The decay of ascorbic acid in a model wine system at low oxygen concentration

The present study investigated the impact of temperature on the degradation of ascorbic acid in low oxygen conditions in a model white wine. The concentrations of ascorbic acid, furfural, sulfur dioxide and phenolic-type products were monitored in a model white wine stored under non-oxidative conditions at 45.0, 36.5 and 24.0 °C for up to 693 days. The concentrations of both ascorbic acid and sulfur dioxide decreased over the analysis period while furfural and other colourless phenolic products increased in concentration, despite the presence of residual sulfur dioxide. The decay of ascorbic acid in the low oxygen conditions followed first-order kinetics and the rate constants were determined to be (3.5±0.2)×10(-8), (1.02±0.07)×10(-8), and (0.184±0.009)×10(-8) s(-1) for 45.0, 36.5 and 24.0 °C (n=5, standard error), respectively, and the activation energy was 110±3 kJ/mol (n=3, standard error). Importantly, these data allow more accurate prediction of the temperature-induced loss of ascorbic acid in low oxygen conditions during transport or storage of wine.