Fermentation to Pressing

"Forsake not an old friend, for the new is not comparable unto him. A new friend is as new wine: when it is old thou shalt drink it with pleasure."

Oxygen is wine's number one enemy. Fermentation produces CO2 as a byproduct, the veil of CO2 over the fermenting wine acts as a barrier and protects the young wine from the exposure to Oxygen. Some CO2 actually dissolves into the wine during the fermentation process. Wine will continue to release CO2 after fermentation is complete. It is important that the grapes/fermented wine combo be pressed before the CO2 is fully dissapated, such that the exposure to Oxygen is minimized.

There are a couple of ways to detect this. Primarily you can check the specific gravity of the wine on a daily basis, measuring the drop in sugar level. A complimentary step is to watch the floating cap of grape skins on the wine. It is kept floating by the CO2 being released. The first hint that the cap is starting to settle, is the best time to press the grapes.

My neighbor and I purchased a grape press manufactured in San Francisco about 80 years ago. It still works fine, and obviously it was built to last.

A typical manually operated grape press has a three legged, chair type base with a curved lip on all sides, except for one opening to allow wine to come out. Up the middle of the chair basic come a heavy, steel, threaded pole, extending up 30 - 36" from the seat base. A round wooden slatted cage (in two semi circle halves) is placed upright on the inside edge of the chair lip. The wooden slats extend vertically. This unit is assembled, a 5 gallon bucket placed at the mouth of the base to capture wine.

The fermented wine and grape skins are then scooped our of their fermenation vessels, and essentially poured into the opening of the wooden cage. The free run wine escapes between the gaps in the slats and runs into the 5 gallon bucket. The gap between each slat is no more than 3/8". Wine/grape skins continue to be added until the wooden cage is filled to the top. Think of a giant Life Saver candy, but in this case made of wood, heavy oak, that has been cut in half. This is want goes on top of the grape skins, inside the slats, surrounding the steel threaded pole. The oak is probably 2 - 3" thick. A heavy ratchet unit is then threaded on top of steel pole and screwed down until in contact with the heavy wooden Life Savor. Basically at this point a pipe is inserted into the ratchet, and you crank the ratchet back and forth pressing downward, pushing the wine throw the wooden slats.

Initially this is easy work, but it becomes very difficult work. 500lbs of grapes will end up producing close to 40 gallons of wine, including sediment, which might be 2 - 3 gallons worth. This sediment is largely the expired yeast cells.

When you are done pressing, what is left is a very dense, round, flattened mass of grape skins, and grade seeds. If done properly this cake is practically bone dry or close to it.

All of the pressed wine is transferred to an airtight glass, steel, or food grape plastic vessel. The the wine is allowed to settle. At this point the PH, is tested again. PH never drops during fermentation. Some of the acid are converted during the process so you may lose acidity. Testing is required to make sure the acidity has not gone above PH 3.5, and if it has, then Tartaric Acid has to be added to lower the PH down to 3.5 or less. Another by product of fermentation is the production of Malic Acid. Malic Acid naturally breaks down in wine over time, but you can accelerate this conversion by adding a malolactic bacteria culture that feeds only on Malic Acid. Malic Acid is unstable, and you do not want to bottle this until the Malic acid has been fully converted. The Malolactic culture will do this conversion in a few weeks, instead of waiting 6 - 9 months to have it done naturally.

Over the next few weeks, loose solids will settle to the bottom of the storage vessels. These are called "Lees". Every week or so, you have to pump off the clear wine off of the Lees. This is called Racking. This is important because the Lees can impact off odors, and flavors to the wine. Racking typically is completed over a couple of weeks and the wine is ready to be placed in an Oak Barrel for aging.