Nonenzymatic Browning Reaction of Glassy Foods: Characterization of Local Reactions Independent of the Glassy Matrix

摘要

The rate of the nonenzymatic browning reaction (NEB) of model freeze-dried foods was investigated at temperatures below their glass transition temperature (T_g). The model samples used were NEB reactants (lysine and glucose) embedded in various glassy matrices (e.g., saccharide and polymer), and NEB reactants (lysine and various reducing sugars) embedded in a glassy trehalose matrix. The T_g of the samples depended on the type of matrix, but the type of reducing sugar had little effect on the T,. In comparison, the NEB rate of lysine and glucose embedded in glassy polymer matrices decreased with increased T_g of the polymer matrices. Although the T_g of saccharide matrices was much lower than that of polymer matrices, the NEB rates in saccharide matrices were lower than those in polymer matrices. In comparison, the NEB rate of lysine and various reducing sugars embedded in a glassy trehalose matrix depended strongly on the type of reducing sugar even though the samples had a nearly equivalent T_g. Previous studies reported that hydrogen bonds between saccharides and amino acids were formed efficiently in the dehydrated state, though hydrogen bonds between polymers and amino acids were restricted by steric hindrance. These observa-tions suggest that the NEB rate in a glassy matrix is affected not only by T_g, but also by hydrogen bonds between the NEB reactants and the matrix.