Corinne Rich and Andrew Waterhouse* 
*Department of Viticulture and Enology, University of California,
Davis, CA 95616 (alwaterhouse@ucdavis.edu)

Riesling wine was treated with an array of different reagents used to promote increased shelf stability in wines not intended for long term cellaring. These reagents included independent and combined treatments of potassium metabisulfide, ascorbic acid, chitosan, potassium polyaspartate, gallic tannins, citric acid, and poly-vinylimidazole polypyrrolidone (PVI). All treated and control wine samples were then subjected to an accelerated aging protocol. This included four weeks of weekly temperature cycling, with 12-hour periods of hot and cool temperatures, followed by a six-day holding period at room temperature. Samples were taken at zero, four, and eight weeks and analyzed for free and total sulfur dioxide, oxidative browning, iron and copper content by flame AA, low molecular weight phenolics and acetaldehyde by HPLC, and volatiles by GC-MS. Results indicated that those treatments containing combinations of stabilizing reagents had mixed results in scaling linearly with their individual components in reducing oxidative products, hazes, and other indicators of instability. The combination of PVI and chitosan proved effective, while a combination of potassium metabisulfide, ascorbic acid, citric acid, and gallic tannins was less effective than the individual components. Overall, those treatments that removed metals from solution most effectively, such as PVI and chitosan, had an increased ability to stabilize wines by preventing increases in markers for advanced oxidation, like acetaldehyde and browning pigments.

Funding Support: Enartis Vinquiry