Chemistry. 81:1071-1075.

Gurtler, J., Jin, Z.T. 2012. Propyl paraben sensitizes heat-resistant Salmonella Enteritidis and Oranienburg to thermal inactivation in liquid egg albumen. Journal of Food Protection. 75(3):443-448.

Yadav, M.P., Strahan, G.D., Mukhopadhyay, S., Hotchkiss, A.T., Hicks, K.B. 2011. Fomation of corn fiber gum-milk protein conjugates and their molecular characterization. Food Hydrocolloids Journal. 26:326-333.

Mukhopadhyay, S., Ramaswamy, R. 2011. Application of emerging technologies to control Salmonella in foods: a review. Food Research International. 45:666-677

Ukuku, D.O., Onwulata, C.I., Mukhopadhyay, S. 2012. Behavior of Escherichia coli bacteria in whey protein and corn meal during twin screw extrusion processing at different temperatures. Journal of Food Processing and Technology. 3(4):1000150.

Mukhopadhyay, S., Ukuku, D.O., Phillips, J.G., Juneja, V.K. 2012. Survival and growth of Salmonella Enteritidis in membrane processed liquid egg white with pH, temperature and storage conditions as controlling factors. Food Microbiology. 75(7):1219-1226.

Li, X., Yun, J., Fan, X., Xing, Y., Yao, T. 2012. Effect of 1-methylcyclopropene and modified atmosphere packaging on chilling injury, and antioxidative defensive mechanism of sweet pepper. African Journal of Biochemistry Research. 10:6581-6589.

Jin, Z.T., Gurtler, J. 2012. Inactivation of Salmonella on tomato stem scars by edible chitosan and organic acid coatings. Journal of Food Protection. 75(8):1368-1372.

Yun, J., Li, X., Fan, X., Yao, T., Xiao, Y., Wan, S. 2012. Effect of gamma irradiation on microbial load, physicochemical and sensory characteristics of soybeans (Glycine max L. Merrill). Journal of Radiation Physics and Chemistry. 81:1198-1202.

Tomasula, P.M., Mukhopadhyay, S., Datta, N., Porto Fett, A.C., Call, J.E., Luchansky, J.B., Renye Jr, J.A., Tunick, M.H. 2011. Pilot-scale crossflow-microfiltration and pasturization to remove spores of Bacillus anthracis (Sterne) from milk. Journal of Dairy Science. 94:4277-4291.

Last Modified: 07/25/2017
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