17H-23 |
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L. HUANG, Food Safety Intervention Technologies Research Unit, USDA-ARS-Eastern Regional Research Center, 600 E. Mermaid Ln., Wyndmoor, PA 19038-8598 The objective of this study was to understand the fundamental mechanisms governing the process of vacuum-steam-vacuum (VSV) surface pasteurization of ready-to-eat meat products. A high-speed instrumentation system was used to measure the surface temperature of hot dogs during VSV processes. Results indicated that the pressure in the treatment chamber responded immediately and accurately to the events of VSV. The surface temperature history, however, did not instantaneously reach the steam temperature, but followed an exponential trend after saturated steam was flushed into the treatment chamber. A mathematical model was developed to simulate the surface temperature history during steam pasteurization processes. Using the mathematical model to estimate the lethality of VSV processes, it was found that treating with 110°C steam for 0.1 s should have been sufficient to achieve a 5-log reduction in L. innocua inoculated onto the surface of hot dogs, provided that the surface was perfectly smooth and bacteria were all distributed on the surface. The incomplete destruction of bacteria on hot dog surfaces using current VSV processes could be explained by the hypothetical theory of capillary condensation. This study suggested using a single long steam treatment cycle, instead of multiple short VSV cycles, for a complete destruction of bacteria hidden beneath the surface of ready-to-eat solid foods. A numerical model was further developed to simulate the processes of VSV surface pasteurization of hot dogs. This model could be used to design the VSV processes for a complete destruction of Listeria monocytogenes on the surface ready-to-eat meat products.
Session 17H, Food Engineering: Thermal processes
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