ORIGINAL PAPER Increasing Stearidonic Acid (SDA) in Modified Soybean Oil by Lipase-Mediated Acidolysis Leslie Kleiner • Luis Va ´zquez • Casimir C. Akoh Received: 1 September 2011 / Revised: 18 January 2012 / Accepted: 18 January 2012 / Published online: 4 February 2012 Ó AOCS 2012 Abstract The objective of this work was to synthesize a structured lipid (SL) enriched in stearidonic acid (SDA, C18:4 x-3), from modified soybean oil (MSO) originally containing *25% SDA. Low temperature crystallization (LTC) of MSO triacylglycerols (TAG) and free fatty acids (FFA) was performed. The TAG and FFA crystallization products (LTC-TAG and LTC-FFA, respectively) had SDA contents of 48.72 and 60.78%, respectively. Enzymatic acidolysis between MSO and LTC-FFA was studied uti- lizing Novozym 435 and Lipozyme TL IM as biocatalysts. Substrate molar ratio, incubation time, solvent, and enzyme load were explored. Equilibrium was reached at 96 and 48 h for Novozym 435 and Lipozyme TL IM-catalyzed reactions, respectively. The best conditions from these studies were also applied to the acidolysis of LTC-TAG and LTC-FFA. Utilizing Lipozyme TL IM and solvent free conditions, SLs with SDA contents of 37.61 ± 1.00% (20.86 ± 6.48% at sn-2 position) and 53.46 ± 1.85% SDA (36.37 ± 3.14% at sn-2 position) were obtained from the acidolysis reaction between MSO and LTC-FFA, and LTC- TAG and LTC-FFA, respectively. Compared to the original SDA content of MSO, this process leads to a 52 and 116% increase in SDA content, respectively. Keywords Acidolysis reaction Á Stearidonic acid Á Winterization Á Structured lipid Á Interesterification Introduction The long chain polyunsaturated fatty acids (LCPUFA), eicosapentaenoic acid (EPA, 20:5 x-3) and docosahexae- noic acid (DHA, 22:6 x-3), have long been associated with many health benefits. These LCPUFA have been found to modify the expression of inflammatory genes, thus becoming potentially powerful antiinflammatory agents [1], able to reduce the incidence of cardiovascular disease in epidemiological and clinical trials [2], and inhibit car- cinogenesis [3]. Stearidonic acid (SDA) is another LCPUFA, and it is a metabolic intermediate in the conversion of a-linolenic acid (ALA, 18:3 x-3) to EPA and DHA [4]. The conversion from ALA to SDA occurs via the rate limiting enzymatic activity of D6 desaturase. However, most ALA appears to undergo oxidation before the conversion to SDA can take place [4]. In contrast to ALA, when SDA enters the metabolic pathway no conversion via D6 desaturase is needed. Therefore, SDA works as a ‘‘pro-EPA’’ fatty acid that can be rapidly converted to EPA [4]. In addition to its health benefits, when used as a functional food component, SDA is less susceptible to lipid oxidation, which leads to the formation of undesirable free radicals, aldehydes and off-flavors, than the more unsaturated EPA and DHA [5]. Based on its ease of conversion to EPA and its physical properties, producing a structured lipid (SL) enriched in SDA would be of interest to nutritionist and food industry in order to increase the availability of EPA in the western diet, as well as to improve the shelf life and sensory characteristics of functional foods enriched in LCPUFA. Sources of LCPUFA include fish and other marine life; however, the quantities present are quite low. EPA and DHA comprise 15–20% of the total fatty acid profile of fish, while SDA represents 0.5–2% of the fatty acids [6]. L. Kleiner Á L. Va ´zquez Á C. C. Akoh (&) Department of Food Science and Technology, University of Georgia, Athens, GA 30602-2610, USA e-mail: cakoh@uga.edu 123 J Am Oil Chem Soc (2012) 89:1267–1275 DOI 10.1007/s11746-012-2022-1