PREDICTION OF CHILLING TIMES OF FOODS IN SITUATIONS WHERE EVAPORATIVECOOLING IS SIGNIFICANT - PART 1 - METHOD DEVELOPMENT

The finite difference method was used to simulate the unsteady state c ooling of spheres, infinite slabs and infinite cylinders of food mater ials subject to both convection and evaporation at the product surface . Simulations were conducted across wide ranges of air temperature, su rface heat transfer coefficient, product initial temperature, surface water activity and air relative humidity Algebraic equations are propo sed for finding three parameters-the product equilibrium temperature a s time-->infinity, a slope parameter of semi-log plots relating unacco mplished temperature change to time and an intercept parameter of the same plots. The first of these equations is based on psychrometric the ory and the other two were derived by using Mon-linear regression to c urve-fit the numerically simulated cooling rates. These equations allo w the numerically simulated cooling times to be predicted within about +/-5%. In Part 2 the accuracy of these equations as a simple chilling time prediction method is tested experimentally for model food system s. In Part 3 their application to real foods is considered. (C) 1998 E lsevier Science Limited. All rights reserved.