Control of bubble-free oxygenation with silicone tubing during alcoholic fermentation

• We design an innovative system for oxygen addition during enological fermentation.
• Precise and reproducible oxygen additions are feasible.
• Oxygen transfer rate is controlled by the liquid velocity inside the silicone tube.
• A mathematical model was developed to calculate OTR from the operating parameters.

The addition of oxygen is a common practice during winemaking to improve fermentation kinetics. However, an important limitation of standard oxygenation systems is that it is difficult to determine the exact quantity of oxygen transferred to wine or must. Tools enabling precise and reproducible oxygen addition would be useful. We developed and validated a bubble-free oxygenation system, at laboratory and pilot scale. In this system, oxygen is added by diffusion through a silicone membrane tube.We evaluated the effects of various parameters on the maximum oxygen transfer rate (OTRm). For fixed characteristics of the silicone tube and the partial pressure, the effects of dissolved CO2 and medium composition were negligible; parameters with the biggest influence on the OTRm were the liquid flow rate and the temperature.These data were used to construct a mathematical model that calculates the OTR as a function of the operating parameters. This phenomenological model allows comprehensive description of physical parameters influencing the OTRm. The model's predictions were very accurate both for the validation experiments in synthetic media and in real fermentation conditions. This work makes a step toward innovative strategies for oxygen management during alcoholic fermentation.