Extraction And Purification Of Natural Astaxanthin

Extraction and Purification of Natural AstaxanthinThe extraction and purification of natural astaxanthin from shrimp wastes were studied. The process includes hydrochloric acid pretreatment, acetone extraction, hydrolysis of astaxanthin esters by catalysis of basic ion exchange resin, and adsorption separation.During pretreatment, 5% hydrochloric acid was added to shrimp wastes at room temperature to obtain a final pH of 4.5-5.0 for 5 h so as to remove mineral substances. Then shrimp wastes were washed with water, and immersed in acetone for about 24 h to extract carotenoids at room temperature.The reaction kinetics for the hydrolysis of astaxanthin esters and the degradation of astaxanthin during hydrolysis of the pigment extract from shrimp wastes were investigated. The dosage of basic ion exchange resin was important for promoting the hydrolysis of astaxanthin esters and minimizing the degradation of astaxanthin during hydrolysis. With a higher dosage of basic ion exchange resin, the reaction rate of hydrolysis was high, but the degradation of astaxanthin occurred significantly. A higher temperature should be avoided to minimize the degradation of astaxanthin. The mixture of dichloromethane and methanol (1:3, V/V) was a suitable solvent. The reaction consists of the first order reaction of the hydrolysis of astaxanthin esters and the zero order reaction of the degradation of astaxanthin. The rate constants of the hydrolysis reaction (first order) of astaxanthin esters and the degradation reaction(zero order) of astaxanthin were directly proportional to the dosage of basic ion exchange resin. When 1.2 g pig extracts (0.11% astaxanthin, 1.23% astaxanthin esters) were dissolved in 50 ml dichloromethane-methanol (1:3(V/V)), hydrolysis at 25*C, the expression of the concentration of astaxanthin, the dosage of basic ion exchange resinand the reaction time is as follows:cAst = 321.84 - 295.02exp[(0.044- 0.042*)/] + (6.342- 5.90&c)/Where CASI is the concentration (mg/1) of astaxanthin in the solution at reaction time t (h); x is the dosage (g) of basic ion exchange resin.In adsorption separation, the effect of different adsorbents including silica and polyamide was studied, the results showed that polyamide was better than silica.The adsorption isotherms of astaxanthin on polyamide were measured. The results showed that the adsorption isotherms were Langmuir type.The purified product with astaxanthin content of more than 8% was obtained.