Characterization of melanoidin in soy sauce and fish sauce by electrofocusing and high performance gel permeation chromatography.

Abstract

Sixteen soy sauce samples and 6 fish sauce samples produced in Asian countries were characterized for melanoidin by electrofocusing on polyacrylamide gel and high performence gel permeation chromatography (HPGPC). Melanoidin of soy sauce was electrofocused into 7 bands at pH range of 2.5-3.5. Melanoidin of fish sauce did not give a clear electrofocusing profile. The model melanoidin of glucose and glycine system was different from the melanoidin of soy sauce which contained components electrophoresed to the direction of the cathode. The pattern of the major bands was almost similar in all the soy sauce samples tested, but the intensity of the pigment which was retained at the charged position greatly varied. The mean molecular weight of the retained brown pigment in most samples was larger than those of electrofocused pigments by HPGPC. Broad HPGPC peakS were noted in the soy sauce samples added with caramel except one Korean soy sauce. Mean molecular weight and color intensity of fish sauce are mostly smaller than those of soy sause. The pH value is higher in fish sauce than in soy sauce.