Valuation of brewer's spent grain using a fully recyclable integrated process for extraction of proteins and arabinoxylans

Abstract

The objective of this work was to design an integrated process to valuate brewer's spent grain (BSG) proteins and arabinoxylans (AX) to be used as food ingredients. For this purpose, a sequential extraction of proteins and AX from BSG with increasing alkali (KOH or NaOH) concentrations of 0.1 M, 0.5 M, and 4 M, was optimized. A ratio of 1:2 (w/v) (weight of BSG by volume of alkali solution) at room temperature for 24 h was preferred to minimize reagents and energy consumption. To fully integrate the process, alkaline extracts were acidified to pH 3 with citric acid, to obtain the protein-rich fractions. The AX were recovered by ethanol precipitation and citric acid and ethanol were recycled. This integrated extraction process allowed a yield of 82-85% of the BSG total proteins and 66-73% of total AX with formation of a cellulose rich residue almost devoid of nitrogen.