Friday, March 26, 2010

Science Saturday: Spicy Spicy Science

So, I like hot food. I like science. Why not combine them together? I was listening to Tom Allen on CBC Radio 2 Shift today (apparently, he provides me with much insight) discuss the Scoville Unit and determining the heat of peppers. Then I got to thinking about converting it into a science lab. Here we go:

So, Wilbur Scoville designed this scale in 1912 to determine and compare the pungency of peppers. This is defined by the amount of capsaicin contained within the pepper. His test, known as the Scoville Organoleptic Test, involves soaking dried peppers in alcohol (capsaicin is alcohol-soluble) and determining by how much it must be diluted with sugar water until it is undetectable to taste. So a pepper with a rating of 2000 Scoville Units must be diluted over 2000 times (its original volume) to render it unpercetable by human taste.

How does this apply to the science classroom? Well, this makes a fantastic open ended science lab that can cover important topics such as: experimental error, subjectivity of methodology, issues with perception, observation and experimental design.

My idea is to provide students with the background information presented above. Have them design an appropriate experiment to determine the Scoville Rating of an unknown sample. Provide each student group with a different sample (I would recommend nothing too hot as it can burn eyes and mucous membranes) and let them run their experiment. Students should have the opportunity to present and discuss the different methodologies chosen by their peers.

Of course, the one outstanding question on your mind is: you want me to have students drink alcohol? Well, it is unfortunate that capsaicin is not water soluble, but it is fat and oil soluble so I would recommend using vegetable/olive oil instead of alcohol in class.

Finally, here is how Scoville did it. He had a minimum of five tasters who were allowed to taste only once per session to prevent prior tastings from influencing their decisions. Because of the subjectivity of the testing, today we test through liquid chromatography.

One more extension is to discuss why drinking water after eating food spiced with capsaicin doesn't work (it is not water soluble). Whereas the drink of choice, beer, has a mild amount of alcohol which can alleviate the burning sensation. The alternative drink, milk, has a compound casein (which is lipophilic or fat-loving) that surrounds the fatty capsaicin molecules and washes them away.

This is a easy to run lab which should provide ample opportunities for students to explore the scientific method while having a bit (or heaps) of fun.

More information on Scoville, capsaicin and peppers:
Chile Pepper Scoville Scale
The chemistry of capiscum

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