100A-13 |
Validation of microwave and circulation water combination (MCWC) heating processes by inoculated pack studies |
D. GUAN1, P. M. Gray2, D. H. Kang2, and J. Tang1. (1) Dept. Of Biological Systems Engineering, Washington State University, L J Smith Hall, RM 213, Pullman, WA 99164-6120, (2) Dept. Of Food Science and Human Nutrition, Washington State University, Pullman, WA 99164-6376 Due to the possible non-uniform distribution of microwave energy within foods, microwave heating has not been used in commercial sterilization of prepackaged foods in the U.S.A. A pilot-scale system was developed at Washington State University to explore the possibility of combining 915 MHz microwave energy with circulation water to reduce non-uniform heating in pouches and trays. Based on a chemical marker method and fiber-optic temperature measurement, previous studies demonstrated it’s ability to reduce processing times for macaroni and cheese entrées by up to ¾ required for similar package sizes by conventional retort with a 6 min F0 process while still maintaining relatively uniform heating. The shortened process time significantly reduced product degradation. To further prove the feasibility of this technology, we need to valid the process with microbiological tests. The objective of this study was to determine the sterilization effect of the Microwave and Circulation Water Control (MCWC) heating process using inoculated pack tests. ATCC 7955 spore suspensions were prepared and stored. The heat resistance of the spores was determined in Macaroni and Cheese products with customized aluminum test tubes using End Point Method. The related Processing Conditions (PC) and Heat Penetration Data (HP) were determined from prior tests using MCWC heating system. F0 values were calculated from temperature-time history. Known numbers of spores were added to the formulated entrées, and then the product was treated under pre-determined processing conditions to a desired lethality level. The final products were incubated to determine the growth of the inoculated bacterium. The 915 MHz pilot-scale MCWC heating system was able to provide desired sterility within 1/4 of the time required for conventional retorting for products packaged in the same trays. The research demonstrated the availability of Microwave Circulation-Water Combination heating system for sterilizing certain food products. The technology may be used to process other heat sensitive products.
Session 100A, Food Microbiology: General II
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