Improved pigmentation of Atlantic salmon

Addition of the pigments, astaxanthin or canthaxanthin, to the diet of salmon is required to achieve the red colour desired by consumers. Given that less than 10% of the added pigment is retained in the salmon flesh, it is crucial to examine the biochemic al mechanisms responsible for limiting the deposition and retention of these pigments. We have found that enzyme activity in liver homogenates that converts astaxanthin and canthaxanthin to unidentified metabolites. Under identical conditions, beta-carote ne reacts to give a product that appears to be a retinoid-related compound, suggesting that the activity is due to a carotene 15,15'-dioxygenase enzyme. This enzyme, typically found in the intenstine and liver of many animals, may be responsible for the d egradation of dietary carotenoids in salmon thus limiting its for deposition in the flesh. We have identified the protein in flesh that binds carotenoids and plan to examine dietary factors that may influence this interaction.