Debranning as a tool for developing innovative milling fractions: application to purple common wheat

The production of food enriched in dietary fiber or antioxidant molecules is a current challenge to satisfy the recommended daily intake of these micronutrients. Cereal products, due to their consumption as staple foods, might be effective for achieving this purpose. However, this kind of incorporation may be detrimental to the properties of final products. Also, conventional milling processes does not consider the selective recover of these compounds, that are frequently lost in bran or germ. In this study, we investigated the effects of a debranning pre-treatment on the antioxidant and fiber content of commercial purple common wheat, an antioxidant-rich variety. Grains were hydrated and underwent two subsequent debranning steps that removed 3.7% and 9.7% of the starting material. Debranned grains were then milled in a lab-scale conventional milling system to obtain three fractions: flour, middlings, and bran. Non-debranned grains were milled as a control. When compared to conventional milling, milling of debranned grains led to a decreased content of dietary fiber in the bran and flour fractions, whereas an increase in dietary fiber was assessed in the middlings. The pre-treatment increased the ratio between soluble and insoluble fiber in both middlings and bran from the milling step, and both fractions were also rich in total phenolic compounds. Debranning did not affect the level of starch damage. After debranning and milling, alpha-amylase activity was associated mostly with the bran, and was essentially absent in the removed layers. Debranning allows removal of the outer-most layers of the grain that are reportedly the most detrimental for the technological performance of grains. Milling of debranned grains provided fractions with a very high concentration of functional compounds. Thus, these fractions may be used in low amounts as ingredients to exploit their positive nutritional properties while minimizing their detrimental technological effects.