Like bitter flavors, sourness is nature’s way of waving a red flag over a substance that is unripe, spoiled, or otherwise inedible. But for those of us who don’t mind a bit of tartness, this warning signal may actually be the first sign of some healthy benefits.
We can taste sourness thanks to receptors on our tastebuds that detect hydrogen ions from organic acids found in certain foods. Many of these acids occur naturally and are part of a food’s flavor profile, such as citric in lemons, tartaric in tamarinds, and oxalic in leafy greens.
Unripe fruits are particularly sour before becoming sweeter, since their acids are eventually broken down during the ripening process and their acerbic taste replaced by natural sugars. Other acids in foods are due to additives like acetic acid (used to make vinegar) or as a result of fermentation, which produces lactic acid in pickled produce like sauerkraut and cultured dairy such as yogurt.