I. SENSOY, R. T. Rosen, C.-T. Ho, and M. V. Karwe. Dept. of Food Science, Rutgers, The State Univ. of New Jersey, 65 Dudley Rd., New Brunswick, NJ 08901-8520
Buckwheat proteins are high in the essential amino acid lysine and therefore are a good supplement to other cereal proteins. Buckwheat protein has 92.3% of the value of nonfat milk solids and 81.5% of whole egg solids. Buckwheat protein reduces the plasma cholesterol level better than soy protein isolate. Buckwheat seeds have high content of unsaturated fatty acids.
The objective of this study was to investigate the effect of extrusion and roasting on the antioxidant activity buckwheat.
Extractions of buckwheat flour were carried out before and after roasting and extrusion. Samples were extracted with methanol followed by ethyl acetate. Folin-Ciocalteu reagent and sodium carbonate were used for total phenolic assay with gallic acid as the standard. Ethyl acetate extracts were analyzed with reverse phase HPLC. Antioxidant activity of methanol extracts of flours were determined with a free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) and results were expressed as Trolox equivalents per gram flour.
Antioxidant activity test (DPPH) showed that roasting at 200 °C for 10 min decreased the antioxidant activity slightly whereas extrusion (170°C) did not cause any change. White buckwheat flour had similar antioxidant activity as corn and whole wheat flour. Folin-Ciocalteu assays indicated that dark buckwheat flour (with hulls) had 3-4 times more phenolic compounds compared to white flour (without hulls). Roasted (200°C, 10 and 15 min) dark buckwheat flour exhibited an increase in non-polar compounds as well as degradation of polar compounds whereas extrusion exhibited increase only in non-polar compounds.
Antioxidant activity is not affected by extrusion but denatured slightly upon roasting. Buckwheat can be used as an ingredient in baked products to deliver health promoting nutraceuticals. The retention of phenolic compounds can be optimized by adjusting processing conditions.
Session 33F, Nutraceuticals & Functional Foods: Antioxidants and phytochemical analysis