Degradation of Sucrose,Glucose and Fructose in Concentrated Aqueous Solutions Under Constant pH Conditions at Elevated Temperature

ABSTRACT

The degradation of sucrose can decrease sucrose yield, reduce the efficiency of sugar factory and refinery processes, and effect end product quality. Characterization of sucrose degradation under modeled industrial processing conditions will underpin further technological improvements. Effects of constant reaction pH on sucrose degradation were investigated using simulated industrial model systems (100 °C; 65 °Brix % dissolved solids]; N₂; 0.05-3 mol NaOH titrant; 8 h), with the use of an autotitrator. Reaction pH values ranged from 4.40 to 10.45. Polarimetry and ion chromatography with integrated pulsed amperometric detection (IC-IPAD) were used to quantify sucrose degradation and first-order reaction constants were calculated. Minimum sucrose degradation occurred between pH 6.45 - 8.50, with minimum color formation between pH's 4.40 - 7.00. Polarimetry, often used in U.S. sugar factories and refineries to monitor chemical sucrose losses, was shown not to be viable to measure sucrose degradation under alkaline conditions, because of the formation of fructose degradation products with an overall positive optical rotation. For comparison, fructose and glucose (80 °C; 65 °Brix; N₂; 3 mol NaOH; 2 h) were also degraded at constant pH 8.3 conditions. For sucrose, fructose, and glucose, formation of organic acids on degradation was concomitant with color formation, indicating they are probably produced from similar reaction pathways. For the glucose and fructose degradation reactions, color and organic acid formation also were highly correlated (R²>0.966) with changes in optical rotation values, confirming that these compounds are formed from similar reaction pathways.