29D-7 |
Modeling heat transfer and microbial lethality in a segmented-flow aseptic system |
A. B. STEPHENS and P. N. Walker. Dept. of Agricutural & Biological Engineering, Pennsylvania State Univ., 239 Agricultural Engineering Bldg., University Park, PA 16802 Innovative segmented-flow aseptic processing allows foods containing particulates to be processed without many of the problems inherent in traditional pipe-flow aseptic processing while still maintaining the benefits of rapid heating and cooling. The recently patented (6,457,513) segmented system controls the residence time of each food particle by emulating a series of cans, and should allow thermal validation of the system. Modeling heat transfer in the system yields data useful in determining process parameters for effectively achieving commercial sterility while retaining food quality. The objective of the study is to develop a model to accurately predict microbial lethality for a food particle processed in a segmented-flow system. Synthetic food comprised of xanthan solution and chickpeas are processed in the system. The collected particle and system temperature data are used to determine heat transfer coefficients as a function of viscosity, chain speed, and particle concentration. From this model, the food particle center temperature through the system can be determined and used to calculate the cumulative microbial lethality for given system conditions. Preliminary results have already made evident the improved quality of food processed using segmented-flow versus retort-processed cans. The lethality model is complete except for the heat transfer coefficients and these data are being collected. It is expected that these data will show increasing viscosity, increasing particle concentration, and decreasing chain speed all decrease the heat transfer in the system, both at the heat exchanger wall-to-liquid boundary and the liquid-to-particle boundary. Because residence time is intrinsically controlled in segmented flow processing, the heat transfer model can be used to determine microbial lethality. As such, thermal validation of the segmented-flow system would be effective, making it a practical system for processing foods containing particulates while improving food quality compared to either canning or conventional aseptic processing.
Session 29D, Food Engineering: Thermal processes
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