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:
Research has been conducted to develop antimicrobial coatings for controlling pathogens, to identify compounds of potential concern formed by novel non-thermal food processing interventions, and to develop/optimize treatment processes and combinations to control pathogens. Detailed progress to achieve the overall objectives is listed below. Ready-to-eat (RTE) meat products can be more vulnerable to cross-contamination due to multiple steps involved in preparation. The newly designed antimicrobial coatings and films with chitosan and lauric arginate ester significantly reduced Listeria innocua and Salmonella on RTE deli meat products. Combining antimicrobial coatings or films with steam flash pasteurization further reduced L. innocua, achieving more than 99.999% reduction of L. innocua. Chlorine is a commonly used chemical sanitizer in the food industry. However, harmful chemical by-products may be formed from chlorine reacting with organic materials. The formation of trichloromethane, a chlorine by-product, was evaluated in fresh-cut produce and wash water. Results suggested that more than 10 times higher levels of trichloromethane were detected in wash water than actual fresh-cut lettuce. Antibrowning solutions contaminated with L. monocytogenes have resulted in recalls of cut fruit in recent years. Several antimicrobials and antibrowning compounds were tested using a central composite design to optimize formulations to preserve the freshness of cut apple while inactivating L. monocytogenes. Most of the experiments have been completed and data are being analyzed. Antimicrobials applied as a coating onto the inner surface of packages need to migrate into packaged food to exert their effect on pathogenic bacteria. The releasing kinetics of two common antimicrobials (benzoate and sorbate) was tested in models systems. Significantly higher amount of benzoate (~800 ppm) compared to sorbate (~500 ppm) was detected in water media from the bottle coating. Migration of these antimicrobial into water followed a first order kinetics. High pressure processing (HPP) is an approved non-thermal pasteurization process that can inactivate pathogens and undesirable spoilage enzymes with minimal alteration of sensory and nutritional qualities. Freshly prepared mixed fruit salad, artificially inoculated with three strains mixture of Salmonella Stanley, S. Newport, and S. Saintpaul, was treated with HPP at various pressures and times. At a pressure of 300 megapascal and temperature of 25 C, a 5-min HPP treatment inactivated 99.999% of three strains mixture of S. Stanley, S. Newport, and S. Saintpaul in freshly prepared mixed fruit salad.
1. Ultraviolet (UV) light to enhance fruit safety. Tree-ripe fruit such as apricots and peaches can not be washed with chemical sanitizers due to their softness. Non-aqueous technologies are needed to minimize the risk of human pathogens on this type of fruit. ARS researchers at Wyndmoor, Pennsylvania evaluated the efficacy of UV-C light for the inactivation of two common pathogenic bacteria on apricot. The population of pathogens decreased with increased doses of UV-C. A short (10 sec) UV-C treatment resulted in immediate reduction of 99% of Salmonella spp. and E. coli O157:H7 on apricot surface. During post-UV storage, the pathogens on UV-C exposed fruit did not survive well and continued to decrease in population. Compared with the non-treated fruit, up to 99.999% of pathogens was reduced after post-UV-C storage. The low-cost UV-C technologies can be employed by the fruit industry to meet the increasing demand of high quality and safe fruit.
2. Antimicrobial coatings in combination with other intervention technologies effectively decontaminate raw and ready-to-eat (RTE) shrimps. ARS researchers at Wyndmoor, Pennsylvania investigated the antimicrobial effects of ozone, antimicrobial coating and cryogenic freezing, used alone or in combination, on the survival of Listeria innocua, a surrogate of L. monocytogenes on raw whole and RTE shrimp. Results indicated that antimicrobial coating in combination with cryogenic freezing reduced more than 99.999% of L. innocua and natural bacteria on raw shrimp and the coating treatments also significantly inhibited Listeria growth on RTE shrimp thawed at 4, 10 or 22 degree C for either 24 or 48 h. The information is valuable for seafood processors and distributors to adopt intervention strategies to enhance the safety and extend the shelf-life of shrimp.
3. Formation of carcinogenic furan from fatty acids. Furan is a potential human carcinogen. ARS researchers at Wyndmoor, Pennsylvania studied the mechanisms for furan formation from different fatty acids as a result of thermal and nonthermal processing and storage. Results suggested that furan was mainly produced from unsaturated fatty acids such as linoleic and linolenic acid. And furan was induced from the unsaturated fatty acids by thermal and UV-C treatments. Furthermore, storage of unsaturated fatty acid emulsions at ambient temperature led to formation of low levels of furan even without the exposure to high temperature or UV-C. The results would help food industry to develop strategies to minimize the formation of furan from fat-containing food, and regulatory agencies to make science-based policies.
Yun, J., Fan, X., Li, X. 2013. Inactivation of Salmonella enterica serovar Typhimurium and quality maintenance of cherry tomatoes treated with gaseous essential oils. Journal of Food Science. 78(3)458-464.