1a. Objectives (from AD-416):
The overall goal of this research is to reduce the risk of foodborne illness associated with the consumption of produce and shell eggs. Effective postharvest intervention technologies for these foods have proven difficult to implement and, therefore, are on the FDA Center for Food Safety and Applied Nutrition's list of highest research priorities. This new project was formed to apply proven engineering expertise to the development of efficient intervention strategies for challenging foods such as shell eggs, fresh produce and frozen produce. While other projects continue looking at intervention methods such as hot water immersion, irradiation and cold plasma for these types of foods, the proposed project will research novel technologies including microwave, radio frequency, UV, and flash steam. The specific objectives of the research program are as follows: 1: Develop, evaluate, and validate through laboratory and pilot-plant processing the effect of single and combinations of intervention technologies on pathogen reduction in eggs. Specifically, conduct research to "pasteurize" shell eggs using technologies, such as microwave heating or ozone-based combination treatments. 2: Develop, evaluate, and validate through laboratory and pilot-plant processing the effect of single and combinations of intervention technologies on pathogen reduction in fresh produce. For example, engineer flash steam and UV treatments and develop antimicrobial/antioxidant compounds of GRAS origin as a processing aid for fruits and vegetables. 2A: Develop and evaluate a hurdle approach to inactivate Salmonella spp. and E. coli O157:H7 from tomato stem scar tissue. Application of thermal energy to the stem scar region of the tomato will be employed for the destruction of pathogens and to expose bacteria to subsequent treatments including antimicrobial immersion. 2B: Develop and evaluate a novel approach to inactivate Salmonella and E. coli O157:H7 on berries by an antimicrobial water agitation treatment. Aerated turbulence and vacuum will be applied to berries in order to remove particulate matter and expose niches within the host tissue to antimicrobials. 2C: Develop and evaluate a hurdle approach to inactivate Salmonella spp., L. monocytogenes and E. coli O157:H7 on fresh fruits and vegetables using individual treatments or a combination of antimicrobials and flash steam. 3: Develop, evaluate, and validate through laboratory and pilot-plant processing the effect of single and combinations of intervention technologies on pathogen reduction for frozen fruits and vegetables. Currently some vegetables are processed through snap freezing. It might be possible to develop a steam pasteurization processing technology that would allow vegetables to be stored refrigerated instead of frozen while having a stable shelf life.
1b. Approach (from AD-416):
Radio frequency (RF) heating intervention technology will be developed that requires less time to pasteurize shell eggs than hot water immersion. A 4 kW RF unit will be modified to enable the application of RF energy to a shell egg. Another option to improve heating uniformity is to immerse the shell eggs in a liquid while applying RF energy. In addition, nonthermal ozone treatment of shell eggs will be evaluated for reducing Salmonella. Combinations of these technologies, such as ozone and RF, will be investigated. Shell eggs will be sent to Dr. Deana Jones (Athens, GA) for extensive quality tests including foaming ability, Haugh unit, yolk index, as well as turbidity and viscosity of the egg white. Tomatoes will be inoculated and the current practice of trimming stem-scar tissue will be tested to determine if subsequent cross-contamination of tomatoes occurs during traditional stem-scar removal. Vacuum perfusion sanitization will be used in combination with chemical sanitizers for the decontamination of Salmonella and E. coli from tomatoes. A novel localized heat treatment for the physical inactivation of Salmonella within the stem scar of tomatoes will be developed. Our engineers will modify existing technology currently used for the electrical thermal dehorning of sheep, goats and cattle. Berries will be inoculated and a hurdle approach to decontaminating berries will be applied by the use of sanitizers in combination with physical treatments such as applied vacuum perfusion, or aerated turbulence of water. Fruit (including melon, apple, tomato, pepper, mango, cucumber, and pear) surfaces will be inoculated and a novel antimicrobial treatment will be developed that will not impact the sensorial quality. The kinetics and mechanism of inactivation of the developed antimicrobial wash solutions will be investigated. Flash steam technology will be used to inactivate bacteria on such fruits and vegetables as peppers, cantaloupes, mangoes, green onions, parsley, cabbage, cucumbers, and radishes. The produce will be evaluated for thermal and mechanical damage using a texture analyzer and colorimeter. Frozen fruit (e.g., berries) and vegetables (e.g., corn and peas) will be inoculated and GRAS antimicrobial compounds will be used to sensitize foodborne pathogens to UV light inactivation and inhibit growth of pathogens on thawed fruits and vegetables. The bacterial inactivation using pulsed UV bulbs, that provide higher intensities than 254 nm UV bulbs, will be investigated. The latest technology to emerge is UV-LED (light-emitting diode). UV-LEDs are compact, do not fail as quickly as other types of UV bulbs, and have a potential for significant energy savings.
3. Progress Report:
The shell egg pasteurization process, developed by ARS scientists at Wyndmoor, Pennsylvania last year using Escherichia coli, was shown to be capable of inactivating 99.999% of Salmonella. This is important because the bacteria of concern related to the consumption of uncooked or undercooked eggs are Salmonella. The process uses radio frequency (RF) to pasteurize shell eggs within 20 min and maintains the transparency of the egg white. The collaboration continues with ARS scientists at Athens, Georgia to evaluate the egg quality. Preliminary results indicate that the functionality of the RF processed eggs was superior compared to that of eggs pasteurized using the conventional 60 min hot water immersion process. A funded CRADA was signed with an industrial partner with the objective of scaling up and commercializing the RF shell egg pasteurization process. The role of pyrolysis biochar in accelerating the inactivation of pathogens in crop soil, in order to inhibit the contamination of fresh produce, was studied. Biochar application accelerated the inactivation of E. coli O157:H7 and Salmonella, inactivating more than 99.9999% in 5 weeks. Work also continued on a 5-year NIFA-funded project in conjunction with the University of Delaware. A post-doctoral research assistant was hired on this project and has been investigating a potential surrogate virus for human norovirus. Tulane monkey virus is being evaluated for its resistance to various sanitizing compounds, to reduce the risk of foodborne illness on fresh produce. Work from an additional industry-funded CRADA involves testing sundry novel industry antimicrobials for inactivating Salmonella, E. coli O157:H7 and Listeria monocytogenes in vitro, as well as following their inoculation onto fresh produce. The interactive effects of temperature, pH, and water activity on the growth kinetics of Shiga toxin–producing E. coli O104:H43 was studied and used to develop second-order predictive models to estimate the growth potential in foods. These models will provide risk assessors and food safety managers a rapid means of estimating the likelihood that the pathogen, if present, would grow. The behavior of native microbial populations of WPC-34 and WPC-80 whey protein stored at different temperatures was investigated using a conventional and a rapid bioluminescent Adenosine Triphosphate (ATP) assay that does not require up to 3 days incubation before results are achieved. Total microbial populations in the whey proteins determined immediately and after 7 days storage did not show significant changes. The results indicate that bioluminescent ATP assay can be used to estimate total microbial populations in the samples. The effects of ultraviolet-C (UV-C) light treatment on inactivation of Salmonella Enterica and E. coli O157:H7 on grape tomato surface and stem scars and quality was investigated. The treatment was effective in controlling native microbial loads during storage at 4 C. The treatment did not affect the firmness of tomato and its color during storage suggesting that UV-C radiation could potentially be used for sanitizing fresh tomatoes and extending shelf-life.
1. Shell eggs pasteurization technology transferred to industry. The shell egg pasteurization technology, recently developed by ARS researchers at Wyndmoor, Pennsylvania, needs to be scaled up in order to supply consumers with safer and higher-quality eggs. Numerous companies expressed substantial interest in the radio frequency shell egg technology during the past year. The lab-scale prototype was demonstrated to several companies. After a thorough review, a funded CRADA was signed with one of the companies to scale up and commercialize the pasteurization process. Pasteurization of all shell eggs in the U.S. would reduce annual Salmonella illnesses by approximately 110,000.
2. Antimicrobial wash solution for fresh and fresh cut produce. The goal of this work was to collaborate with an industry partner through an established CRADA to develop an antimicrobial wash solution to inactivate pathogens on fresh produce. ARS researchers at Wyndmoor, Pennsylvania, tested numerous combinations of GRAS (generally recognized as safe) compounds for inactivating foodborne bacterial pathogens. The selected antimicrobial solution inactivated bacteria in rinse water under clean conditions and dirty conditions as follows: A provisional patent has been filed for this solution, which will provide processors another option for reducing foodborne pathogens in fresh produce.
Yan, R., Mattheis, J.P., Gurtler, J., Sites, J.E., Fan, X. 2014. UV-C inactivation of Escherichia coli and dose uniformity on apricot fruit in a commercial setting. Postharvest Biology and Technology. doi.org/10.1016/j.postharvbio.2014.04.005.
Juneja, V.K., Mukhopadhyay, S., Ukuku, D.O., Hwang, C., Wu, V.C., Harshavardhan, T. 2014. Interactive effects of temperature, pH, and water activity on the growth kinetics of Shiga-toxin producing Escherichia coli O104:H4. Journal of Food Protection. 77(5):706-712 doi:10.431/0362-028XJFP-13-387.
Mukhopadhyay, S., Ukuku, D.O., Juneja, V.K., Fan, X. 2014. Effects of UV-C treatment on inactivation of Salmonella and Escherichia coli O157:H7 on tomato surface and steam scars, native microbial loads, and quality of grape tomatoes. Food Control. http://dx.doi.org/10.1016/j.foodcont.2014.03.027.
Yan, X., Gurtler, J. 2014. Cronobacter (Enterobacter) sakazakii. Encyclopedia of Food Microbiology. vol 1. In: Batt, C.A., Tortorello, M.L. (Eds.), Elsevier Ltd, Academic Press. pp. 528-532.
Yun, J., Yan, R., Fan, X., Gurtler, J., Phillips, J.G. 2013. Fate of E. coli O157:H7, Salmonella spp. and potential surrogate bacteria on apricot fruit following UV-C light. International Journal of Food Microbiology. 166:356-363.
Guo, M., Jin, Z.T., Geveke, D.J., Fan, X., Sites, J.E., Wang, L. 0203. Evaluation of microbial stability, bioactive compounds, physicochemical properties, and consumer acceptance of pomegranate juice processed in a commercial scale pulsed electric field system. Food and Bioprocess Technology. DOI:10.1007/s11947-013-1185-6.
Sampredo, F., Mcaloon, A.J., Yee, W.C., Fan, X., Geveke, D.J. 2014. Cost analysis and environmental impact of nonthermal technologies. Food and Bioprocess Technology. DOI:10.1007/s11947-014-1298-6.
Ukuku, D.O., Onwulata, C.I., Thomas-Gahring, A.E., Mukhopadhyay, S., Tunick, M.H. 2014. Behavior of native microbial populations of WPC-34 and WPC-80 whey protein stored at different temperatures. Journal of Food Processing and Technology. DOI: 10.4172/2157-7110l.1000304.