Fat Tests

There are three ways to test for fats in food.

The first involves grinding up the food and mixing it with water. Pass the liquid part of the solution through filter paper, squeezing out any 'gunge' - thick bits of the suspension into the same test tube. You should now have a slightly opaque liquid mixture in your test tube. Because fat is less dense than water, if you leave this mixture it will separate out into a layer of fat and a layer of water.

The second test is even easier. Rub the food sample on filter paper and then hold the filter paper up to the light. If the paper is translucent (slightly see-through) there was fat present in the food. Don't try this with watery foods - the water will make the paper translucent and you'll get a false positive.

The third method involves adding ethanol to a very small amount of the test substance. Shake or crush the food to make it dissolve. Filter or dilute the food and ethanol mix so that you get a clear liquid (a solution of fat in ethanol). Add this to a test tube of water. A white (milk-like) emulsion indicates the presence of fats or oils.

This video shows how a test for Fats can be carried out