Test for Starch
Dilute iodine solution reacts with starch, forming a very dark blue colour. This test will work on a solid sample of food, such as potato, or a suspension of starch on water.
Test for Glucose
Glucose is called a reducing sugar. This is because the test for glucose involves chemically reducing an alkaline solution of copper sulphate to copper(I) oxide.
The test for glucose is called the Benedict’s test. Simply add a few drops of Benedict’s solution, which contains alkaline copper sulphate, to some glucose. Add enough to turn the mixture blue. Then heat the mixture in a boiling water bath. The clear blue solution will gradually change colour, forming a cloudy orange or brick red precipitate of copper(I) oxide. All ‘single’ sugars such as fructose are reducing sugars, as well as some ‘double’ sugars, such as the milk sugar
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