Yeast propagation

Fore · May 18, 2017

OK, I'm finally getting into this. Ordered a stir plate and a separatory flask. 250ml & 2l Erlenmeyer flasks in the pipeline. Using liquid yeast will finally become financially viable.

Been reading up on the subject, but still have a few questions I hope you can help with...

1) I think behind this first question is the biological changes that occur during growth, but I let you explain. Imagine I harvested & washed yeast from the yeast cake of my last brew. I understand that's a lot of yeast, so when I start my next brew 1 or 2 days later, I should only use about 1/5th or 1/4 of what I collected. Now if I didn't start my next brew within 2 days, then the viability of my collected yeast starts to drop, and it is recommended to use a starter. And here my question... why use a starter when I have at least 4 times the yeast I need? Why not just pitch more, like a 1/2 of what I collected, or something?

2) What is considered better, to grow the vial beyond what you need, and store the excess, or to harvest from the cake? Why would you chose one over the other? I'm guessing breweries harvest, so I'm thinking that has advantages over repeated propagation of the original strain.

3) I use Brouwland, and can't find any yeast nutrient other than Vinoferm Nutrisal. Can that be used in beer yeast propagation?

Simonh82 · May 18, 2017

1. You can do this but it isn't just about viability of yeast it is also about the vitally. You want healthy happy yeast ready to reproduce and make beer. Yeast stored for a while will have started to use their energy reserves and this means they will take longer to start fermentation when you pitch them. Look up 'vitality starters' which you could use to get a big pitch of harvested yeast back to peak condition in a few hours rather than a day or so for a normal starter.

2. Growing the vial and harvesting the excess is probably a better way of maintaining a clean yeast culture. You are dealing with smaller volumes and the propagation happens over a shorter timescale. Harvesting yeast from the slurry after a beer is finished works fine but there is more opportunities for undesirable organisms to get in.

Breweries work a bit differently. They are harvesting large quantities of fresh yeast and sticking it straight in the next brew where it will take off like a rocket and out compete anything else. They also have very good sanitisation procedures, if they are worth their salt. Most breweries will also reculture from a pure source every few (maybe 10) brews.

3. A standard yeast nutrient should work fine. White Labs sell a 'complete' nutrient which appears to include some dead yeast as part of the mix. On a couple of occasions I've chucked in a packet of bakers yeast at the beginning of the boil (for beer, not a starter). I don't know if it's made any difference. I think the idea is that the yeast breaks down and the nutrients from the inner cell are available to your brewing yeast.

Fore · May 19, 2017

Simonh82 said:
1. You can do this but it isn't just about viability of yeast it is also about the vitally. You want healthy happy yeast ready to reproduce and make beer. Yeast stored for a while will have started to use their energy reserves and this means they will take longer to start fermentation when you pitch them. Look up 'vitality starters' which you could use to get a big pitch of harvested yeast back to peak condition in a few hours rather than a day or so for a normal starter.

2. Growing the vial and harvesting the excess is probably a better way of maintaining a clean yeast culture. You are dealing with smaller volumes and the propagation happens over a shorter timescale. Harvesting yeast from the slurry after a beer is finished works fine but there is more opportunities for undesirable organisms to get in.

Breweries work a bit differently. They are harvesting large quantities of fresh yeast and sticking it straight in the next brew where it will take off like a rocket and out compete anything else. They also have very good sanitisation procedures, if they are worth their salt. Most breweries will also reculture from a pure source every few (maybe 10) brews.

3. A standard yeast nutrient should work fine. White Labs sell a 'complete' nutrient which appears to include some dead yeast as part of the mix. On a couple of occasions I've chucked in a packet of bakers yeast at the beginning of the boil (for beer, not a starter). I don't know if it's made any difference. I think the idea is that the yeast breaks down and the nutrients from the inner cell are available to your brewing yeast.

Thanks for your reply Simon.

1) I thought it would be something like that. A starter it is then. Can I assume that you should still run with say 1/4 of the collected yeast even when running the starter?
2) Right, I'll prioritise growing rather than harvesting from the cake. Need to start looking over the calculators again.
3) I don't have any alternatives. I'll ask my supplier in any case, but anyone happen to know if Vinoferm Nutrisal is acceptable for beer yeast?

Fore · May 20, 2017

After playing with the calculators, I start to see the cost involved in stepping up. You are looking at about the same cost as a cheap packet of dry yeast for a single 2l starter; the cost is in the DME. Which got me thinking. What would be wrong in creating 2l more sweet wort than I need for a brew, then freezing that 2l ready for the next starter (gravity checked of course)? I don't see anyone recommending this approach and wonder why. It seems like an ideal solution to keep the starters cheap and avoid DME. And the wort will be boiled before use in any case. A good idea or not?

My stir plate arrived today. I plugged in the plug and it exploded! The plug that is. I have a universal plug and the stir plate works fine, but it was a bit of a shock.

MyQul · May 20, 2017

Fore said:
After playing with the calculators, I start to see the cost involved in stepping up. You are looking at about the same cost as a cheap packet of dry yeast for a single 2l starter; the cost is in the DME. Which got me thinking. What would be wrong in creating 2l more sweet wort than I need for a brew, then freezing that 2l ready for the next starter (gravity checked of course)? I don't see anyone recommending this approach and wonder why. It seems like an ideal solution to keep the starters cheap and avoid DME. And the wort will be boiled before use in any case. A good idea or not?

My stir plate arrived today. I plugged in the plug and it exploded! The plug that is. I have a universal plug and the stir plate works fine, but it was a bit of a shock.

No problem at all doing this. I've done this myself. Even if your sweet wort is a lot higher OG than about 1.040 just dilute it down