Enhanced food sterilization through inclination of the container walls and geometry modifications

摘要

It is desirable to reduce the time taken for sterilization without compromising on the criterion of the slowest heating zone (SHZ) in the container reaching the minimum prescribed temperature. In this study, the required sterilization times for food cans of equal volumes but different shapes ranging from full cone through truncated cones to full cylinder were investigated. Further, the effect of orientation of the can was also investigated by inclining these geometries from 0-180°. The non-Newtonian fluid (0.85% w/w CMC) was taken as the test food material and its laminar flow behavior analysed using computational fluid dynamics. It was observed that among these geometries the lowest sterilization time was observed for a vertically oriented upright full conical can. The cylinder gave lower sterilization time when oriented horizontally than vertically. The sterilization times of truncated conical cans were intermediate to those determined for full cone and cylinder. Even a small inclination in the orientation of the cans may lead to significant increase in the sterilization times due to decrease in the convective velocities. The slowest heating zone movement in both axial and radial directions was tracked for various geometries and typical results are presented. The convective velocities, volume of region above and the surface area below the slowest heating zone determine the time taken for sterilization. When geometry modifications are made for aesthetic reasons to the food container, the utilization of known sterilization times for the conventional cylindrical can of the same volume may be inappropriate for suitable thermal treatment.