Why use pump over systems in winemaking？

All the red grapes have as green flesh as the green grapes (Try to peel the skin of  a red grape and see for yourself).All the color, most of the aroma compounds and tannins are in the skins ( the seeds contain tannin as well) and thus we ferment our red wines on the grape skins to extract as much of these fundamental building blocks for the wine in perfect amounts.

As the must ferments, carbon dioxide gas is produced, and as this gas escapes, the grape skins, seeds, and pulp float to the surface, called the "cap." The solids in the cap contain most of the polyphenols that give the wine its color, aroma, and body, so if you want a rich, flavorful wine, you'll want to definitely push down on the cap to extract those elements. The cap can also be a breeding ground for bacteria if you leave it alone, so that's another good reason to keep it circulating!

There are two main methods of extraction: capping and pumping. 

Capping can be done by hand (using a giant device that looks like a potato masher), by foot (preferably with waterproof pants on), or by machine. Breaking and submerging the cap usually requires more force than you might think.

Wine pumping is the process of pumping the red wine juice from the bottom of the fermentation tank through a hose and then spraying and splashing it on top of the grape juice to make contact with the skins, thereby extracting the color, taste and aroma from the skins into the juice. The wine pumping process is usually used in large closed and open red wine fermentation tanks for the main red wine fermentation process. The number and frequency of wine pumping required in each tank is determined by the winemaker based on the grape variety, fermentation stage and wine being made.

As you can imagine, these two methods, as well as the intensity and frequency of their execution, have a great impact on the amount of color, tannin and flavor extracted, which is more convenient when using a pump over system.

Another method, not so common, is called “rack and return.” (“Racking” is a fairly common practice for removing fermented wine off of the sediment, or lees, to clarify it.) 

This is pretty much what it sounds like: the wine is drained into a second tank, the solids are left behind, and then returned to the original tank along with the grape solids. It's a bit like extreme pumping. This method is too labor-intensive and has been phased out.

Pretank provides customizable stainless steel pump-over wine tanks. If you are interested, please contact us now!

Other benefits of pump over system

- Aerates the must to increase and activate yeast.

- Prevents the caps from drying out, which would otherwise allow bacteria and mold to grow on the surface.

- Keeps the caps cool (the skins in the caps can reach very high temperatures, pumping cools them down and helps prevent the growth of thermophilic bacteria).

- Provides a more even distribution of yeast.