Characteristics of sardine muscle hydrolysates prepared by various enzymic treatments.

In order to develop a protein material that is soluble and highly nutritious, fish protein hydrolysates (FPH) were prepared from defatted sardine meal by enzymic treatment using various proteases including three alkaline, two neutral and three acid ones. Ability to solubilize protein was compared among these proteases, and tryptophan content, bitterness and molecular weight distribution of each FPH were evaluated as indicies to quality. The results showed that all the alkaline proteases had higher ability to solubilize protein compared with neutral and acid ones. FPH prepared with alkaline proteases had higher tryptophan content and lower molecular weight than those prepared with neutral and acid ones. Especially, FPH prepared with alcalase or actinase, which were alkaline proteases, had weaker bitteness than other FPH. Furthermore, it was found that FPH prepared with alcalase followed by treatment with synthetic adsorbents or peptidases had much weaker bitteness.