Automated Determination of Reducing Sugars, Total Sugars, and Starch in Plant Tissue from One Weighed Sample

Abstract An analytical scheme for the simultaneous quantitative analysis of reducing sugars, total sugars, and starch in plants from a single sample is presented. Sugars are removed by an acidic methanol extraction and starch is extracted by shortening the AOAC method. Nonreducing sugars and starch are hydrolyzed to reducing sugars and determined by automated colorimetry, utilizing AutoAnalyzer modules. This colorimetric system employs the potassium ferricyanide-potassium ferro-cyanide oxidation-reduction reaction. The yellow color of ferricyanide, when heated with reducing sugars, diminishes in proportion to the quantity of sugar present, due to the production of colorless ferrocyanide. The sampling rate is 30 samples/hr. Results compare well with the much longer AOAC methods for each respective component. The method is rapid and relatively simple, and gives accurate, reproducible results. The amount of total carbohydrates is obtained by adding the total sugar and starch values.