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ABSTRACT:
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^sup 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.
Paper no. J10793 in JAOCS 81, 853-859 (September 2004).
KEY WORDS: Fried bread cubes, frying oil stability, high-oleate soybean oil, low-linolenate soybean oil, sensory evaluation, volatile compound analysis.
Although soybean oil (SBO) has a good nutritional profile, it has poor oxidative stability and is prone to flavor deterioration because of its high proportion of unsaturated FA. The FA linoleate (18:2) and, especially, linolenate (18:3) in SBO oxidize quickly and are the major contributors to the poor flavor stability of SBO (1). Hydroperoxides formed by the 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 (2). Hydroperoxides formed by the oxidation of 18:2 can break down to undesirable flavor compounds, such as hexanal, under mild conditions and 2,4-decadienal at high temperatures (2).
To improve oxidative and flavor stability, SBO may be hydrogenated to reduce the concentration of PUFA (and increase the saturated FA); however, trans FA (tFA) are...