Fish processing generates a substantial amount of head by-product material, which comprises 20-30% of the total body weight depending on fish species. The utilisation of fish head generates relatively low revenue as most are processed into animal feed and plant fertilizer. By-products of fish processing are reported to contain a considerable amount of n-3 fatty acids, including eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA), both as the triglyceride and phospholipid forms. The phospholipid form is more bioavailable for brain health than the triacylglycerol or ethyl ester forms. This led us to investigate the n-3 phospholipid profile of New Zealand commercial fish species head by-product. Total lipid was extracted by a novel extraction method (ETHEX) from the head by-product of five commercial New Zealand fish species (blue mackerel, salmon, gurnard, ribaldo and snapper). The phospholipid composition and positional distribution of n-3 fatty acids were determined by 31P and 13C NMR, respectively. A considerable amount of n-3 fatty acids (EPA, DPA and DHA) and phospholipids were found in the head samples of all of the fish species investigated. King salmon (10.76 µmol/g) and blue mackerel (9.89 µmol/g) head were found to contain the highest phospholipid content and in a similar amount.  DHA was found by 13C NMR to be present in the sn-2 position in considerable amount in the head samples (blue mackerel=6.15%; salmon=0.77%; gurnard = 6.03%; ribaldo = 3.12%; and snapper =4.13%;)  of all of the fish species analysed. This indicates that head by-products generated from the New Zealand fish processing industry have potential as a source of n-3 phospholipid. Thes analysed fish heads contain considerable amounts of bioactive fatty acids and could be utilized for nutraceuticals derived from marine sources.

Omega-3 phospholipidomic profiling by nuclear magnetic resonance spectroscopy of commercial New Zealand species fish head by-product

ACS Fall 2021

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