Studies on Discoloration of Fishery Products-V

Mechanism of Rusting in Amino Acid-Reducing Sugar-Lipid System

Abstract

It has been known that nonenzymatic browning in fish muscle is caused by Maillard reaction or lipid oxidation, however no report has been presented about the correlation between them. In an attempt to elucidate it, browning in lysine-ribose-fatty acids (R), lysine-ribose (M) and lysine fatty acids (L) systems was studied in model dehydrated systems (Table 1).
The colored products were extracted from these systems and fractionated into dialyzed water soluble fraction formed by Maillard reaction and CHCl₃-MeOH soluble fraction by lipid oxidation (Fig. 1). These colored fractions from R system were compared with those from M system, i. e. Maillard system or from L system, i. e. lipid oxidation system respectively, in color intensity (Table 2) and by spectro analyses and thin layer chromatography (Figs. 2-6). In R system, Maillard reaction was accelerated by lipid oxidation, while lipid oxidation was inhibited by Maillard reaction (Table 3). Consequently, browning in R system was due mainly to Maillard reaction, suggesting that browning by Maillard reaction might play an important role in rusting of fish muscle containing nitrogenous compound, reducing sugar and unsaturated lipid. Further, the reason why sodium bisulfite did not inhibit browning in the presence of lipid was that it could not inhibit Maillard reaction (Table 4).