Antiplasticization effect of water in amorphous foods. A review

Water is the most effective plasticizer in food matrices, decreasing glass transition temperature (T-g) and mechanical resistance and determining a softening effect with the increasing of its concentration. However an opposite effect (i.e. hardening, toughening) could be observed in some food and in specific moisture or a(w) range and this is referred to an anti-plasticization effect. Several are the possible causes for this phenomenon and various are the factors that have been recognized to affect its occurrence in a food matrix: mechanical testing method, mechanical parameter tested, type of food (composition and micro-macrostructure). In this paper, several studies on anti-plasticization effect of water are reviewed by focusing the attention on the interactions waterfood matrix and in particular to those occurring in amorphous cell foods. The different chemical and physical factors that affect this phenomenon are also discussed. The simultaneous occurrence of a plasticization and anti-plasticization effect of water, even if in different aw range, and the results of studies on amorphous food matrices may suggest an important effect of water-matrix interaction on the textural properties. (c) 2007 Elsevier Ltd. All rights reserved.