Brewer's spent grain (BSG) as an ingredient for leavened bread making: challenges and opportunities

Beer production generates a high quantity of by-products, including brewer's spent grain (BSG), spent hops, and spent yeast, which often have little to no use after brewing and are typically discarded in landfills, contributing to greenhouse gas emissions. BSG has been valorized in developing various food prototypes, such as bread, to mitigate this issue. Leavened bread is traditionally prepared using wheat flour, as wheat possesses glutelins and gliadins, which are responsible for creating the gluten network. During the gluten network formation, gas gets trapped in the structure, making bread rise. The differences in the chemical composition between BSG and wheat flour generate changes in the chemical composition of bread by improving the dietary fiber, mineral, and protein content. Additionally, incorporating BSG improves the content of bioactive compounds of leavened bread. However, the dilution of the gluten network due to the increased dietary fiber content modifies the texture of bread, consequently changing consumers' acceptability. In general, a partial substitution of up to 10 % has shown better results than using higher concentrations of BSG. This review article aims to gather and discuss the effect of incorporating brewer's spent grain (BSG) into bread, focusing mainly on the impact of the BSG on the bread texture, bioactive compounds, and sensory analysis.