Effects of chemical, enzymatic and mechanical treatments on the phenolics and water holding capacity in wheat bran.

Abstract

Epidemiological studies have demonstrated that consumption of whole grain products is beneficial for human health due to its high dietary fiber content, and the consumption of fruits and vegetables can prevent chronic disease due to their high antioxidant activity. However, whole grain is also a good source of antioxidant, which has been underestimated by literature because most antioxidants in grains exist in their bound form, which cannot be detected using previous analysis methods. With the development of new approach to analyze the bound phenolics, scientists find the bound phenolics can take up almost as high as 70-80% of the total phenolics. Wheat bran is a good source of dietary fiber and also phenolics. The phenolics in wheat bran are mainly ferulic acid, which is bound to arabinose, the side chain of arabinoxylans, through ester linkage. The bound phenolics reduce the bioactivity and bioaccesibility of wheat bran. Therefore, releasing them from the complex polysaccharides structure is beneficial for the functionality and bioactivity of wheat bran. This objective of this study is to optimize the conditions to improve the bioavailability of free phenolics from wheat bran using combined physical, chemical, thermal, and enzymatic treatments. The treatments include alkaline treatment, enzymatic treatment, high shear mixing, and high-pressure homogenization. In this study, the optimal conditions of enzymatic treatment and combined alkaline and enzymatic treatments were evaluated. The phenolics acids content, flavonoids content, ferulic acid content and the water holding capacity were determined in processed wheat bran. Results showed that alkaline treatment was the most efficient in releasing bound phenolics in wheat bran due to its strong hydrolysis capacity of cleaving the ester linkage. Enzymatic treatment was the most efficient in releasing flavonoids in wheat bran due to its effects on opening the polysaccharide structure. Mechanical treatments helped to reduce the particle size and opened the polysaccharide structure and improve the functionality and bioactivity of wheat bran as well.