THE FLUOROMETRIC-DETERMINATION OF REDUCIN G SUGARS IN SUGAR-BEET USING BENZAMIDINE

The invert sugar content of sugar beets is an important indicator of t heir quality owing to the fact that its acidic degradation products (l actic, acetic, formic, and other organic acids), formed during juice p urification, reduce the natural alkalinity reserves of the beets. This has adverse consequences for sugar manufacture, which makes it highly desirable to be able to predict the alkalinity of technical juices. T o this end, two independent proposals have recently appeared in the li terature, which include, besides other characteristics, the invert sug ar content of the beets as a variable in the estimate of their alkalin ity reserves. However, the inclusion of invert sugar in the quality as sessment of sugar beets presupposes the existence of a serial analytic al method which meets the practical requirements of automated beet lab oratories. The fluorimetric determination of reducing sugars in beets (or in beet brei degirates clarified with aluminium sulfate) with benz amidine, according to Kai et al. (1985), constitutes a method which, b esides satisfying other conditions, is sufficiently simple and cost-ef fective to be introduced as a serial method into routine beet analysis . The method is selective and sensitive enough to register reducing ca rbohydrates, which in sugar beets are represented almost exclusively b y glucose and fructose in an average ratio of 1:0.4 (described as ''in vert sugar)'' Interference in the fluorescence reaction by unidentifie d constituents of the beet matrix can be overcome by the addition of E DTA. In principle, fluorescence measurements can be carried out with t he fluorimeters developed for beet laboratories. These must be constru cted as two-beam devices and also be equipped with a reaction chamber (oven unit) and a flow cuvette maintained at reaction temperature (90- degrees-C). Comparison with the Berlin Institute method (ICUMSA standa rd) shows that the benzamidine method registers reducing sugars in sug ar beets with comparable accurarcy and reproducibility. With that, the most important preconditions for the incorporation and routine applic ation of this fluorimetric analytical method in the various automated beet laboratory systems are satisfied.