Using A Sequence of Experiments with Turmeric Pigments from Food to Teach Extraction, Distillation, and Thin-Layer Chromatography to Introductory Organic Chemistry Students

This experiment encourages students to use deductive reasoning skills to understand the correlation between different techniques used in a chemistry laboratory and to extract and analyze curcuminoids using natural products and processed food from a grocery store. Turmeric pigments were used to teach continuous or discontinuous extraction, vacuum or atmospheric pressure distillation, and thin-layer chromatography (TLC) in an introductory organic chemistry laboratory course in three laboratory sessions of 3-4 h each. Pigment extracts from the rhizome of turmeric, commercial dehydrated vegetable soup, and chicken-flavored instant bouillon (with turmeric as an ingredient) were used. The three techniques were discussed in the first laboratory session before students proposed a methodology to identify pigments in food extracts through a problem-based format. Students were assessed in a final exam where they presented a more detailed discussion of the chemistry laboratory techniques used. These results were compared to exam results from previous years. On the basis of students' and teacher's feedback, the sequence of laboratory experiments was considered interesting, and students were motivated to participate more actively during instruction.