Gravity is almost a magic word in today’s winemaking world. Anyone visiting a winery will see the gleam in the winemaker’s (or the owner’s) eye when they say, “everything here is gravity fed.”
From the crush pad at the top of the building to the cellar room below, equipment in a gravity facility is set so that grapes, must and juice can be moved from one vessel to the other by simply dropping them from a higher level to a lower one. This avoids the use of pumps, allowing—or so the principle goes—a more gentle handling of the wine-to-be.
Is gravity better in all respects? It’s worth questioning.
What about pumps?
Of course, it’s relatively rare that a winery designed to use gravity will manage to avoid the use of pumps entirely. Whether it’s to move the wine from barrels to a blending or holding tank, or to get the wine into a bottling line, it’s likely that some pumping will be required.
That being said, minimizing the number of pumpings is still the best solution, right?
One thing to keep in mind is oxygen pick-up, which should always be a major consideration however wine is moved about in a winery. Older pump models like centrifugal pumps could be relatively hard on the materials being transferred and introduce a fair amount of air into the wine.
However, more recent models like peristaltic pumps are much gentler, partly because of the way the must or wine is moved through the pump, but also because the pumps minimize if not eliminate oxygen pick-up. And while the more sophisticated pumps are costly, so is a gravity-based winery design.
Gravity designs do not inherently guarantee that the wines will always be transferred gently or without oxygen pick-up. Dropping must from one tank into another one below can mean a lot of weight coming down at once, and it can also mean a lot of material going through open air. During red wine fermentation, this might be positive (in fact, some large wineries use cranes to drop one tank into another as an alternative to pumping over or délestage), but it all depends on winemaking choices and objectives.
At later stages, oxygen pick-up becomes less and less desirable, and wine transfers must be managed with additional care. Here gravity has its advantages, but it also has its challenges. “If you just open a valve into a pipe that is full of air, or just drop wine into a tank full of air,” comments Nomacorc researcher and enologist Maurizio Ugliano, “a lot of oxygen will wind up going into the wine.”
As with pumping, it is essential to think the process through and take necessary precautions. Gravity is a tool, not a magic solution. As with many other tools, it is not really about how well they work in absolute terms, but rather about how they are used. Preventing air leaks in pipes and pumps, inerting the whole system with an inert gas, and checking oxygen pick-up with a NomaSense analyzer remain crucial regardless of whether pumps or gravity are at work.
Like just about any other winemaking method or technique, gravity has its own logic and limitations, and its use must be well thought-out and planned.
Photo credit: Halter Rach