Effect of enzymatic treatment of starch gelatinized with sodium hydroxide

Abstract

Different Kinds of starches were subjected to gelatinization under the action of sodium hydroxide solution at room temperature and treated with alpha-amylase enzyme in the gelatinized form. To achieve this goal, maize starch was subjected to gelatinization using sodium hydroxide at room temperature under different conditions. The latter comprise, starch concentration, sodium hydroxide concentration, pH value, time and temperature as well as the concentration of α-amylase enzyme. The modified starches were evaluated via measuring the solubility and the apparent viscosity at various rates of shear. The modified starches were evaluated as thickeners in printing wool fabrics with acid dye and polyester using disperse dye. The results of these investigations demonstrated that increasing the apparent viscosity by increasing starch concentration is expected. The apparent viscosity increases by increasing the amount of sodium hydroxide.Increasing of α-amylase enzyme concentration is accompanied by a decrease in the apparent viscosity.The most suitable pH for starch modification by enzyme was found at pH 7.The temperature highly influences the apparent viscosity of maize starch at any specific rate of shear. However 50◦C is the most suitable degree for modification of maize starch to obtain a suitable viscosity and cold water solubility and also avoid the higher decrease in the viscosity. The treated starches were evaluated via measuring the solubility and rheological properties.