Wheat bran: from by-product to new food products?

The agri-food sector generates significant quantities of by-products and waste, the disposal of which produces negative environmental and economic impacts. The adoption of an industrial symbiosis approach to transfer and share resources between dissimilar industries reflects recent European strategies on decoupling economic growth from environmental impacts. The durum wheat bran was suplied by an Italian producer. Five different bran layers were selected, isolated according to their sieving mesh size during the flour milling process and identified with an increasing number (L1-L5) from the outter to the inner layer, respectively. From each layer, the lipid fraction was extracted by soxhlet procedure1, using petroleum ether (40-60 °C) for 6 h, and the humidity was determined by means of a gravimetric method. Main lipid classes (triacylglycerols (TAG), diacylglycerols (DAG), monoacylglycerols (MAG), free and esterified sterols, free fatty acids (FFA)) and total fatty acid (FA) composition2 of each lipid extract, were also determined. The humidity content was higher (~ 15%) in L1 with respect to the other layers, showing the lowest amount in L5 (~ 14%). The lipid content ranged from 8% (expressed in dry basis) (L3) to 5% (L1, L4 and L5). The lipid matter was mainly constituted by FFA (89–94% of total fat), followed by total sterols (3.4–4.0% of total fat), DAG (1.5–4.0% of total fat), TAG (0.6–2.4% of total fat) and MAG (0.7–1.1% of total fat). In general, FFA decreased from the outer to the inner layers, whereas TAG showed the opposite trend; this could be ascribed to a lipolytic phenomena related to an on-going fermentation process. Total FA were mainly constituted by polyunsaturated fatty acids (PUFA; 53–58% of total FA), followed by monounsaturated fatty acids (MUFA; 21–24% of total FA) and saturated fatty acids (SFA; 17–20% of total FA). More than 50% of total FA was represented by linoleic acid (C18:2 n-6; 51–54%); oleic acid (C18:1 n-9) ranged from 19% (L1) to 22% (L5), while the palmitic acid (C16:0) content was about 17% of total FA without significant differences among bran layers. This preliminary study demonstrated that by-products from durum wheat bran could represent a source of added-value edible oil. The extracted oil could be potentially used as a functional ingredient due to its high content of PUFA and low amount of SFA, with an important contribution of linoleic acid (essential fatty acid). However, to ensure its stability and the preservation of its nutritional and sensory characteristics, a shelf-life study of the functional bran oil is necessary.