Oxidative stability of natural and randomized high‐palmitic‐and high‐stearic‐acid oils from genetically modified soybean varieties

Abstract

The oxidative stability of soybean oil triacylglycerols (TAG) obtained from genetically modified soybeans was determined before and after chemical randomization. Soybean oil oxidative studies were carried out under static oxygen headspace at 60°C in the dark and oxidative deterioration was monitored by peroxide value, monomeric and oligomeric oxidation products, and volatile compounds. Randomization of the soybean oil TAG improved the oxidative stability compared to the natural soybean oil TAG. Oxidative stability was improved by three factors. Factor one was the genetic modification of the fatty acid composition in which polyunsaturated acids (such as linolenic and linoleic acids) were decreased and in which monounsaturated fatty acids (such as oleic) and saturated acids (palmitic and stearic) were increased. Factor two was the TAG compositional modification with a decrease in linolenic and linoleic-containing TAG and an increase in TAG with stearic and palmitic acids in combination with oleic acid. Factor three was the TAG structure modification accomplished by an increase in saturated fatty acids and a decrease in linoleic and linolenic acids at the glycerol moiety carbon 2.Research has been directed toward the improvement, through plant genetic manipulation, of the properties of vegetable oils for uses such as frying oils, salad oils, margarines, confectionery products, and baking shortenings by altering the fatty acid (FA) composition and the triacylglycerol (TAG) composition (1-6). Also, food products can be prepared from blends by randomization of vegetable oils and by interesterification of vegetable oils such as cottonseed, peanut, soybean, corn, and canola with hydrogenated soybean or cottonseed hard stocks (7). The physical properties (solid fat index and drop melting point) of the soybean oil (SBO) for food formulation requirements (margarines) were previously found to be improved after randomization. The interesterification reaction may be chemically or enzymatically catalyzed, and the result is a slight change in TAG composition and a major change in TAG structure to produce improved food products (3-7). In addition to analysis of structured fat physical properties such as melting range, solid fat index, and crystal structure as determined by dropping point, dilatometry, pulsed nuclear magnetic resonance, differential scanning calorimetry, and X-ray analyses (7), it is important to analyze TAG composition and structure. Correlation of fat physical properties can be made with TAG composition (quantity of individual TAG in the structured fat) (7). Also, it is important to know the oxidative or storage stability of the structured fat in regard to TAG composition and structure (8-12). We report here studies on the oxidative stability of SBO high in palmitic and stearic acid, which had previously been found to be suitable margarine base stock candidates after randomization. EXPERIMENTAL PROCEDURESMaterials. SBO were laboratory-refined, -bleached, and -deodorized oils (13). Non-TAG components were removed...

Oil content and fatty acid composition of soybean (Glysine max L.) genotypes evaluated under rainfed conditions of Kashmir Himalayas in India

“…Our results therefore almost corroborate with the earlier reports. It is because of high percentage of polyunsaturated fatty acids (18:2 and 18:3) that soybeans are considered to be unstable (Neff and List, 1999). Fatty acid composition is a major determinant of oil quality in oilseeds and is therefore, an important consideration for breeding programs (Daun, 1998).…”

Docosahexaenoic Acid is More Stable to Oxidation when Located at the sn‐2 Position of Triacylglycerol Compared to sn‐1(3)

“…However, Park et al [5] who also observed that chemically randomized soybean oil oxidized more rapidly than the parent oil, found that when the tocopherols level in the randomized oil was restored to the original level there was no difference in the oxidation rates, suggesting that position of the PUFA did not influence oxidative stability. On the other hand, Neff and List [25] reported that chemical randomization of high stearic soybean oil improved oxidative stability suggesting that PUFA is more stable when located at the sn-1 and sn-3 positions. Furthermore, it has been reported that oxidative stability of fish oil increases after chemical randomization [26].…”

Evaluation of Genetic Diversity and Comparison of Biochemical Traits of Soybean (Glycine max L.) Germplasm Collections

“…In addition, the high content of oleic acid, one of the fatty acid compositions, contributes to desirable odors and flavors to consumers (Neff et al 1999;Lopez et al 2000;Pham et al 2010). For this reason, continuously, breeders have tried to increase these contents.…”

“…The high content of oleic acid contributes to the oxidative stability (Neff et al 1999;Cahoon 2003;Lopez et al 2000) and increase the oil quality (Wilson et al 2001). …”