ASTAXANTHIN EXTRACTION FROM CRAWFISH SHELLS BY SUPERCRITICAL CO2 WITH ETHANOL AS A COSOLVENT
Imparting red or pink pigmentation to species raised in aquaculture such as salmonids and crustaceans increases their market value. These species must be supplied with pigments such as astaxanthin to produce a pigmented flesh, since they cannot biosynthesize carotenoids, including astaxanthin. Commercially synthesized astaxanthin is worth about $1,000/kg.
Expansion of the crustacean processing industry has been accompanied by large amounts of waste. The recovery of carotenoids from this waste is desirable. Extracting crustacean wastes with organic solvents to produce carotenoid concentrates resulted in degraded pigments in many literature reports. The purpose of this research was to optimize the extraction of astaxanthin from crawfish (crayfish) shells by supercritical carbon dioxide with ethanol as a cosolvent. Control experiments employing solvent extraction of pigments were performed. The independent variables in preliminary experiments were temperature, pressure, particle size, cooking, ethanol content, and moisture. The dependent variable, astaxanthin content, was measured by high performance liquid chromatography (HPLC). It was found that temperature, pressure, and moisture were the main effects. These independent variables were studied in the second part of the study by using an incomplete 3^3 factorial (Box-Behnken) design.
The model fitted to the data was y= -169.3 + 5.36T + 8.847P + 7.32M - 0.0435TP - 0.10TM + 0.0435MP - 0.02T^2 -0.12622P^2 - 0.033M^2, where y=extracted astaxanthin (mg/kg dry shell); T=temperature (oC); P=pressure (MPa); M=moisture (% wet basis). Moisture had the greatest effect on astaxanthin extraction followed by TM, M^2, and P^2. The optima for the three variables, moisture, pressure, and temperature were 13%, 24.1 Mpa, and 75oC, respectively.