Date of Award
Doctor of Philosophy
Food Science and Human Nutrition
Soybean oil (SBO) is an oxidatively unstable oil, largely because of the high concentration of linoleic acid (18:2) and linolenic acid (18:3). The unsaturated fatty acids, oleic acid (18:1), 18:2, and 18:3 in SBO oxidize in a ratio of 1:10.3:21.6. To improve oxidative and flavor stability, the SBO may be hydrogenated to reduce the concentration of PUFA (and increase the saturated FA); however, trans fatty acids (t FA) are formed and saturated fatty acids are increased during this process. There are health concerns over the consumption of a diet high in trans FAs and high in the ratio of saturated fatty acids to PUFA. Lowering the 18:3 content to a level similar to that obtained by partial hydrogenation, but without trans formation and increasing saturation has been objectives of plant breeders. A diet high in monounsaturated has been shown to help reduce health risks. Elevating 18:1 in seed oils has become more and more common.;The objectives of this study were to (1) study the effects of two low levels of 18:3 concentration (~1.0% and 2.2%) on the oxidative and flavor stabilities of SBO and (2) determine the optimum percentage of oleic acid (OA) in six SBOs (including high-oleic SBO (79%OA), conventional SBO (control), three blended oils containing 36.9%, 50.7%, and 64.7%OA, abbreviated as 37%OA, 51%OA, and 65%OA, respectively, and a low-linolenic (LL, contained 1.4% linolenic acid) SBO, to obtain maximum frying stability while retaining good flavor potential.;In general, results of the storage study suggested that the SBO containing 1.0% 18:3 had generally significant better oxidative and flavor stability during storage at 21 and 32°C than did SBO contained 2.2% 18:3. Results of the frying study suggested that the order of oxidative stability of the six oil treatments was: 79%OA > 65%OA > 51%OA > LL ≥ 37%OA > Control, and that the order of flavor stability and eating quality of foods fried in them was: LL ≥ 79%OA > 65%OA > 51%OA > 37%OA > Control.;These findings should help soybean breeders more precisely decide compositional targets to produce SBO that have desirable properties.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu
Su, Caiping, "Fatty acid composition of oils, their oxidative, flavor and heat stabilities and the resultant quality in foods " (2003). Retrospective Theses and Dissertations. 1466.