Why Does Mint Make Your Mouth Feel Cold?

iStock/bhofack2
iStock/bhofack2

Reader Lisa from Anderson, California, wrote in with a question: "Chew a piece of mint gum and then drink something. It seems colder. Why is that?"

Mint gum or candy might make everything in your mouth feel sub-zero, but like the hot water that sometimes feels cold I wrote about in 2008, the feeling is just a thermal illusion that happens when our sensory receptors get fooled by stimuli.

At the heart of the minty matter is a protein called the transient receptor potential cation channel subfamily M member 8 (TRPM8), which is expressed in sensory neurons. TRPM8 is an ion channel, a type of protein that regulates the movement of ions across the membranes of cells. Just like only certain keys can open a lock on a door, only certain stimulants can open the ion channel and access the cell. TRPM8 opens in the presence of cold temperatures and allows Na+ and Ca2+ ions to enter the cell. This changes the electrical charge within the neuron and the information being sent from the neuron to the central nervous system, eventually leading to the perception of cold.

TRPM8 doesn't just respond to cold temperatures, though.

It also activates in the presence of menthol, a waxy, crystalline organic compound found in peppermint and other mint oils. (It responds to other "cooling agents," too, like eucalyptol and icilin. Why, exactly, is unknown; menthol just happens to fit the cellular "lock.") In the presence of menthol, TRPM8 ion channels open up the same way they would if the ambient temperature in your mouth dropped. The same "hey it's cold in here!" signal is sent to the brain, even though menthol doesn't actually cause the temperature in the mouth to change. And just like that, the wondrous human brain is tricked by a piece of Doublemint.

Even after you spit the gum out, a little menthol will remain and the sensory neurons will stay sensitized. Drinking anything cold or even taking in a big breath of cool air will cause the neurons to fire again, and the double whammy of the cool temperature and the menthol will make your mouth seem extra cold. Even a hot drink will seem weirdly cool and refreshing.

TRP-V1, another ion channel on the sensory neurons, displays a similar quirk. TRP-V1 is activated by hotter temperature, but also responds to capsaicin, the chemical responsible for the spiciness of hot peppers. This can cause even ice cold drinks to feel hot.

So what would happen if you ate a chili pepper that's been in the freezer, or a warmed up mint? Or ate a hot pepper and a cool mint at the same time? Would the hot and cold perceptions cancel each other out? To be honest, we're not sure. Has anyone ever tried this at home?

You Can Now Order—and Donate—Girl Scout Cookies Online

It's OK if you decide to ignore the recommended serving size on a box of these beauties.
It's OK if you decide to ignore the recommended serving size on a box of these beauties.
Girl Scouts

Girl Scouts may have temporarily suspended both cookie booths and door-to-door sales to prevent the spread of the novel coronavirus, but that doesn’t mean you’ll be deprived of your annual supply of everyone’s favorite boxed baked goods. Instead, you can now order Thin Mints, Tagalongs, and all the other classic cookies online—or donate them to local charities.

When you enter your ZIP code on the “Girl Scouts Cookie Care” page, it’ll take you to a digital order form for the nearest Girl Scouts organization in your area. Then, simply choose your cookies—which cost $5 or $6 per box—and check out with your payment and shipping information. There’s a minimum of four boxes for each order, and shipping fees vary based on quantity.

Below the list of cookies is a “Donate Cookies” option, which doesn’t count toward your own order total and doesn’t cost any extra to ship. You get to choose how many boxes to donate, but the Girl Scouts decide which kinds of cookies to send and where exactly to send them (the charity, organization, or group of people benefiting from your donation is listed on the order form). There’s a pretty wide range of recipients, and some are specific to healthcare workers—especially in regions with particularly large coronavirus outbreaks. The Girl Scouts of Greater New York, for example, are sending donations to NYC Health + Hospitals, while the Girl Scouts of Western Washington have simply listed “COVID-19 Responders” as their recipients.

Taking their cookie business online isn’t the only way the Girl Scouts are adapting to the ‘stay home’ mandates happening across the country. They’ve also launched “Girl Scouts at Home,” a digital platform filled with self-guided activities so Girl Scouts can continue to learn skills and earn badges without venturing farther than their own backyard. Resources are categorized by grade level and include everything from mastering the basics of coding to building a life vest for a Corgi (though the video instructions for that haven’t been posted yet).

“For 108 years, Girl Scouts has been there in times of crisis and turmoil,” Girl Scouts of the USA CEO Sylvia Acevedo said in a press release. “And today we are stepping forward with new initiatives to help girls, their families, and consumers connect, explore, find comfort, and take action.”

You can order cookies here, and explore “Girl Scouts at Home” here.

Can't Find Yeast? Grow Your Own at Home With a Sourdough Starter

Dutodom, iStock via Getty Images
Dutodom, iStock via Getty Images

Baking bread can relieve stress and it requires long stretches of time at home that many of us now have. But shoppers have been panic-buying some surprising items since the start of the COVID-19 crisis. In addition to pantry staples like rice and beans, yeast packets are suddenly hard to find in grocery stores. If you got the idea to make homemade bread at the same time as everyone on your Instagram feed, don't let the yeast shortage stop you. As long as you have flour, water, and time, you can grow your own yeast at home.

While many bread recipes call for either instant yeast or dry active yeast, sourdough bread can be made with ingredients you hopefully already have on hand. The key to sourdough's unique, tangy taste lies in its "wild" yeast. Yeast is a single-celled type of fungus that's abundant in nature—it's so abundant, it's floating around your home right now.

To cultivate wild yeast, you need to make a sourdough starter. This can be done by combining one cup of flour (like whole grain, all-purpose, or a mixture of the two) with a half cup of cool water in a bowl made of nonreactive material (such as glass, stainless steel, or food-grade plastic). Cover it with plastic wrap or a clean towel and let it sit in a fairly warm place (70°F to 75°F) for 24 hours.

Your starter must be fed with one cup of flour and a half cup of water every day for five days before it can be used in baking. Sourdough starter is a living thing, so you should notice is start to bubble and grow in size over time (it also makes a great low-maintenance pet if you're looking for company in quarantine). On the fifth day, you can use your starter to make dough for sourdough bread. Here's a recipe from King Arthur Flour that only calls for starter, flour, salt, and water.

If you just want to get the urge to bake out of your system, you can toss your starter once you're done with it. If you plan on making sourdough again, you can use the same starter indefinitely. Starters have been known to live in people's kitchens for decades. But to avoid using up all your flour, you can store yours in the fridge after the first five days and reduce feedings to once a week.

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