Characterization of cod (Gadus morhua) frame composition and its valorization by enzymatic hydrolysis

This study aimed at evaluating proximate composition, phosphorous content, amino acid (AA) and fatty acid (FA) profiles of cod (Gadus morhua) frame at five different sampling times (March 2017 to March 2018). Furthermore, the valorization possibility of cod frame by application of enzymatic hydrolysis was investigated using the samples from September 2017. In terms of protein content, this sample showed a significantly (P < 0.05) higher level (16.5 %) compared to the other samples, whereas lipid and phosphorous contents varied in a narrow range of 0.9–1.1 % and 2.9–4.4 %, respectively, (P < 0.05). Furthermore, the total amino acids (AAs) content varied from about 98–155 mg/g in minced cod frame. Enzymatic hydrolysis of minced cod frame (MCF) and heated cod meat (HCM) was carried out by application of Alcalase and Neutrase, either individually or sequentially to obtain fish protein hydrolysate (FPH) and bone powder rich in phosphorus and calcium. The protein content of FPH varied from 76 % to 84 % and soluble-nitrogen in trichloroacetic acid (SN-TCA) index varied from 30.6 to 40.3%, resulting in similar trends for yield and nitrogen recovery. Considerable amounts of phosphorus and calcium (330 and 583 g/kg, respectively) were recovered from the cod frame bones after enzymatic hydrolysis. This study showed that it is possible to produce bone powder rich in phosphorous and calcium as well as peptides from the cod frame. Thus, the cod frame side-stream can be converted from its current use as mink feed ingredient into higher value products for human consumption, without generating new waste products.