The high-tech way to test spicinessS

As science marches on, it’s nice to know that one area it will never neglect is food. We have not just one, but two ways to test the spiciness of chili peppers. One relies on the tongue. The other is a bit more high tech.

Chili peppers used to be ways for plants to keep their precious seeds from getting chomped up by herbivorous mammals. Then they became special spices for food. They’re now on their way to becoming chemical weapons, as people seek out spicier and spicier peppers. How, though, can we know that we’re not just getting wimpier? Fortunately, there's a test.

The business chemical of a chile pepper is its capsaicin. It's the chemical that produces the burning sensation on the tongue. And in the nose. And anywhere else an unfortunate human might rub it on their body. The original test to see how much capsaicin was in a pepper was known as the Scoville Test. It relied on a group of five unfortunate humans to taste the pepper, generally ground up in a solution of water and sugar. The solution was diluted again and again, until the panel couldn’t taste the spice anymore. The amount of dilution translated to the number of Scoville heat units the pepper was assigned. Sweet peppers averaged about 100, while hotter ones could get up to 350,000.

Today, we’ve gotten chiles that earn millions of Scoville heat units, and contests are set up around eating them. But when you turn something into a sport, it requires more accuracy than a panel of five. Enter the new high-tech spiciness test. It’s called High Pressure Liquid Chromatography, and it bears a resemblance to the tests you can do at home to find out what dyes are in your candy.

The test involves grinding the peppers up, mixing them with a solvent, and putting them in a long column. The top of the column is hollow, allowing the mixture to settle. Below is a packing material. The packing material can be anything from sediment beads to silica gel. The important thing is it fills the column, and the mixture has to filter down through it. A lot of things make a difference with how the liquid will filter down, but it all comes down to coherence and adherence. Coherence is the degree to which each molecule in a liquid sticks to the other molecules in the liquid. Adherence is the degree to which the liquid molecules stick to a new substance.

The different materials in the solvent alter its qualities. It will adhere to the packing material to different degrees, depending on what's dissolved inside it. Instead of the entire solution filtering down, different materials inside it will filter down at different rates. The solvent with the capsaicin will be separated out from the rest of the material as it slowly seeps down the column. Once the capsaicin is separated out, it can be measured.

The entire process can be done using gravity, but adding a lot of pressure – making it high-pressure chromatography – speeds up the test. And really, when you’re measuring chilis, don’t you want to get it over with as fast as possible?

Top Image: Darwin Bell

Second Image: Andra Mlhali

Via Chemguide, Chemguide, and Kitchen Chemistry.