Changes in the Oxidation Stability of Walnut Blend Oil at Different Cooking Temperatures
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Abstract:
In order to maintain nutritional and thermal stability of walnut oil during thermal processing, walnut oil was blended with flaxseed oil, peanut oil, safflower oil and rapeseed oil. According to the intake of fatty acids recommended by the Chinese Nutrition Society, the proportion of each raw material in walnut blend oil was calculated by a mathematical model. Nutritionally balanced walnut blend oils containing 1%, 5%, 15% and 25% walnut oil, respectively, were developed. The changes in peroxidation value, anisidine value and total oxidation value as well as quality and fatty acid content of walnut oil were analyzed at the temperatures of Chinese cooking. The results showed that the ratios of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) of the four kinds of blended oils were close to 0.27:1:1, and n-6/n-3 fatty acids were all within the recommended value range of (4~6):1, which met the human body’s requirement for a balanced intake of fatty acids. The peroxidation value, aniside value and total oxidation value of the 1%, 5%, 15% and 25% blend oils increased with an increase of heating temperature, and the PUFA/SFA ratio at 210 ℃ decreased by 0.30%, 0.39%, 0.70% and 0.96% compared with pure walnut oil, respectively. Compared with the pure walnut oil, the MUFA/PUFA ratio increased by 0.03%, 0.07%, 0.11% and 0.14%, respectively. The ratio of n-6/n-3 fatty acids ranged within 4.42~5.76, with the peroxide value, anisidine value and total oxidation value all lower than those of the pure walnut oil. These results indicate that the blending of pure walnut oil with certain oils could help to slow down the formation of oxides while improving oil’s thermal stability and maintaining a dietary balance of fatty acids.
