PREDICTION OF CHILLING TIMES OF FOODS IN SITUATIONS WHERE EVAPORATIVECOOLING IS SIGNIFICANT - PART 3 - APPLICATIONS

Heuristics (rules of thumb) are proposed for extending the chilling ti me prediction method proposed in Parr I and tested for model substance s in Part 2 to real foods with non-unity water activity. Guidance is g iven for selecting three water activity values-one representing the ma ximally wetted starting condition, one representing the mean value dur ing the active chilling phase, and the third describing the surface co ndition in the quasi-equilibrium state reached at the end of chilling. Chilling rimes of a product retaining a well-wetted surface during ch illing (peeled carrots) were predicted to within approx. -10 to +15% o f measured values. At least part of this difference can be attributed to experimental error: For a product not retaining a well-wetted surfa ce due to skirt resistance (unpeeled carrots) predictions of only slig htly lower accuracy were achieved. Accurate prediction of chilling tim e across a wide range of conditions by a simple algebraic prediction m ethod is possible in spite of the complexity introduced by evaporative cooling at the product surface with water activity less than I. (C) 1 998 Elsevier Science Limited. All lights reserved.