Effect of Reducing Sugar on the Maillard Reaction Rate of Freeze-dried Food in the Glassy State

Abstract

Maillard reaction rates of model freeze-dried foods which consist of lysine and various reducing sugars (i.e. ribose, arabinose, xylose, galactose, glucose, and maltose) embedded in glassy trehalose matrix were examined at various temperatures below the glass transition temperature (T_g), and the effect of reducing sugar on the Maillard reaction rate was studied. The extent of Maillard reaction was examined spectrophotometrically from the absorbance at 280 nm (ABS₂₈₀), and the reaction rate (k₂₈₀) was evaluated as a pseudo zero order reaction rate from the time course of ABS₂₈₀. The T_g of each sample was almost same value, however, the k₂₈₀ showed a considerable different value depending on the kind of reducing sugar. From the comparison of the k₂₈₀, it was found that the k₂₈₀ became lower as T_g of the reducing sugar itself which was contained in the sample became high. From this result and our previous result, it was suggested that the reducing sugar and lysine embedded in glassy matrix can react partially independently of the molecular mobility of the matrix, and the contribution of the molecular mobility of Maillard reaction reactants itself to the reaction rate in the glassy matrix should be considered.