Ferulic acid in rye and wheat grain and grain dietary fiber
1993
Rybka, K. | Sitarski, J. | Raczynska-Bojanowska, K.
The aim of the present work was to examine the effect of cross-linking of rye and wheat arabinoxylan by ferulic acid on grain nutritive value, measured in vitro by an enzymatic test. Determination of ferulic acid was based on spectrophotometric measurements of defatted samples at 320 nm. Approximately 80% of the trans-ferulic acid, the dominant phenolic acid of rye and wheat grain, was found in the bran of both species. Total content and extractability of free and esterified ferulic acid by water, ethanol, and alimentary enzymes (soluble dietary fiber) from grain meal were significantly higher in rye than in wheat. The activity of peroxidase, the enzyme thought to be responsible for the formation of diferulic bridges, was also significantly higher in rye. Most (85-90%) of the alkaline-soluble ferulic acid in grain was localized in the insoluble dietary fiber, and only about 5% was in the soluble fraction. In spite of the higher solubility of rye arabinoxylans and the higher arabinose-xylose ratio in rye than in wheat grain, the ratio of the number of arabinose residues per ferulic acid molecule was not significantly higher in the soluble fiber of rye. Thus, cross-linking of grain hemicellulose components by ferulic bridges does not appear to contribute to the known differences in the structure, molecular weight, and nutritive properties of soluble fiber of rye and wheat.
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