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.