How we experience what we eat or drink very much depends on our sense of taste and smell. Many foodstuffs and some drinks have a cocktail of chemicals that stimulate different smell and taste receptors. Eating or drinking different things together can seem pleasant, bland or even obnoxious. This is because of the interaction between the substances in the food or drink.
Think of peanut butter and jam, strawberries and cream, egg and steak. Each of these combinations seems to “taste” better than any of the single items by themselves.
Brushing one’s teeth is an important way to keep teeth healthy and prevent accumulation of food scraps and bacteria that can ultimately cause tooth decay. But have you ever noticed how brushing your teeth either soon before or just after eating or drinking certain things makes them taste foul? One well known example is orange juice. Something about brushing your teeth makes the taste of orange juice seem weird, but why?
It’s all about the chemistry of orange juice and toothpaste
Orange juice contains a lot more than you might think, but the two main ingredients, apart from plain water, are sugar and a weak, organic acid, citric acid. What we taste when we drink orange juice depends on two of our five types of taste buds. Our taste buds are divided up into those that can sense “acid / sour”, “sweet”, “salt”, “bitter” and “umami”. The latter is the taste that meaty foods have in them. Of these five taste buds, the “sweet” and “sour” buds are stimulated by orange juice, together with various odours, which are sensed by smell sensors in the nose.
Mix in toothpaste, which contains various substances itself, but the key ingredient that affects the flavour of orange juice is something called sodium lauryl sulphate (SLS). This substance is put into toothpaste to make it frothy when you brush your teeth. Now, frothy toothpaste isn’t strictly necessary, but it does spread the paste around more easily.
SLS also affects two of the taste buds by masking the sweet bud sense and counteracting any fats that themselves mask bitter tastes. The basic result is that when orange juice and SLS are in your mouth together, the sweet taste of the juice is removed, and any latent bitter tastes are exaggerated, making the orange juice quite unpleasant.
Don’t mix orange juice with toothpaste!
The simple answer if you find one of these strange flavour distortions is to not brush your teeth so soon before or after drinking or eating the thing that then tastes weird.
Funnily enough, if you ever asked a dentist about why orange juice tastes strange when drunk after brushing your teeth, they would probably advise you not to brush your teeth right after taking orange juice anyway for a different reason. Orange juice contains two substances that are not that good for teeth. The sugar in it is definitely not good for your teeth as it attracts bacteria.
The acid in the juice actively erodes the hard enamel on the outside of your teeth. By brushing your teeth right after drinking orange juice, it tends to spread the acid component around the mouth, compounding its damaging effect on your teeth’s enamel.