Background: In the course of production of buckwheat groats by-products are produced, such as bran and hull, which apart from high content of dietary fiber, may also constitute valuable sources of antioxidants. The aim of these investigations was to determine the antioxidant activity of extracts from by-products produced during processing of buckwheat for groats.
Material and method: Analyses were conducted on bran and hull of buckwheat cv. Kora. Extraction was run using acetone, methanol and water at room temperature for 24 h. The level of phenolics was determined spectrophotometrically with the Folin-Ciocalteau reagent, using (+) catechin as a standard. Antioxidant activity of extracts was analysed in relation to linoleic acid, running incubation for 19 h, by scavenging of stable radicals of DPPH (2,2-diphenyl-1-picrylhydrazyl) and on the basis of metal chelating ability. Recorded results were compared with the activity of BHT (butylated hydroxytoluene).
Results: The highest content of polyphenols was found in the methanol extract of hull (168.5 mg/g d.m.), which was also characterised by the best antiradical properties. The lowest content of total phenols was found for water extracts of bran after grinding and final bran, at 20.3 mg/g d.m. and 10.2 mg/g d.m. In the emulsion system the highest activity was found for methanol extracts of hull and bran after grinding (Wo = 0.89), as well as the extract of final bran (Wo = 0.85). A higher chelating ability in relation to Fe (II) ions was observed for bran extracts (after grinding - 76.1%, final bran - 62.2%) than for hull extracts (26%).
Conclusions: Extracts obtained from by-products of buckwheat were characterised by high antioxidant activity in the applied model systems.