Study On The Solid Food Fluidization Ultra High Temperature Sterilization Technology

With investigating on general scope of sterilization technologies, it was found that there was not any sterilization technology that has obvious advantages of products quality over traditional retort sterilization technology being applied to solid food with low acid, high water activity and long shelf life. This situation resulted in both the low utilization ratio of themolabile components of foods and the limit of foods species that can be applied to sterilization, and was a choke point for industrialization of domestic traditional diets. This problem is possible to be dissolved via the fluidization solid foods ultra high temperature (UHT) sterilization, which has a novel technological principle, that is, in non-evaporation condition food particles are heated in fluidization bed to attain commercial aseptic demand, then are cooled by decompressing evaporation cooling or fluidization cooling, so is accomplished the UHT sterilization course. This technology achieves the efficient to meet the demand of industrial scale by rapid sterilization for a small quantity of particulate foods. The fluidization solid foods UHT sterilization is the unique sterilization method in which the final products are pure solid foods with low acid, high water activity and long shelf life.The process of fluidization solid foods UHT sterilization technology were respectively analyzed in hydrodynamics, heat transfer, food quality kinetics, microorganism lethal kinetics, and mass transfer, the basic controlling equations for transfer process and the key parameters of sterilization were established, therefore the appropriate theoretical basis and computational formula were selected or derived. Based on the results of the computation of the operating condition of fluidization and surface heat exchange, the inner distribution of temperature and dissoluble component concentration of particles were acquired via analytical and numerical computation with code programmed by Matlab6.5 and/or ANSYS8.0, then, the analysis of food quality kinetics, microorganism lethal kinetics and mass transfer were done, finally, the primary technology characteristics, key parameters and application field of this technology were obtained. The results revealed that there is wide fluidization operating rate range in fluidization solid foods UHT sterilization, the flow regime of liquid-solid fluidization is particulate fluidization and the flow regime of gas-solid fluidization is mostly aggregative fluidization, and liquid-solid fluidization are limited by density different between two phases; Fluidization convectional heat has the advantages of high surface heat exchange coefficient and uniform surface heat transfer to all particles, the heat conduction inside particle is obviously affected by hfp and diameter of particle, hence so is the quality retention of foods sterilized, the more the diameter and the lower the quality retention. The dimensionless correlation between dimensionless sterilization time and Bi number was expressed as hyperbolic function via numeric simulation and nonlinear data fitting for the effect of hfp on the sterilization time, the correlation displayed radical principle of convectional heat sterilization for particulate foods and could be used to estimate processing parameter. The approximate computation for mass transfer showed that loss of soluble component was acceptable in the fluidization solid foods UHT sterilization.The fluidization solid foods UHT sterilization pilot equipment for the principle validation was conceived, designed and finally manufactured, which have the function of liquid-solid fluidization UHT sterilization, atmospheric pressure/vacuum decompressed evaporation cooling, fluidization...