Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to [email protected].
Why does orange juice taste bad after you brush your teeth? – Seth G., age 10, Bloomington, Indiana
It’s a mistake you hopefully only make once. In your morning rush to get ready, you brush your teeth before you head to the kitchen and down a big glass of orange juice. Yuck!
What makes your clean, minty mouth taste so gross when it meets OJ?
The short answer is that toothpaste contains a detergent that dissolves fat. And since your taste buds are partly made of fat, they are disrupted whenever you brush your teeth.
Before you decide you need to stop brushing your teeth to save your taste buds, know that this disruption is temporary, lasting only a few minutes. Brushing with toothpaste is still important for your health.
But how does this change in taste happen? And how are the taste receptors that are all over the surface of your tongue supposed to work?
I’m a psychologist, and I’ve spent more than 40 years researching the science of how people experience taste and flavor.
Let’s look at the science behind this phenomenon:
A bittersweet symphony
Thanks to evolution, your brain is wired to make you love the sweet sugars your body and brain need for fuel and hate the bitter poisons than could kill you. So your receptors for these two particular tastes are vital to your survival.
All of the cells in your body are held together by an outer layer, known as the membrane, that is made up of fats called lipids. And in sweet or bitter taste receptor cells, the cell membranes also contain a special molecule called a G protein-coupled receptor, or GPCR.
Some GPCRs are designed to detect sweet tastes. They tune out all compounds that aren’t sweet and respond only to the sugars your body can use. Others detect bitter tastes, tuning in to the large number of compounds in nature that are poisonous. They act as a built-in alarm system.
Salty chips and sour candies
Your perception of saltiness and sourness happens a little differently. These tastes are detected when positively charged ions called cations pass through tiny openings in the cell membrane of your salty and sour receptors.
In the case of saltiness, the cation is the positively charged sodium found in sodium chloride – common table salt.
For acidic, or sour, tastes, the cation is a positively charged hydrogen ion. While different types of acids may contain different chemical compounds, they all contain the hydrogen cation.
When you eat potato chips, the positively charged sodium cations from the salt pass through special openings in a receptor’s membrane, producing the salty taste. Similarly, the hydrogen cations in your favorite sour candy slip through other special openings in your sour receptor’s membrane and send a “sour” signal to your brain.
