Why Toothpaste Makes Orange Juice Taste Bad - Instant egghead #43

Ew, why does orange juice taste so bad after brushing your teeth? To find out why, let's take a close look at the human tongue. The little bumps on our tongues are dotted with taste buds, which are made up of taste receptor cells. It's the receptors on these cells that let us identify different tastes, like bitter, sweet and the savory taste known as umami. Ion channels pick up on salt and acid levels in our food, letting us taste salty and sour. When a taste molcule, say, a sugar molecule in our OJ, binds a sweet receptor, it triggers a series of signals that tells our brain we're tasting something sweet. Toothpaste contains the detergent Sodium Lauryl Sulphate, also known as SLS, ... ... which creates foam while brushing. When they say it gets your teeth cleaned, they really mean it. Unfortunately, SLS also temporarily gets rid of the molecules called phospholipids, which block our bitter receptors. This makes the receptor much more sensitive to the bitter flavors in OJ, causing that awful taste. Of course, SLS isn't the only substance that can alter our sense of taste. The compound miraculin, found in so-called magic berries, binds sweet receptors so they only respond to acids. After chewing a magic berry, a spoonful of vinegar tastes a lot more like a spoonful of syrup. And a much less pleasant phenomenon is something called pine nut mouth. For some people, eating pine nuts leaves a nasty metalic aftertaste, which affects everything they eat for days, or even weeks. Something gets caused by a species of pine nut imported from China, ... ... but the mechanism is still a mystery. Luckily your receptors aren't the only factors affecting taste: ... ... temperature, texture and smell can change what you sense too. So, next time maybe try plugging your nose when you're having OJ at brunch, or even better, go for a coffee, or a Bloody Mary instead. For Scientific American's Instant Egghead I'm Yasmin Tayag.