THE EFFECT OF ANTIOXIDANTS ON THE OXIDATION PROPERTIES OF VEGETABLE OILS DURING DEEP FRYING

Author

• Tamany M. Alanezi, Southern Illinois University CarbondaleFollow

Date of Award

5-1-2026

Degree Name

Doctor of Philosophy

Department

Agricultural Sciences

First Advisor

AbuGhazaleh, Amer

Abstract

In food safety and quality, as well as related fields, the oxidative stability of frying oils has always been a field of study for several reasons. First, the impact on human health was directly dependent on the oil’s temperature, origin and other characteristics of the oil. Second, the shelf life of the product under specific cooking conditions also varied significantly. In three separate studies reviewed in this dissertation, the effects of blending refined oils with antioxidants, both natural and synthetic, on oxidative stability were assessed in detail using frying simulations.One of them assessed the effectiveness of blending refined corn oil with antioxidant-rich oils, including black cumin, blueberry, sesame, olive, and pomegranate oils, in a ratio of 85:15. The blends were used to fry falafel at a temperature of 175 ± 5ºC for a total of 12 hours and then analyzed for several parameters, including acid value, free fatty acids, viscosity, and others. In this case, pomegranate and olive oils showed the best results, which was reflected in better resistance to oxidative aging compared to other combinations. The protective effect was reflected in the reduced formation of trans-fatty acids and less pronounced degradation of unsaturated fatty acids, such as linoleic acid (C18:2) and linolenic acid (C18:3) . Accordingly, these products, due to the obtained characteristics, have proven themselves to mitigate the detrimental effect of high temperature frying on the quality of the oil. Focusing on oxidative stability during deep frying, the second study combined corn oil with olive oil in different proportions and added turmeric essential oil to the mixtures as a natural antioxidant. The methodology covered 36 cycles and again showed a significant improvement in oxidative parameters for mixtures enriched with olive oil. A similar result was shown by turmeric oil, again in terms of acid value, peroxide value, p-anisidine value, and fatty acid profile, which were also assessed in the first study. The beneficial properties of turmeric oil not only suppress the formation of harmful trans fatty acids but also better preserve the vital unsaturated fatty acids. The main thesis of the work, reflecting the position of the authors, is the emphasis on the use of naturally occurring antioxidants such as turmeric oil with olive oil as a viable alternative to synthetic compounds due to the functionally beneficial benefits for health and cooking. Finally, the latest work assessed the oxidative degradation of refined canola oil during frying, focusing on mixtures with olive oil in a ratio of 95:5 and the addition of either synthetic antioxidants such as butylated hydroxytoluene (BHT) or natural oils of turmeric, basil, rosemary, and oregano. This indicator was reduced in all cases, both synthetic and natural, but the strongest effects were found in oregano and turmeric oils. Significant improvements were observed in oxidative stability indices, fatty acid retention, and reduced formation of trans fatty acids, especially trans-C18:1. Again, like the previous work, the study highlights the potential of natural antioxidant solutions in the food industry, providing comparable efficiency with traditional synthetic agents and calling for the use of natural products instead of artificial solutions. In conclusion, this dissertation or aspect is the most evident feature inside the setting of all three chapters. Illustration of the transformative potential of oil blends with natural antioxidants demonstrates a clear potential in solving the problem of oxidative degradation during frying. This aspect is manifested by the general synthesis in three planes. Firstly, in all the studies reviewed, blends with oils rich in antioxidants, such as olive, pomegranate, and turmeric, showed increased oxidative stability, reducing harmful indicators of the total oxidation number and peroxide value. Secondly, competition with synthetic additives again speaks in favor of natural ones. Finally, the overall focus is on consumer health due to the softening of the breakdown of unsaturated fatty acids and the reduction of the formation of trans fats.