The Effect of Low Levels of Antioxidants on the Swelling and Solubility of Cassava Starch

Abstract

When starch is heated in an excess amount of water above its gelatinization temperature, the granule swells and carbohydrate is released. The extent of swelling and the composition of the material that leaves the starch granule depend upon the botanical source of the starch as well as the heating and shearing procedure. It seems possible that a significant contribution to swelling and subsequent disintegration of the granule at high temperatures is the depolymerisation of the carbohydrate. Breakage of some linkages particularly in the amylopectin component, could facilitate the loss of this material from the swollen granule structure. Extensive work on xanthan (Wellington, 1983) and galactomannans (Mitchell et al., 1991) has demonstrated that the use of binary antioxidant systems, consisting of sodium sulphite and propyl gallate, were effective in reducing viscosity loss that normally occurred on heating the biopolymers. If an effect of heat on starch is due to oxidative reductive depolymerisation (ORD) reactions, it may be expected that this process could be controlled by the binary antioxidant system. This idea prompted us to investigate the effect of sodium sulphite and propyl gallate and their combinations on the swelling volume and carbohydrate release from cassava starch pasted at high temperature