The application of gelatinisation techniques in modification of cassava and yam starches using precipitation method.

Abstract

Starches modified using the precipitation method which are added to edible film formulation were shown to lower water vapor transmission rates and increase the mechanical strength of the film. The effect may not only be due to the changes in starch morphology, but other aspects of the starch granules, such as their size and chemical properties in particular, are also suggested as reasons for improvements to the quality of edible film by modified starches. The aim of this research was to determine physicochemical changes in modified cassava and yam starches using several gelatinisation techniques in the precipitation method. The gelatinisation techniques used in this study were two methods of heating (using a hotplate and autoclave reactor + oven heating) and two types of starch solvent (distilled water and a mixture of distilled water and ethanol 1:1, v/v). The results showed that both cassava and yam starch granules modified using a hotplate at a heating temperature of 100°C for 30min were more badly damaged and smaller than those modified using autoclave reactor + oven heating at 140°C for 1h. However, the latter suffered more damage and were smaller in size when the heating time was increased to 3-5h. All techniques applied in the modification increased the intensities of stretching vibration of O-H and C-H, and bound water bending vibration. The use of ethanol in the starch solvent enabled the starches to retain the shape and size of the granules despite the rearrangement of intra and intermolecular bonding as confirmed by FTIR spectra.