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Y. MENG, Food Science and Agricultural Chemistry, McGill University, Macdonald Campus, 21,111 Lakeshore Road, Ste. Anne de Bellevue, QC H9X 3V9, Canada and H. S. Ramaswamy, Dept. of Food Science & Agricultural Chemistry, McGill Univ., Macdonald Campus, 21111 Lakeshore Rd., Sainte-Anne-de-Bellevue, QC H9X 3V9, Canada. Thermal processing, or canning, is still one of the most effective methods for food preservation. Heat transfer models can be valuable in the design, optimization and validation of thermal processing of foods. Many heat transfer models have been established, but little is know about modeling of heat transfer for processing of particulate non-Newtonian liquids under agitation process conditions. Most of canned particulate fluids are non-Newtonian in nature. The objective of this study was to develop a methodology to evaluate heat transfer coefficients associated with canned particulates suspended in non-Newtonian liquids during end-over-end rotation. The subsequent objective was to study the effects of some system parameters on the heat transfer coefficients. The experiments were performed with a pilot scale rotary, single cage and full water immersion retort. Flexible thin wire thermocouples were used to measure the temperature of particle centre. CMC aqueous solutions were treated as non-Newtonian fluid models. Nylon particles were treated as food particle models. Temperature distribution in the canned fluid was measured and large temperature gradient was found as the concentration of CMC solution increased beyond 0.4%, which made the conventional evaluation of overall heat transfer coefficient (U) and fluid to particle heat transfer coefficient (hfp) impractical. An apparent heat transfer coefficient hap between retort and particle surface was proposed. hap combines hfp and U values and can be used to calculate particle lethality directly based on retort temperature. The effects of retort temperature (110-130°C), rotation radius (0-240mm) and rotation speed (0-20rpm) on hap were studied by respond surface methodology. It was found that rotation speed was the most significant factor (p<0.005) followed by retort temperature (p<0.05) in influencing hap. The effect of rotation radius was not significant (p>0.05). The concept of using hap gives an approach to study the heat transfer process in canned particulate high viscous non-Newtonian liquids.
Session 111, Food Engineering: Modeling heat transfer and microbial inactivation
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