Determination of the dry matter content of cassava (manihot esculenta, crantz) tubers using specific gravity method

Abstract

The determination of the dry matter content of cassava tubers using oven dry method is a major constraint in tropical developing countries where the source of electricity is unreliable. In this study a prediction equation was developed as an alternative approach to dry matter determination with the oven dry method. The study was conducted for two years with eleven cassava accessions (using 13 and 15 month old tubers). In the first year, the specific gravity and the dry matter content (oven dry method) of the same tubers were used to derive the prediction equation that can be used for easy and faster estimation of the dry matter content of cassava tubers. The specific gravity and dry matter content based on the oven dry method ranged from 1.0966-1.1469 and 31.45-40.74%, respectively. There was a perfect correlation (R2 = 0.9979) between specific gravity and oven dry matter content of cassava tuber. The middle portion of the cassava tubers gave the true representation of the dry matter content. The prediction equation developed was Y = - 175.46 + 188.61 X where: X = specific gravity and Y = percentage dry matter content. The dry matter content based on the prediction equation for the various accessions was found to be between 31.88-41.53% with a mean of 38.39%. The chi-square test conducted at probability level of 0.05 shows that there was no significant difference between percentage dry matters estimated using the oven dry method and the prediction equation. Hence, the prediction equation could be used to estimate the percentage dry matter content of cassava tuber if the specific gravity is known.