Determination of the degree of substitution of hydrolysed octenylsuccinate-derivatised starch

Aim of the present study was to compare two methods for the determination of the degree of substitution of starch esterified with octenyl succinic anhydride (OSA). A maximum degree of substitution of 0.034 was analysed in commercial samples of hydrolysed OSA starch using a method based on acidification of the free carboxyl group of the OSA-starch molecule after its optimization. In contrast a high degree of substitution up to 0.134 was determined when analysing the same samples using a method based on saponification of the OSA groups. An interference with reducing sugars was hypothesized as possible reason and confirmed by control experiments using different reducing and non reducing low molecular weight carbohydrates.