73C-18 |
Variable process temperature profiles to improve nutrient retention in different geometries of conduction-heated foods |
F. ERDOGDU, Dept. of Biological & Agricultural Engineering, Univ. of California, Davis, 1308 Bainer Hall, Davis, CA 95616 and M. O. Balaban, Food Science & Human Nutrition Department, Univ. of Florida, PO Box 110370, Gainesville, FL 32611. The conventional methods for thermal processing of foods use constant processing temperature profiles (CPTPs) for a prescribed processing time, which is based on achieving a required microbial lethality to comply with public health standards. This also results in degradation of nutrients and quality factors. The variable process temperature profiles (VPTPs) obtained by using optimization methods can reduce quality losses and/or processing time compared to CPTPs. The objective of this research was to evaluate VPTPs using the Complex Method (non-linear constrained optimization), to reduce the processing time and/or improve quality retention for a specified level of lethality in thermal processing of foods heated by conduction. The VPTPs were obtained using the Complex Method for the objective function of volume average retention of thiamine considering different sizes of spherical (r=15 mm, r=30 mm) and finite cylindrical shapes (r=15 mm, 2L=15 mm; r=30 mm, 2L=60 mm). The results were compared with a conventional method (processing at 121.1 C) for a specified lethality level for Bacillus stearothermophilus (Fo=4 min at 121.1 C, z=10 C). The use of VPTPs resulted in and 37 and 10% decrease in processing times in spherical and 40% and 6% for finite cylindrical shapes, for the same objective function value and specified lethality compared to the CPTP process. For the same processing time, the improvements in thiamine destruction were 3.7 and 2% for spherical, and 3.9 and 2.2% for finite cylindrical shapes. An outstanding issue is whether the profiles can be followed in industrial practice. The VPTPs obtained using optimization methods can be used to reduce the processing times significantly, resulting in the same quality retention level, or to increase the retention level for the same processing time. However, more research is needed for industrial applications.
Session 73C, Food Engineering: Transport Processes and Kinetics
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