Abstract
Brewers' spent grain (BSG) is the most abundant byproduct of the brewing industry, rich in dietary fiber and proteins but limited in bioaccessible phenolics due to their entrapment in the lignocellulosic matrix. In this study, solid-state fermentation (SSF) using Aspergillus oryzae was employed to enrich the phenolic profiles and antioxidant capacity of BSG, followed by its integration into functional composite flours. Over a 120-hour fermentation period, the temporal production of hydrolytic enzymes (xylanase and beta-glucosidase) was correlated with the release of free phenolic acids. SSF significantly enhanced the total phenolic content (TPC) by 2.4-fold, peaking at 72 hours (7.42 mg gallic acid equivalents per gram). HPLC analysis revealed a substantial increase in free ferulic and p-coumaric acids, which directly corresponded to improved DPPH and ABTS radical scavenging activities. Fermented BSG (FBSG) was incorporated into wheat flour at substitution levels of 5%, 10%, 15%, and 20% (w/w). Rheological evaluation of the composite flours demonstrated increased water absorption and mixing tolerance with higher FBSG substitution. Sensory analysis of baked crackers revealed that a 10% substitution level was highly acceptable, providing a twofold increase in dietary fiber and antioxidant activity compared to control crackers. This study demonstrates a sustainable, bioprocess-driven strategy to upcycle industrial food byproducts into functional food ingredients.
