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Why Is Too Much Yeast 'too Much'?


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#1 drunkagain

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Posted 06 February 2005 - 07:58 PM

Now I'm just curious, I'm hoping some of the more experienced people know the answer to this.

I have been told that a second pack of yeast may be pitched to a 5 or 6 gallon batch of wine, but that you should not do any more than that.

If the yeast colony multiplies to several times the initial culture size anyhow, why only 2 packs?

Does the initial culture you get in a pack of Red Star Montrachet have a different taste than the multiplied colony, or should I say, can it impart a different taste?


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#2 P Cuthbert

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Posted 06 February 2005 - 08:04 PM

Drunkagain;

There should be no need to use more than one package of yeast for up to 6 USG/23 litres.

When fermenting a high opening gravity must, you may consider double dosing the batch. This would help to ensure a good level of yeast at the start.

The reason for this is that the yeast may suffer some losses from the high osmotic pressure they encounter in a high gravity must.

Hope this helps;

Pat

#3 Seb

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Posted 07 February 2005 - 09:15 AM

Also, the wine will have a "yeasty" taste if too much yeast are added. Too much of anything is always bad for our wines.
Sébastien Mailloux
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#4 leiavoia

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Posted 07 February 2005 - 10:25 AM

QUOTE (Seb @ Feb 7 2005, 09:47 AM)
Also, the wine will have a "yeasty" taste if too much yeast are added. Too much of anything is always bad for our wines.

I disagree. The yeast population will grow until it colonizes the entire must and levels out at a certain concentration. Theoretically, it does not matter if you pitch a single yeast cell of or if you pitch 10 packets of dry yeast. It all levels out at the same point. The difference is in startup time. Pitching a single yeast cell will take forever to divide up to the required amount to fill the must.

#5 P Cuthbert

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Posted 07 February 2005 - 11:57 AM

QUOTE (leiavoia @ Feb 7 2005, 08:57 AM)
I disagree. The yeast population will grow until it colonizes the entire must and levels out at a certain concentration. Theoretically, it does not matter if you pitch a single yeast cell of or if you pitch 10 packets of dry yeast. It all levels out at the same point. The difference is in startup time. Pitching a single yeast cell will take forever to divide up to the required amount to fill the must.

This is almost like the old "Certs" commercial.

Stop you are both right (I feel).

Using a lot of yeast to get things going is uneconomical. If the yeast is added at differing times in the fermentation, the subsequent additions may well be killed by the alcohol in the wine and contribute to an off flavour.

True, one yeast cell may well be enough to get a fermentation going, but it is believed that yeast will only reproduce about 50 times before the budding scars are too much for continued growth.

Another factor is that genetic drift comes into play, and the yeast may not produce the same results as the original culture.

This said, I still maintain that one 5 gm package of dried yeast is generally sufficient to get a 23 litre batch of wine fermented correctly.

Pat

#6 breumyster

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Posted 07 February 2005 - 01:06 PM

Overpitching yeast can definitely result in a less efficient fermentation due to competition for nutrition. Yeast require a lot of nutrients in the "growth" phase of the process, much more than for alcohol production. If over pitched, all of the nutrients will be used up in this phase and there will be nothing left to finish the fermentation. Yeasts require more than sugar to get the job done.

Think of a country with a huge population of children and a fixed food supply. If all of the food is consumed before the children have finished growing, many will be stunted due to lack of nutrition. The same concept applies to yeast.

#7 Seb

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Posted 07 February 2005 - 01:56 PM

QUOTE (leiavoia @ Feb 7 2005, 10:57 AM)
I disagree. The yeast population will grow until it colonizes the entire must and levels out at a certain concentration. Theoretically, it does not matter if you pitch a single yeast cell of or if you pitch 10 packets of dry yeast. It all levels out at the same point. The difference is in startup time. Pitching a single yeast cell will take forever to divide up to the required amount to fill the must.

You said you disagree with my statement relative to the yeasty taste if too much yeast are added but you did not give any explanations. I agree with you at 100% with your text above. I only said that too much yeast will give off-taste which will be a yeasty taste and I don't see your disagreement here ?
Sébastien Mailloux
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Domaine & Vins Gélinas
www.domainegelinas.com

#8 Hippie

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Posted 09 February 2005 - 08:54 PM

I guess he chickened out SEB! I never argue with a well seasoned winemaker such as yourself.

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#9 leiavoia

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Posted 09 February 2005 - 11:36 PM

First of all, i'm quite male.

Second, i've never actually attempted to pitch 10 packets of yeast into a batch of wine, so i won't speak from experience on that particularly. However i have done several different pitching techniques from simple water rehydration, rip-'em-open-toss-'em-in, and lately i've been doing a 24-hour culture. There does not appear do be any difference in taste. There also does not appear do be any difference between a packet of yeast per 8-gallon batch vs. a packet of yeast per 1-gallon batch (theoretically, 800% more yeast at startup as compared to the liquid volume)

As for the yeasty flavor, i notice this is some of my batches. I do not believe it's caused simply from too much yeast, because the whole mess is really just a big yeast culture anyway, right? When the wines are fermenting actively, it's repulsively yeasty. So much so that i usually don't dare taste anything until fermentation is over. Residual yeasty flavor i believe is caused from the wine sitting on the leese too long. If the yeast are left to decompose at the bottom too long, that may cause problems. I have a few batches where i suspect this may have been an issue (but i can't tell for sure without a side-by-side test).

So basically, dead yeast may be the cause of the off flavor. As Pat pointed out, adding a lot of new yeast in mid-ferment might kill off a lot of them. But at the start? I still do not believe it matters how much you add as long it's reasonable. Adding more would not hurt IMHO, but i'm sure we all agree it's still not a good idea. Why waste two packets when one will do, you know? ;-)

#10 Hippie

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Posted 10 February 2005 - 02:22 AM

Sorry, I didn't realize I had added the s. I usually DO have those on my mind. Anyway......

Your turn Sebastian!

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#11 Seb

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Posted 10 February 2005 - 08:49 AM

QUOTE (leiavoia @ Feb 10 2005, 12:08 AM)
Second, i've never actually attempted to pitch 10 packets of yeast into a batch of wine, so i won't speak from experience on that particularly.



I do not believe it's caused simply from too much yeast, because the whole mess is really just a big yeast culture anyway, right?

Residual yeasty flavor i believe is caused from the wine sitting on the leese too long. If the yeast are left to decompose at the bottom too long, that may cause problems.

I still do not believe it matters how much you add as long it's reasonable. Adding more would not hurt IMHO, but i'm sure we all agree it's still not a good idea. Why waste two packets when one will do, you know? ;-)

leiavoia, I continu to agree with you on almost every point.

I just mention that too much yeast can yield to a yeasty taste and this is true.

You can made research about that. I do not know exactly what quantity will cause this yeasty taste as I never experiment the problem myself. I have read many text and have ask Lalvin about that in the past and every one confirm that too much yeast will give bad tasty flavors. I never use more than 10 gr. of yeast per 5 gal. ( ice wine ) so it is certainly not enough for this yeasty taste. I have heard from amateur winemakers the yeasty problem happen after a stuck fermentation and 2-3 repitching with different yeast strain to save the batch. We have to know that the more yeast you add, the more dead yeast you will have and I suspect that the contact time with these big dead yeast sediment will shorten the time required to get bad offtaste.


So we both mainly agree with the quantity of yeast we should or could use to avoid problem. But I was answering the main question regarding why is too much yeast "too much" and one of the fact is that it can give bad off-taste like a yeasty taste.
Sébastien Mailloux
Certified Wine Judge, WJC
Consultant Winemaker
Domaine & Vins Gélinas
www.domainegelinas.com

#12 Borisbbadd

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Posted 10 February 2005 - 09:08 AM

Very interesting discussion, it is something I have wondered about......

Randy
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#13 Vinmaker

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Posted 10 February 2005 - 10:23 AM

I have good luck with one packet of yeast for my 5 or 6 gallon batches. They tend to multiply just fine. Never had any problems yet.

I say save your money and save the other packet of yeast for another batch. biggrin.gif

Happily Winemaking.

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#14 Hippie

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Posted 10 February 2005 - 07:53 PM

I unequivocally concur! Or something like that!

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