Buffer

A buffer is a combination of a weak acid and its conjugate base (or vice versa) that resists changes in pH when small amounts of acid or base are added. It neutralises additional hydrogen or hydroxide ions, keeping the hydrogen ion concentration relatively stable.

How buffers work and why they matter

Buffers function through reversible reactions between acid and base forms. When an acid is added to a buffered solution, the conjugate base component reacts with the hydrogen ions, forming more of the weak acid and preventing a large drop in pH. When a base is added, the weak acid donates a proton to neutralise hydroxide ions, limiting the rise in pH. This ability to moderate pH is essential in food and drink formulation. In sports drinks, maintaining a narrow pH range helps preserve flavour, prevents the breakdown of vitamins and pigments, and slows microbial growth. A mixture of citric acid and sodium citrate, for example, keeps a drink’s acidity around pH 3–4 even when diluted. Stable pH also reduces the risk of tooth enamel erosion because the acidity does not spike abruptly.

Examples in hydration formulas

Common buffer salts used in electrolyte beverages include sodium phosphate, potassium citrate, and sodium lactate. These compounds not only help control acidity but also contribute electrolytes that support muscle function. A drink containing both citric acid and sodium citrate will remain consistently acidic, whereas a solution without a buffer could become much more acidic or alkaline when mixed with other ingredients. Athletes who consume buffered drinks are less likely to experience stomach discomfort from sudden acidity changes. In physiological terms, blood maintains pH around 7.4 using its own buffers such as bicarbonate and proteins.

In summary, buffers stabilise the hydrogen ion concentration of a solution by neutralising added acids or bases. This property is vital in sports drink formulation to ensure consistent taste, shelf stability, and gentle acidity during consumption.

Related Terms: pH, Acidulant, Solvent, Colligative properties, Carbohydrate concentration