SudanIV

Like lipids, the chemical Sudan IV is not soluble in water; it is, however, soluble in lipids. In this test dark red Sudan IV is added to a solution along with ethanol to dissolve any possible lipids. If lipids are present the Sudan IV will stain them reddish-orange (positive test).

Procedure:

1. Pour 5 mL of your test substance into a test tube.

2. Add 5 drops of Sudan IV to your test tube. (Caution: use care when handling Sudan III to avoid staining hands or clothing!) Sudan will dissolve in lipids and stain them red. (Sometimes, red globules or droplets will form in the substance. This is also positive for lipids.)

3. Gently shake/swirl the contents of the test tube. Look for any color change in the test substance.

4. Clean your test tubes thoroughly.

Another way to test for Lipids

You can also use a piece of brown paper to indicate the presence of lipids, as the paper will absorb the lipid and be visible.

1. Obtain a small piece of brown paper bag & label it with your test substance.

2. Place a small drop of the test substance onto the brown paper. Wipe off any excess pieces of food, if needed.

3. Set the paper aside until the spot appears dry (approx. 10 min.)

4. Hold the paper up to a bright light or window. If the test substance leaves a translucent spot on the brown paper, there are lipids present.

Sources:

https://www.emsisd.com/cms/lib/TX21000533/Centricity/Domain/1145/Identifying%20Macromolecules.ppt

http://faculty.uncfsu.edu/jraynor/BIOL%20200%20Online%20Lab/Biological%20Molecules%20Lab.htm