Submitted to: Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/27/2006
Publication Date: 10/2/2006
Citation: Nystrom, L., Achrenius, T., Lampi, A., Moreau, R.A., Piironen, V. 2007. A comparison of the antioxidant properties of steryl ferulates with tocopherol at high temperatures. Food Chemistry 101, p.947-954.
Interpretive Summary: Foods that contain vegetable oils and other lipids are vulnerable to oxidation and their shelf life can be extended if they contain sufficient levels of natural antioxidants such as vitamin E (alpha tocopherol). In addition to alpha tocopherol, some vegetable oils (such as rice bran oil and corn fiber oil), contain a second type of natural antioxidant, steryl ferulates. Some experts have suggested that combining these two types of natural antioxidants may result in greater antioxidant benefit than the sum of the contribution of both components individually. The current study was designed to test this hypothesis under baking and frying conditions. The conclusion was that both types of antioxidants protected the oil from oxidation and the net effect was equivalent to the contribution of the sum of the two components. However, steryl ferulates were degraded at a lower rate than alpha-tocopherol, so if they were used in frying oils, they would be effective for a longer period. These results indicate that adding natural steryl ferulates to frying oils may be an effective way to help to extend their useful lifetime in commercial frying operations, resulting in a lower cost to the user.
Technical Abstract: Steryl ferulates (esters of phytosterols and ferulic acid) have long been studied for their health-promoting properties partially owing to their capacity to inhibit oxidation. The good heat stability of rice bran oil has been attributed to its high content of steryl ferulates and tocopherols. It has been suggested that these compounds have a synergistic effect as antioxidants. In this model experiment we determined the capacity of sitostanyl ferulate and a-tocopherol (alone or as a mixture) to prevent polymerization of high oleic sunflower oil at 100°C and 180°C. The formation of polymers was significantly reduced at both temperatures and by both antioxidants as well as their mixture, though no synergistic effect was seen. Further, we followed the decrease in antioxidant levels and found that sitostanyl ferulate was degraded at a lower rate than a-tocopherol indicating that sitostanyl ferulate is a promising antioxidant for high temperature applications.