Food Tests Flashcards

Used to test for reducing sugars. A positive result shows a colour change from blue to green, yellow, or brick red depending on sugar concentration.

Used to test for proteins. A positive result shows a colour change from blue to purple.

Used to test for starch. A positive result shows a colour change from brown-orange to blue-black.

Used to test for lipids. A positive result shows a cloudy white emulsion when ethanol and water are added.

A colour change from blue to green, yellow, or brick red indicates the presence of reducing sugars.

The solution remains blue, indicating no reducing sugars are present.

Add Biuret solution (sodium hydroxide and copper sulphate) to the sample. Observe for a colour change to purple.

Add iodine solution to the sample. Observe for a colour change to blue-black if starch is present.

Mix the sample with ethanol, then add water. A cloudy white emulsion indicates the presence of lipids.