Comparison of proximate and water extractive components in raw mackerel with those in a fermented mackerel food heshiko

Proximate composition and several water extractive components in heshiko, a kind of rice-bran-fermented mackerel food, and raw mackerel muscle were de termined and compared with each other. Fish muscle was dehydrated to decrease the moisture content markedly, with the permeation of sodium chloride and sugars from the rice-bran mixture, Al though partial amounts of lipids eluted from fish bodies, most of them were retained and concentrated in fish muscle owing to the decrease of moisture . As the outflow or the loss of proteins from fish muscle was faster than t hat of lipids, the protein content in several heshiko samples consequently became lower than that of raw mackerel. Heshiko, on the other hand, contain ed large amounts of peptides and such free amino acids as Glu, Asp, Gly, Al a, Val, Ile and Leu, suggesting that remarkable proteolysis took place duri ng processing. Organic acids considerably increased in heshiko, whereas nuc leotides, which existed abundantly in raw mackerel, decreased to trace leve ls. Sensory evaluation indicates that free amino acids with peptides princi pally and organic acids supplementally are expected to contribute to the in tensive taste of heshiko.