Development of an up-grading process to produce MLM structured lipids from sardine discards

•Structured lipids were produced employing sardine discards as raw material.•The process involves: oil extraction, winterization, esterification and purification.•Sardine discards are a suitable source for the production of structured lipids.•Oxidative state of produced triacylglycerols was comparable to refined oil.•Two steps enzymatic esterification presented high regioselectivity.

The aim of the work was to produce MLM structured lipids with caprylic acid (M) as medium chain fatty acid located at the external bonds of the glycerol backbone and concentrated polyunsaturated fatty acids (L) from sardine discards (Sardine pilchardus) in the central bond of the glycerol. To that end, the following steps were conducted: (i) fish oil extraction, (ii) Omega-3 free fatty acids (FFA) concentration (low temperature winterization), (iii) two-steps enzymatic esterification and (iv) triacylglycerols (TAG) purification (liquid column chromatography). The resultant purified triacylglycerols accomplished with the oxidative state (peroxide and anisidine value, PV and AV) required for refined oils. As enzymatic treatment, Omega-3 concentrate FFA (Omega-3 > 600 mg Omega-3 per g oil) were esterified with dicaprylic glycerol employing Novozyme 435. This process presented high regioselectivity, with ∼80 mol% of concentrated fatty acids esterified at the sn-2 position.