Enzymatic Modification of Menhaden Oil to Incorporate Caprylic and/or Stearic Acid

Abstract

Menhaden oil was enzymatically modified with caprylic (8:0) and/or stearic acid (18:0) to produce structured lipids (SL). The goal was to produce SL with high amounts of polyunsaturated fatty acids (PUFA), a low level of saturation, and a melting point of 25–35 °C. Substrate (menhaden oil to acyl donor) molar ratios were 1:1, 1:3, and 1:5 for 8:0, and 1:1, 1:2, and 1:3 for 18:0. Enzyme load was 10% of the total weight of substrates. Time course study determined optimal time for maximum acyl donor incorporation. Linear interpolation estimated molar ratios that yielded SL with 20 or 30 mol% incorporation of 8:0 or 18:0. Enzymatic reactions were also conducted with molar ratios of menhaden oil to acyl donors:8:0:18:0 (1:1:3, 1:2:2, and 1:3:1). Lipases from Candida antarctica, Lipozyme® 435, and Rhizomucor miehei, Lipozyme® RM IM (Novozymes North America, Inc., Franklinton, NC, USA), were compared for all reactions. Total and sn-2 fatty acid compositions, triacylglycerol (TAG) molecular species, thermal behavior, volatile lipid oxidation products, solid fat contents, and oxidative stability were compared. When 8:0 was the acyl donor, the 1:3.03 and 1:4.58 ratios resulted in incorporation of 20 and 30 mol% 8:0, respectively. With 18:0 as the acyl donor, the 1:1.32 and 1:2.41 ratios led to incorporation of 20 and 30 mol% 18:0, respectively. The 1:3:1 ratio SL had a crystallization onset (C0) of 15.3 °C and a melting completion (Mc) of 33.1 °C. The physicochemical properties of these SL suggest that some may be useful in formulating food products such as margarines and spreads.