Making Wine, Part 3

Primary and secondary fermentation, preparing for aging

Here are the links to Part 1 and Part 2 in case you missed them!

Step 5: Primary Fermentation

After a few days, the yeast becomes active and begins consuming the sugars to produce CO2 and alcohol:

White wines (juice only) require twice-a-week stirring, whereas red wines (skins still in the container) require twice-a-day stirring:

Mixing 100lbs of grapes twice a day is a great shoulder workout

The stirring keeps everything mixed and makes sure the yeast can thoroughly do its job.

After about a month, all the sugar had been consumed. (in winemaking terms, this is referred to as 0° Brix) When red wines complete the fermentation, I press them (separating skins from juice) to prepare for the next step:

Doin’ it old school with a basket press

Step 6: Secondary Fermentation

Next I introduce special bacteria that metabolize malic acid (the harshest acid naturally found in the grapes) and turn it into lactic acid (the softer- flavored acid). This lowers acidity, helps the wine become more rounded, and produces compounds that add to the body of the wine.

While the primary fermentation completed when all the sugar was consumed, this secondary fermentation completes when all the malic acid has been consumed. Acid levels are measured using a chromatography test:

Throwback to high school chemistry lab

Step 7: Transfer and Adjust Levels

After both fermentations are complete, the wine is racked again (transferred out of its current container and into another one to separate out everything that has settled on the bottom).

To prepare the wine for aging, I adjust the pH. This is important not only for taste but also because too high a pH and the wine will not age well.

I also adjust SO2 (Sulfur Dioxide), a chemical compound to protect the wine from oxygen exposure as well as spoilage microorganisms. If you’ve seen “contains sulfites” on a wine bottle, this is where that comes from.

Testing SO2 levels — more throwback to chemistry lab

Once I am happy with the pH and SO2 levels, it’s time for the aging process to begin. Oak spheres are added to help with the flavor of the wine — at the small scale of personal production, it’s not economical to use a barrel so oak spheres are the next best thing.

I’m told to expect the white wines to be ready in the spring (about 6 months after I received the grapes) and red wines should be ready around the next spring (about a year and a half after I received the grapes).

After the aging process comes filtering and bottling, which you can read about in Part 4!