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This Chili-Shaped Smartphone Accessory Can Measure a Pepper’s Spiciness

New device can measure concentrations of capsaicin, the compound that gives peppers their burning heat

A new chili pepper-shaped device that connect with a smartphone to reveal how much capsaicin is in a hot pepper. (Adapted from ACS Applied Nano Materials 2020, DOI: 10.1021/acsanm.0c02079)
smithsonianmag.com

The Carolina reaper pepper currently holds the Guinness World Record for the hottest chili pepper in the world. On the Scoville scale, a numerical rating aimed at quantifying spiciness, individual Carolina reapers typically fall somewhere between 1.5 and 2 million Scoville heat units (SHU). For reference, the more pedestrian jalapeno tops out at around 8,000.

But for those looking to singe their mouthparts on the hottest peppers on Earth, the fiery calculus behind the Scoville scale is a bit vague. Individual peppers are subject to variation—they’re plants after all—leading spice junkies to rightly wonder: Was that taste bud inferno a weapons-grade 2 million SHU reaper or a more run of the mill 1.5 million SHU pepper?

Now, a new device can swiftly detect just how hot a chili pepper truly is, reports Andrew Liszewski for Gizmodo.

The portable device, called the Chilica-Pod, is shaped like a red hot pepper and plugs directly into a smartphone. It works by detecting concentrations of capsaicin, the chemical compound responsible for the burning sensation produced by eating spicy peppers, reports Erin Garcia de Jesus for Science News.

Researchers describe the new gadget in a paper published last month in the journal ACS Applied Nano Materials. Warakorn Limbut, a chemist at Prince of Songkla University in Hat Yai, Thailand, who led the development of the Chilica-Pod prototype, tells Science News the device could become an essential tool for people allergic to capsaicin or for farmers looking to measure their harvest’s heat.

The spice-detector's mobile app allows the user to view the results of a test on their phone. The test itself uses strips of paper with thin, stacked sheets of graphene that have been infused with nitrogen atoms to increase their electrical conductivity, according to Gizmodo. To measure a chili’s spiciness, the user mixes a small amount of the pepper, which can be fresh or dried, with ethanol.

Per Science News, placing a drop or two of the chili-infused alcohol solution on the paper strip causes electrons to move between the graphene atoms on the strip. The more capsaicin the solution has, the stronger the electrical current conducted by the sheets. This chemistry lets the device rapidly detect concentrations of capsaicin.

The researchers used six samples of dried chilis to check the Chilica-Pod’s accuracy. After Limbut and his team tested the samples with their prototype, they tested them again with a more laborious, equipment-intensive method called spectrophotometry that is generally considered to be quite accurate, reports Jennifer Ouellette for Ars Technica.

The Chilica-Pod’s results checked out, finding concentrations of capsaicin ranging from 7.5 to 90 micromoles per liter of solution, according to Science News. Mixing up a batch of pepper-ethanol solution before tucking into a meal may not be practical, but the device could offer an easier and more accurate method of measuring spiciness for chefs or farmers looking to dial in the heat of their wares.

Speaking with Science News, Paul Bosland, a plant geneticist and chili breeder at New Mexico State University, notes that capsaicin isn’t the only compound responsible for a pepper’s zing. In fact, he says there are 24 related compounds that bring the heat, and suggests any device aimed at quantifying spiciness would need to “read them all.”

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