Extractability and characteristics of proteins deriving from wheat DDGS

•Aqueous ethanol conditions enhanced prolamin extraction compared to alkaline ethanol.•Thermally processed DDGS demonstrated low protein extractability.•Wet solids were the most suitable material for protein extraction in 70% ethanol.•Wet solid extracts had higher glutamic acid and proline content than DDGS.•Solid residues after protein extraction had high carbohydrate content (50%).

Wheat Distillers’ Dried Grains with Solubles (DDGS) and in-process samples were used for protein extraction. Prolamins were the predominant protein components in the samples. The absence of extractable α- and γ-gliadins in DDGS indicated protein aggregation during the drum drying processing stage. Prolamin extraction was performed using 70% (v/v) ethanol or alkaline–ethanol solution in the presence of reducing agent. DDGS extracts had relatively low protein contents (14–44.9%, w/w), regardless of the condition applied. The wet solids were the most suitable raw material for protein extraction, with recovery yields of ∼55% (w/w) and protein content of ∼58% (w/w) in 70% (v/v) ethanol. Protein extracts from wet solids were significantly rich in glutamic acid and proline. Mass balance calculations demonstrated the high carbohydrate content (∼50%, w/w) of solid residues. Overall, the feasibility of utilising in-process samples of DDGS for protein extraction with commercial potential was demonstrated.