SOLID-STATE C-13 NMR INVESTIGATION INTO INSOLUBLE DEPOSITS ADHERING TO THE INNER GLASS-SURFACE OF BOTTLED RED WINE

C-13 nuclear magnetic resonance spectroscopy with cross polarization and magic angle spinning was used to analyze insoluble, lacquer-like pigmented deposits that adhere to the inner glass surface of bottled red wines. The deposits were found to be composed of a phenolic polymer of anthocyanins, procyanidins, and protein. Glucose was also present, probably as the glucoside moiety of the anthocyanidin units involved in the phenolic polymer. Formation of the deposit is likely to result from extensive cross-linking between the phenolic polymer and protein, rendering the complex insoluble.