STRUCTURE AND STABILITY OF THE GLASSY STATE IN RAPIDLY AND SLOWLY COOLED CARBOHYDRATE SOLUTIONS

Solutions of 30% aqueous fructose with and without sodium carboxymethy l cellulose (CMC) were frozen either rapidly in a cryogen or slowly an d examined by cryo-scanning electron microscopy (SEM) and by different ial scanning calorimetry (DSC) to determine microstructure and glass t ransition temperatures (T-g). Rapidly frozen samples were then stored for 3 or 14 days at either -75 or -25 degrees C and re-examined by SEM to determine the extent of ice crystal growth that had occurred. All solutions showed evidence of recrystallization after storage at -75 de grees C for 2 weeks. After storage at -25 degrees C for 2 weeks, ice c rystal sizes had increased by 20x that seen at -75 degrees C. Samples that were frozen slowly and stored at -25 degrees C produced larger ic e crystals than those rapidly frozen; however, as a result of more com plete ice crystallization during freezing, they underwent less recryst allization. The presence of stabilizer in the frozen systems reduced r ecrystallization during storage. Copyright (C) 1996 Published by Elsev ier Science Ltd on behalf of the Canadian Institute of Food Science an d Technology