2007 Annual Report
1a.Objectives (from AD-416)
Determine the kinetics and mechanisms of inactivation of pathogens and their surrogates by PEF and RFEF technologies; Develop, evaluate and validate PEF and RFEF alone and in combination with other processes to ensure safety and security of fresh apple cider, fresh orange juice and liquid egg; and Evaluate quality, shelf life and cost of products processed by PEF, RFEF and combinational processes, and packaged aseptically or with antimicrobial agents, in comparison to thermal pasteurization.
1b.Approach (from AD-416)
Integrate disciplines of microbiology, engineering and chemistry to provide consumers with safe and high quality food products. Our microbiologists will lead the research in determining the mechanisms and kinetics of microbial inactivation, microbial shelf-life evaluations and product safety evaluations. Our engineers and food technologists will develop and validate novel processes and packaging technologies and evaluate associated cost. Our chemist and food technologists will lead the quality and shelf-life evaluations and consumer acceptance studies. From a food product point of view, the raw food materials will be processed and packaged to ensure safety and to maintain the fresh quality. Process conditions will be determined to achieve the food safety objectives set forth by the log reduction required for the pathogen of concern. Kinetics of microbial inactivation and models provide process set points to achieve food safety objectives. The kinetic models also serve as tools for risk assessment when deviations take place in raw product composition, microbial load and/or processing conditions. Identification of the mechanisms of microbial inactivation will help understand the process and define the direction in process optimization. We will also work with our collaborators in regulatory agencies, industry and other ARS laboratories, to identify the pathogens of concern and suitable surrogates and to define food safety objectives for each product.
Kinetics and Mechanism of Microbial Inactivation
Liquid egg may contain harmful bacteria such as species of Salmonella. Processing technologies are needed to inactivate these pathogens while maintaining the quality of the food. Combining pulsed electric field (PEF) and mild heat at 55C for 3.5 minutes resulted in inactivation of Salmonella typhimurium comparible to the heat treatment at 60C for 3.5 min and maintained quality and functionality of liquid whole egg. Repeated pressure treatment at 350 MPa 50C every 2 min for a total of 8 min at 4 cycles caused 5 log reduction to the Salmonella population without protein coagulation. The mechanism of bacteria inactivation using radio frequency electric fields (RFEF) was found to be membrane damage of the bacteria leading to the efflux of intracellular ATP, nucleic acid and protein in the juice matrix. This finding will help developing RFEF process to its potential. NP 108 Food Safety 2006-2010 Action Plan Component(s) 1.2.4 Processing Intervention Strategies.
Controlling the growth of pathogen during storage can be achieved by antimicrobial packaging. Films with pectin plus polylactic acid were developed using extrusion and coated with nisin for inhibiting pathogenic Listeria monocytogenes. The films with nisin significantly inhibited the growth of Listeria in a growth medium, liquid egg and orange juice over 48 hour incubation at 24C. Nisin incorporated pectin/polylactic acid films have the potential to effectively control Listeria in liquid foods. NP 108 Food Safety 2006-2010 Action Plan Component(s) 1.2.4 Processing Intervention Strategies.
Furan in Ultraviolet Light Treated Apple Juice
Furan, a possible carcinogen, is found in some thermally processed foods. Ultraviolet (UV) light is used commercially by some cider processors to disinfect apple cider. Our results showed that UV induces furan formation in apple cider, and fructose solution. However little furan was formed from solutions of sucrose, glucose, ascorbic acid or malic acid, suggesting that fructose was the likely source of furan in apple cider. When fresh apple ciders were UV treated to achieve the 99.999% reduction of E. coli, less than 1 part per billion of furan was found. The information is useful for regulatory agencies to evaluate UV technology. NP 108 Food Safety 2006-2010 Action Plan Component(s) 1.2.7 Risk Assessment, and 2.1.6 Toxicity Evaluations and Mechanisms of Action.
5.Significant Activities that Support Special Target Populations
|Number of non-peer reviewed presentations and proceedings||15|
|Number of newspaper articles and other presentations for non-science audiences||2|
Ukuku, D.O., Fett, W.F. 2006. Effect of cell surface charge and hydrophobicity on attachment of 16 salmonella serovars to cantaloupe rind and decontamination with sanitizers
. Journal of Food Protection. 69(8):1835-1843.
Bari, M.L., Mori, M., Ukuku, D.O., Kawamoto, S., Kawamoto, K. 2007. Effct of high-pressure treatment on survival of escherichia coli 0157:h7 population in tomato juice. International Journal of Food, Agriculture, and the Environment. 5(1):111-115.
Geveke, D.J., Kozempel, M.F., Feze, N., Vang, T., Johnson, N., Goldberg, N.M., Hanson, R., Radewonuk, E.R. 2007. Confirmation of the vacuum/steam/vacuum process for the reduction of bacteria on cantaloupe using a commercial prototype. Fruit Processing. 160-163.
Geveke, D.J., Brunkhorst, C., Cooke, P.H., Fan, X. 2006. Nonthermal inactivation of e. coli in fruit juices using radio frequency electric fields
. In: Juneja, V.K., Cherry, J.P., Tunick, M.H., editors. Advances in Microbial Food Safety. Washington, D.C.:American Chemical Society. p. 121-139.
Zhang, H.Q. 2007. Pulsed Electric Fields: Processing System, Microbial and Enzyme Inhibition, and Shelf Life Extension of Foods. IEEE Transactions on Plasma Science. 35(1):59-73.