Visualizing Capsaicinoids: Colorimetric Analysis of Chili Peppers

A colorimetric method for total capsaicinoids in chili pepper (Capsicum) fruit is described. The placental material of the pepper, containing 90% of the capsaicinoids, was physically separated from the colored materials in the pericarp and extracted twice with methanol, capturing 85% of the remaining capsaicinoids. The extract, evaporated and reconstituted in acetonitrile, was treated with Gibbs reagent to produce a beautiful blue product, easily detected by eye. Semiquantitative measurement was made by comparison to a printed color chart. The simple analysis required no electronic equipment or chromatographic separations, so is amenable to classroom demonstration, introductory laboratory, and the field. Accuracy was demonstrated by favorable comparison of results with those from a standard liquid chromatographic method for eight varieties of chili pepper.