Abstract
Heuristics (rules of thumb) are proposed for extending the chilling time prediction method proposed in Part 1 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 times 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 skin 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 1.
Published Version
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