Study On The Application Of Oil-soluble Natural Antioxidants In Grape Seed Oil And Walnut Oil

Oil oxidation is one of the leading causes of the spoilage of oil and oily food. The products of oil oxidation not only affect the flavor and color of oil and oily food, but also will produce many toxic and harmful substances that will threaten the health of those who eat the food. Grape seed oil and walnut oil are two kinds of small varieties of oil, because of their high nutritional value, and contain a variety of functional health ingredients beneficial to human health, have become increasingly favored by the vast number of consumers, sales also increased year by year. Since grape seed oil and walnut oil contain rich unsaturated fatty acid, they are very likely to be oxidized and go bad during the process of processing, storage and sales, which thereby brings lots of troubles to relevant enterprises. Adding antioxidants in oily food is one of the most effective means to prolong the shelf life of oily food. However, as it is known to all, the commonly used artificially synthesized antioxidants might contain potential safety hazards. So they are banned or limited to be used due to the strong objection of people in some countries. Therefore, researches on antioxidants have gradually begun to focus on the application of natural antioxidants. With four fat soluble natural antioxidants, tea polyphenol palmitate, ascorbyl palmitate, rosemary extract and vitamin E, as the research objects, the paper studies their antioxidant effect in grape seed oil and walnut oil, and carries out appropriate compound and ratio test of them to confirm the proportioning and additive dosage of the four antioxidants in the two kinds of oils, in the hope of providing reference for the practical production of oil manufacturers. The main research results are as follows:(1) By studying the antioxidant effects of the four fat soluble natural antioxidants, tea polyphenol palmitate, ascorbyl palmitate, rosemary extract and vitamin E, in grape seed oil and walnut oil respectively, the paper makes a test to find out whether there is a synergistic effect among the four antioxidants. As shown by the result, all the four antioxidants have certain antioxidant effect in the two kinds of oil, but when vitamin E is used together with the other three antioxidants, there is not a synergistic effect as expected by the author. However, there is a synergistic effect among the other three antioxidants.(2) Based on the above preliminary screening results, the paper explores how the combined application of tea polyphenol palmitate, ascorbyl palmitate and rosemary extract in grape seed oil and walnut oil is going to prolong the shelf life of oil. The response surface method, D-optimal design, is applied to design the experiment and measure the oxidation stability of grape seed oil and walnut oil added with various antioxidants. Meanwhile, since natural antioxidants will affect the flavor of vegetable oil, the experiment also makes a sensory evaluation of the oil. A variance analysis of the experimental data is carried out and a regression model is built. The paper adopts software to control the sensory evaluation results of the vegetable oil added with antioxidants within an acceptable range and optimize the most suitable formula. The optimized formula for grape seed oil is:tea polyphenol palmitate 0.39 g/kg, ascorbyl palmitate 0.04 g/kg and rosemary extract 0.11 g/kg; the optimized formula for walnut oil is:tea polyphenol palmitate 0.40 g/kg, ascorbyl palmitate 0.02 g/kg and rosemary extract 0.15 g/kg. Verified by the oxidation stability test, this formula has a better antioxidant effect in walnut oil and grape seed oil than BHA and BHT, but its antioxidant ability is slightly worse than that of TBHQ.(3) The paper studies the variation of AV, PV, p-AnV, MDA and composition of fatty acid during the continuous heating process at a frying temperature so as to further verify the effectiveness of the optimized formula. The result shows that this formula has a significant antioxidant effect in both of the two kinds of oil. Generally speaking, the antioxidant effect is weaker than that of TBHQ, but better than that of BHA, which agrees with the verified result of oxidation stability. And it's worth noting that when this formula is applied in grape seed oil, its ability to restrain the increase of MDA and to slow the oxidation of PUFA is better than that of TBHQ.The test formula is composed of three fat soluble natural antioxidants. They are tea polyphenol palmitate, ascorbyl palmitate and rosemary extract. The formula which has been optimized is applied in the grape seed oil and walnut oil, has good antioxidant effect, can effectively extend the shelf life, and can slow the rising velocity of various physical and chemical indicators in the high temperature heating.