The alcoholic fermentation of wine is a biological process, triggered with the addition of yeasts, in which the sugars in the must turn into ethyl alcohol, CO2, heat and other by-products.
Gaseous carbon dioxide (CO2) causes the solids, mainly the skins, to rise to the surface of the must. This phenomenon forms a compact layer at the top, called the cap. The cap protects the must from bacteria and oxidation.®
The must can be pumped over to make the mixture in the tank consistent. This technique consists of transferring the fermenting must from the bottom to the top of the tank to soak the cap. Spraying devices can also be used to distribute it evenly over the surface and they also prevent the formation of channels that could affect the maceration process.
Other benefits of pumping over:
- Aeration of the must to increase and activate the yeasts.
- Preventing the cap from drying to avoid the formation of bacteria and mold on the surface.
- Keeping the cap cool (the skins in the cap can reach high temperatures and pumping over cools them down and helps prevent the growth of thermophilic bacteria).
- Distribution of the yeasts.
- Extraction of substances from the skins, especially tannins, colors and aromas.
The seeds of the grapes gather at the bottom of the tank during fermentation and, unlike the skins, carbon dioxide cannot make them float to the surface. Therefore, it is necessary to pump them up onto the top of the cap so that more of their tannins can be extracted.
The number of times and frequency with which the wine needs to be pumped over in each tank is decided by the oenologist depending on the grape variety, fermentation phase and the wine being made.
The ideal pump for pumping over
To perform the process of pumping over in the best conditions, INOXPA offers the RV range of centrifugal pumps with the helicoidal impeller.
These pumps are ideal for pumping over since they are designed to pump high flow rates of liquids with solids in suspension and avoid damage to the solids (different sizes depending on pump size, maximum particle size ø = 75 mm).
Advantages of RV pumps
- The lower energy input to the wine: thanks to their excellent design with CFD tools, they obtain very high-performance levels (>70%). This means a lower increase in the temperature of the pumped liquid.
- Low energy consumption thanks to their high performance.
- Minimal damage to solids (skins, seeds, pulp…): the helicoidal impeller and the very precise clearances between the impeller, cover and pump casing guarantee minimum recirculation inside the pump and let solids through without damaging their structure.
- Easy maintenance.
- No need to place a grid to serve as a strainer in the tank.
- CE-1935/2004 and FDA compliant food-grade materials.
- The motor in compliance with the IEC standards (RV version) and with NEMA standard (RVN version).