Extraction and characterization of major valuable compounds from prawn waste

Most prawns are prepared as frozen or canned meat and the remaining waste is used as a feed supplement or directly disposed on to the land, which affects the environment. Fresh prawn bio-waste contains protein, astaxanthin, flavor compounds and chitin. The use of chitin in various applications is limited due to its water insolubility. In this research, a new method is developed to prepare water-soluble colloidal chitin (WSCC) from prawn waste. WSCC having the percentage of degree of deacetylation same with that of chitin follows non-newtonian shear thinning behaviour. The characteristic study showed that the breakage of polymer chains during processing thus reduced the molecular weight and bulk density of WSCC. Therefore, functional properties of WSCC can be controlled by optimizing the processing conditions.Astaxanthin complex has attracted considerable interest in relation to its health benefits because of its powerful antioxidant activity. Traditional extraction of astaxanthin complex from prawn waste using organic solvents requires post-purification steps, creates solvent disposal problem and degrades the pigment. This research develops an efficient way of recovering astaxanthin complex from prawn waste that eliminates the problems associated with solvent extraction methods and offers possible recyclability of the solvents used. Post-harvest blackening in prawns adversely affects both quality and consumer acceptability. However, consumer safety over the chemicals, especially sulphites used in inhibiting prawn blackening is of a major concern. This study shows that the antioxidant, astaxanthin complex can inhibit the poly phenol oxidase (PPO) catalyzed blackening reaction in prawns. Although prawns have astaxanthin complex present in their natural state, its concentration in vivo may not be sufficient to act against PPO. Therefore, astaxanthin complex-enriched feed in prawn culture may prevent prawn melanosis and may eliminate the post-harvest handling methods