Effects Of Sowing Date On Morphology,Grain Size Distribution And Physicochemical Properties Of Starch In Wheat

Starch is an important part of the wheat grain,accounting for about 80%of the wheat endosperm.The physical and chemical properties of starch have an important influence on the quality of dough.Many studies have shown that cultivation and cultivation measures have a greater impact on the quality characteristics of wheat starch.In this study,wheat varieties Xinong 369,Xinong 836,Xinong 979,Xiaoyan 22,Zhoumai 18 and Bainong 207were planted in Yangling,Shaanxi province in early sowing（October 2,T1）,medium sowing（Suitable sowing,October 12,T2）and late sowing（October 22,T3）to study the effects of sowing dates on starch granule morphology,granule size distribution,starch content and starch physicochemical properties of different wheat varieties,providing theoretical basis for the promotion and application of excellent varieties.The main research results are as follows:（1）The sowing date had a significant effect on starch granule size distribution.With the delay of sowing date,the volume average particle size D[4,3]of Xinong 369,Xinong 836and Bainong 207 increased gradually,Xinong 979 and Xiaoyan 22 decreased first and then increased,and Zhoumai 18 increased first and then decreased.The surface area average particle size D[3,2]of Xinong 369,Zhoumai 18 and Bailing 207 increased first and then decreased,Xinong 836 and Xinong 979 decreased first and then increased,and Xiaoyan 22decreased with the delay of sowing date.Meanwhile,the proportion of B-type small starch granules in Xinong 369,Xinong 836 and Zhoumai 18 decreased while LA-type starch granules increased,and xiaoyan 22 showed an opposite trend.（2）There were significant differences in total starch content,amylose content and amylopectin content in different wheat varieties with different sowing dates.With the delay of sowing date,the total starch content and amylopectin content of Xinong 836 and Xiaoyan22 increased gradually,while those of Xinong 369,Xinong 979 and Bainong207 decreased gradually;The amylose content of Xinong836 and Xiaoyan22 showed an increasing trend,Xinong 979 and Bainong 207 showed a decreasing trend,and Xinong 369 had no obvious change.In terms of the effect of sowing date on the amylose/amylopectin ratio of wheat varieties,Xinong 836 and Xinong 369 showed a gradually increasing trend,Bainong 207showed a gradually decreasing trend,and other varieties had no significant changes.（3）The sowing date has different effects on the solubility of different varieties of wheat starch.With the delay of sowing date,Xinong 369 and Xiaoyan 22 showed an increasing trend,Xinong 979,Xinong 836,Zhoumai 18 and Bainong 207 on the opposite.But the sowing date had no significant effect on the swelling force,1022/995 cm^-1peak intensity ratio and 1045/1022 cm^-1 peak intensity ratio of different wheat starch varieties.（4）The sowing date had significant effect on the thermal characteristics of wheat starch of different varieties.In terms of the influence of sowing date on enthalpy of thermal transition（ΔH）change,with the delay of sowing date,Xinong 369,Xinong 979,and Xiaoyan 22 showed a trend of first decreasing and then increasing,and Xinong 836 was first increasing and then decreasing.The thermal degradation temperature（T_d）of Xinong 369,Xinong 979,Xiaoyan 22 and Bainong 207 showed a downward trend,while Xinong 836 and Zhoumai 18 first decreased and then increased.Sowing date had no significant effect on the onset temperature（T_o）,denaturation peak temperature（T_p）,conclusion temperature（T_c）,water loss rate and mass loss rate of wheat varieties.（5）The sowing date has a significant effect on the peak viscosity（PV）,breakdown viscosity（BD）,final viscosity（FV）,setback viscosity（SB）and peak time（PT）of wheat starch of different varieties,but has little effect on through viscosity（TV）and pasting temperature（PTP）.For example,with the delay of the sowing date,BD of Xinong836,Zhoumai18 and Bainong 207 showed a decreasing trend,and Xiaoyan 22 showed an increasing trend;However,SB of Xinong 836,Xiaoyan 22 and Zhoumai 18 showed an increasing trend.In conclusion,the sowing date had a significant effect on the physicochemical properties of wheat starch,which showed differences among cultivars.According to the use of wheat starch and actual sowing conditions,choosing the appropriate sowing date is of great significance for the popularization and application of different wheat varieties,and also provides a reference for the integration of high-yield and high-quality cultivation techniques for wheat varieties in the future.