Implication of Glass Transition and Sticky Point Temperatures in Food Processing

Abstract

The collapse of dehydrated food during freeze drying, stickiness of the product during spray drying, caking and agglomeration of powder during processing and storage are some of the problems of amorphous foods, which can be related to glass transition temperature (Tg). The glass transition temperature is the temperature at which transition occurs from a hard, solid and amorphous to soft, rubbery liquid state due to the increase in temperature of the material beyond a particular limit. Moisture content, glass transition temperature and water activity are the parameters affect most of sugar rich food processing. Food mainly fruits and vegetables are containing amorphous food polymers that are having very low glass transition temperature and very sensitive to change in moisture content. They are hygroscopic and cause stickiness by reducing the Tg. The most significant difference between food polymers and synthetic polymers is found in their chemical composition. Food are complex mixtures of solid and water, while synthetic polymers are composed of repeating units of well-characterized molecules. Introducing the principles of polymer science to the characterization of food materials would improve the understanding of the physicochemical principles that affect the structural changes in food materials. Sticky point temperature of food polymers is also a useful indicator for storage and handling properties of food polymers.