Effects of nitric acid concentration, hydrolisis time and particle size on moisture content and acid degree of dexrin from janeng starch

Abstract

Janeng (Dioscorea hispida Dennest) is an excellent source for starch raw materials in the manufacture of dextrin, a product resulting from starch degradation through hydrolysis with acids or enzymes. The various methods of dextrin production, the dry hydrolysis method of starch using an acid catalyst is the most popular, and in this study, citric acid (HNO₃) was selected. The purpose of this study was to determine the effect of HNO₃ concentration (0.5N, 1N, 1.5N), hydrolysis time time (20, 30, 40 min) and particle size (60, 80, 100 mesh) on the moisture content and acid degree of dextrin and to see the optimum conditions of the those variables. This research used response surface method (RSM) based on central composite design (CCD). The result showed that HNO₃ concentration, hydrolysis time and particle size had a significant effect on water content and acid degree. The higher the HNO3 concentration, the longer the hydrolysis time and the larger the particle size, the lower the water content. The higher the HNO3 concentration, the longer the hydrolysis time and the finer the particle size, the higher the acid degree. The optimum condition was obtained at a HNO3 concentration of 0.5 N with a hydrolysis time of 20 minutes and a particle size of 60 mesh with optimum predicted dextrin content of 7.12%, moisture content of 6.53% and acid degree of 0.92%.