Abstract: This study was performed in order to investigate the impact of steaming and boiling on the color, free and ester-type astaxanthin contents and in vitro antioxidant activity of different parts of crayfish. The results demonstrated that both cooking treatments had significant effects on the astaxanthin contents, color, and antioxidant activity of the different parts of crayfish. The astaxanthin contents of all crayfish parts increased initially and then declined with cooking time. Fresh crayfish tail shells were found to contain free astaxanthin and five astaxanthin monoesters. Free astaxanthin and one astaxanthin monoester were found in boiled crayfish tail shells, suggesting that boiling could promote the hydrolysis of esterified astaxanthin and the consequent generation of 98% free astaxanthin. With cooking time increasing, the L* value of crayfish increased slowly, and the a* value initially increased and later decreased, while the W value showed no significant change. Moreover, the a* value was strongly correlated with the astaxanthin content (r > 0.4). Both hydroxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging capacity increased first and subsequently declined. All parts of crayfish maintained high scavenging capacity against 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radicals. For all parts of steamed crayfish, astaxanthin contents showed a strong correlation with DPPH radical scavenging capacity (r > 0.9), but had a significant positive correlation with hydroxyl radical scavenging capacity for both claws and meat (P < 0.01). For all parts of boiled crayfish except the head, astaxanthin contents were significantly positively correlated with hydroxyl radical scavenging capacity (r > 0.9, P < 0.05).

Key words: crayfish; astaxanthin; color; antioxidant properties