Physicochemical properties, bioactive ingredients, and antioxidant activity of cheonggukjang added with brewer’s spent grain

Brewer’s spent grain (BSG), a major by-product of the brewing industry, is often discarded despite its high nutritional and functional components. This study aimed to utilize BSG as a food material by incorporating it into cheonggukjang. The physicochemical properties, bioactive components, and antioxidant activity of cheonggukjang were measured with varying BSG addition ratios. There were no significant differences in crude fat, crude protein, and carbohydrate contents based on BSG addition. Crude saponin and taurine contents increased with BSG, with cheonggukjang (15% BSGC) containing 15% BSG showing the highest levels at 232.52 μg/g diosgenin equivalent (DE)/g DW and 213.95 μg/g DW, respectively. Eighteen types of free amino acids were detected, and total and essential amino acid contents were highest in 15% BSGC at 17.80 mg/g DW and 12.50 mg/g DW, respectively. The addition of BSG to cheonggukjang increased the contents of reducing sugar and glutamic acid, which impart sweetness and umami, respectively. The total polyphenol content also increased with higher BSG, and IC50 values for DPPH and ABTS scavenging activities decreased, indicating enhanced antioxidant activity. As a result, it is anticipated that cheonggukjang, with improved palatability and biological activities, could be manufactured by adding BSG.