- The wine yeast pitched into the must was old or significantly compromised, or
- The primary fermentation was conducted under an airlock. Any yeast desperately needs air available to it in the beginning so that the colony can multiply into sufficient numbers. If an airlock is used during the primary fermentation this can not happen very well. A standard packet of wine yeast needs to multiply between 100 and 200 times itself.
I purchased 5 - 6 gallon buckets of wine juice on 10/17/13. All the juices where pH-acid balanced and inoculated with wine yeast. All completed fermenting quite quickly and have been racked to and stabilized in glass carboys, except the Sauvignon Blanc. My starting Specific Gravity (SG) for this juice was 1.080. On 10/31/13, I racked the Sauvignon Blanc from the primary fermenter (plastic bucket) at SG 1.020 for secondary fermentation under airlock in a glass carboy as per the manufactures directions. I then checked the SG on 11/7/13 and it had dropped to 1.010. I rechecked the SG last evening (11/13/13) and it has remained unchanged at 1.010. Is this a stuck fermentation? I really don't want to stabilize this wine at 1.010 since it is Sauvignon Blanc and at that Specific Gravity it taste too sweet. This wine has had a bit of a sulfur odor indicating that the yeast may be having problems fermenting this juice. Any suggestions? Pitch another package of yeast? Appreciate your help as always, thanks! Name: Michael N. State: Pennsylvania ----- Hello Michael, Yes, I would consider this a stuck fermentation. The sulfur odor is the biggest clue here. This indicates that the fermentation was occurring while the wine yeast was under much stress. The yeast was not happy. My best guess is that the amount of viable yeast in the fermentation was lacking. This can happen in one of two ways: