Metatartaric acid: physicochemical characterization and analytical detection in wines and grape juices

Seven commercial metatartaric acid (MTA) products used for tartaric stabilization of wines were investigated regarding molecular masses and composition. Combined size-exclusion chromatography with MALS detection showed that the products had medium molecular masses in a range of 2–9 kDa. All samples were highly polydisperse products with a broad molecular weight distribution. Beside oligomeric or polymeric contents, the products contained on average 13 g/100 g monomeric tartaric acid, thus reducing the effectiveness of MTA in respect of achieving tartaric stability. An analytical method to determine MTA in wines and grape juices based on an anion-exchange cleanup step, HPLC separation, and MS detection was developed. The method shows a sufficient robustness to evaluate important enological or food legal aspects in connection with MTA.