Degradation of sucrose during sugar processing III: Conditions for clear liquor storage

The best conditions for clear liquor storage from the weekly shut down on e arly Saturday to start up on early Monday at the Marseilles Saint-Louis Suc re cane sugar refinery (France) were determined. An accurate method for car bohydrate analysis (High-Performance Anion-Exchange Chromatography with Pul sed Amperometric Detection, HPAE-PAD), was used to evaluate the formation o f invert sugar and oligosaccharides, and the corresponding sucrose losses. Mannose, acetic acid and L-lactic acid levels were also estimated using com mercial enzymatic kits, although these compounds did not appear to be relev ant refinery liquor degradation markers during the period tested. Other con ventional refinery parameters including Brix, colour and pH were also deter mined. Storage of clear liquor (initial parameters: 73 degrees Brix, 85 deg rees C, pH 8.3 and 249 ICUMSA units colour) over the weekend was found to b e associated with a 2.5 unit drop in pH, a two-fold increase in colour, abo ut ten-fold increase in invert content, and 10% sucrose loss. Consequently, the clear liquor could not be satisfactorily used in the refinery process. Storage tests for refinery liquor samples at 85 degrees C for 96 h in the laboratory clearly indicated that the pH should be maintained at its initia l value to avoid deteriorative reactions. It was found that liquor stored o ver the weekend, in the 60 m(3) clear liquor tank tested, should be kept at 70 - 75 degrees C and pH 7 - 8 to prevent significant sucrose losses and i nvert production.