Studies On The Crayfish By-products Comprehensive Utilization

The crayfish is one of the major freshwater shrimp in China. The by-products of crayfish are rich in protein, fat, minerals, as well as active ingredient such as astaxanthin and chitin,and in China there are almost85%material freshwater shrimp discarded after processing. In this paper, the extraction and ultilization of crayfish by-products’effective ingredients were studied also formed a complete set of continuous process. The studies are as follows:(1) This paper took the crayfish head and shell as raw material,combined ultrasonic method with organic acid extraction. And established a process for preparing citrate-malate quadratic polynomial regression equation and optimize the process through single factor experiment, Plackett-Burman and Box-Behnken experimental trials. The results showed that the optimal process parameters of preparing the Calcium Citrate Maltrate using the crayfish by-products were that adding the mass concentration of30%malic acid and20%citric acid according to the acid material addition (acid to shrimp powder)3:1and mixed acid proportion (citric acid to malic acid)1:1.5;adding distilled water according to solid-liquid ratio(shrimp powder to water)1:50;then extracting calcium under the condition of ultrasonic such as ultrasonic power200w, ultrasonic time and utrasonic temperature50℃. Under these conditions, the Calcium ion extraction ratio is94.85%.(2) This paper studied the enzymatic extraction of protein from crayfish by-products which Calcium was removed.The best extraction conditions which obtained through single factor and orthogonal tests were as follows:the ratio of papain to flavourzyme1:1.5,enzyme dosagel.0%, temperature50℃, extraction time3h, pH value6.5, and solid-liquid ratio1:10. Under these optimal conditions, the extracti-on ratio of protein could reach54.22%.(3) This paper studied the best extraction condition of astaxanthin from crayfish by-products which Calcium and protein were removed. At the same time, in order to improve the purity of astaxanthin, astaxanthin was saponificated by using KOH-uniform experiment results showed that the optimal extraction conditi- ons of astaxanthin extraction were as follows:Ethyl acetate:Ethanol5:1, solid-liquid ratiol:50, temperature70℃and extraction time20min.Under these optimal conditions, astaxanthin content could reach92.55ug from1g shrimp powder. And the optimal saponification conditions of astaxanthin were as follows:The ethanol concentration95%, KOH-C2H5OH concentration1%, solid-liquid ratio1:28, temperature5.0℃and saponification time50min.Under these optimal conditions, astaxanthin ester was almost completely saponificated and free astaxanthin content was85.42%which was much higher than7.7%.