Preparing the Must for Fermentation
At this point, the freshly crushed must is extremely vulnerable to oxidation, white more than red. You must make your first sulfur addition. In addition, you must test the must for total acidity and sugar level (Brix) before beginning the all-important fermentation. Too little acidity and the must is fair game for microbial spoilage, and the wine will be flabby and lifeless. Too little sugar and the wine will not reach a respectable alcohol level.
Sulfur should be your first concern, however. Raise the total sulfur dioxide of your wine, whether white or red, to 50 ppm (mg/L) by adding
After you have added sulfur to your container of white juice, seal the container securely and leave it in a cool place. After at least twelve hours have passed, check the juice and you will see that even more grape matter has precipitated out of the wine and settled at the bottom of the container. Using your siphon and tubing, transfer the clarified juice directly into your fermentation vessel, which, ideally, should be composed of stainless steel.
Any winemaker, whether working at home or in the winery, will be extremely careful not to add too much sulfur. Too much will not only kill the added yeast, which you need for fermentation, but create extremely unpleasant aromas.
Now, you must check the acid and sugar levels. For the former, follow the instructions in your acid test kit. For the former, your target pH should be no higher than 3.7. Use your pH test strips. Add your tartaric acid slowly, no more than a teaspoon at a time, to get to the correct reading. If your total acidity is too high, the yeast you need to add for fermentation will not function!
Next, check the sugar level using your hydrometer. A reading of 21° Brix means you can expect an alcohol level of 12 percent in your finished wine. The magic number is 0.575, which you multiply by the Brix reading to get your potential alcohol. If the sugar level is higher than you desire, you can add water to lower it, but check your acid levels again, because adding water affects acidity. If your sugar level is too low, you can add grape concentrate bit by bit until the desired level has been achieved. You can also dissolve one cup of pure cane sugar in one-third cup warm water to create a syrup, which you can also add in small amounts to achieve the desired Brix.
Do not acidify with citric acid, an option which may be appealing at first due to its low cost. If you only use tartaric acid, you have a better chance of making a cleaner wine. If you acidify with citric acid before fermentation, the yeast can convert it into acetic acid, and your wine could be rendered undrinkable.
When you are ready to start fermenting, make sure that you do not fill your fermentation vessel to the very top. In fact, only fill about 80 percent of it. When fermentation begins, carbon dioxide in the form of foam will rise from the juice/must, and you don't want this to overflow. Also, if you are making red wine, you need room in the tank to punch down the cap.
