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United States Department of Agriculture

Agricultural Research Service

Title: Thermal Degradation of Concentrated Aqueous Solutions of Sucrose, Glucose and Fructose under Constant Ph Conditions

Authors
item Eggleston, Gillian
item Vercellotti, John - SUGAR PROCESSING RES INST

Submitted to: Journal of Carbohydrate Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 15, 2000
Publication Date: N/A

Interpretive Summary: The U.S. sugar industry loses millions of dollars in profit each year because of the break down of sucrose in the factory and refinery. The extent of such losses is not accurately known because the currently used factory/refinery technique of polarimetry only estimates losses. This work has shown conclusively that polarimetry actually underestimates sucrose losses. This work will aid the sugar industry in developing new and better techniques to measure losses.

Technical Abstract: The thermal degradation of sucrose can decrease sucrose yield, reduce the efficiency of sugar factory and refinery processes, and affect 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 deg C; 65 deg Brix [% dissolved solids]; N2; 0.05-3 M NaOH titrant; 8h), with the use of an autotitrator. Reaction pH values ranged from 4.4 to 10.45. Polarimetry and ion chromatography with integrated pulsed amperometric detection (IC-IPAD) were used to quantitate sucrose degradation and first-order reaction constants were calculated. Minimum sucrose degradation occurred between pHs 6.45 - 8.5, with minimum color formation between pH's 4.4 - 7.0. Polarimetry, ubiquitously used in U.S. sugar factories and refineries to monitor sucrose losses, was shown not to be viable to measure sucrose degradation, because of formation of compounds with a positive optical rotation, and this distortion is especially severe under alkaline conditions. For comparison, fructose and glucose (80 deg C; 65 deg Brix; N2; 3M NaOH; 2h) were also degraded under low water activity and constant pH 8.3 conditions. For sucrose, fructose and glucose, total organic acid formation 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 were also highly correlated (R2>.966) with optical rotation values, confirming that these compounds are major contributors to the underestimation of sucrose losses by polarimetry,

Last Modified: 10/20/2014
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