The preventive effect of several kinds of sugars against denaturation of carp myofibrillar protein caused by freeze-drying was studied by measuring the inactivation of its Ca-ATPase. Even in the presence of sugar, the activity of Ca-ATPase decreased rapidly in the initial 2 hours and then remained level during the subsequent freeze-drying period. According to the method previously proposed by us, the preventive effect was estimated by the following two equations: E = DELTAlogk(D)/a and R = DELTAlogA/a, where k(D) is the first order rate constant for inactivation of Ca-ATPase in the early period, a is the concentration (molarity) of sugar, and A is the remaining Ca-ATPase activity in the subsequent period. Both E and R values were found to diminish in the order of maltotetraose, lactitol, maltotriose, maltitol, maltose=sucrore, sorbitol, glucose, and mannitol. The level of preventive effects of sugars against denaturation of myofibrillar protein by freeze-drying was closely related to the number of OH groups of sugar molecules, although there is the possibility that their effects are also induced by the configuration of the OH group.
