As mentioned in my posts “Musts for Your Must” and “Warning: This Post May Contain Sulfites”, there are certain products that are added at specific times. Let’s put these all together to prepare our juice for fermentation.
The first thing to do is to add enzymes. The very best time to add enzymes is at the crusher. I dump mine into the must pump a little at a time throughout the crushing so that it travels into the press with the grapes and juice. The enzymes help extract juice and allow the wine to clear more easily later on.
If it is determined that sulfite will be added, remember that it should be added at the end of pressing so it will not harm the enzymes. I usually put it in with the last juice pumping in. In addition to being needed when the grapes are not in pristine condition, sulfite may also need to be added if the grapes are very warm. Depending on what time of day they were picked, the grapes may even be hot. You should probably add some sulfite to these as the heat of the grapes will activate any wild yeast on them pretty quickly. This will stun the wild yeast until you get your good wine yeast added.
The next common additive is bentonite, used to help the juice settle (remember, white wine only). This is generally done in conjunction with chilling down the juice to about 45 degrees to help keep it from fermenting with wild yeast. Since bentonite should be added later, after the enzymes have had some time to do their job, a good time to add it is the next morning after the wine has chilled down – although sometimes I do it late the same day. Keep in mind that all of these products need to be mixed into the juice in some manner.
The next day, you can rack the clearing juice off of the sediment and bentonite. There is no need to agonize over keeping every last bit of the sediment out of the juice. The juice does not need to be crystal clear and, in fact, a little of that sediment is actually good for the yeast. The idea is to get the main solids out. One caution regarding bentonite, though. Whatever you do, don’t let this stuff go down the drain. It is a clay that is very gummy and sticky when wet (it’s actually used to line ponds so the water won’t go out). Certainly this would not be something you would want in your plumbing. I would recommend dumping it out somewhere on your property where a little clay will not be a problem.
While your juice is settling, you need to do some testing to see what else, if anything, you need to add to it to get a satisfactory fermentation. The common tests are sugar (brix), pH, and total acidity. Professional winemakers may do some other tests such as the one to determine nitrogen. But everyone should do at least these 3 standard tests.
Yeast feeds on sugar and creates alcohol and carbon dioxide, which eventually blows off into the atmosphere as it finishes fermentation. It is important to have enough sugar to end up with a good keeping quality wine. What you are looking for is a minimum of 11% to 12% alcohol. Alcohol also creates viscosity and mouth feel and can make a wine taste fuller and richer. However, too much alcohol will make the wine taste hot and is unpleasant. Some people like it a little higher and certainly evidence of that exists in the new trend for California wines to be over 14%, many over 15%.
In order to raise your brix (sugar level), you will need to measure the juice with a hydrometer (triple scale preferred, so you know your start point). A triple scale hydrometer will show you brix, specific gravity (used in Europe) and potential alcohol. I have encountered many calculations over the years for adding sugar and most of the time, the alcohol comes up shorter than I want it. I believe this is due to how certain yeasts use that sugar and also depends on your growing region. A while ago I read an article by Jacques Recht, who is a renowned winemaker, wine writer, and wine chemist recently honored with the Award of Merit by the American Wine Society for all of his contributions to the industry. His information on sugar addition has worked so much better for me than anything else, so I will share it with you. The calculation is complex but the end result is this. To increase alcohol 1% in white wine, you need to add 2.27 ounces of sugar per gallon and in red wine, 2.41 ounces of sugar per gallon. These are rounded calculations and close enough. You may use either cane sugar or beet sugar and it should be well dissolved in some of the juice before adding it.
Here is an example: If your white juice is 20 brix, which would result in slightly over 10.5% alcohol, and you would prefer it to be 12.5%, obviously you need to increase it by 2%. The calculation would be 2 X 2.27 ounces X no. of gallons. If you had 15 gallons of juice, this would be 2 X 2.27 X 15 = 68.1 ounces or 4.24 pounds of sugar. If this had been red that is fermenting on the skins (more on that later), you would not add the additional sugar until you press those grapes so that you know exactly how much liquid you would have.
Next Week: A side trip to the Finger Lakes