Abstract

A new spectrophotometric method has been developed for the determination of fructose, glucose and sucrose in fruit juices. The method is based on the oxidation of sugars with zero valent iron powder in acidic pH aqueous solution and bubbled with air. Oxidized by-products were complexed with 2-thiobarbituric and monitored by UV-Vis spectroscopy. The recorded spectra are specifically characteristic for fructose, glucose and sucrose respectively. Calibration curves were studied for each compound and the quantitative determination of carbohydrate concentrations was carried out using an internal standard addition method. The average relative standard deviation is 4% and recovery rate range from 98% to 103% for spiked concentrations of 0.05 – 4 mM carbohydrates. The detection limit are 13, 15 and 12 µM for fructose, glucose and sucrose respectively. The oxidation of carbohydrates gives rise to certain by-products, presents a new method of indirect measurement of carbohydrates. This method is applied in the determination of carbohydrates in juices and other foods in a precise, easy and inexpensive way.

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