Protein enrichment of oat flour by fine milling and air classification

Dry fractionation is a sustainable and mild alternative to wet extraction for producing protein-enriched ingredients. This study evaluated the dry fractionation potential of two oat cultivars through fine milling and air classification. Preliminary trials showed that conditions optimized for starch-rich pulses were not directly applicable to oats, partly due to their smaller starch granules. Therefore, in this study, we systematically varied the classifier wheel speed during milling (5000–8000 rpm) and air classification (12,000–18,000 rpm), with specific combinations applied to each cultivar, to identify optimal parameters for protein enrichment. Pre-milling and hexane-based defatting were necessary to enable fine milling. Increased classifier wheel speed during milling improved starch disentanglement and enhanced protein concentration in the fine fraction after air classification. Classifier wheel speeds of 8000 rpm for milling and 14,000 rpm for air classification produced oat protein concentrates with up to three times higher protein content (36.5–40.0 g/100 g dry matter) than the initial groats, a mass yield of 1.4–3.0 %, and protein recovery of 7.9–10.4 % across cultivars. Compositional analysis showed distinct macronutrient distributions between the fine and coarse fractions, and relative to two commercial oat protein concentrates, suggesting they could be targeted for different food applications. Although promising, dry fractionation of oats still requires a defatting step, which limits its overall sustainability. Future work should prioritize developing more sustainable defatting strategies and evaluating the techno-functional properties and protein digestibility of the resulting oat ingredients. • Milling and air classification can triple oat protein content in oat flours. • Classifier speed boosts protein enrichment but lowers protein recovery. • Pulse-based dry fractionation settings are not optimal for oat protein enrichment. • Defatting is essential for efficient fine milling of oat flours. • Fine and coarse fractions may serve as functional oat-based ingredients.