Effect of Physical Separation with or without Ultrasound Application on Brewers’ Spent Grain to Obtain Powders for Potential Application in Foodstuffs

Brewers’ spent grain (BSG) is the major by-product of beer production (70-80% moisture) and the feasibility of its application in foodstuffs depends primarily on its drying. Our objective was to evaluate the effect of physical separation with or without ultrasound application on color, total phenolic content (TPC), antioxidant activity, proximate composition, total dietary fibers, and particles size distribution of BSG powders. From wet BSG (W), two processes, without (A) or with (B) ultrasound, encompassing pressing, convective air-drying, sieving, fraction separation, and milling were evaluated. Powders A1, A2, B1 and B2 were generated. The total color difference compared with W increased throughout both processes, ranging from 1.1 (B1 x A1) to 5.7 (B1 x A2). No significant difference was observed for TPC, while lower antioxidant activity (ABTS+) was observed for process B powders, especially for B2, likely due to the release of antioxidant compounds to the liquid during pressing after ultrasound application. Nevertheless, process B powders showed higher content of total dietary fiber (p < 0.05). In conclusion, process B, with ultrasound application, may be interesting for further extraction of soluble fibers. However, the developed process A may be feasible for industrial and craft brewers, and further studies regarding the effect of their application in foods should be encouraged.