A successful fermentation will naturally finish when yeasts end up all sugars. Of course, if you want to make a dry wine. But, there is always a tiny quantity of sugar left behind (~ 2g/l).
On the other hand, how can you stop the fermentation early?
There are several ways. It can be stopped naturally or by manipulation. It depends on how sweet or dry you wish your wine to be. Let’s see what we can do :
TRAP THE CO2
Trapping CO2 from alcoholic fermentation above the wine in a pressure vessel will increase the pressure. ~ 7 atm yeast cannot survive. However, if the pressure drops, the yeast will start feasting on sugars again.
PLAYING ON TEMPERATURE
The temperature increases yeast metabolism and enzymatic activities. If the temperature drops too much (~ 5oC ), the yeast becomes inactive.
KILL THE YEAST
Pasteurization may be the most effective way. Around 80 oC afew seconds or 50-70 oC 10-20 min. After the treatment, it is better to cool-down the wine as quickly as possible (10-16 oC). Then, bottle it immediately.
REMOVE THE YEAST
Filtration or Centrifuge
A simple or less time-consuming way (Port & Vin Doux Naturel). Just raise the alcohol level above which yeast can tolerate. It means around 14-16 % by vol. (depending on the yeast strains, 18 % vol.).