Gamma-tocopherol as a marker of Brazilian coffee (Coffea arabica L.) adulteration by corn

The adulteration of coffee with cereals, coffee twigs, etc. is apparently widespread in Brazil with corn being considered the most widely used. No adequate methods are available to detect such contamination in commercial coffee. A new method, based on high-performance liquid chromatography (HPLC) tocopherol determination was developed to detect coffee adulteration by corn. Percentages of alpha-, beta-, gamma-, and delta-tocopherol determined by HPLC in six coffee varieties were 29.0, 61.7, 3.3, and 6.0, respectively. Similar values were obtained in six popular coffee brands. The percentages of alpha-, gamma-, and delta-tocopherol in six corn samples were 3.6, 91.3, and 5.1, respectively. These differences could be applied to detect corn in a pure coffee sample intentionally contaminated with corn with the best result obtained with gamma-tocopherol. With this methodology, one coffee brand was apparently adulterated (8.9%), most likely with corn. Tocopherol fingerprinting offers the potential to detect adulteration.