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Wheat Pentosans. I. Cultivar Variation and Relationship to Kernel Hardness

1989; Volume: 66; Issue: 5 Linguagem: Inglês

Byung Hee Hong, G. L. Rubenthaler, R. E. Allan,

Phytase and its Applications

Cereal Chem. 66(5):369 373 A wide range of water-soluble, enzyme-extractable, and total pentosans were correlated with grain hardness, suggesting that the differences in was found among the hard, soft, and club wheat market classes. A hardness from one environment to another could be due to the correlated significant correlation was observed between each of the three types for variations of protein and water-soluble pentosans. However, genotype pentosans and kernel hardness. Hard wheats had significantly higher levels variance was 1.6 times greater than that of environment, which indicated of water-soluble pentosans than soft or club wheats. Club wheats were significant proportions of heritability in the total variations of waterconsistently lower in all types of pentosans than the common soft wheats. soluble pentosans. In addition to water-soluble pentosans, protein content and vitreosity Hardness of wheat endosperm is of considerable importance to milling quality and functional properties of dough. Hardness of endosperm can be explained as the degree of adhesion between the major endosperm components such as starch granules and proteins (Simmonds et al 1973). The amount of soluble materials from wheat flour prepared from a range of wheat classes was shown to be associated with endosperm hardness. The soluble materials comprise protein, xylose, arabinose, mannose, and glucose in a ratio of 2:1 carbohydrate/protein. Fractionation of the water-soluble pentosans by diethylaminoethyl cellulose chromatography (Kuendig 1961) established that the major fraction was arabinoxylan and the minor constituents were xylose, arabinose, and protein-bound galactose. The minor constituents were responsible for oxidative gelation of aqueous extracts of wheat flour. Simmonds (1974) referred to the buffer-soluble cementing material on the starch granule and protein matrix interface as a reinforcing space filler. The amount is both environmentally and genetically controlled. Water-soluble pentosans in the different market classes of wheat were studied by Perlin (1951), who reported identical structures and functions in both bread and durum wheat varieties. Medcalf et al (1968) conducted detailed wheat pentosan studies by fractionating pentosans into water-soluble and water-insoluble pentosans; the latter are mainly associated with the starch tailings portion of flour. In the water-soluble fraction, Nugaines, a soft white winter wheat, had lower molecular weight pentosan and less branched arabinose than Thatcher, a hard red spring wheat. Pomeranz et al (1985) used various hardness parameters and tests on wheat genotypes grown in diverse environments. Nearinfrared reflectance (NIR) spectroscopy at 1,680 nm expressed consistent positive correlations with hardness parameters within cultivars across environments and among genotypes. Despite the theories that favor a continuous structure of protein matrix (Stenvert and Kingswood 1977) to explain hardness of wheat endosperm, most studies have demonstrated poor relationships between protein content and endosperm hardness. However, variances for hardness are greater for genotype than environment.