Oxygen measures and consumption in must and wine Original Research Article

The aim of this work is to point out a system of oxygen measure on real scale and to estimate the oxygen concentrations in must in red winemaking, in particular during maceration and alcoholic fermentation. The experimental vat had two different controlled aeration systems of must: during pumping-over or during the re-circulation of a fraction of the liquid. For the evaluation of the oxygen dissolved during maceration, the vat was equipped with devices to carry out the measure in the must before the aeration, in the must aerated during the re-circulation, after the pumping-over and in the total mass. The measure of dissolved oxygen were made with an instrument based on the Clark electrode, provided with automatic compensation for the temperature and the salinity. In order to obtain the consumption kinetics, the measures were made in the time range necessary to reach the values determined before aeration. During maceration, the oxygen concentration returns to the initial value in variable times, ranging from few minutes to 20 min. In the first 2–3 min the oxygen dissolved in the total mass is reduced of 50–60% during the tumultuous fermentation and of the 35–50% at the end of alcoholic fermentation. Subsequently the decrease is gradual and slower and the oxygen concentration was closed to the instrumental detection limit. The consumption kinetics, apart from the mechanism, can be represented by an exponential equation.