This chapter includes information on the composition of soybeans, soybean oil, and other soybean lipids, especially as affected by environment, variety, and genetic modification. Other topics discussed are the physical properties of soybean oil, grading of soybeans, oil extraction, and the effect of various extraction techniques on oil quality and the various soy protein ingredients. Basic refining and processing of soybean oil includes degumming, neutralization, bleaching, hydrogenation, and deodorization, but alternative refining methods are also discussed along with soybean refinery coproducts (lecithin, deodorizer distillate, and soapstock). The major uses of soybean oil are itemized and trading rules for crude and refined soybean oil are provided. The major food products produced from soybean oil are cooking and salad oils, frying fats, mayonnaise, margarine, shortening, confectionary and imitation dairy products, and “low‐calorie fat substitutes.” The oxidative quality of soybean oil is reviewed, including flavor reversion, factors affecting oil oxidation, measures of control and measures of finished oil quality, storage and handling, and special processing for off‐quality soybean oil. The chapter concludes with a discussion of the health aspects of soybean oil, including the health effects of cholesterol, unsaturated oils, trans ‐isomers, and total fat intake.
The objective of this work was to study the frying stability of soybean oil (SBO) with reduced linoleate (18:2) and linolenate (18:3) and elevated oleate (18:1) contents. Higholeate SBO [HO SBO, 79% oleic acid (OA)] and a control (conventional SBO, 21.5% OA) were tested as is, as well as blended in different ratios to make three blended oils containing 36.9, 50.7, and 64.7% OA, abbreviated as 37%OA, 51%OA, and 65%OA, respectively. In addition, a low-linolenate (LL) SBO containing 1.4% 18:3 and 25.3% 18:1 was tested. Bread cubes (8.19 cm 3 ) were fried in each of 18 oils (6 treatments × 3 replicates). We hypothesized that stability indicators would be indirectly related to the total 18:2 plus 18:3 percentages and/or the calculated oxidizability. In general, the results were fairly predictable based on total 18:2 and 18:3 concentrations. The overall frying stability of the six oil treatments, from the best to the poorest, was: 79%OA, 65%OA, 51%OA, LL ≥ 37%OA, and the control, with respective total compositions for 18:2 plus 18:3 of 10.3, 23.6, 36.3, 59.6, 48.9, and 62.8%. The greatly reduced concentration of 18:3 in the LL SBO made it more stable than the 37%OA, even though the combined composition of 18:2 and 18:3 of LL was greater than that of the 37%OA. Blending conventional SBO with HO SBO had a profound effect on the oxidative stability index and color of the blended oils, but the values were not linearly predictable by the percentage of control in the blended oil. Other stability indices, including calculated oxidizability, calculated iodine value, conjugated dienoic acid value, and viscosity, changed in linear response to an increased proportion of the control in the blends.Paper no. J10773 in JAOCS 81, 783-788 (August 2004).KEY WORDS: Conjugated dienoic acid, free fatty acids, fried bread cubes, frying oil stability, high-oleate soybean oil, lowlinoleate soybean oil, low-linolenate soybean oil, oxidative stability, polar compounds, viscosity.Soybean oil (SBO) has a good nutritional profile because of its high proportion of unsaturated FA, but the oil has poor oxidative stability and is prone to flavor deterioration. The FAME of linoleic (18:2) and linolenic acids (18:3) in SBO oxidize quickly and are the major contributors to the poor stability of SBO (1). To improve oxidative and flavor stability, SBO may be hydrogenated to reduce the concentration of PUFA and increase the content of saturated FA; however, trans FA (tFA) are formed and saturated FA are increased during this process. Unfortunately, consumption of a diet high in tFA has been reported to raise total and LDL cholesterol and lower HDL cholesterol levels (2), and a diet having a high ratio of saturated FA to PUFA has been shown to increase serum total cholesterol (3), all of which are indicators of increased risk for cardiovascular diseases. Thus, lowering the 18:3 content to a level similar to that obtained by partial hydrogenation, but without trans formation, has been an objective of plant breeders. Various SBO with different lowered levels o...
The effects of linolenic acid (18:3) concentration, combined with TBHQ addition, temperature, and storage time, on the oxidative and flavor stabilities of soybean oils (SBO) were evaluated. During storage under fluorescent light at both 21 and 32°C, the SBO with ultra-low-18:3 concentration (1.0%, ULSBO) generally had greater oxidative stability than did SBO with low-18:3 concentration (2.2%, LLSBO). The ULSBO had about half the p-anisidine value of LLSBO throughout storage. Although the ULSBO initially had significantly greater PV and poorer (lower) sensory scores for overall flavor quality than did LLSBO, significant differences disappeared with storage. The ULSBO had a lower content of polar compounds and greater oil stability indices than did LLSBO when TBHQ was present. All oils were more oxidatively stable with TBHQ addition, but the TBHQ addition did not result in improved flavor stability early in storage. In all tests, oils stored at 32°C were less stable than oils stored at 21°C. The TBHQ had a better antioxidant capacity when the 18:3 concentration was lower. The retardation effect of TBHQ on lipid oxidation and the improved stability of ULSBO over LLSBO were more easily detected when the storage temperature was higher.Paper no. J10364 in JAOCS 80, 171-176 (February 2003). KEY WORDS:Fatty acid composition, flavor stability, linolenic acid concentration, oxidative stability, soybean oil.Soybean oil (SBO) has a good nutritional profile because of its high proportion of unsaturated FA, but SBO has poor oxidative stability and is prone to flavor deterioration. The FA linolenic acid (18:3) oxidizes very quickly and is the most important precursor of flavor deterioration in 18:3-containing oils (1,2). Hydroperoxides formed by oxidation of 18:3 can break down to many undesirable flavor compounds such as 2,4-heptadienal, 2-butylfuran, 2-and/or 3-hexenal, 2-pentenal, and butanal (3).To improve oxidative stability and flavor quality, the SBO may be hydrogenated to reduce the concentration of PUFA; however, trans FA (tFA) are formed during this process. Because of health concerns over the presence of tFA in our diets (4,5), lowering the 18:3 content to a level similar to that obtained by partial hydrogenation, but without trans formation, has been an objective of plant breeders. Another advantage to producing oils needing no additional processing is that fewer processing costs should result in more profit for farmers and processors (6). Previous studies (7-9) determined that the oxidative and flavor stabilities of oils were inversely proportional to the initial 18:3 concentration. Although considerable information is available regarding the relationship between oxidative and flavor stability of SBO and 18:3 concentration, soybean breeders need more precise compositional targets to produce SBO that have good oxidative and flavor stabilities. The objective of this research was to study the effects of two low levels of 18:3 concentration (~1.0 and 2.2%) combined with TBHQ addition, temperature, and storage time on t...
The percentages of oleate (18:1), linoleate (18:2), and linolenate (18:3) in blended soybean oils (SBO) were evaluated for their impact on flavor stability and quality in fried foods. Six SBO treatments, including a control (conventional SBO, 21.5% 18:1) and a high-18:1 SBO (HO, 79% 18:1), were tested. In addition, these two oils were mixed in different ratios to make three blended oils containing 36.9, 50.7, and 64.7% 18:1, abbreviated as 37%OA, 51%OA, and 65%OA, respectively. Also, a low-18:3 (LL) SBO containing 1.4% 18:3 and 25.3% 18:1 was tested. Bread cubes (8.19 cm 3 ) were fried in each of 18 oils (6 treatments × 3 replicates). The fresh and stored bread cubes fried in 79%OA were second to the cubes fried in LL in overall flavor quality, were the weakest in intensity of stale, grassy, fishy, cardboard, and burnt flavors by sensory evaluation, and contained the least amounts of hexanal, hexenal, t-2-heptenal, t,t-2,4-nonadienal, and t,t-2,4-decadienal in volatile analysis. Other treatments were intermediate in these sensory and instrumental evaluations, as related to their 18:1, 18:2, and 18:3 concentrations. In general, the results suggested that the overall flavor stability and eating quality of foods fried in the six oil treatments from the best to the poorest would be: LL ≥ 79%OA, 65%OA, 51%OA, 37%OA, and control. FIG. 1. Volatile compounds from (A) fresh fried bread and (B) stored fried bread. a For each volatile compound, values with label letters in common were not significantly different (P < 0.05). Y axis units: GC area count.
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