Mint is the perfect ingredient for a refreshing summer drink because it makes your mouth feel cold. But mint feels cold even when it’s not crushed with ice. The scientifically inclined connoisseur of mint juleps might stop to ask: how?
The answer turns out to be a quirk of neurology. The neurons in charge of sensing cold emit a protein called TRPM8. When this protein gets cold, it opens like a gate, and lets ions in the environment enter the neuron. This changes the electrical charge within the neuron and the message “cold receptor activated!” is passed up the central nervous system to the brain.
So far, so biological. The twist is that TRPM8 doesn’t just respond to cold. It also responds to menthol, the crystalline compound found in peppermint and mint oils. Why, exactly, menthol fits TRPM8’s chemical handle is unknown, but once that handle is turned, the TRPM8 opens its gate and the cold receptor neurons are activated.
Cold receptors only send one kind of message, and so – remarkably – the taste of mint is indistinguishable from the feel of cold. Cheers to that!
HOW TO MAKE MINT SYRUP
1/3 cup sugar
1/3 cup water
1/2 cup packed fresh mint
Ice and water
Bring sugar and water to a boil in a small saucepan; cook until sugar dissolves. Meanwhile, put ice and some water into a bowl, to serve as an ice-water bath.
Add mint to the boiling sugar water; cook until vibrant green, about 30 seconds. Remove from sugar water and carefully transfer mint to ice-water bath. Drain through a sieve; squeeze out excess water with a paper towel or fine cloth. Let syrup cool.
Once cooled, puree mint and sugar syrup in a blender until smooth. Let stand for 15 minutes.
Strain through cheesecloth or other thin cloth; discard solids. Refrigerate until ready to use.
Use mint syrup to make mint lemonade tea, as a garnish for desserts, or for cocktails like mojitos and mint juleps.