The effects of low molecular weight additives on the viscosities of cassava starch

The influence of a range of additives on the change in the viscosity of cassava starch pastes on ageing following gelatinisation has been investigated. The inclusion of sulfite with pasted starch markedly decreases the viscosity of the paste with time and this is prevented by the addition of propyl gallate. Intrinsic viscosity measurements strongly support the view that sulfite addition promotes polysaccharide degradation. Ascorbate has a greater degradative effect than sulfite, whereas only limited degradation is observed with glutathione. Salts such as sodium chloride and sodium sulfate show no effect on viscosity. If the chelating agent EDTA is added as well as sulfite, the reduction in viscosity is smaller, although the effect is not cancelled out completely. Interestingly, the degradative effect of sulfite and ascorbate can be shown at 30, 60 and 80° C. The results presented uphold the previous suggestion that sulfite addition promotes oxidative reductive depolymerisation (ORD) and largely rule out any residual enzyme activity as the cause. It is suggested that the strong degradative action of ascorbate on starch could be one of the explanations for its action in baked products.