Effect of manufactured diets on the yield, biochemical composition and sensory quality of Evechinus chloroticus sea urchin gonads

Sea urchins (Evechinus chloroticus) were held in sea cages and fed either one of two manufactured diets, or seaweed. Physical (gonad index, maturity index and colour L*a*b*), biochemical (lipids, glycogen, soluble protein, moisture and free amino acids) and sensory characteristics of the gonads from caged and wild sea urchins were measured at the end of a 13- week trial. The gonad index of sea urchins fed the manufactured diet which was highest in protein, was approximately double that of wild sea urchins, and significantly (p <= 0.05) higher than sea urchins fed seaweed. Gonads from sea urchins fed the manufactured diet highest in protein had significantly (p <= 0.05) higher glycogen and total free amino acid concentration, and a lower triglyceride concentration than gonads from sea urchins fed seaweed or collected from the wild. Ovaries had a significantly (p<0.01) higher soluble protein concentration than testes, and there were significant (p <= 0.05) differences in the concentration of individual free amino acids between genders and diet. Descriptive analysis carried out using a trained sensory panel reported differences in gonad sensory quality. Ovaries from wild sea urchins were significantly higher for sweet and umami taste, than ovaries from sea urchins fed the manufactured diets, which had a higher rating for bitter taste. Testes from wild sea urchins had a significantly harder texture than testes from sea urchins fed manufactured diets or seaweed. Sweet taste was significantly (p <= 0.05) positively correlated to glycine concentration in testes but not ovaries, while bitter taste was positively correlated to valine, leucine, and isoleucine concentration in both testes and ovaries. This study demonstrated that diet had a significant influence on the physical, biochemical and sensory characteristics of E. chloroticus gonads, and highlighted the importance of analysing E. chloroticus testes and ovaries separately. (C) 2010 Elsevier B.V. All rights reserved.