Tips for Making White Wine
Harvesting the Grapes
The first thing is to make sure the grapes are picked at exactly the right time to ensure the acids and sugars are at the proper balance. The timing can vary even by the time of day and the location in the vineyard. Remember the amount of sugar will determine the alcohol content, and the amount of acid has a major impact on the wines flavor. The winemaker may taste the grapes and use a chemical test to determine the PH and sugar content to determine exactly when to pick.
The grapes are picked carefully to prevent bruising, cleaned to get rid of vineyard dirt and debris, and sent right to the crusher were the juice is extracted from the skins and stems removed. It is important to crush gently and not try to get all the juice since this will produce an inferior wine. In some cases sugar and or acid may be added to improve balance. The juice is sent to a stainless steel vat to begin the next step.
Fermentation and Stabilization
Fermentation needs to begin to turn the sugar into alcohol. The grapes have some yeast already in the juice and at one time this caused the fermentation, but now most winemakers use prepared yeasts so they have better control over the process. Normally it takes about 3-4 weeks for this process to complete. Many wine making kits have fermentation equipment included. During this process you must monitor the temperature carefully since in the beginning the fermentation produces a great amount of its own heat and cooling must occur. In most cases temperatures should be kept around 65 degrees Fahrenheit although there are some yeasts that will work at lower temperatures. The juice is now racked, or decanted from one vat to another to remove any sediment and leftover yeast.
After fermentation is complete, white wine is put through a process know as cold stabilization. Here they bring the vat temperature down to near freezing which causes tartaric crystals to form and precipitate out of the wine. This has no effect on the flavor, but prevents the tartaric acid and potassium from forming these crystals after the wine is bottled. Most consumers don’t want to go to the trouble of decanting there white wines. Once again the wine is racked to remove any leftover crystals.
Ageing and Bottling
Ageing for white wines normally takes place in steel vats to preserve the fruit flavors and light body of the wine. Normally this type of wine will age in stainless for up to a year. For wines such as Chardonnay where a fuller body and oak flavor is desirable, ageing is oak barrels follows this process and can last for several more years. Many winemakers like to cause a secondary fermentation at this point by introducing a bacteria that causes Malolactic Fermentation. In this process, the malic acid which has very sharp taste is converted to lactic acid which is much smoother and gives the wine a buttery flavor.
Once ageing is complete, the wine is ready for a final filtering and bottling. The wine is now ready to drink and bottle ageing is not required.