The Effects of Hypochlorite-Oxidation on the Physico-Chemical Properties of Starch Obtained from Tacca Involucrata

Abstract

Tacca involucrata tubers are a staple source of starch in the Middle belt region of Nigeria. In this study, hypochlorite oxidation is utilized as a means of improving the physicochemical properties of the starch, to obviate problems posed by high moisture absorbing capacity (risk of microbial contamination) and poor flow properties, etc. Samples of the starch were treated with calcium hypochlorite to provide an oxidative concentration of 10 g per litre of active chlorine, for times ranging from 15 minutes to 2 hours at 28 °C and pH 9. Suitable properties of the bleached starches: particle size, relative viscosities, true and loose densities, gelatinization temperature and equilibrium moisture content, were assessed in relation to the native unoxidized starch. The results indicate that oxidation produces starch of whiter colour and optically clearer mucilage. It causes depolymerisation of the starch, hereby yielding lower viscosity grades with lower molecular weights. The process produces starch with smaller grain particles due to structural breakdown along fissure lines. The gelatinization temperature became lowered on oxidation. The moisture absorbing capacity and hence risk of microbial attack was also reduced, but starch of slightly poorer flow was produced.

Keywords: Tacca involucrata; starch; modification; hypochlorite; oxidation physiochemical

Nigerian Journal of Pharmaceutical Research, Vol. 8 No 1 pp. 270 - 280 (September 2010)