Steam Distillation of Spices

Week 5: This week we took a break from our Peer Developed Peer Lab experiment project in order for the students to firm up the final copies of their experiment handouts and webpages. We did the “Steam Distillation of Spices” experiment this week. It may be better described a “hydrodistillation” rather than steam distillation since we simply put the ground up spices in water and, boil the concoction, and collect the condense steam. The classic version of this experiment used cloves. Cloves smell nice and give a fair amount of essential oil. From cloves, I have expanded to anise, caraway, cumin and cinnamon. I like the steam distillation lab because of its application to natural products chemistry, my specialty. This year we have the benefit of analyzing the samples by GC-FID. Other years we have done the analysis with UV, IR, and, or course, TLC. These methods do not show the blend of compounds that typically constitute essential oils. It seems like most steam distilled essential oils are made up a one or two major compounds with several minor components that would be detectable only with a technique like GC. This year we were able to detect both the “trees” and the “grass.” Using several spices instead of one, allows students to contrast and compare their results with others. I put up representative GC chromatograms for each spice on the internet as well as a few standard compounds. Please see our steam distillation page for an expanded discussion of this experiment.