Genetic diversity in properties of starch from Zimbabwean sorghum landraces

Starch was isolated from 95 sorghum landraces from Zimbabwe using an alkali steep and wet-milling procedure. The physicochemical properties of sorghum starch were examined for potential use in Southern Africa. All the landrac es evaluated had a normal endosperm indicated by the amylose content of the starches. Starch properties were not correlated to most of the physical gr ain quality traits evaluated. Grain hardness was weakly correlated to starc h gel adhesiveness (r = 0.36) and amylose content (r = 0.38) (P < 0.001). T he mean peak viscosity (PV) of the sorghum starches was 324 Rapid Visco Ana lyser units (RVU) compared with 238 RVU in a commercial corn starch sample; PV was 244-377 RVU. Some landraces had low shear-thinning starches, implyi ng good paste stability under hot conditions. Pasting properties were highl y correlated among the sorghum starches. The starch gel hardness showed con siderable variation (44-71 g) among the landraces. Gelatinization peak temp eratures were 66-70<degrees>C. The thermal properties of starches were not correlated with starch swelling and pasting properties. Genotype grouping b y highest and lowest values in each category would allow selection of sorgh ums based on a specific attribute depending on the desired end use.