Nutritional and functional properties of durum wheat bran protein concentrate

Background and objectives Plant industrial by-products are relatively low cost and rich in organic material. Although these by-products are a good source of various nutritional compounds, they represent the main disposal problem for the food industry. Wheat bran, one of the main by-products of the wheat milling industry, contains more than 15% high-quality proteins. However, these proteins are present in a form which is poorly digested as they are enclosed within a matrix of cell wall polysaccharides. About 15.5 million tonnes of usable protein could be recovered from bran if a commercial extraction process can be made viable. The purpose of this work was to extract protein from durum wheat bran using an alkaline acid method to study its nutritional and functional properties with the goal of using it as a fortifying material in cereal-based foods such as pasta and bread. Findings Durum wheat bran protein concentrate (WBPC) was prepared by using an alkaline extraction method (pH 9.5 for two hours) followed by isoelectric precipitation (pH 4.2). Chemical, nutritional, and functional properties of WBPC were obtained. WBPC had a protein content of similar to 61% (protein yield 20.5%-24.8%), containing also lipids, fiber, and small quantities of starch. WBPC was enriched in phytosterols compared to wheat bran (11.59 vs. 5.14 mg/g) with beta-sitosterol the predominant (4.37 mg/g). WBPC was also enriched in all the amino acids compared to bran, especially lysine and threonine. WBPC retained some phenolic acids, but at an eightfold lower quantity than in bran and retained about half the antioxidant activity (DPPH) of bran. WBPC showed excellent functional properties in terms of high solubility over a wide range in pH and good water and fat absorption capacity. The main protein components were albumin and globulin proteins. Conclusion The extraction method used produced a protein concentrate in reasonable yield with high protein content enriched in essential amino acids and phytosterols compared to wheat bran with good functional properties and phenolic acids and antioxidant potential. Significance and novelty The nutritional and functional properties of WBPC make it a promising ingredient for various food products such as cereal and baked foods, processed meat, and beverages.