Examination of a Simple Carbohydrate Determination by the Weinmann Method

Abstract

As a substitute for the fractionation method for the determination of tea plant carbohydrate, the Weinmann method of estimating the “total available carbohydrate” was investigated.
Take a 0.3 gram sample and 20 ml. of distilled water into a flask, heat for % hour on a boiling water-bath to gelatinize starch. Pipette 20 ml. of buffer solution of pH 4.45 and 20 ml. of takadiastase solution into a flask. Stopper the flask tightly and incubate for 44 hours at 37 to 38°C.
After digesting, nearly neutralize, pipette 2 ml. of basic lead acetate, shake, and allow precipitate the protein, tannin and etc. in the digest solution. Filter quantitatively into a 100 ml. standard flask containing 800 mg. of powderd potassium oxalate, and make to volume.
Filter and hydrolyze a 2.5 ml. of the cxtract solution with 0.25 ml.of hydrochloric acid (specific gravity 1.103) for % hour on a boiling water-bath. Cool and neutralize, and determine the reducing power of the extract by the Hanes method. Results are calculated as glucose, and reported as “total available carbohydrate”.
When the selection of a sort of Takadiastase was suitable for tea plant digestion, it was not recognized the retardation of digestion by the tea tannin.
Results obtained with this new method were higher than the combined amounts of total sugars and starch by the fractionation method. However, the correlation coefficient of the data between the fractionation method and the new method was +0.908.
The variation coefficients of the determination were 3.6 to 5.0%. A comparison of the variation coefficicnt between the fractionation method and the new method showed that the latter had lower accuracy than the former. But, a considerable number of determinations can be completed with this method in a relatively short time, making 72 determinations per week.
The Weinmann method is simple and suitable for a large-scale analysis of the available carbohydrate in tea plant.