Studies on Body Color Expression of Cultured Black Tiger, Prawn

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Carotenoids and carotenoproteins in the exoskeleton and the muscular epithleium of cultured black tiger prawn Penaeus monodon were analyzed to establish a strategy to improve their body color. First, carotenoid content and composition in the exoskeleton of the prawns exhibiting different body colors were determined. A consistency was observed between the depth of body color and the carotenoid content of 2.3-33.1mg/100g in the exoskeleton. The major carotenoid, astaxanthin, existed in three forms, namely diester, monoester, and free ones. Second, a blue carotenoprotein of 120kDa was purified from the exoskeleton. Another of 21.4kDa was also isolated from the muscular epithelium with a collagenase solution. Finally, carotenoids in both fractions were analyzed and compared between dark gray and blue prawns. A blue carotenoprotein fraction was liberated from the muscular epithelium by extraction with a collagenase solution, leaving another carotenoid fraction in the tissue. The main carotenoid in the carotenoprotein fraction was free astaxanthin, of which content showed no significant difference between the two prawn groups. The muscular epithelium after removal of blue carotenoprotein turned red owing to the remaining carotenoids which were composed largely of astaxanthin esters. The total content of the remaining red carotenoids was about six-fold higher in the dark gray than blue group. Thus the different body color of cultured black tiger prawns is suggested to be due to the varied composition of the blue carotenoprotein and red carotenoid fractions in the muscular epithelium.