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

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 degrees 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 (R) 435, and Rhizomucor miehei, Lipozyme (R) 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 degrees C and a melting completion (Mc) of 33.1 degrees C. The physicochemical properties of these SL suggest that some may be useful in formulating food products such as margarines and spreads.