Studies On The Simulation And Optimization Of Thermal Sterilization Of Different Types Of Canned Food

The subject of this paper is the simulation and validation during thermal processing of model liquids (sodium carboxy-methylcellulose (CMC) and water) and tuna fish using COMSOL Multiphysics. Experiment were run using a metal can containing model liquid or tuna fish and the temperature of geometric center were determined by the wireless real-time temperature recorder. After validation of the model, further simulation were carried out about the effects of viscosity, ratio of height to diameter, orientation angle and rotation rate on canned liquid food sterilization, and effect of thermal sterilization on the quality of canned tuna fish. The main results were presented as follows:1. The temperature and velocity magnitude were highly affected by viscosity during thermal sterilization. The higher the viscosity was, the smaller the effect of natural convection was. The slowest heating zone(SHZ) was located at a height of about10%～30%of the can height from the bottom. The lethality difference in the can increased with the increased of viscosity, which indicated that sterilization was uneven.2. The sterilization time increased with ratio of height to diameter and orientation angle and passed through a maximum around an ratio of height to diameter0.75～1, then reduced gradually. When ratio of height to diameter was less than0.75, the sterilization time reduced to a minimum around an orientation angle0°; when ratio of height to diameter was more than0.75, the sterilization time reduced to a minimum around an orientation angle90°; when ratio of height to diameter was equal to0.75, the sterilization time reduced to a minimum around an orientation angle0°nd90°. The maximum and minimum velocity were found to be2.83mm/s and1.22mm/s with ratio of height to diameter0.75, orientation angle0°and ratio of height to diameter0.25, orientation angle45°respectively in all of cans for the SHZ to reach the value of100℃。This study was expected to be a significant contribution for further optimization studies.3. The brine had a greater effect on the heat transfer during thermal sterilization. Under the condition of industrial sterilization(10min-60min-10min/116℃), SHZ were located at a height of about22.9%～50%of the can height from the bottom. The lethality in center point was very closely to the minimum lethality in the can. This study was expected to be a significant contribution for further optimization studies.4. Thunnus albacares was processed in brine in metal cans to a common lethality value of8min at six different retort temperatures, namely110,116,119,121,124and127℃. The total process time (TPT) was found to be significantly influenced by the retort temperature. Cook value (C) and C to F0value ratios maintained an inverse relationship with retort temperature (P<0.01). Analysis of color showed that the L*value increased, while the a*value and b*value decreased with increase of retort temperature (P<0.05). Instrumental analysis of texture showed that hardness increased with the increase of retort temperature(P<0.05), Cohesiveness and chewiness decreased with retort temperature and passed through a minimum around an retort temperature116℃, then increased gradually. Chemical analysis showed that total volatile basic nitrogen value (TVB-N) increased with extension of process time (P<0.05), which shows that better quality can be achieved at high retort temperature to a common lethality.