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UBC Theses and Dissertations

End-over-end agitated thermal processing of canned model food particles Knap, Rafal Peter


Heating efficiency at 0 rpm of a Lagarde steam/air simulator evaluated with water filled plastic bowl cans (size 307) revealed no statistically significant differences (p>0.05) in heating rate indices between the 15 different positions, indicating uniform and predictable heat delivery within the retort load. Furthermore, heating rate index (fh) , heating lag factor (jh) and accumulated lethality (F0) were also determined in the plastic, retortable bowls during tests at 7 agitation levels (0-30 rpm) , and at 3 radial positions (R₁=0 mm, R₂=115 mm, R₃=175 mm). Temperature histories were recorded in the centre of water filled bowls, and in both the liquid and particle portions of bowls filled with water and 6 potato/alginate simulated food particles (18 mm diameter). End-over-end rotation from 0 to 30 rpm significantly influenced all parameters. Response to agitation (rpm) was non-linear, such that higher rpm did not always improve heating rates. Substantial improvements in heating of particle portion were seen at relatively low rpm. Although less important than rpm, even small (115 mm) radial position differences significantly altered F₀ in some cases. The effect of immobilization of simulated food particles on the end of a thermocouple investigated using bacterial spores (Bacillus stearothermophilus ATCC 7953) sealed in DSC pans revealed significantly higher lethality delivered to immobilized, as opposed to freely moving particles. Use of DSC pans with bioindicators for verification of delivered lethality was shown to be reproducible, and this method may find application not only in the canning industry, but also in testing of aseptic processing systems.

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