Glass Transition-Associated Structural Relaxations and Applications of Relaxation Times in Amorphous Food Solids: a Review

Abstract

The glass transition and corresponding glass transition temperature (T g ) as found for food solids have received considerable attention, and their relationships with food solid behavior in various processes and food storage have been disputed. However, understanding glass transition-associated relaxations and their coupling with physicochemical properties of food materials is still a challenging and developing area of food material science. This review shows the improved understanding of the glass transition, structural relaxations, and corresponding relaxation times (τ) as well as their relevant applications on glassy food solids. Above information contributes to understanding of physical changes, molecular mobility, and solid flow characteristics of food components around their glass transition during processing and storage. We also emphasized the limitations of “fragile” concept in food solids and introduced a “strength, S” parameter to measure and describe solid flow characteristics of amorphous food mixtures by using a William-Landel-Ferry (WLF)-based approach for the analysis of α-relaxation derived τ above T g . The use of the S concept, therefore, can provide a quantitative measure to estimate compositional effects on τ and the control of solid properties, such as stickiness, caking, collapse, and crystallization.