Pressing Grapes

In the wine making process the crushing and de-stemming process releases the “free run” juice from the grape. While this is top notch quality juice there is still quite a bit of juice remaining in the grapes. This is where pressing comes in. After all, more juice means more wine! Red wines are nearly always made from both free run juice and pressed juice. White wines on the other hand are not always pressed. The very best white wines are made from only the free run juice. Historically pressing grapes was done by hand or by people stomping grapes. This is not a very sanitary way to go about making wine! Imagine drinking a Zinfandel with an athlete’s foot aftertaste. Today most wineries use a mechanical press of some sort. These come in two basic varieties, batch presses and continuous presses. Two Types of Presses A batch press can handle up to 1-5 metric tonnes per hour with an appropriate team of winemakers on the job. By in large this is the type of press used by amateur wine makers as well as small to medium sized wineries. Grapes are loaded in one “batch” at a time. Different presses can handle different quantities of grapes. Continuous presses on the other hand are generally motorized and fed a continuous stream of grapes. Because of this automation continuous presses can press up to 100 metric tons per hour. As you might have guessed a continuous press is geared more for a factory winery pressing thousands of tons of grapes at harvest. For now let’s concentrate on batch presses. Two Types of Batch Presses Basket Presses The earliest known mechanical press is the basket press. Still used today at the amateur and professional level this iconic piece of machinery is still a reliable way to go. A basket press has a ring of vertical staves with gaps between them where the pressed juice pours forth. Grapes are loaded in the top. Then a wooden plate is lowered down over the grapes and a ratchet is used to slowly apply pressure to the grapes. When using a basket press wine makers will often add rice hulls to the layers of grapes. These hulls are inert and do not impart any flavor into your wine. What they do is pierce the skins to a) release more tannins and color from the skins and b) provide a path for the pressed juice to flow. If you don’t use the rice hulls the juice will flow very slowly and you’ll leave a lot behind. Bladder Presses Also known as pneumatic presses these are quite common in small to medium sized wineries. These presses have either vertical staves as on the basket press or a cylindrical piece of sheet metal with holes in it for the pressed juice to flow through. The difference is the pressing mechanism. In the middle of the press is a rubber bladder than is filled with either water or air. As it expands from the center of the press the grape skins are pushed up against the outter ring. Because air is compressible this...

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Crushing and Destemming Grapes

Crushing and Destemming Grapes

As you well know, grape juice comes from grapes. Extracting that juice is therefore the very first step in making wine from fresh grapes. Not to be confused with pressing grapes the crushing of grapes merely breaks open with skin allowing the “free run” juice to pour fourth.  Pressing on the other hand is where you flatten the things to get out as much juice (or wine in the case of reds) as you can. Crushing and Destemming Machines Modern crushing and destemming machines consist of a large steel or aluminum trough with a screw in the bottom. As the screw turns the grapes are gently squeezed and pulled from the stems at the same time. Out one end pops the stem and out the other is your elixir of life (to be). The crusher / destemmer shown here has a rubber edge on the screw so that the grapes are crushed as gently as possible. If you crush grapes too hard you’ll end up crushing the seeds. This imparts more tannins and astringency in your finished wine. It also can impart a stemmy or “green plant” taste. Crushers can be purchased or rented without the destemmer. This is a bad idea in most circumstances. Unless you’ve hand picked the grapes and they are already stem free you’re going to want the destemmer.  Otherwise you’ll be spending hours picking stems out of your must! There are a few different kinds of crushers that are made for specific fruits. Apples and pears must be crushed in a different crusher. Keep this in mind if you ever want to venture out into making fruit wines. Why is Destemming Critical? Tannins my friend. Grape stems and seeds contain high concentrations of tannins. Leaving them in the must during fermentation will result in a wine so tannic you likely won’t enjoy drinking it. Grape skins also contain tannins so don’t feel like your eliminating all tannins by excluding the stems. The grape skins will provide plenty of tannins without all the funky flavors. Things to Watch For While Destemming The destemming process is a perfect time to look over all the grapes you’ve purchased and are processing as you load them into your machine. Make sure that nothing funky is getting into your wine such as bugs, sticks, or bad grapes. Look over your grapes for evidence of mold, dehydrated grapes, and botrytis. Moldy grapes just don’t make good wine. You’ll taste that mold forever more in that wine. Dehydrated grapes will make for a sweet and raisony wine. Which isn’t a bad thing…if that’s what you want in your wine. Botrytis, also known as the noble rot, is a fungus that infects ripe grapes. The presence of botrytis is not always a bad thing. It can make your wines quite sweet and delightful if that’s what you want. The fungus attaches itself to the grapes, penetrates the skins and basically drinks the water in the grape. In so doing the flavors within the grape are concentrated and the sugar content relative to the amount of juice is increased as the water is removed. This is...

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