Estimation of starch and total fermentables content in storage roots of cassava (Manihot esculenta Crantz.)

The relationships between the percentage of dry matter (DM), specific gravity, percentage of starch and percentage of total fermentables in cassava storage roots have been examined in detail. The results confirm the findings of earlier workers that specific gravity can provide a reliable estimate of storage root DM in the absence of drying facilities. A curvilinear relationship of the form 1/y = a + bx was found to exist between storage root DM and percentage of starch or fermentables within one cultivar over a range of ages and seasonal conditions. This relationship shows that the proportion of total DM present as starch or fermentables increases for samples of higher DM percentages. A similar relationship was shown to exist between specific gravity and percentage of starch or fermentables. A linear relationship was also developed between the percentage of DM and of fermentables based on 28 cultivars harvested at the same age and under the same seasonal conditions. More information is required on cultivar differences in these relationships over the entire range of DM and fermentable percentages, before widespread use is recommended. Once correctly established, relationships based on DM or specific gravity provide a simple and reliable method of estimating percentage of starch or total fermentables in the storage roots of cassava. Comparisons are made between these results and those reported earlier in the literature, using less precise methods of starch measurement