21 Oat fractions and products as sources of phenolic antioxidants.

C. L. EMMONS and D. M. Peterson. USDA, ARS, Cereal Crops Research Unit, Madison, WI 53705.

Antioxidant activity and phenolic compounds from extracts of oat (Avena sativa) fractions and products were measured. Seven commercially processed oat products from one cultivar and whole oats, groats, and hulls from four cultivars were extracted with 80% ethanol. Alcohol-extracted flour from whole oats, groats, and hulls was hydrolyzed with either NaOH or HCl and extracted with ethyl acetate. All solvents were removed by vacuum and extracted components were dissolved in methanol. Extracts were tested for inhibition of linoleic acid oxidation (AOA) and total phenolic content (TPC). Phenolic compounds were separated by HPLC and identified and quantified via external standards. AOA of ethanol extracts from groats were higher than AOA of hull or whole oat extracts. Groats were higher in caffeic acid and tentatively identified avenanthramides (AVS), whereas hulls were higher in most other components. Hydrolysis released phenolic components with AOA. Extracts from hulls treated with NaOH had the highest AOA of all fractions and hydrolysis methods tested. AOA of this fraction was most highly associated with the levels of AVS and vanillin. Extracts from acid hydrolyzed fractions had lower AOA, TPC, and levels of phenolic components than extracts from NaOH hydrolyzed samples or ethanol extracts. Commercial processing of oats, such as drying, steaming, rolling, or grinding to flour, reduced TPC of oat extracts 16– 22%, with no significant change in AOA.