Abstract
Effect of the glass transition in various freeze-dried amorphous food systems on the rate of Maillard reaction was summarized in this review. The rate of Maillard reaction of amino acid and reducing sugar embedded in an amorphous matrix by freeze-dry shows a remarkable change at the glass transition temperature (T_g), that is, the reaction rate below the T_g becomes much slower than that above the T_g. Maillard reaction, however, progresses on the scale of several days even in the glassy matrix below the T_g, although the molecular diffusivity is limited enough in the glassy state. From results of our systematic studies on the rate of Maillard reaction of six kinds of reducing sugar (i.e., ribose, arabinose, xylose, galactose, glucose, and maltose) and lysine embedded in various glassy matrices, it was suggested that the reaction rate in glassy matrix was affected not only by the molecular mobility of matrix and/or Maillard reactants, but also by the forming of hydrogen-bond among them.
