Physicochemical characteristics of starches and flours from cassava varieties having different cooked root textures

Starches and flours from 12 cassava varieties having differences in cooked root texture - mealy, firm and mealy & firm - were investigated, with a particular focus on aspects of physicochemical characteristics. It was found that chemical composition (protein, lipid, fiber, ash), pasting properties, firmness of gel, thermal properties, morphology and granular size distribution and crystalline pattern of starches from the 12 varieties were not significantly different. On the contrary, cassava flours which consisted of both starch and non-starch components exhibited wider variations in these properties, especially pasting properties and firmness of gel, than the starches. All flour samples had lower paste viscosities than their corresponding starches. Pasting temperatures of flours were in a range of 70-74 °C, which was higher than those of starches (67-70 °C). Fluctuation in the values of pasting parameters of flours among the varieties was associated with the variations in the chemical composition and α-amylase activity, i.e. paste viscosity and setback were positively correlated to starch content and negatively correlated to α-amylase activity, while protein, lipid and fiber did not show correlation with pasting parameters. Cassava starches from all varieties, except the F-18 variety, had higher firmness of gels than their corresponding flours. Firmness values (except the F-18 variety) of starches were in a range of 149-207 g, whereas those of flours were 75-163 g. Firmness of flour gels was negatively correlated to lipid and fiber content, while strong positive correlation was found with the amylase activity.