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Applying state diagrams to food processing and developmentThe physical state of food components affects their properties during processing, storage, and consumption. Removal of water by evaporation or by freezing often results in formation of an amorphous state (Parks et al., 1928; Troy and Sharp, 1930; Kauzmann, 1948; Bushill et al., 1965; White and Cakebread, 1966; Slade and Levine, 1991). Amorphous foods are also produced from carbohydrate melts by rapid cooling after extrusion or in the manufacturing of hard sugar candies and coatings (Herrington and Branfield, 1984). Formation of the amorphous state and its relation to equilibrium conditions are shown in Fig. 1 [see text]. The most important change, characteristic of the amorphous state, is noticed at the glass transition temperature (Tg), which involves transition from a solid "glassy" to a liquid-like "rubbery" state. The main consequence of glass transition is an increase of molecular mobility and free volume above Tg, which may result in physical and physico-chemical deteriorative changes (White and Cakebread, 1966; Slade and Levine, 1991). We have conducted studies on phase transitions of amorphous food materials and related Tg to composition, viscosity, stickiness, collapse, recrystallization, and ice formation. We have also proposed that some diffusion-limited deteriorative reactions are controlled by the physical state in the vicinity of Tg (Roos and Karel, 1990, 1991a, b, c). The results are summarized in this article, with state diagrams based on experimental and calculated data to characterize the relevant water content, temperature, and time-dependent phenomena of amorphous food components.
Document ID
Document Type
Reprint (Version printed in journal)
Roos, Y. (University of Helsinki Finland)
Karel, M.
Date Acquired
August 21, 2013
Publication Date
December 1, 1991
Publication Information
Publication: Food technology
Volume: 45
Issue: 12
ISSN: 0015-6639
Subject Category
Man/System Technology and Life Support
Distribution Limits
Non-NASA Center
NASA Discipline Life Support Systems
NASA Discipline Number 61-10