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Back to the Forum 2006
Archives In this essay I will discuss the general steps in the winemaking process. In a follow up essay, I can discuss the equipment and the consumables used and how they fit into the general process. Each of the items I listed in my second report does have a purpose. For this essay, I will discuss the steps in making grape wine. For other fruits, the process will be similar. Beyond harvesting the grapes there are several other distinct steps in the winemaking process. I will emphasize here that everything we use in this process must be clean and sterile. I cannot point this out enough times. Any failure in cleanliness and sterilization will risk the loss of the wine. That is too much to lose and it is too easy to avoid. Washing and sterilizing are simple and easy procedures. Now, to making grape wine. The first step is simply to crush and destem the grapes. We crush the grapes so the sugar and juice will be available in the fermentation process. We remove the stems to limit the amount of tannic in the wine. Stems contain tannic. Some tannic is good, but too much will affect the flavor negatively. If you buy your grapes from a wine supply outlet, there is a good chance they will be able to do this crushing and stem removal for you. If not, you have a bit of a messy task to do. To be sure, avoiding this step is a decided advantage of using wine kits. What we get after the grapes are crushed and the stems are removed is a bucket or more of stuff called must. It is just juice, skins, seeds, stems, and probably a few bugs. Because we are going to introduce a fermentation process, these buckets or containers should not be more that 3/4 full. We don't want overflow. One very important part of working with this must is to prevent any activity from wild yeasts or bacteria of any kind. We want wine. We definitely do not want vinegar or some other product. To make sure we get wine, we add a product called sodium metabisulpfite to the must. That will kill any bacteria or yeast excepting wine yeast. This is one of the consumables used. It can be purchase in the form of tablets or powder. We will add one metabisulphite tablet for each gallon of must. The tablets should be dissolved in water of juice before adding to the must. The second step in winemaking is to make sure we have the right chemistry. By that I mean the acidity and the sugar content of the wine. For grape wine, the acidity will usually be okay, but we can test it using a litmus paper test. If it is off, we can add acid or water too correct it. Since these papers are used up in the process, they are consumables. We can test for sugar content by testing the specific gravity (SG) of the must. This is where the hygrometer comes in. I'll get to the how of testing in the following discussion of equipment. At this time, for grape wine, we want an SG of 1.095. We can raise the SG by adding sugar and lower it by adding water to the must. If we have a good ripe grape, sugar will not be necessary. The next step is to do what is called a primary fermentation. Fermentation, in this case, is just the conversion of the sugars in the juice to alcohol. That is what our yeast does for us. It consumes sugar to produce alcohol and carbon dioxide (CO2). The yeast is dissolved in warm water or grape juice and allowed to start foaming. Then it is added to the must. The bucket is covered with plastic film to block out air and the primary fermentation goes on. From this point until fermentation is complete it is important to maintain a temperature range of from 65 to 75 degrees F. This primary fermentation should begin within 48 hours of adding the yeast. It is characterized by a vigorous visible foaming of the must. The foam is cause by the release of the carbon dioxide in the form of a gas which foams out of the must. For this step, it is important to make sure the gas can escaped without allowing air to get to the must. Trapped CO2 can create enormous pressure and cause explosions while air can introduce contaminants. It is wise to assume that air will always carry unwanted contaminants. We can allow for both needs by covering the must container with a plastic film like polyethylene. Primary fermentation will go on for 6 or 7 days. During this time a crust of grape skins, seeds, and stems will form on the surface of the must. To promote good fermentation, it is important to break up this crust and push it down twice a day using a sterilized spoon or paddle. Once the foaming has begun to subside it is time to test the SG again. For grape wines we look for a SG Of 1.050 or lower. That means a great deal of the sugar has been converted to alcohol. At this point it is time to begin the secondary fermentation. To begin the secondary fermentation, the wine must be transferred from the primary fermentor to a sterilized jug, which is called a carboy in winemaking. It's just a chemist's thing to call them carboys. By any other name they smell as sweet. This transfer can be accomplished by using a syphon tube or by straining the must through a large strainer. One way or the other, we must get the juice out of the must and into a carboy. At this point we want to leave some space in the carboy to allow for CO2 to form and escape. The wine level should be about 4 or 5 inches below the plug or bung. Any extra juice can be held in a smaller jug for later topping off of the wine. What is left after we have strained the juice from the must is called lees. It is just grape skins, seeds, yeast, and whatever juice we could not extract. This mess can be squeezed to get the remaining juice. Some folks also use these lees to make what is called a second wine. The procedure is to add water equal to the amount of juice extracted, then add sugar to reach a SG of 1.095. After that the procedure is the same as for first wine. This will make wine with a bit less color and a softer flavor that the first wine, but It will still have the same alcohol kick. With the wine in the carboy we must install a drilled rubber stopper, sometimes called a bung. The bung is drilled to allow the insertion of a vapor lock. The vapor lock is a device which allows gas to escape from the jug, but does not allow air or any other gas to enter the jug. CO2 escapes and air is kept out. The vapor lock is partly filled with sterilizing solution which makes it act as a one way valve. You have to really see one to understand how they work. If there is extra wine in a smaller jug this must also have a bung and a vapor lock. Now, in about two weeks we can transfer the wine to another carboy and leave behind the sediment which will have settled out. We call this transfer of wine from one container to another racking. It is usually done with a syphon of some kind. If we try to pour the wine, it can get messy and we risk the introduction of contaminants. At this point fermentation will be very slow and the wine can be topped to bring it within 2 inches of the bung. We still install the fermentation vapor lock. Then starts the waiting game. The days will seem to drag by when we wait to get a taste of this stuff. It is necessary to wait three of four weeks while this stuff settles out and clears up. In three or four weeks, when fermentation is almost over we again rack the wine and add Campden tablets (metabisulphite). This is sometimes called sulphiting the wine. We add one Campden tablet for each gallon of wine. It is best to dissolve the tablets in water before adding them. Then we install the bung and add the vapor lock and wait again. In two or three months, the SG can be checked. If all the sugar has been converted, the SG will be 0.995. When the SG is 0.995 or if it has not changed in four or five days it is time to fine the wine. Fining is the addition of a product which helps small particles to precipitate out of the wine. It's purpose is to make the wine very clear. Ten days later, the wine can be racked and sulphited again
and then bottled. The wine is drinkable at this stage, but waiting
six months to a year will yield a much better wine.
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