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Physiochemical and thermal characteristics of starch isolated from a waxy wheat genotype exhibiting partial expression of Wx proteins

Taek-Hee Jung, Jae Yoon Kim, Byung-Kee Baik, Chul Soo Park
Cereal chemistry 2015 v.92 no.1 pp. 14-21
X-radiation, amylopectin, amylose, cold, enthalpy, gelatinization, gels, genes, genotype, hardness, loci, melting, microstructure, pasting properties, proteins, retrogradation, starch granules, swelling (materials), temperature, thermal properties, transmittance, viscosity, water holding capacity, wheat
A unique wheat genotype carrying waxy type allelic composition at the Wx loci, Gunji-1, was developed and its starch properties were evaluated in comparison to parental waxy and wild type wheat varieties. Gunji-1 was null in all three of the Wx genes, but exhibited a lower level of Wx proteins than the wild type. Starch amylose content and cold water retention capacity were 10.1% and 70.5% for Gunji-1, 4.2% and 76.6% for waxy, and 27.9% and 65.0% for wild type, respectively. No significant differences were observed in microstructure, granule size distribution and X-ray diffractograms of the starch granules isolated from Gunji-1 compared to those of waxy and wild type wheat varieties. Starch pasting peak, breakdown and setback viscosities and peak temperature of Gunji-1 were intermediate between waxy and wild type wheat. In starch gel hardness, Gunji-1 (1.1 N) was more similar to waxy wheat (0.5 N) than to the wild type variety (17.6 N). Swelling power, swelling volume, paste transmittance during storage, and gelatinization enthalpy of Gunji-1 were lower than those of waxy wheat but greater than those of wild type wheat. Retgrogradation of starch stored for one week at 4'C expressed with DSC endothermic enthalpy was absent in the waxy wheat variety, whereas Gunji-1 exhibited both retrogradation of amylopectin and amylose-lipid complex melting similar to the wild type parent, even though enthalpies of the former were much smaller than the latter.