Valorisation of Brewers Spent Grain from Nigerian Sorghum Beer for Bioactive Compound Extraction and Functional Food Application

Brewers spent grain, the primary by-product of the brewing industry, is generated in substantial quantities by sorghum-based beer production in northern Nigeria and represents an underutilised source of dietary fibre, arabinoxylans, and phenolic compounds with functional food application potential. This study develops a comprehensive valorisation framework for brewers spent grain from three major sorghum beer breweries in Kano, Kaduna, and Jos, encompassing bioactive compound extraction, structural characterisation, and functional food application development. The theoretical contribution is a mass integration model for brewery by-product valorisation that quantifies the theoretical maximum recovery of ferulic acid, arabinoxylans, and protein hydrolysates from brewers spent grain using sequential extraction processes. Ferulic acid was extracted by alkaline hydrolysis and characterised by high-performance liquid chromatography with mass spectrometry. Arabinoxylan was extracted by aqueous alkaline extraction and characterised by nuclear magnetic resonance spectroscopy, size exclusion chromatography, and dynamic oscillatory rheometry. Protein hydrolysates were produced by alcalase hydrolysis and evaluated for degree of hydrolysis, antioxidant activity, and angiotensin-converting enzyme inhibitory activity. The extracted bioactives were incorporated into sorghum-based flatbread at optimised levels, and the functional properties, sensory quality, and in vitro digestibility of the fortified products were evaluated. Techno-economic analysis quantified the economic potential of the valorisation strategy. The study provides an original integrated valorisation framework with specific application to the Nigerian brewing by-products sector. Keywords: brewers spent grain, sorghum beer, valorisation, ferulic acid, arabinoxylan