Principle
Glucose (= grape sugar) can be detected with Fehling's solution and so be differentiated form sucrose. Vegetable foods, such as fruits, fruit juices and honey, contain glucose. The most important monosaccharides, glucose and fructose, act as reducing agents in alkaline solution. The disaccharides lactose (milk sugar) and maltose (malt sugar) also have reducing properties. All of them are in an open chain aldehyde or ketone form in alkaline solution. They react with Fehling's solution by reducing the copper(II) ions to copper(I) oxide. Sucrose does not react with Fehling's solution, as this disaccharide of fructose and glucose (2,1 glycosidic linkage) has no free aldehyde or ketone groups.

Learning objectives

• Detection methods for glucose
• The "Fehling" reaction

Benefits

• Easy teaching and efficient learning by using interactive experimentation PHYWE-Software
• Experiment is part of a complete solution set with experiments for the topic Food Chemistry matched with international curriculum: all topics are covered