Enrichment of Oat Antioxidant Activity by Dry Milling and Sieving

Oats contain a range of functional ingredients; these are concentrated to a greater or lesser extent in different parts of the kernel. Dry milling of oats using roller milling offers the opportunity to produce, at a lower processing cost, fractions enriched in antioxidant activity. Oats were roller milled and the stocks separated by size using sieving; the fractions were analysed for compositional differences. A clear difference was seen between the larger particles, which were richer in bran and its associated components, and the smaller, starch-rich particles, with a natural cut-off point occurring at 420 μm. This established the feasibility of using dry milling and sieving oats to yield enriched fractions. Oats (cv. Gerald) from a variety of sources were dehulled then milled once and fractionated to yield a bran-rich fraction (>420 μm) and a starch-rich fraction (<420 μm). Polar lipid extracts were derived from these fractions and their antioxidant activity measured by chemiluminescence (CL). Bran-rich fractions had significantly higher antioxidant activity than the corresponding starch-rich fraction and appeared to have a more potent population of phenolic antioxidant compounds.