Dissolved and headspace oxygen concentrations were monitored during microoxygenation (MOX) treatments before and after malolactic fermentation (MLF) of Pinot noir. The implementation of a noninvasive, fluorescence-based measurement system allowed precise oxygen determination in red wine and in the gaseous headspace above the wine surface. Dissolved oxygen (DO) concentrations increased up to 1 and 0.5 mg/L in the second half of pre-MLF and post-MLF MOX experiments, respectively. Untreated control wines showed maximum DO concentrations of only 0.1 mg/L at the end of the pre-MLF and post-MLF MOX trials. For both pre- and post-MLF MOX experiments, the measurement of DO was sufficiently sensitive to discriminate between untreated control and oxygenated wines. Furthermore, different levels of applied oxygen dosages could be differentiated using DO monitoring. Except for the end of post-MLF MOX treatments with high oxygen dosage, no DO gradients were observed within the tanks, suggesting appropriate oxygen distribution during the treatment periods. The novel concept to compare the rate of applied oxygen with DO lead to the expression of the oxygen consumption rate. Plotting this parameter together with the applied oxygen dosage allowed for the assessment of the balance between the ingress and the consumption of oxygen. During pre-MLF and post-MLF MOX treatments, the oxygen consumption rate was consistently ±10% of the applied oxygen dosage. However, wines receiving oxygen post-MLF reacted more sensitively to an elevated oxygen dosage than those treated pre-MLF.
- Copyright © 2010 by the American Society for Enology and Viticulture