Fish protein powders - characterisation of composition and properties

Abstract

Fish resources are limited and large amounts of by-products produced after filleting are either discarded or utilized for feed production in the aquaculture industry and are in general underused. Therefore, it is a need to optimise utilization of the catch. With a growing world population, it is important that the fish material is used as sustainably as possible. By-products have great potential in the production of high-quality biomolecules for human consumption which will increase the profitability of the industry. The aim of this master thesis was to characterise the chemical composition of different fish powders and to study the relationship between the chemical composition and the functional properties of protein powders from cod head. The total content of amino acids in FPH from cod head ranged between (300-1015 mg/g) and amount of free amino acids was between (7 48 mg/g). The dominating free amino acids were not the same as the dominating in the total amino acid. The amount of soluble protein and acid soluble peptide showed wide variation, and in some samples the content of acid-soluble peptides were higher than the content of soluble protein. For most of the samples the acid-soluble peptides made up (15-76 %) of soluble proteins. The results from the determination of emulsion properties shows that in some samples the stability of the emulsion decreased with increasing protein concentration. This indicates that even if some of FPHs were able to form an emulsion, they were not able to stabilize it. The ash content varied between (7 10 %) which was quite high. This indicates that ash content is largely contributed by bones of fish by-products including head, fin, tail and frame. The degree of hydrolysis varied between (10.90 15.85 %). No significant relationship between the DH and free amino acid was found. There was also no correlation between DH and acid soluble peptide. However, the study has shown that it is possible to produce high-quality FPH from cod head.