18E-8 |
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C. M. LIYANA-PATHIRANA, Dept. of Biology, Memorial Univ. of Newfoundland, 300 Prince Phillip Dr., Saint John's, NF A1B 3X9, Canada and F. Shahidi, Dept. of Biochemistry, Memorial Univ. of Newfoundland, 300 Prince Philip Dr., Saint John's, NF A1B 3X9, Canada. Pearling refers to sequential removal of bran layers from wheat kernel by friction and abrasion operations; the resultant pearled grains and by-products contain varying proportions of bran. The objectives of this study were to determine the effects of pearling on the phenolic content and composition as well as antioxidant activity of pearled wheat grains and their by-products. Whole grains were pearled 10-50%, in 10% increments, and pearled wheat and corresponding by-products were collected separately at each level and extracted into 80% ethanol. The total phenolic content in the extracts was 9.8-15.9 and 9.6-26.8 mg sinapic acid equivalents/g crude extract, respectively, for pearled grains and by-products. The corresponding total antioxidant capacities were 47.6-86.9 and 76.8-108.1, μM Trolox equivalents. The HPLC analysis of wheat extracts revealed the presence of vanillic, p-coumaric, ferulic and sinapic acids, the latter being predominant. The extracts of pearled wheat grains and their by-products exhibited a dose-dependent activity against hydroxyl radical-mediated cleavage of DNA ranging from 55-72% and 69-91% of retention of pBR 322 DNA, respectively, at 6mg/mL concentration. Oxidative stability of stripped-corn-oil in presence of extracts of pearled grains and their by-products was increased by a factor of 1.38-1.46 and 1.47-1.93, respectively and corresponding oxygen radical absorbance capacities were 1.21-1.64 and 1.69-1.92 ìmol Trolox equivalents/ mg. The results obtained by a photochemiluminescence assay were 48.0-92.6 and 67.3-116.7 nmol ascorbic acid equivalents/mg and 52.4-86.0 and 87.2-124.0 nmol tocopherol equivalents/mg for water- and lipid-soluble antioxidants, respectively. Thus, increased pearling levels resulted in a decrease in the antioxidant compounds as well as their activities. The by-products always possessed a greater antioxidant potential than their corresponding grain products. Thus, endogenous antioxidants can be preserved when wheat is consumed as whole grains.
Session 18E, Nutraceutical & Functional Foods: General I
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |