Definition of a Mechanical Glass Transition Temperature for Dehydrated Foods

• Published in: Journal of agricultural and food chemistry 2004-04, Vol.52 (8), p.2262-2268
• Main Author: Kasapis, Stefan
• Format: Article
• Language: English
• Subjects: abalone; Animals; apples; apricots; Biological and medical sciences; Carbohydrates; dates; deformation; dried fish; dried foods; dried fruit; equations; Fishes; Food industries; Food Preservation; Fruit; Fundamental and applied biological sciences. Psychology; Gelatin; Glass - chemistry; glass transition temperature; Mechanics; mixtures; pears; plums; shear modulus; shear stress; sucrose; Temperature; Thunnus; Thunnus tongol; time-temperature superposition position; tuna; viscoelasticity
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf030468w

A new concept of the mechanical glass transition temperature (T g) is presented with application in dehydrated high-sugar/gelatin mixtures, fish, and fruits. The macroscopic basis and manner of relaxation processes during vitrification of these foodstuffs are developed using small deformation dynamic oscillation, the master curve of viscoelasticity, and the time−temperature superposition principle. The quantitative features of the mechanical T g are based on the combined framework of free volume/WLF theory and the Andrade equation. It is proposed that the thermal profile of storage modulus on shear is a fundamental index of monitoring changes in a glassy structure, and several cases are presented in support of this concept. Keywords: Dried foods; dynamic oscillation; glass transition region; glassy state; WLF equation