Sustainable use of marine resources - turning waste into food ingredients

Fish by-products are considered low value and discarded. With proper handling and processing, fish by-products may provide high nutritional value to consumers. This study aimed at establishing compositional differences in valuable compounds from fish by-products of selected species, including Salmon, Flathead, Silver warehou and Barramundi. Simple extraction methods were employed, and obtained fractions were analysed for their chemical and physical properties. The chemical composition of four fish species differed significantly (P < 0.05) with the protein content ranging from 14.7 +/- 0.09 to 16.8 +/- 0.41%. Adjusting pH to 2.5 yielded two times more of extracted oil than at pH 4.5. Salmon and Barramundi oils contained high amounts of monounsaturated fatty acids (MUFAs) (39-50%), while Silver warehou and Flathead oils contained 46-49% of saturated fatty acids (SFAs). The particle size of the protein fractions was small, ranging from 126.9 to 489.5 nm. Molecular weight of extracted proteins was fish species dependant - Silver warehou and Barramundi samples contained proteins of 250, 120 and 100 kDa, while these bands were absent from Salmon and Flathead samples. The data obtained indicate that extracted fractions from fish by-products likely have high nutritional value and could find a potential use in food formulations.