| Using thermocouples that are positioned within the test container, time temperature profiles can be easily obtained for establishing selected thermal processes. In bi-axial agitation processing of liquid particulate canned food products, modeling and biological validation are used as alternative methods to validate such processes. This involves processing of cans filled with alginate based simulated particles, with known counts of spores of heat resistant microorganisms uniformly distributed in their matrices, and computing the accumulated process lethality from their count reduction following processing. For this purpose, the heat resistance of two non-pathogenic surrogates microorganisms, Geobacillus stearothermophilus and Clostridium sporogenes, in two food matrices, carrot and meat alginate purees, was investigated and modeled using the conventional log-linear as well as Weibull models. D-values for G. stearothermophilus ranged between 1.9 and 40.8 min with a z-value of 11.7°C and Dvalues for C. sporogenes ranged between 0.9 and 28.7 min with a z-value of 10.1°C. For carrot alginates, D-values for G. stearothermophilus ranged between 1.9 and 42.6 min with a z-value of 11.5°C and D-values for C. sporogenes ranged from 1.1 and 31.0 min with a z-value was 10.2°C. The results were also fitted to Weibull model, but the model did not result in any better fit than the conventional first-order model.Alginate fabricated food particles need to have the appropriate textural rigidity to withstand the processing conditions and to have similar thermophysical properties to those of real food particles. Using a response surface methodology, optimum conditions of meat and carrot alginate fabricated particles giving the desirable hardness, adhesiveness and similar thermophysical properties to the real food particles were determined. Carrot alginate particles fabricated using these optimum conditions showed no changes in their hardness when subjected to thermal processing, unlike fresh carrot particles. Modeling of the associated heat transfer process required data on overall heat transfer coefficient ( U) and fluid-to-particle heat transfer coefficient (h fp) in the cans during the thermal process. Effect of process variables on U and hfp in canned particulates suspended in non-Newtonian fluid undergoing bi-axial rotation was then evaluated in a pilot-scale rotary autoclave using spherical Nylon particles (d = 1.9 cm) and optimum heat transfer... |
