17H-4 |
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G. B. AWUAH1, H. S. Ramaswamy2, S. Economides1, and P. Mallikarjunan3. (1) Center for the Development of Research Policy & New Technologies, National Food Processors Association, 1350 I St. N.W., Ste. 300, Washington, DC 20005, (2) Dept. of Food Science & Agricultural Chemistry, McGill Univ., Macdonald Campus, 21111 Lakeshore Rd., Sainte-Anne-de-Bellevue, QC H9X 3V9, Canada, (3) Dept. of Biological Systems Engineering, Virginia Polytechnic Institute & State Univ., 312 Seitz Hall, Mail Code 0303, Blacksburg, VA 24061-0303 Radio frequency (RF) heating has been recognized to provide uniform heating due to its ability to penetrate into products with uniform field patterns. Thus, the RF heating concept has been touted to have the potential of providing high quality foods economically for relatively short heating time applications. Like any proposed new technology or concept, RF heating applications need to be evaluated in terms of its microbiological capabilities and safety. The objective of this study was to evaluate the log reductions associated with Listeria and E. coli surrogates in milk under continuous flow through the applicator tube of an RF heater. These organisms were chosen to cover both gram positive and negative strains that could contaminate milk and pose health-related risks. Pasteurized whole milk was purchased from a local supermarket and inoculated with both Listeria innocua and E. Coli k-12 cells to form a composite sample. The sample was refrigerated at 5 oC for 30 min for the cells to acclimatize to the environment and then heated in a 2-kW, 27.12 MHz RF dielectric heater with incident power levels ranging from 1100 to 1300 W. The associated fluid flow rate that ranged from 270 to 304 mL/min (laminar flow), provided a total residence time of 50 to 56 s in both the applicator and “holding” tube. Depending on the residence time and power level, RF heating was found to be capable of inactivating both Listeria and E. Coli in milk, with E. Coli being the most heat sensitive of the two. For a total residence time of 56 sec, up to 5 and 7-log reductions were found for heating Listeria and E. Coli, respectively at 1200 W, and applicator tube exit temperature of approximately 65.2 oC.
Session 17H, Food Engineering: Thermal processes
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