Sugar Content Experiment

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FDE 310 Food Materials Laboratory Report

Determination of Reducing Sugar Content

INTRODUCTION The objectives of this experiment is to determine reducing sugar content of food sample by performing Fehling method and to identify invert sugar content of sugars by using polarimetry and also to learn property of invert and reducing sugar.
Carbohydrases represent a large class of enzymes hydrolyzing polysaccharides and low-molecular-weight glycosides. They belong to the class of hydrolases. Carbohydrases are classified according to their specificity
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First of all, calibration solutions, which are formed from glucose and fructose stock solutions, are prepared. Prepared calibration solutions are placed in polarimeter which is calibrated with water before.

In this experiment, Fehling method was used for reducing sugar content determination in honey sample and polarimetric method was used for invert sugar determination in different concentrations. In Polarimetric method, fructose and glucose solution were used to prepare mixture. Then, mixture was used to measure the angle of rotation of different solutions.
Fehling’ method;

25 ml Fehling + 25 ml glucose soln.
Volume of glucose used as titrant 1,2 ml Honey
Volume of glucose used as titrant 1 0,5 ml
Volume of glucose used as titrant 2 0,6 ml

2) Determination of Invert Sugar Content by Polimetric Method sample Vfructose soln. optical rotation(a) degrees
1 0 2,255
2 4 1
3 8
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The resulting mixture of glucose and fructose is thus called "invert sugar".(optical activity, n.d.) Fructose is levorotatory and it has negative rotational angle value. According to Baker, increase in the amount of fructose causes decrease in optical rotation (1990) as it was seen in the results. Hence, experimental data was determined correctly. On the other hand, levorotatory activity of fructose is greater than dextrorotatory activity of glucose (Chen & Chou, 1993). Although amount of fructose and glucose in our samples was close to each other, optical rotation was highly negative resulting that fructose dominates as explained

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