Effects of reaction pH and concentration of phosphorus oxychloride on cross-linking of tapioca starch

I. Khatijah

Abstract

The tapioca (Manihot esculenta) starch was cross-linked with 0.005, 0.007 and 0.010% phosphorus oxychloride under controlled pH (10.5, 11.0 and 11.5) and temperature (30 °C). The modified starches obtained had improved functional properties suitable for industrial usage. The moisture content and pasting characteristics of native as well as the prepared modified starches were determined. The pasting viscosities of 6% (dry basis) modified starches at pH 6.5 increased readily unlike that of its native starch. The viscosity stability values of 6% (d.b.) cross-linked starches at pH 6.5 were low or absent while those at pH 3.0 were comparatively higher. The increase in reaction pH and quantity of phosphorus oxychloride resulted in greater acid stability which indicates an increase in the level of cross linking. The acid stability was highest at a reaction pH of 11.5 with 0.01% phosphorus oxychloride.

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