Difficulty: Challenger (Level 2)
What makes your clean, minty mouth taste so gross when it meets orange juice?
Before you decide you need to stop brushing your teeth to save your taste buds, know that this effect is temporary, lasting only a few minutes. Brushing with toothpaste is still important for your health.
But how does this change in taste happen? Let’s look at the science behind this phenomenon.
Toothpaste changes your taste
The orange juice many people drink with breakfast is naturally high in sugar. But it also contains citric acid. As a result, it’s a delicious combination of both sweet and a little sour.
But if you brush your teeth before breakfast, your orange juice tastes terrible. What’s changed?
Toothpaste contains the detergent sodium lauryl sulphate, which helps remove germs from your teeth.
If you ever do the dishes, you’ve probably seen what happens when you squirt detergent into a sink full of greasy water: the detergent breaks up the greasy fat, making it easy to wipe off the dishes and rinse them clean.
But there’s another type of fat in your mouth that the detergent in toothpaste disrupts – the lipids in the cell membranes of your taste receptors.
Brushing your teeth breaks up that layer of lipids, temporarily changing how you perceive taste.
Put to the test
Back in 1980, I conducted a study with a couple of my colleagues. We wanted to know how the tongue responds to sweet, bitter, salty and sour after being exposed to sodium lauryl sulphate, a detergent found in toothpaste.
We conducted an experiment with seven student volunteers. They tasted very high concentrations of sweet sucrose, sour citric acid, salt and bitter quinine, both before and after holding a solution of sodium lauryl sulphate in their mouths for one minute.
We found that a small amount reduced the intensity of the tastes of sucrose, salt and quinine, but the most important change was that a bitter taste was added to the sour taste of citric acid.
This is why, instead of tasting sweet with a bit of nice tang, your orange juice tastes bitter after you brush your teeth.
You could conduct your own version of this experiment with something sweet like sugar, a little table salt, orange juice and tonic water. Taste them before you brush your teeth and then after.
This article was first published in The Conversation. It was written by Linda Bartoshuk, a research professor of psychology at George Washington University.
