Did I over stress my yeast?

[slcdawg]

I am trying to harvest some commercial yeast from a few bottles of Rogue Dead Guy. I started with the the last half inch of 2 bottles. Pitched into a small starter (500ml) at 1.037. Chilled, decanted and pitched into an 800ml 1.037 starter. Chilled, decanted and pitched again into a 1200 ml starter. And finally, chilled decanted again into a 1600 ml starter.

I have yet to notice a krausen, but know that you don't always see a krausen with starters. The last starter smelled like beer...which is good. But, my question is did I over stress the yeast by pitching immediately into 1.037? In reading several threads after attempting this, I see most people recommend initially pitching into a low gravity starter to wake them up and not stress them.

Wondering if I should use this batch or throw it out and start again?

 

[finsfan]

I have been told that doing a starter no larger than 1.010 for the first step is what you want to do. How long did you leave it one the stirplate the last step? Normally you see krausen anywhere from 12-48 hours but it varies.

 

[slcdawg]

Its been days.

I have been told that doing a starter no larger than 1.010 for the first step is what you want to do. How long did you leave it one the stirplate the last step? Normally you see krausen anywhere from 12-48 hours but it varies.

 

[dannysk]

I have never seen evidence to suggest that a gravity of 1.037 would cause problems and based on what I know about yeast, seriously doubt that this is the problem. More likely would be lack Of O2 and temp too low. As long as you were using wort from a standard mashing schedule, where the ratio of fermentable sugars is "typical", there should be no problem.

 

[EarlyAmateurZymurgist]

Ideally, you want to start less than 100ml of wort by using the last 10mls of liquid in the bottle to swirl the sediment in to suspension. I use 20 to 40mls of absolutely sterile wort to start the dregs from a bottom of a bottle-conditioned beer. Using the last 10mls of liquid to suspend the yeast and pitching it into a small volume of wort allows the culture to "own" the wort much faster; thereby, reducing the possibility that anything else will gain a foothold in the culture.

It really doesn't matter if the gravity is 1.010 or 1.020. The Crabtree effect is going to prevent respirative growth at any gravity above 1.005 (respirative growth is much more efficient than fermentative growth). The reason why we want to use a lower gravity wort is that it places less stress on the remaining viable yeast cells.

 

[slcdawg]

It really doesn't matter if the gravity is 1.010 or 1.020. The Crabtree effect is going to prevent respirative growth at any gravity above 1.005 (respirative growth is much more efficient than fermentative growth). The reason why we want to use a lower gravity wort is that it places less stress on the remaining viable yeast cells.

I'm not following. Are you saying the initial starter at 1.037 wouldn't have any negative affects? Or, that it would?

 

[finsfan]

I'm not following. Are you saying the initial starter at 1.037 wouldn't have any negative affects? Or, that it would?

it would

 

[EarlyAmateurZymurgist]

I'm not following. Are you saying the initial starter at 1.037 wouldn't have any negative affects? Or, that it would?

No, 1.037 is too high for culturing the yeast from a bottle of bottle-conditioned beer. When culturing yeast from a bottle of bottle-conditioned beer, the first stage is about resuscitating the culture; therefore, one wants to keep the gravity low. One also wants to limit the amount of wort to less than 100ml, preferably 50ml or less. Ideally, the wort should be autoclaved (pressure cooked) in the container in which the yeast will be started to ensure that it is absolutely sterile. There should be at least 50% head space in the container, and it should have a screw-on lid, so that one can tighten the lid and shake the living daylights the culture. Absolutely sterile wort affords the culture the time that it needs to restore its health without having to compete with any other microflora.

 

[slcdawg]

Thanks for the explanation. Why do you want to keep the gravity low? Are you saying that it won't propagate or that it will have off-flavors if you use too high a SG?

No, 1.037 is too high for culturing the yeast from a bottle of bottle-conditioned beer. When culturing yeast from a bottle of bottle-conditioned beer, the first stage is about resuscitating the culture; therefore, one wants to keep the gravity low. One also wants to limit the amount of wort to less than 100ml, preferably 50ml or less. Ideally, the wort should be autoclaved (pressure cooked) in the container in which the yeast will be started to ensure that it is absolutely sterile. There should be at least 50% head space in the container, and it should have screw-on lid, so that one can tighten the lid and shake the living daylights the culture. Absolutely sterile wort affords the culture the time that it needs to restore its health without having to compete with any other microflora.

 

[EarlyAmateurZymurgist]

Thanks for the explanation. Why do you want to keep the gravity low? Are you saying that it won't propagate or that it will have off-flavors if you use too high a SG?

The are several reasons for using lower gravity wort when culturing yeast:

• Osmotic pressure is directly proportional to wort density. We need to strike a balance between providing sufficient nutrients for growth and the amount of osmotic pressure being placed on the cells walls.
  
  
• Oxygen dissolves more readily in a less dense solution. Yeast cells need to oxygen to repair their cell walls via the biosynthesis of ergosterol.
  
  
• With brewer's yeast, all cell growth is fermentative growth due to the Crabtree effect, which means that the cells are producing ethanol while budding. Ethanol affects yeast health.

The goal of propagation is to increase yeast biomass, not make beer; therefore, we want to maximize cell health and cell biomass at every stage.

 

[EarlyAmateurZymurgist]

Thanks for the explanation. Why do you want to keep the gravity low? Are you saying that it won't propagate or that it will have off-flavors if you use too high a SG?

The are several reasons for using lower gravity wort when culturing yeast:

• Osmotic pressure is directly proportional to wort density. We need to strike a balance between providing sufficient nutrients for growth and the amount of osmotic pressure being placed on the cells walls.
  
  
• Oxygen dissolves more readily in a less dense solution. Yeast cells need to oxygen to repair their cell walls via the biosynthesis of ergosterol.
  
  
• With brewer's yeast, all cell growth is fermentative growth due to the Crabtree effect, which means that the cells are producing ethanol while budding. Ethanol affects yeast health.

The goal of propagation is to increase yeast biomass, not make beer; therefore, we want to maximize cell health an cell biomass at every stage.

 

[slcdawg]

Well, I've gotten growth. ...that's not an issue. Just wondering if there can be off flavors from starting at 1.037 and potentially over stressing the yeast.

What you're saying makes sense and I'll take that into account the next time I harvest from a bottle. Appreciate the input.