sourness

Sourness is one of the five basic tastes detected by the human gustatory system. It is typically elicited by acidic substances and is often described as sharp, tangy, or tart. The perception arises when hydrogen ions (protons) from acids interact with taste receptor cells in the taste buds, initiating signaling that is interpreted by the brain as sour. The precise molecular receptors are still a subject of research, but proton concentration and titratable acidity influence perceived intensity, with pH not always directly proportional to sourness.

Common sour agents include citric acid in citrus fruits, malic and tartaric acids in many fruits, lactic acid in fermented products, and acetic acid in vinegar. In foods, sourness can be increased or moderated by blending with sugars, salts, or fats, and is a key component in fermentation and preservation techniques such as sourdough, yogurt, pickles, and wines.

Beyond cuisine, sourness serves ecological and nutritional roles, signaling acidity in foods and affecting flavor balance and enjoyment. It also intersects with health considerations; excessive exposure to highly acidic substances can erode tooth enamel, while naturally acidic foods can aid digestion and flavor enhancement when consumed in moderation. Individual and cultural differences, influenced by genetics, age, and dietary exposure, shape the perceived intensity and acceptance of sour tastes.