EFFECTS OF FLOUR-TO-WATER RATIO AND TIME OF TESTING ON SORGHUM PORRIDGE FIRMNESS AS DETERMINED BY A UNIAXIAL COMPRESSION TEST

A compression test was conducted on specimens of porridge made from se ven sorghum cultivars with different endosperm textures. Porridge was prepared using three flour-to-water (F-W) ratios and was tested at 15, 30, or 60 min after cooking. Two parameters, apparent deformability m odulus (E(app)) and yield stress (S(max)), were compared as measures o f porridge firmness. Sticky porridges, which are usually softer than n onsticky ones, scored higher in terms of S(max) because of frictional or bonding effects. This discrepancy was absent for E(app), which was observed at lower strain levels. E(app) was also more reproducible tha n S(max), and it was sensitive enough to detect differences between cu ltivars. The effect of the F-W ratio was highly significant, as was th at of time of testing (TT) (P < 0.001). A cultivar X F-W ratio interac tion was significant (P < 0.01), indicating that the F-W ratio effect was not consistent across cultivars. Most cultivars exhibited improved porridge firmness as the F-W ratio increased, but they were ranked di fferently at the three ratios investigated. A cultivar X TT interactio n was significant (P < 0.01) and revealed that the rate of firmness de velopment was higher for hard-endosperm cultivars than it was for soft ones. Cultivar ranking according to porridge firmness was also differ ent at TTs of 15, 30, or 60 min after cooking. Firmness measured after 60 min correlated significantly with grain vitreousness and amylose c ontent.