How Do You Know When Wine Fermentation Is Finished? Info from Vineyard Appraisers in Napa County, CA

As a general rule, most active fermentation will slow down after about two weeks when making wine. By this point, most of the sugar will have been eaten up by the yeast in the vat, and the fermentation process will slow down. If you wish, though, you have the option to stop fermentation early on and leave some residual sugars behind.

But technically, fermentation is considered complete as soon as you reach your desired sugar level, or if you reach “dry” at zero degrees Brix.

Dryer wines typically have 0.2 percent to 0.3 percent sugar, which means they’ll have two or three grams of sugar in a liter. Off-dry wines fall between one and five percent, which means they’ll have 10 to 50 grams in a liter. Sweet dessert wines are between five and 10 percent, meaning they’ll have 50 to 100 grams in a liter. Knowing your desired sugar level is important when you are making wine.

What to know when making wines with residual sugar

Fermenting for dryness in your wines involves allowing fermentation to continue until all the sugars are consumed by the yeast. This makes creating the wine much simpler.

But when making wines with residual sugar, you have a couple different options for how you will ferment that wine. Either you can ferment it to dryness and then sweeten during the bottling stage, or you can stop fermentation before reaching dryness to preserve residual sugar in the bottle:

• Fermenting to dryness: When fermenting to dryness, you should keep a small percentage of the refine and sulfite aside by itself in the freezer. This reserve will be what you use to sweeten the wine before you put it into bottles. The rest of the wine gets fermented to dryness, and once it’s bottled, you simply take that sweet reserve and add it into the dry wine until you reach the desired sugar level.
• Stopping fermentation before dryness: Once you have reached your desired sugar level, you sulfite the wine inside the fermenter and then immediately chill that wine to 40 degrees Fahrenheit or lower. You might wish to start cooling slightly before the wine reaches the desired sugar level, just in case you care about being extremely accurate, as the yeast will still consume sugars while they are cooling down until they get to the temperature at which they will no longer be active.

Any of these options will result in a good flavor—the fermentation method you use for sweeter wines depends primarily on your personal preferences.

If you have any additional questions about the wine making process, particularly as it relates to fermentation and the different types of fermentation methods commonly used in winemaking, we encourage you to contact us. As vineyard appraisers in Napa County, CA, we are highly familiar with the wine making process and work with many wine makers who own vineyards of all sizes. Reach out to County Appraisals Inc. to learn more about how we go about the process of valuating vineyards and wineries!

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