A wine kit comes with a very clear set of instructions. Generally, the instructions tell you to perform the primary fermentation in a large plastic pail. I have done this in the past, but this time I used a carboy with an air lock (Pic 1). Why? Because in wine making, oxygen should be excluded as much as possible. The head space in a carboy is much smaller than what you would have in a plastic pail, which means there is less oxygen in the system. Also, I had the bad habit of peeking into the pail during fermentation, just to see what was going on, and to enjoy the aromas that waft out. This is another way to introduce oxygen - maybe not much, but it should be avoided. With the glass carboy, I can watch everything that is happening and not worry about oxygen getting in.
(1) All ready to start fermenting...
Once the fermentation gets going, it's fun to just watch all the bubbles rising through the must (Pic 2).
(2) Primary fermentation, well under way
Now, I'm a scientist and I love to measure things so I can understand how those things work. Sometimes, this spills over into my hobbies. In the first couple of days of the primary fermentation, I noticed that the bubbles in the airlock were spaced at regular intervals of time, and that these intervals seemed to be getting shorter. I started counting the number of bubbles in a fixed period of time and recorded the number of bubbles per minute. This is how I obtained the graph shown below. I only started measuring at the 72 hour mark, which explains the absence of points between 0 and 72, and I don't really know what that part of the curve should look like. (For now, a straight line will suffice!)
As shown on the graph, the primary fermentation is basically complete at around 10 days. The instructions say to let it go until 14 days, when you stabilize the wine. In Pic 3, you can see about an inch of sediment at the bottom of the wine. This is all the yeast that settled out. To separate the wine from all that yeast, you simply siphon the wine into another carboy. I use an "autosiphon" which has a special plug on the end that helps keep the solids from being siphoned off along with the wine.
(3) Siphoning to a 2nd carboy
Stabilization involves the addition of two chemicals: potassium metabisulfite and potassium sorbate. The metabisulfite reacts to form sulfur dioxide, inhibits microbes (e.g. bacteria, yeast) and also reacts with any oxygen that gets into the wine. Sorbate acts to suppress any yeast that are leftover. Apparently, sorbate is very important to add to sweet wines, where yeasts might start fermenting the sugar that is still there. When these two chemicals are added to the wine, a lot of bubbles can be generated (Pic 4).
(4) Lots of bubbles after the potassium metabisulfite was added
After the wine was stabilized, I added the pomegranate/acai juice to the wine (Pic 5). This stuff smelled really good!
(5) Stabilized wine in carboy. Pomegranate/acai juice in the bag.
Shortly after the juice was added, I added the "finings", which consist of two separate solutions. One is "chitosan", which is a polysaccharide made from crustacean shells. The other is "kieselsohl", which is colloidal silica. These two thing work in tandem to remove tiny particles from the wine, clearing it. Pic 6 shows the wine after the finings were added.
(6) Finings added. Somewhat cloudy in appearance.
Twelve days after the finings were added, the wine is very clear (Pic 7). In the photo, you can see the fine sediment at the bottom of the carboy.
(7) Clear wine.
Bottling is a lot of fun. I carefully siphoned the clear wine into another carboy, making sure to not disturb the sediment. Then, I siphoned the wine into bottles (Pic 8) and sealed them with corks. It is so satisfying to have prepared 30 bottles of wine like this.
(8) 30 bottles of wine
(9) Bottles with labels. (Professional looking, or what?)
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