Winery Activities You Don’t Know About
We all love the sights and smells of those harvested grapes coming into the wineries. Perhaps you are one of those lucky people who have helped to harvest the grapes and probably assisted in the winemaking process. When those grapes arrive at the winery to be de-stemmed and crushed, the equipment has been disinfected with Potassium Meta-Bi-Sulfites. In some cases, it has been sterilized with an iodine solution and then the iodine is rinsed off. The receiving equipment is now ready to go. When the grapes arrive, they are directly put into the equipment either manually by bucket or by gravity as dumped by hoppers into a screw conveyor system to go to the first piece of equipment. However, the grapes are not washed. Sometimes, the leaves are manually removed from the incoming grapes. Many people do not know that grapes are not washed before the process begins.
Many people still believe that people manually stomp the grapes with their feet to crush the grapes. That is no longer done. The incoming grapes are conveyed into a long tube with holes around the perimeter of that round tube sized for the incoming grapes. Grapes have different sizes so some wineries have different tubes with holes sized for the incoming grapes. There are rubber paddles along that tube that throw the grapes to the perimeter through those holes with the stems left in the tube and conveyed to the opposite end. Those stems literally have no grapes left on the stems. Those stems are normally placed back in the vineyards to rot into compost for the vineyard soils. What comes out of those holes along the perimeter of that long tube consists of grape juice, grape skins, grape seeds, grape pulp, and dead bugs that were in the grape bunches but obliterated in the de-stemmer tube. In addition, there could be some dust and allergens that were on the grape skins which is now in the grape juice. Sipping on the resulting grape juice, you could never tell such was in the juice since the juice is two to three times sweeter than what you get from store-bought grapes.
If the grapes were a white wine grape, the skins and seeds would be screened from the grape juice and the pulp would be squeezed to get the remaining juices out from the pulp. This process is called “pressing” since an interior bladder in a tank is inflated with either air or water outward to press against a fine screen to get the available juice without breaking the seeds. Each grape has four seeds so there are a lot of seeds.
The white wine grapes are fermented without the skins since those skins would turn the wine brown. The red wine grapes are fermented with the seeds and grapes skins to add color to the wine. Normally, Potassium Meta-Bi-Sulfites are added to kill off the rogue bacteria and yeasts. The next day, the winemaker will add a selected yeast for the fermentation process to begin. Normally, the yeast is selected by the winemaker from about 4,000 or so commercially available yeast to bring out a component in the wine that the winemaker want to enhance. Some yeast do better with certain grape varietals along with varying nitrogen levels. This is a science that requires some art and goals to make the wines. These yeasts are freeze dried and need to be re-activated with 110-degree water with growth additives added to the water. This process of activating the yeast takes several hours and is then manually added to the grape juice. The winemakers I know use Scott’s for their yeast, yeast starters, and wine enhancers like color stabilizers. There are no flavors or smells added to this process. What you taste and smell in the wine is all what Mother Nature has instilled in those grapes.
These fermenting wines produces lots of carbon dioxide gases. Those wines fermenting inside buildings require special ventilation to remove that CO2 gas which is poisonous. The winery industry loses several people each yard due to CO2. The CO2 gas is denser than air so it hugs the ground and can building to several feet thick inside buildings.
The resulting CO2 gas bubbles up to the top of the wine. Winemakers usually add about 15% extra room in their fermentation tanks for this bubbling effect. In red wines, it will cause the grape skins to rise and clump at the top of the tank. These skins can get so compacted if not manually pushed down (aka punching the grapes) or grape juice pumped from the bottom to break up the skin clumps that it could support the weight of a man on top of those compacted skins. Winemakers want those skins down in the wines for the fermenting juice to extract tannins, esters, and aromatics from those skins.
Once fermented, the red wine juice is decanted off the skins with the skins on the bottom raked into bins to press the remaining wine out of those skins.
The winemaker will use either a clay powder of egg whites to coagulate the suspended solids in the wine to allow them to settle. The fermented grape juice is then filtered through filters that can remove solids as small as 10 microns! More is about to happen to the wine such as oak aging and more, but I think that should be reviewed in a future article.