Extraction of high value compounds from fish waste

Abstract

Worldwide fish production has continued to increase and reached 171 million tonnes as of 2016. Concurrently, large volumes of fish waste are generated, with an estimated 35% of fish mass, being discarded, usually with negative environmental effects. This also represents a huge economic loss since a wide range of chemicals, including proteins (enzymes, collagen), protein hydrolysates, PUFAs, as well as bioactive peptides and hydroxyapatite could be recovered from these discards. The aim of this study was to investigate the potential of extraction and quantification of high value extracts from fish waste. An estimated 5900 metric tons of waste are generated by the local Atlantic bluefin tuna (Thunnus thynnus) fattening industry. Protocols for the retrieval of high value fractions from the discards of the local fisheries industry were reviewed. Discarded tuna heads were harvested for skin, cheek muscle and subocular fat from a local tuna farm operator; gilthead seabream heads were obtained for comparison. Different fish tissues were treated for lipid retrieval. Enzymatic collagen extraction was also carried out on tuna skin and tuna bone tissue. Yields obtained from oil and collagen extraction indicated that there are considerable amounts of these valuable fractions in tuna waste: sub-ocular Tuna fat gave the highest yields recorded whereas Gilthead seabream waste gave considerably lower lipid yields. ATR-FTIR spectra obtained for tuna oil samples were characteristic of high EPA and DHA omega 3 fatty acids. The most effective method to extract tuna oil samples proved to be enzymatic (pepsin), closely followed by warm extraction. Mixed tuna tissue, which most closely represents approximate composition of tuna heads, gave a 19.8% lipid yield. This means that from the lipid containing tuna waste generated yearly, upwards of 700 metric tonnes of fish oil may potentially be retrieved. Collagen extracted from tuna skin gave an approximate yield of 10.9%, this is still substantial when considering the €41,465/MT value for marine collagen. If such valuable products are properly retrieved using state-of the art methods which prevent the breakdown of important components, they may prove to be the basis a lucrative local industry.