Can you over pitch yeast?

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Pfeffer

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Hi all,

Although I'm brewing a kit I threw this in the general beer discussion section anyway, as it's not really limited to kit brewing.

As some might know I started some la Chouffe cultures in the lab, so I ended up with some beautiful yeast suspensions. I was to planning to use one for my Muntons belgian style ale kit, but to spread my risk I thought it would be best to risk my cheap 9 liter Brewferm Diabolo kit first.

So what happened? I brewed as instructed.. used white candi sugar (550gr as it says to use 10% more of candi than the instructed 495 grams for crystal sugar) and pitched in a whopping 165ml of freshly cultured yeast suspension (very high cell count) ... which might be a bit much. At 20c I pitched the yeast suspension and had a 1.077 OG.

So what happened NEXT? Well. It's day 1 of the fermentation.. and I walked down stairs to see if fermentation started... Well, it did. It pushed virtually all water out of the air lock. As it is in my living room for temperature control (19-20c), I thought I'd move it to my attic to 18c to calm the fermentation down a bit. So I refilled the water lock before moving.

When I picked the fermenter up, the fermentation become so vigoruous that it actually pushed out all of the water from the airlock and than it actually pushed out the whole airlock all together. The brewferm brew bucket looked like it might explode so I decided to put it down and relieved some of the pressure by lifting an edge of the lid.

So in short, I think I don't have to worry about a stuck fermentation (ha..ha..) but I'm a bit worried what it might do to the flavour of the beer.

I'm not even thinking about tossing it, but I'm trying to find out what the effect might be without having to wait 2 months to see.

1. Can you over pitch yeast?
2. Will this negatively influence the beer?
3. Can I put the fermenter at 16-18c to calm the fermentation or will this negatively influence the flavour.

My lab experience says the yeast sediment will eventually drop out of suspension and won't be that much of an issue, but I have no clue what the fast fermentation does to the beer. I thought 165ml would be a realistic amount from what I read, but apparently the cell counts in store bought liquid suspension is still quite low compared to fresh culture.
 
1. On a homebrew level generally no. Everthing I've read suggests it's more of a commercial brewing problem. You have to overpitch huge amounts on a HB level. Plenty of people (including myself) re-pitch whole yeast cakes from previous brews into 23L brewlengths no problem. I'm aware you have access to all the lab type equipment for mycologly. Did you perchance do a yeast cell count (basically how many cells per ml)?
2. There are possible consequences to over pitching such as higher attenuation (more cells to do the work) and less ester (you may or may not want esters depending on beer style). Possible off flavours and problems related to overpitching over a number of generations
3. I'd keep to the suggested yeast temps. It would be better to put a blow off tube on the FV as I undestand belgian /yeastbeers need higher temps
 
I only did a quick check after centrifuging it using a hemocytometer. I did use some trypan to dye out the dead cells, but I only did a small grid count so it's not a 100% accurate. It's giving me about 1.22*109/ml. So about 201.3 billion living yeast cells in my pitch.

Edit: Googled it; 201.3 billion yeast sells might be a tad much for 9 liters with 1.077 OG but still realistic.
 
I only did a quick check after centrifuging it using a hemocytometer. I did use some trypan to dye out the dead cells, but I only did a small grid count so it's not a 100% accurate. It's giving me about 1.22*109/ml. So about 201.3 billion living yeast cells in my pitch.

Edit: Googled it; 201.3 billion yeast sells might be a tad much for 9 liters with 1.077 OG.

I put your figures through a yeast calc and you need 122 billion cells. So you pitched about 80 bill over pitch. Definately an overpitch but I dont think your going to have massive problems
 
According to Mr Malty a 20% overpitch is enough to have a noticeable impact. You've overpitched by about 60% there but like Myqul I don't think it'll do much harm.
 
To those not as lucky as Pfeffer would a starter or yeast cake I salvaged from a brew yield a good amount of love yeast e.g. Will I be able to salvage the yeast from a demijohn I am making cider in and then just putting it into a 23/25 litre fermenter in with more apple juice etc ? I have only read of people giving it a rest first in the fridge and then using some of it - not all of the yeast cake
 
The problem with using yeast cake is that a large portion of them are dead cells. Depending on the fermenting temp, nutrients used, age of the cake it can be quite unpredictable with regards to viability.

As yeast are living organisms they reproduce, so yes.. it should work. If the cake was bad it might give you a slow start or stuck fermentation though.
 
Just got a message from the lab that another cup had 1.97*109/ml in a larger grid count. So that would be 325 billion cells in the pitch. Which makes sense as it was centrifuged to get them to drop out of suspension.

As I did my last cell count around 2005 I was most likely to slow (causing the trypan to dye viable cells as well). This might also explain the very vigoruous fermentation.

I was planning to give away the other cultures, but I can't figure out on how to pack them for shipping as they are still producing co2. Having them consume most of the nutrients, chilling them and then packing them on coldpacks seem most practicle but they might still produce some. Any ideas on how to do that? And anyone interested in trying some la Chouffe yeast?
 
I was planning to give away the other cultures, but I can't figure out on how to pack them for shipping as they are still producing co2. Having them consume most of the nutrients, chilling them and then packing them on coldpacks seem most practicle but they might still produce some. Any ideas on how to do that? And anyone interested in trying some la Chouffe yeast?

You could slant the yeast to send it out. Never done it slanting myself
http://www.homebrewtalk.com/wiki/index.php/Yeast_Slants
 
Slanting is easy and practical, but it requires the consignee to grow it out again. I was hoping to send a 165ml pitch suspension without it exploding.

I can simply put some sabouraud in a corning tube if anyone is interested though.
 
Slanting is easy and practical, but it requires the consignee to grow it out again. I was hoping to send a 165ml pitch suspension without it exploding.

I can simply put some sabouraud in a corning tube if anyone is interested though.

I've never heard of a HBer sending out a ready amount of yeast for fermenting only the proffessional east labs.
 

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