Effect of water content and mucilage on physico-chemical characteristics of Yam (Discorea alata Purpurea) starch

Effects of water content and mucilage on physico-chemical characteristics of yam (Discorea alata Purpurea) starch have been investigated. Particle size analysis by laser light scattering showed the size of the isolated yam starch granules to be mostly in the range of 10–80 μm, and about 1% of starch granules was smaller than 1 μm. Decreasing water content from 90% to 40% did not significantly alter the onset temperature (To) and peak temperature (Tp), but raised the conclusion temperature (Tc). Mucilage exhibited greater storage modulus (G′) and smaller loss modulus (G″) than the isolated yam starch at water content of 90%. Water content also influenced the effect of mucilage on the rheological properties of starch–mucilage mixture, but did not significantly affect To and Tp. The swelling power measurement and scanning electron microscopy illustrated the presence of mucilage to retard the pasting of starch granules during heating.