Wheat bran protects vitamin A from oxidation during storage

Food fortification is an efficient strategy to prevent vitamin A deficiency, a widely occurring health issue. However, vitamin A is rapidly degraded during food processing and storage, mainly due to oxidation. Therefore, there is a strong need for stabilising agents. In this study, we showed that wheat bran can be used as a natural, healthy and affordable stabilising agent slowing down vitamin A oxidation and lipid oxidation, which are closely related. The stabilising vitamin A-bran interaction was shown during an accelerated storage experiment (60°C, 70% relative humidity) using a model system consisting of wheat bran, soy oil and vitamin A. While vitamin A was degraded entirely after ten days of storage in the absence of wheat bran, vitamin A recovery after two weeks in the presence of native wheat bran was 10%. This increased to 70% when the wheat bran was toasted (30 min, 170°C). The more pronounced stabilising effect of toasted wheat bran may be explained by the absence of endogenous lipase activity, preventing free fatty acid production during storage. While free fatty acid production in the sample with native wheat bran resulted in accelerated vitamin A oxidation, it did not result in accelerated lipid oxidation, suggesting that vitamin A acts as an antioxidant protecting lipids from oxidation. Moreover, wheat bran antioxidants are thought to delay the oxidation of both vitamin A and lipids. In conclusion, toasted wheat bran mixed with oil and vitamin A can be used as a cost-effective and healthy aid in food fortification by providing high vitamin A stability. To successfully apply this stabilisation technique, a good understanding of the interplay between lipase activity, lipid oxidation, wheat bran antioxidants and vitamin A oxidation is crucial.