Ask Wine Wizard

Judging Fermentation Completion

TroubleShooting

Brent Mooney — Forest Hill, Maryland asks,
Q

 

What is a good rule of thumb to conclude wine fermentation is complete? I have received the same reading for several days in a row but still see bubbling at the top of my container. The specific gravity is right below 1.000 but I have heard it needs to get below 0.995. Is this true?

Also, what is good protocol after fermentation has completed? Would you recommend chilling down to 50 °F (10 °C) then racking?

A
It certainly sounds like you are getting into the dryness zone. Specific gravity is the ratio of the density of a liquid in relation to the density of water, calibrated at a specific temperature (usually 60 or 68 °F/16 or 20 °C). Depending on which source you check (various winemaking books, websites, etc.) folks seem to agree that “dry” table wine usually clocks in around 0.990–0.996 specific gravity. Why the range? Every wine is different and as such, every wine does actually contain a small amount of non-fermentable sugars and it’s unusual for a wine to go so low as to achieve “no sugar” 0.00 g/L glucose + fructose. “Dry” is philosophically defined (in my opinion) as not enough sugar left to taste or that any yeast cell will ferment as well as the place where the fermentation naturally stops and the yeast just can’t ferment anymore. Most professional winemakers I know chemically define this point as 2 g/L residual sugar (RS) or less (<0.2%) though I have seen wines naturally settle at around 3 g/L RS or 0.3%. Also
Response by Alison Crowe.