This research aimed to conduct a comparison of 8 different forms of brewery spent grain (BSG) on their polyphenolic content and antioxidant capacity as part of their potential as a functional food ingredient. The BSGs were dried until they reached a stable weight, grounded to pass through a 385 µm sieve and were vacuum packed in non-transparent packaging for further analysis. The results showed that BSG contained a high dietary fiber content which was dominated by a insoluble dietary fiber level of about 38.0–43.9% and a soluble dietary fiber content of about 3.9–9.6%. There were three groups of polyphenolic identified: flavan-3-ols, phenolic acids and flavonols at quantities of 362.1–1165.7 mg/kg, 65.8–122.5 mg/kg and 3.6–13.8 mg/kg, respectively. Antioxidant capacity was examined using an in vitro assessment: the 2,2′-Azinobis-(3-Ethylbenzthiazolin-6-Sulfonic Acid) (ABTS) capacity ranged from 0.086 to 0.241 mmol Trolox/100 g while the ferric reducing antioxidant potential (FRAP) capacity ranged from 0.106 to 0.306 µmol TE/100 g. In conclusion, BSG as a brewery waste can potentially be used as a functional food ingredient due to its properties. It is suggested that further studies are needed to explore BSG’s impact on the development of functional food products.

Keywords: brewery spent grain; valorization; agricultural by-products; functional food; dietary fiber; polyphenolic compounds; antioxidant