Utilisation of fish industry residuals: Screening the taurine concentration and angiotensin converting enzyme inhibition potential in cod and salmon

Fillet and residuals of farmed Atlantic salmon (Salmo salar) and wild caught cod (Gadus morhua) have been analysed for taurine concentration and angiotensin converting enzyme (ACE) inhibitory effect. With respect to taurine concentration, the residual fractions showed great variations, with the lowest concentration found in cod eye, 0.8 mg/g, and salmon fillet muscle, 0.7 mg/g, while for both cod and salmon the highest concentration was found in the heart with 8.3 mg/g and 5.6 mg/g, respectively. For the analysis of the ACE-inhibitory effect, the fractions were subjected to a simplified gastrointestinal digestion to produce hydrolysates which were then subjected to an ACE (1 mU) inhibitory assay to find the inhibition coefficient, IC50%. The lowest ACE-inhibitory effect was found in cod bile with an IC50% at 7.6 μg/mU. Also the skin from both cod and salmon showed a low effect with 6.3 μg/mU and 6.0 μg/mU, respectively. For both the species the highest inhibitory effects were found in hydrolysates from the fillets, with 1.6 μg/mU and 2.2 μg/mU, respectively. Lesser used residuals, like organs connected to the cardiovascular system, such as heart, kidney and gills, with high taurine concentration and medium ACE-inhibitory effect, may be interesting as raw materials for niche products.