Charater1zation Of A-, B-starch And Its Relationship With Wheat Quality

In this study, different varieties of wheat were used to study the wheat qualitycharacteristics firstly, then study the content and composition, particles characteristics andpaste properties of A-starch and B-starch. A, B-starch properties and the relationship betweenwheat quality indicators were discussed. The main results shown:(1) Twenty-five wheat varieties were used to determine the wheat grain hardness, basicquality indicators of flour, gelatinous and farinograph parameters, etc. The results shown: thedistribution of wheat grain hardness were23.80~88.03, particle size distribution were2.73~3.31mm. There were differences in the damaged starch and gluten index among varieties,coefficient of variation17.28%and48.75%respectively. The coefficient of variation aboutflour gelatinization and farinograph parameters were9.52%～36.89%and7.53%～95.72%respectively, there were significant differences among varieties. There was extreme significantcorrelation between wheat grain hardness and ash cotent (r=0.743), damaged starch and ashcotent (r=0.761). There was a significant or extreme significant negative correlation betweenflour gelatinization parameters and softening degree of Farinograph, correlation coefficientwas-0.396~-0.658.(2) The total starch, A-starch and B-starch were extracted from wheat flour, and theparticles characteristics were analyzed. The results shown: total starch and A-starch yieldwere higher (64.09～75.25%,51.95～67.63%), and B-starch yield relatively lower (6.58～16.23%). The impurity of B-starch was higher, ash and crude protein content was0.8%and3.22%respectively, higher than the corresponding total starch (0.34%and1.01%) and Astarch (0.26%and0.8%). Starch granule morphology can be observed by Scanning ElectronMicroscope (SEM) directly, results indicated that A-starch grains were larger, mainly forround in shape, B-starch grains were smaller, mainly for oval in shape (DA=9.43～36.33μm，DB=1.78～10.83μm). It can be observed by polarizing microscope that A, B-starch grains hada more obvious polarization cross. The X-ray diffraction patterns of the A, B-starch grainsexhibited the character of an A-type crystal, the relative crystallinity of A-starch grains washigher than A-starch grains.(3) Comparing with the paste properties, the results shown: the differences betweenA-starch and total starch were smaller and with B starch were larger. The transparency,freeze-thaw stability, peak viscosity and gel texture properties of A-starch paste were better than B-starch, but the viscosity attenuation value, solubility and gel stability of B-starch werebetter than A-starch.(4) The relations between the A, B-starch properties and wheat quality indicators wereanalyzed. The results shown: there existed extremely significant negative correlationsbetween A-starch yiled and wheat grain hardness (r=-0.712), damaged starch and waterabsorption (r=-0.677), while B-starch yield had extremely significant positive correlation withdamaged starch (r=0.602). A-starch grains size had a extreme significant positive correlationwith wheat grain hardness (r=0.913) and stability(r=0.834), B-starch grains size had noobvious correlation with wheat quality indicators. Significant correlations were existedbetween A, B-starch gelatinization parameters and damaged starch and flour gelatinizationparameters(r=0.392～0.733). There was significant correlation between B-starch gelatinizationparameters and flour gelatinization parameters.