Factors affecting protease activity of ginger and its application in milk clotting products.
2004
Chen, Y.Y. | Su, H.P.
Ginger rhizome (Zingiber officinale Roscoe) is a perennial herbaceous root. The purpose of this study was to extract the protease which belongs to the cysteine protease family from ginger root, investigate its milk clotting activity and proteolytic activities, and produce a new kind of milk clotting product. Extraction of protease from ginger roots was conducted by adding acetone to remove the volatile substances and using phosphate buffer to purify the protease. In order to study the effects of reacting conditions on the milk clotting activities of ginger protease, the different reacting temperatures (30-80 C) and pH (5-10) were evaluated. The results indicated that the optimal temperature of milk clotting activity and proteolytic activity were 80 C and 60 C respectively, and the optimal pH value was 5. Comparing the casein fragments proteolyzed by ginger protease, rennet and papain, all showed different results. Both the milk clotting activity and proteolytic activity from ginger protease were significantly lower than rennet and papain (P0.05). However, the lower proteolytic activities of ginger protease might be advantageous for food processing as the protein could not be extremely proteolysed and could form a better shape curd. Calcium could increase the curd qualities. According to the above results, milk could be coagulate by ginger protease to form a soft curd. This can increase the varieties for dairy products.
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