Study On The Quality Of Bighead Carps After Liquid Quick Freezing

Bigheadfish(Aristichthys nobilis),is a unique freshwater fish which widely distributed in rivers and lakes of China.Bighead carp has many market advantages,such as the fast growth rate,easily breeding,low cost of living,high market demand,the fish is the favorite of farmers.However,fresh bighead carp is easy to get deteriorated after death because of it's high protein storage in effect of the body's endogenous enzymes and theexternal microorganisms.However,the bighead carp is mainly stored by air freezingmethods,which takes a long time to get frozen,yet the storage effect is poorand it is easy to waste the resources.In order to change the situation,it is urgent to find a simple,efficient and effective method to preserve bighead carp.In this paper,the effects of different freezing conditions on bighead carp were compared in both of physical and biochemical properties.The main conclusions are as follows:(1)The basic components of fresh bighead carp were tested comprehensively.The results showed that the water content of the bighead carp was 76.28%,the crude protein content was 18.45%,crude fat content was 3.14%,ash content was 1.00%,And.the total carbohydrate content was 1.33%.Bighead carp is a kind of healthy food which is rich in polyunsaturated fatty acids,DHA and EPA,and its amino acid composition is reasonable to be absorbed by human being.(2)Bighead carp's T-t curves of liquid freezing and air freezing showed that it cost 9 min for liquid freezing to pass through the zone of maximum ice crystal,and its freezing rate was 5.3 times of air freezing.The effects of rapid liquid freezing and gas freezing on the biochemical properties such as pH value,actomyosin content,total thiol group and Ca2+-ATPase activity of.bighead carp were discussed furthermore,the results were as follows:Compared with air freezing,liquid freezing could delay the change of pH value.The content of actomyosin,total sulfhydryl group and Ca2+-ATPase activity of liquid frozen samples decreased,and the descending rate was lower than that of air freezing(P<0.05),the degree of denaturation of fish protein was less than which of air freezing.The effects of freezing temperature and storage temperature on the biochemical properties of bighead carp were studied.The results showed that the lower the freezing temperature was,the lower the descending rate of actomyosin,total thiol group and Ca2+-ATPase activity were.The difference of biochemical indexes between-25? and-18? was not significant(P>0.05).(3)The effects of liquid freezing and gas freezing on the micro structure,water holding capacity and texture properties of bighead carp were studied.The results showed that as the prolonging of storage time,the structure of myofibers was degraded to a certain extent.However,the liquid freezing was better than that of air freezing.The water holding capacity and texture properties of bighead carp decreased gradually.The descending rate of the samples was significantly lower than that of air freezing(P<0.05).The effects of different freezing temperatures and storage temperatures on the biochemical properties of bighead carp were studied.The results showed that the lower the freezing temperature,the lower the degradation degree of muscle fiber structure was,the slower the descending rate of water holding capacity,elasticity and hardness were.The difference of biochemical indexes between-25? and-18? was not significant(P>0.05).