food tests (copy)

Test for starch

Add iodine (potassium iodide solution) to the sample. If the solution goes from brown-orange to blue black starch is present.

Test for lipids (Sudan III)

Add Sudan III stain solution to the sample and shake gently. A red-stained oil layer will separate out and float on surface if lipid is present.

Test for lipids

The emulsion test - add ethanol to the sample and shake the test tube then add water to it. Lipids are present if a white emulsion appears.

Test sugars

The Benedict's test - add Benedict's reagent to the sample then heat the solution gently. A green/yellow then orange then brick-red colour indicates that how much sugar is present.

Test for proteins

Biuret test - add sodium hydroxide solution to the sample. Add copper sulphate solution. If proteins are present the solution will turn purple, if not it will stay blue.