Reflectometric determination after enzymatic conversion.
Chemical analysis of foods and beverages is performed to ensure safe consumption, product quality, and product integrity. As a part of quality control, soft-drink producers must monitor the concentration of sugar (sucrose) in their final products and during the manufacturing process. In this application note, we describe a method to determine sucrose in soft drinks with the Reflectoquant® Sucrose (Saccharose) Test and RQflex® 20 reflectometer.
Sucrose (saccharose) is cleaved by sucrose phosphorylase into fructose and glucose-1-phosphate. The latter is converted by phosphoglucomutase into glucose-6-phosphate. This is in turn oxidized by NAD under the catalytic effect of glucose-6-phosphate dehydrogenase to gluconate-6-phosphate. In the presence of diaphorase the NADH formed in the process reduces a tetrazolium salt to a blue formazan that is determined reflectometrically.
*This application note pertains to RQflex® 20 and all discontinued instruments (RQflex® 10, RQflex® plus).
Dilute the sample depending on the anticipated sucrose content, e. g. for a 1:100 dilution, pipette 0.5 ml of sample into a 50-ml volumetric flask and make up to the mark with distilled water. The measurement results should preferably lie in the middle of the measuring range. It may be necessary to repeat the dilution step with a further dilution.
The measurement value [g/l] is saved automatically. (See the operating manual for RQflex® and the instruction for use for Reflectoquant® Sucrose (Saccharose) Test.)
After the first measurement, any number of further measurements can be made by pressing the start button. This, however, requires the use of a stopwatch since the countdown function of the reflectometer is available only for the first measurement. The detection zones of the test strip must be appropriately protected from light during the reaction time.
Sucrose content [g/l] = measurement value [g/l] x dilution factor
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