|Vercelotti, John - RETIRED USDA ARS|
Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 7, 1996
Publication Date: N/A
Interpretive Summary: Salts are known to increase the thermal break down of concentrated sucrose solutions under industrial sugar processing conditions. This leads to losses of sugar, formation of break down products and reduction of industrial unit process efficiencies. Data is required to better predict the rate of sugar losses, and also physico-chemical and thermal data for process engineers and designers to make improvements. Thermal break down of pure sucrose in aqueous solution in the presence of salts was investigated. All salts significantly increased sucrose break down as monitored by optical properties. The initial condensation break down reactions were more rapid than expected and subsequent elimination reactions were slower. The thermal analysis results, indicate that special bonding between the salt and sucrose is occurring.
Technical Abstract: Thermal degradation of pure sucrose in concentrated aqueous solution (100 C; 65 Brix) in the presence of salts was investigated. Polarimetry was used to quantify sucrose degradation and pseudo-first order kinetic constants of initial degradation rates were calculated. All salts significantly increased sucrose degradation; colored degradation products were only formed in the presence of Na2B4O7. Thermal degradation characteristics of crystalline sucrose and dried, crystalline residues from sucrose-salt model solutions heated at 100 C for 0 and 3 h, were further investigated by differential scanning calorimetry (DSC), thermogravimetric (TG) and differential thermogravimetric (DTG) analyses. Rate of heating was 15 C/min from 50 to 500 C. DSC and TG studies confirmed the catalytic nature of salts on the thermal degradation of sucrose. Salts affected thermal degradation in various ways. The initial condensation degradation reactions were more rapid than expected and subsequent elimination reactions were slower. The thermal analysis results, indicate that complexation between the salt and sucrose is occurring, and further study at the molecular level is required.