Experiment No. 11
Vanilla Extract
Pour into a test tube 5 cc. of the extract to be tested. Evaporate to one third. Then add sufficient water to restore the original volume. If a brown, flocculent precipitate is formed, the sample contains pure vanilla extract. Resin is present in vanilla beans and is extracted in the essence. The resin is readily soluble in 50 per cent alcohol. If the alcohol is removed from the extract, the excess of resin is precipitated, or if free from alkali, it may be precipitated by diluting the original solution with twice its volume of water. Test the two samples and compare.
(Adapted from Leach, "Food Inspection and Analysis.")
1. Describe the appearance of each sample after evaporating and adding water. 2. Which sample contains pure vanilla extract? 3. State the principle underlying this test.