Valorisation of horse mackerel, a discard fish

In 2012 global fish production (158 million tonnes) comes from fishery (58%) and aquaculture (42%). In Italy, only few species are commercialized and appreciated by consumers thus resulting in the production of high volumes of discards. Atlantic horse mackerel (Trachurus trachurus) despite its high nutritional value is one of the most underutilised species. Recently, mechanical separation process (MSM) has been demonstrated to be successfully applied in fish sector. Nevertheless, scarce information on its possible role in fish discard recovery are presented in literature. Thus, this study focused on the chemical changes, antioxidant content as well as oxidative stability of horse mackerel subjected to mechanically separation process and stored up to three months at -20 °C. Thirty-six horse mackerel were fished in the Tyrrhenian Sea. Fish were slaughtered by asphyxia in ice slurry. Immediately after death, twelve fish were minced by the MSM machine and utilised for obtaining 6 MSM burger (MSM samples), whereas the other were filleted. Twelve fillets (right) were stored as fillet (WF samples), twelve fillets (left) were grounded in order to obtain 6 fishburger (FB samples). Samples for each treatment were analysed at time 0 (T0), and after 90 days of frozen storage (– 20 °C) (T90) for proximate composition, total lipids, fatty acid composition (FAs), primary (conjugated dienes) and secondary (thiobarbituric acid substances, TBARS) oxidation products, and antioxidant capacity (ABTS, FRAP, and DPPH). Some advantages and disadvantages emerged. Horse mackerel showed a low fat content (<1 g/100 g muscle), a high PUFAω3 content (around 57 g/100 g total fatty acids), especially EPA and DHA (around 52 g/100 g total FAs) regardless the treatment. However, polyunsaturated fraction increases its susceptibility to oxidation, as revealed by the high TBARS content at T0, calculated as 8 mg MDA-eq/100g muscle for WF, FB, and MSM. However horse mackerel had a high antioxidant power which may protect muscle against oxidative damages both during treatment and storage. Indeed no significant increase in TBARS content was found whilst at the same time antioxidant capacity significantly decreased. In conclusion, mechanical separation process seems can be applied without many detrimental effects on horse mackerel.