Ever Wonder? How is Wine Made? Part 2

Last time we began looking at the wine making process, starting with the grapes. While the grapes certainly are the most important ingredient in wine making, there is another very important ingredient - yeast. So, let’s take a look at the fermentation process.

Once the grapes are harvested and prepared for the wine making process, it time to turn the grape juice to wine. Large tanks are used in this process and here is where yeast is added.  It's the natural sugar in the juice of the grape that gets consumed by the live yeast. The bi-product of the yeast's consumption of sugar is alcohol and carbon dioxide (CO2).  Remember that red wines have the juice and skins together in the fermentation tank and the production of CO2 causes all the skins to float to the top of the tank.  So winemaker's have to periodically 'punch down' the skins to intermix them with the juice or 'pump over' the juice as another means of keeping the skins mixed in with the juice. But regardless of the grape type, the fermentation process is relative quick, lasting typically from ten days to two weeks. And, another factor limiting the fermentation time is the life of the yeast. Depending on the strain of yeast, the fermentation process will stop once the alcohol level reaches levels of 16-18% when the yeast dies or after all the sugar is consumed.

Once fermentation is complete, white wines will be transferred to stainless steel tanks or oak barrels for aging. Red wine will then be separated from the skins and moved to vessels for aging. And, that’s where we’ll pick up next time - aging of wine. Cheers!

Wine Flavors From Fermentation

Wine's flavors come from the grapes, the fermentation process, and through aging. Last time we looked at the grapes that are the primary player in a wine's flavor. So, let's now explore how the fermentation process adds flavors to wine.

The only other ingredient in wine making, other than the grapes, is the yeast.  And, yes, yeast adds flavor. Just think of freshly baked bread.  Not that yeast makes wine taste like bread, but it certainly can impart flavor. Wine can be made from the natural yeast that forms on the skin of the grape, appearing as a white haze, as shown in the photo.  Or, winemakers can choose to use one of many strains of yeast that are produced in the laboratory in order to achieve the end result they are looking for.

The fermentation vessel also plays a role in a wine's flavor. Fermentation that is done in stainless steel tanks impart no flavor and allows the fruit flavors of the grapes to shine through. But, when fermentation is done in oak vessels the wine can take on woody flavors as well as flavors of spices, vanilla, and smokiness, as well as tannin that gives wine its mouth-drying, astringent, sensation.

Once fermentation is complete and the yeast has given its life for the production of alcohol, the yeast can either be immediately removed or the dead yeast (called lees) can be left in the fermentation vessel for some additional time to add yet additional flavor. This often adds a bit of bread-like aroma to the wine and makes for a richer mouth-feel of the final wine. Battonnage, or the stirring of the lees in the wine, can also enhance these flavors.

The fermentation process can also result in wines that are a bit sweet. Typically, the yeast will consume all the grape's natural sugar, turning it all to alcohol. But, if the fermentation is halted before all the natural sugar is consumed by the yeast, the wine will retain 'residual sugar' and be a bit sweet.

Oh, and by the way, the grapes, not just grape juice, can also play a role during fermentation. But, we'll leave that for next time. Until then, Cheers!

What is Residual Sugar in Wine?

One of the terms that gets thrown around in the wine world is 'Residual Sugar.' But it's not something you are going to read about on a wine's label. So, what is it and why should you care?

Let's take a quick step back and review the basics of the wine making process. Simply put, grapes are grown, picked, crushed and fermented into wine then aged and bottled. It's the fermentation process where sugar comes in. 

Grapes naturally contain various types of sugar. Glucose and Fructose are the two most common sugars, but there are others. Grapes also contain varying levels of sugar. Grapes that are allowed to fully ripen, in warm climates, will contain more sugar than grapes that struggle to ripen in cooler climates. And, wine makers will closely monitor the sugar levels (Brix) in grapes while still on the vine, and choose to pick their grapes when the sugar levels are 'just right' for the grape-type they are growing and their style of wine making.

During the fermentation process, yeast is added to the sugary grape juice. The yeast feeds on the sugar and produces alcohol. If there is any sugar remaining after fermentation, it is referred to as 'residual sugar' (usually noted as RS) and is typically recorded in grams per liter (g/L). This is somewhat of a technical term for a wines' resulting sweetness.

Residual sugar is one component that can contribute to a wine tasting sweet. Next time we'll further explore sweetness in wines.  Until then, Cheers!