Ever get a craving for something salty? Or maybe you're more of a sugar fiend? Or perhaps you prefer something with a sour punch? We all have our own weaknesses for different flavors. But how do we perceive these different tastes?
It all comes down to chemistry.
Humans perceive taste through taste buds. Taste buds are sensory organs found on our tongue, the roof, sides, and back of our mouth, and even in the throat.
Historically, way back in the day (after dinosaurs but before Facebook), our perception of how something tasted would help warn us if something was energy-rich or poisonous.
The sensation of taste is produced when the chemical composition of a substance in the mouth reacts with the receptors of these taste buds.
For instance, saltiness is perceived when alkali metals enter the taste buds. If you've got a craving for fries and potato chips, you can thank your friends in the first group of the periodic table: lithium (Li), sodium (Na), potassium (K), rubidium (Rb), caesium (Cs), and francium (Fr). Remember that these alkali metals are more likely to form ionic bonds due to their positioning in the periodic table having only one valence electron.
Sweetness, on the other hand, comes from substances that consist of carbonyl groups like aldehydes and ketones, which are composed of covalent bonds.
But if you'd prefer a nice glass of lemonade or a bag of sour patch kids, then your taste buds are more likely to encounter hydrogen ions. Sourness is the taste that detects acidity, and is measured relative to dilute HCl, which has a sour index of 1. As a comparison, citric acid found in some soft drinks has a sour index of about 0.46.
Did you know that molecules with the same chemical formula can have significantly different tastes? Let's look at the molecule C10H12O2. This molecule is responsible for giving nutmeg and cloves their own distinct tastes. The difference lies in how the atoms are configured and the bonds formed between the atoms. The displacement of one double bond is all it takes to change this molecule from eugenol (responsible for the taste of cloves) to isoeugenol (responsible for the taste of nutmeg). Go here to learn more.