Prediction of chilling times of foods in situations where evaporative cooling is significant - Part 3. Applications

Heuristics (rules of thumb) are proposed for extending the chilling time prediction method proposed in Parr I and tested for model substances in Part 2 to real foods with non-unity water activity. Guidance is given for selecting three water activity values-one representing the maximally wetted starting condition, one representing the mean value during the active chilling phase, and the third describing the surface condition in the quasi-equilibrium state reached at the end of chilling. Chilling rimes of a product retaining a well-wetted surface during chilling (peeled carrots) were predicted to within approx. -10 to +15% of measured values. At least part of this difference can be attributed to experimental error: For a product not retaining a well-wetted surface due to skirt resistance (unpeeled carrots) predictions of only slightly lower accuracy were achieved. Accurate prediction of chilling time across a wide range of conditions by a simple algebraic prediction method is possible in spite of the complexity introduced by evaporative cooling at the product surface with water activity less than I. (C) 1998 Elsevier Science Limited. All lights reserved.