Physical aspects of the softening of cassava tubers upon fermentation with a mixed culture inoculum

Abstract

Softening of cassava tubers occurs upon fermentation with a mixed culture inoculum, facilitating size reduction and easy recovery of starchy flour. Force-deformation behaviour of tubers from two popular hybrids of cassava (viz. H-1687 and H-2304) under axial compression loading was studied when fresh and after having been fermented for 18, 24 and 48 h. Compressie strength of the tubers declined (from 6.827 to 0.583 kg/cm 2 for H-2304 and from 10.634 to 2.133 kg/cm 2 for H-1687) with longer durations of fermentation, while deformation at failure values increased (from 10.92 to 17.53% for H-2304 and from 10.07 to 13.38% for H-1687) rendering the tuber soft and weak. Fresh cassava tubers were relatively hard and brittle, more so in the case of H-1687 when compared to H-2304. Fermentation of cassava tubers for a period of 24 h was optimum in order to soften them substantially for subsequent crushing, without causing any disintegration during their bulk handling.