Air classification modifies the susceptibility of Brewer's spent grain to enzymatic hydrolysis and the protein content and functional properties of derived hydrolysates

Abstract

Brewer's spent grain (BSG), a residual output from beer production, is abundant in protein yet remains largely underutilized. This study investigates the separation of BSG into fine (FF) and coarse fractions (CF) using air classification. At an optimal frequency of 60 Hz, the FF achieved a 62.63 % yield and 80.30 % protein recovery, characterized by a smaller mean particle size of 27.31 μm and enhanced structural flexibility. In contrast, the CF, with a larger mean particle size of 259.46 μm, exhibited superior water- and oil-holding capacities and greater gastrointestinal digestibility due to its composition and structure. Enzymatic hydrolysis of these fractions revealed that FF hydrolysates had higher protein recovery and improved foam and emulsion stability, while CF hydrolysates showed a higher degree of hydrolysis and superior foaming and emulsifying properties. These findings suggest that air classification followed by enzymatic hydrolysis is an effective strategy for fractionating BSG into fiber-rich and protein-rich components, facilitating the development of BSG into diverse food products with distinct nutritional and functional benefits.