Dynamic measurement and mathematical modeling of the temperature history on hot dog surfaces during vacuum-steam-vacuum processes

The objective of this study was to develop an instrumentation system 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, 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. According to the model, a 5-log reduction in L. innocua inoculated onto the surface of hot dogs could be achieved using 110 degrees C steam for 0.1 s, provided that the surface was perfectly smooth and bacteria were all distributed on the surface. However, bacteria still survived the VSV treatment even when higher temperatures were used. The incomplete destruction of bacteria on hot dog surfaces using current VSV processes may be due to the fact that the pores are filled with water and heat must penetrate into a certain depth under the surface of hot dogs in order to eliminate L. monocytogenes. 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. Published by Elsevier Ltd.