ARTICLE:

• STRESSES AND STRAINS IN THE FREEZING OF SPHERE SHAPED FOODS  download article

Q. T. Pham
University of New South Wales, Australia

J. Paterson
University of New South Wales, Australia

A. McKellar
University of New South Wales, Australia

F. Olivia
University of New South Wales, Australia

Alain Le Bail
UMR GEPEA (UMR CNRS 6144), ENITIAA, BP 82225, 44322 Nantes Cedex 03, France

ABSTRACT

When water freezes, its volume expands by about 9% creating severe stresses and strains. As water turns into ice, it forms a shell which restrains further expansion of the yet unfrozen water in the core. At some point, micro-cracks may form and the ice shell may flow plastically to relieve the stress. With rigid solid foods such as some fruit and tubers, another mechanism may take place where the food freezes and expands, causing tension in the core (instead of compression). These models give very different predictions of stress, strains and mechanical damage in the food. The paper presents models of the mechanical effects of phase change and contraction in a spherical food, and results of a preliminary investigation using photographic techniques to follow the volume changes caused by freezing.

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