Unusual fermentation

Fermentation until now has always followed the same pattern.
First there is the lag phase as the yeast multiplies
Followed by a vigorous phase generally with some foam
After which the foam disappears and the fermentation slows over time until it eventually quits.

This year I had one carboy go through a vigorous stage but with little foam before slowing to what I thought was going to be a steady fermentation. But somehow it went through a second vigorous phase with foam that push all the way through the airlock.

Background on this. I have two carboys from the same harvest. Essentially the same chemistry with very slight differences due to the press juice in one. Cleanest fruit I have ever harvested. Considered letting it go spontaneously but the wife didn’t want to risk it. Hit it with some SO2 and let it settle. Racked off the muck and pitched. Once carboy took but the other didn’t. Figured it was old yeast so repitched and it still didn’t take. Things get fun now as I tried a number of things. Pulled juice from the carboy that started, pitched a different yeast as well as more of the original yeast that I found in the back of the refrigerator. Eventually, something started and I did notice that fermentation looked different than the carboy that started first. That carboy had foam during the vigorous phase where this second one did not in what turned out to be the first phase. There is no off orders. In fact it smells wonderfully of mango.

Any ideas what happened? I am guessing that the first fermentation was a delayed spontaneous that was eventually overcome by whatever viable yeast I pitched and this explains the two vigorous phases with different foam production.

Foam totally varies with yeast. Some are super foamers, some almost none.

I’m assuming you are talking white or rosé. Did you say these were different press lots? When you add yeast are you adding a nitrogen nutrient source at the same time? So I assume not and thus the two lots might have a different level of nitrogen nutrients, or something else, at the start based on the racking and settled lees removed. The lot that was hard to get started did you by chance add a second yeast which had low nitrogen nutrient requirement and was thus able to make use of what was in the juice and thus was able to get started? Troubleshooting from a distance is always difficult so take my interpretation with a grain of salt.

Correct on assumptions. White to be sparkling. Separated by press, the one that didn’t start was the free run/light press. Didn’t add any nutrient or DAP.

I believe that the issue with starting was old yeast. Not sure why one packet that started my other carboy wasn’t effected when others were but assume that was random variation. Yeast used is low nitrogen requirement, QA-23. Pitched that at least three times plus pulled a starter sample from the other carboy. Also pitched a D254 that was even older and probably dead. D254 has a moderate nitrogen requirement so higher than what I pitched first.

I am not as concerned with the problem starting as I believe that to be due to old yeast. I am curious about what seems to be two vigorous phases that I am assuming are two different strains fermenting. Assuming first is a delayed spontaneous and the second is QA-23 from whatever viable I managed to get into the carboy.

Does that seem right?

Hi Brian,

I am certainly not the most experienced winemaker on this forum, but I suspect your differences in fermentation are related to different YAN levels.

The free run/light press was probably deficient in nitrogen and ammonia. This would make a difficult environment for cultured yeast, even those with so-called low nitrogen requirements. It seems probable that QA-23 never took off and was eventually out-competed by a native yeast that was able to succeed in the low YAN environment.

Based on the information you have provided, I would also suspect D254 never took off as well. By that point however, the native fermentation would have been underway.

In my experience, even the most nutrient-deficient grape juice will eventually ferment. Whether or not it produces anything desirable is a whole other question.

Would love an update on how the batch is progressing!

I haven’t checked the juice since fermentation initiated. My standard lazy process is to leave it to rest until bottling time. I justify that to myself by believing that it is best to not introduce air since the CO2 of fermentation should predominant the carboy head space.

If the issue is YAN levels and it certainly could be, this would be the first time in 15 years. And it was restricted to the white grapes as the reds started without issue. As both were for sparkling wine, the process for the reds was the same as for the whites.