Describe the chemical composition of 'wine diamonds' and how their formation is influenced by temperature and pH.

Wine diamonds are crystalline deposits that form in wine, primarily composed of potassium bitartrate (KHT) and, to a lesser extent, calcium tartrate. Potassium bitartrate is a salt of tartaric acid, the most abundant organic acid in grapes. Calcium tartrate's formation is less common than potassium bitartrate, but it can still occur and contribute to crystal formation. These crystals are harmless and do not affect the wine's flavor or aroma, but consumers often perceive them negatively. Temperature and pH significantly influence the formation of wine diamonds. Potassium bitartrate's solubility decreases as temperature decreases. At lower temperatures, potassium bitartrate becomes less soluble and is more likely to precipitate out of the wine, forming crystals. This is why cold stabilization is used to prevent tartrate crystal formation. pH also affects potassium bitartrate solubility. Lower pH (higher acidity) increases the solubility of potassium bitartrate, while higher pH (lower acidity) decreases its solubility, promoting crystal formation. This is because at lower pH, the tartaric acid is more likely to be in its undissociated form, which is more soluble. The presence of potassium ions (K+) also influences the formation of potassium bitartrate crystals. Higher concentrations of potassium ions increase the likelihood of crystal formation. Alcohol concentration also plays a role, as higher alcohol levels can decrease the solubility of potassium bitartrate. The formation of wine diamonds is a complex process influenced by multiple factors, but temperature and pH are the most critical. Cold stabilization manipulates temperature to force tartrate precipitation before bottling, while adjusting pH can also influence tartrate stability. Other stabilization methods, such as adding carboxymethyl cellulose (CMC), work by inhibiting crystal growth rather than removing tartrates directly.