Yeast activity with small vs large batches

[MasterBlaster]

I have two fermenters going with apricot wine right now. Both batches started 3 days ago at SG 1.100. One batch is 5 gallons, the other is 3. The differences between them are that I accidentally added an extra 1/2 tsp of energizer in the small batch, and I left the yeast to rehydrate for a lot longer on the bigger batch. Other than that, the only difference in the recipes are that I added slightly different amounts of sugar and fruit to get my starting SG.

I just opened them for the first time to take a reading and noticed the 3 gallon batch is really foamy, while the 5 gallon batch looks much less active. The smaller, more active batch has also fermented a lot faster. Tonight, the 3 gallon batch has already gone to 1.083. The larger, less active batch is only at 1.092. Both airlocks are bubbling at about the same rate, so I was expecting them to be much closer than that. My question is, would this big difference be because I pitched one pack of yeast in each? I was always told that the amount of yeast you pitch really doesn't have much of an effect. Or is it likely the extra energizer that I added?

Finally, should I just let them go, or should I try and adjust something like adding extra energizer to the big batch to try to to get them to even up?

 

[DoctorCAD]

Nothing to worry about. Leave it alone.

 

[SouthernChemist]

Just let them do their thing. Remember, the yeast in the larger batch will take longer to propagate because of the volume compared to those in the smaller batch. Different sized batches will not necessarily ferment at the same rate.

Also, the amount of yeast you pitch can affect how your wine turns out, but one packet of yeast for each batch should be plenty.

 

[JohnT]

Agree with the others, nothing to worry about.

If you added the exact same amount of yeast to both batches, it is to be expected that they will ferment at different rates.

 

[Turock]

The reason for the increased activity is the energizer. I don't see a good nutrient protocol being used and that's always a mistake because it leads to a sluggish or stuck ferment and/or H2S problems. Yeast needs nitrogen in order to take a ferment to completion and nitrogen is the main component of nutrient. You need to split your total nutrient dose in half and pitch the first half of the dose when the yeast takes off and the second half at 50% sugar depletion. Do not add nutrient after the 50% dry stage because the yeast can no longer utilize the nitrogen and it can make a good environment for competitive organisms to use.

 

[fabrictodyefor]

So, I have a question...do you have tight lids with airlocks attached? I've been taught to just drape a towel or piece of muslin on the ferment bucket as during this time the must needs oxygen and you needs to release CO2. If the larger batch is only at 1.092, what was your starting sg? I've found that with my fruits if the abv is too high the high alcohol content masks the lighter flavored fruits.

 

[BernardSmith]

... You need to split your total nutrient dose in half and pitch the first half of the dose when the yeast takes off and the second half at 50% sugar depletion. Do not add nutrient after the 50% dry stage because the yeast can no longer utilize the nitrogen and it can make a good environment for competitive organisms to use.

Turock, Your protocol is the one I was taught to follow but I always have the question: how does the yeast know when 50 percent of the sugar has been converted? I know, because I measure the starting gravity but is the yeast so sensitive to the sugar content of any liquid that it "knows" (that is , does it respond to changes in gravity in very specific micro-biological ways?) when half the sugar is consumed or half remains? In other words, If The original gravity was 1.100 then half is 1.050 but if the original gravity was 1.050 then half is 1.025... The protocol makes sense in that you need to provide additional nitrogen after a few days but the starting gravity is frequently going to be very different so the half way stage is going to be be very different. What is the rationale for feeding more nutrient at the half way stage rather than after say, two or three days of active fermentation?

 

[MasterBlaster]

Thanks to everyone for the advice. Sorry for my delay replying. I saw the posts this morning, but didn't have time before work to post back.

I have never done two different sized batches at once like this, so it is new for me. I'm glad to hear it's normal for the smaller batch to propagate faster, I won't worry about it now.

I will try the recommendation to do half of the nutrient in the beginning next time, it makes sense.

Yes, my fermenters are air tight. I actually didn't realize my fermenters would seal for the past couple years, because they are really difficult to close. I looked carefully at the lids this time and noticed they were made to seal. So in the past batches, I never sealed it. This is the first run with an air tight fermenter. Should I not be sealing it? I did just put a towel over it before I pitched the yeast, but as soon as I pitched, I sealed it. Our wine turned out beautifully without a seal in the past, so I'm open to suggestions.

OG was 1.100. I shot for little higher OG with a plan to try stopping it a bit early before completely dry instead of backsweetening. I'm not sure how well that will work, so I might just do it with one batch and let the other go dry.

I just did my daily SG reading, and they are both exactly the same at 1.07. So, I will be looking forward to seeing what they are at tomorrow!

 

[Turock]

The yeast doesn't know when the 50% sugar depletion has happened, but if you wait to add nutrient well past this level the yeast is exhausting its reproduction because the sugar it uses for food is going away. So the yeast can't utilize the nitrogen any more because new generations of yeast cells are not being reproduced in large numbers.

High sugar musts need nutrient. Lower sugar musts such as beer don't need it--and that is why it's always bad to take the advice of a beer maker when you are making wine. A beer maker will say you don't need nutrient. Well--yes you do because you aren't making beer!

Use the SG after you've adjusted the brix--that is, if your adjusted SG is 1.0918 which is a 22 brix, then 50% sugar depletion is an SG of 1.0441 or an 11 brix. It's just simple division and no more complex than that.

The yeast is going around, looking for nitrogen because nitrogen is used for amino acid generation. In the absence of enough oxygen based amino acids, some yeast will go after the sufer based ones and generate H2S as a by product.

 

[sour_grapes]

In the absence of enough oxygen based amino acids, some yeast will go after the sufer based ones and generate H2S as a by product.

I don't believe this is quite the actual mechanism for H2S production, although there was earlier evidence that supported that view. From an earlier post:

From my reading of the primary and secondary literature, this is my understanding of H2S production and its relation to N deficiency. Proteins are made of amino acids, and two important amino acids contain sulfur. The yeast has to provide the sulfur to form these compounds to the proper organelle during protein synthesis. It does so in the form of H2S, which it extracts from more complex sulfur-containing compounds. One organelle passes the H2S off to the organelle responsible for protein synthesis.

However, nitrogen is a major component of amino acids (hence the root amine, from ammonia.) If there is a dearth of N, the organelle responsible for synthesizing the sulfur-containing amino acid cannot do its job; this results in a surfeit of H2S, which the yeast then excretes.

There is a lot of room for confusion, as amino acids are BOTH a feedstock for nitrogen (as Turock alludes to above) AND a principal product/component of growing yeast as they reproduce. However, there just isn't that much naturally occuring sulfur-containing amino acids in grape juice to serve as a feedstock to begin with; the source of S is actually the inorganic compounds sulfite and sulfate. (This has been established with radioisotopic labeling.)

Even this description is vastly oversimplified compared to the primary literature. The net implication is the same, of course, viz., provide proper nutrients to your yeast at the proper time. As Turock says, the nutrients are needed during the exponential growth phase, and not afterwards. I believe (but do not know) that "1/2-sugar depletion" is just a convenient rule of thumb by which to time your additions so that they fall in the exponential growth phase.

 

[fabrictodyefor]

Thanks to everyone for the advice. Sorry for my delay replying. I saw the posts this morning, but didn't have time before work to post back.

I have never done two different sized batches at once like this, so it is new for me. I'm glad to hear it's normal for the smaller batch to propagate faster, I won't worry about it now.

I will try the recommendation to do half of the nutrient in the beginning next time, it makes sense.

Yes, my fermenters are air tight. I actually didn't realize my fermenters would seal for the past couple years, because they are really difficult to close. I looked carefully at the lids this time and noticed they were made to seal. So in the past batches, I never sealed it. This is the first run with an air tight fermenter. Should I not be sealing it? I did just put a towel over it before I pitched the yeast, but as soon as I pitched, I sealed it. Our wine turned out beautifully without a seal in the past, so I'm open to suggestions.

OG was 1.100. I shot for little higher OG with a plan to try stopping it a bit early before completely dry instead of backsweetening. I'm not sure how well that will work, so I might just do it with one batch and let the other go dry.

I just did my daily SG reading, and they are both exactly the same at 1.07. So, I will be looking forward to seeing what they are at tomorrow!

So, Masterblaster, the way I see it is you started with a high sugar content so a nutrient half way through would be a good thing. Neither Turok or Sourgrapes weighed in on the cover issue, but IMHO you need to just lay the lid on your ferment bucket with a towel under it, or not use the lid at all. I don't even use the lid with and airlock....only after I transfer to a carboy. Making beer is different and you do clamp the lid down tight for beer, but not during wine fermentation.

 

[Turock]

Most ferments need oxygen during fermentation so leaving the lid off is a good idea. If you are making some whites and want to retain the volatiles, then you can limit O2 exposure so the volatiles don't gas off.

 

[MasterBlaster]

Dang it! I will say that I was using the airlocks at the recommendation of a so called "expert". It occurs to me now that this guy is an expert, but in beer, not wine. So, I just took the lids off right now and checked my SG. One batch is at 1.06, the other is at 1.051. At the time of removing the airlocks, they were still bubbling pretty good, but the visible bubble and foam have settled down quite a bit already. Given those readings, should I opt to give it another dose of energizer? Or since I already put a full dosage in, would it affect flavor if I add more now?

I am planning on using the slurry to start a batch of skeeter pee right after this. So I really hope I didn't do enough damage to the yeast that it wont start back up again for that.

 

[fabrictodyefor]

I would just leave it alone for now, give it a good stirring to add some oxygen into the must. As long as it doesn't stop completely you will be fine. I don't know all the chemistry involved, but I have had a wine ferment to dry in 3 days and I've had a different one take almost 3 weeks. And yes, when making beer you lock down the lid! But not with wine.

 

[Turock]

Beer and wine are 2 totally different things and you'll have problems if you take the advice of a brewer who is not familiar with wine fermentation. Stir the must once a day and leave the lid off.