FEASIBILITY OF THE USE OF A TIME-TEMPERATURE INTEGRATOR AND A MATHEMATICAL-MODEL TO DETERMINE FLUID-TO-PARTICLE HEAT-TRANSFER COEFFICIENTS

The growing interest in mathematical modelling of heat transfer to heterogeneous foods, i.e. foods comprising a liquid and solids, forces food technologists to look for adequate input parameters for these models. Here, possibilities of the combined use of a mathematical model and a Time-Temperature-Integrator (TTI), suggested to determine the fluid-to-particle convective heat transfer coefficient (h(fp)) in conditions which prohibit the use of conventional measurement techniques, is considered theoretically. The relative importance of the kinetic characteristics of the TTI, the carrier material, the location in/on this carrier, the immersion temperature and immersion time are systematically studied for idealized modelled processing conditions. The feasibility of existing TTIs and experimental results previously obtained with this methodology are critically evaluated. This theoretical study indicates that this technique should be used with extreme caution and that the response of each TTI towards different boundary conditions in a specific processing condition should be identified prior to experimentation. The need for such an a priori sensitivity study, specific for each processing condition, TTI and carrier material makes it a cumbersome methodology.