FRACTURE-STRESS OF FISH MEAT AND THE GLASS-TRANSITION

Freezing a high moisture food may involve the crystallization of pure water and therefore concentrate the solute, which sometimes forms a co ncentrated amorphous solution (CAS). The CAS may be formed via hot air drl,ing as well, although most hot air dried foods available on the m arket are porous and/or in powder form and are inconvenient for use in fracture tests. In this paper, the traditional Japanese dried food 'k atsuo-bushi' a highly smoked, dried fillet of bonito fish meat (which can be regarded as a CAS in itself) was used as samples to measure the compressive fracture stress. The compressive fracture stress of 0% mo isture Katsuo-bushi was found to be constant at temperatures between 2 5 degrees C and -196 degrees C, and this value was comparable to that of 0% moisture CAS of completely frozen bonito meat estimated using a simple model for a frozen food. On the other hand, fracture stress of katsuo-bushi with 15-20% moisture changed greatly at temperatures betw een 0 degrees C and -90 degrees C, showing the feature of yielding. Th e temperature of brittle-ductile transition was different from the gla ss transition temperature as defined by DSC. Copyright (C) 1996 Elsevi er Science Limited