Comparison of physicochemical properties of different varieties sorghum starches

In this study, the grain composition of different varieties of non-glutinous sorghum (Aozhouhong, Aidunliangwang) and glutinous sorghum (Hongyingzi, Yinuohong, Luzhounuohong) was studied, and the micromorphology, crystallization, gelatinization and thermal characteristics of starch were determined. The correlation between the physicochemical properties of sorghum starch was analyzed. The results showed that the physiochemical indexes of different sorghum grains were significantly different. The contents of water, protein and fat were all in line with the standard GB/T 8231—2007 "Sorghum". The contents of tannin and starch were the highest in Hongyingzi and Aidunliangwang, respectively (1.21% and 69.34%). The amylose contents of non-glutinous sorghum (14.25%-29.61%) were higher than that of glutinous sorghum (1.17%-2.24%), while the amylopectin contents of non-glutinous sorghum (33.60%-55.09%) were lower than that of glutinous sorghum (60.27%-61.48%). The grain shape of sorghum starch was similar, and it was irregular spherical or polyhedron and typical A-type crystal. The grain diameter of non-glutinous sorghum starch was larger (15.44-15.55 μm), while the relative crystallinity and attenuation values of glutinous sorghum starch were higher (28.60%-35.35%, 2 564.33-3 096.67 cP), and the pasting temperature was lower (78.58-80.05 ℃). The gelatinization enthalpy ranged from 12.22 to 14.65 J/g. Correlation analysis showed that crystallinity, peak viscosity and decay value were highly significantly negatively correlated with amylose content (P<0.01), while recovery value, pasting temperature and amylose content were significantly positively correlated (P<0.05). Considering comprehensively, glutinous sorghum was more suitable as brewing material.