Stationary phase a.k.a declining phase of fermentation?

[Finlandbrews]

In the general certificate on Brewing the Institute of Brewing and Distilling indicates that in that last phase of the fermentation (commercial brewing set up) as indicated in the title of this post, the rate of cell deaths exceeds new cell formation.

I would like to ask as I had been told or read elsewhere, is it true that yeast cells die? What I had learnt before is that they go dormant at this stage and will only die after a too long period without oxygen...

 

[xpops]

not all die, otherwise we wouldn't be able to build starters, or wash yeast or repitch on existing trubs....but i'm sure some do die since autolysis is a real thing.

 

[IslandLizard]

"Rate" is the keyword. Toward the end of fermentation not many new cells are formed, due to lack of food, oxygen, etc., while at the same time many of them die off because of old age, exhaustion, alcohol poisoning, and what not.

 

[Finlandbrews]

"Rate" is the keyword. Toward the end of fermentation not many new cells are formed, due to lack of food, oxygen, etc., while at the same time many of them die off because of old age, exhaustion, alcohol poisoning, and what not.

Is a perfect brewing process one that doesn't include that 4th stage and includes a transfer of the beer just before the stage where first cells die?

 

[Yooper]

Is a perfect brewing process one that doesn't include that 4th stage and includes a transfer of the beer just before the stage where first cells die?

Cells die- they just do. Not all of them at the same time, of course, but you can't avoid having some of them die. You can't transfer a beer before any cells die, as they die at different rates.

 

[eric19312]

I'm confused...I don't think stationary phase is something to be avoided. I searched and kept coming up with this explanation on various sites, always attributed to Chris White (lol even on he Wyeast site they attributed Dr White)


Stationary phase of yeast growth- 3-10 days:
At this point, yeast growth slows down, and yeast enter into a stationary phase of growth. Most of the flavor and aroma compounds have been produced, which include fusel alcohols, esters, and sulfur compounds. The beer is called "green beer" because it does not yet have the acceptable balance of flavors.

Beer is matured in the stationary phase of growth, also known as the conditioning phase. Yeast reabsorb diacytyl that was produced during fermentation, and hydrogen sulfide escapes from the top of the fermentor as a gas. The krausen falls, and yeast begin to settle out, or "flocculate". It is important to check the degree of attenuation at this point to confirm that the yeast has completed fermentation. Some strains of yeast will begin to flocculate out before terminal gravity has been reached, and need to be "roused" back into solution.

Professional breweries will cool the contents of the fermentor gradually to 35-40F, which will force most of the yeast to flocculate. Most homebrewers do not have the facilities to do this, so they must wait for the fermentor to "clear". If the homebrew is to be bottled, flocculation can be allowed to complete in the bottles.

 

[Finlandbrews]

I'm confused...I don't think stationary phase is something to be avoided. I searched and kept coming up with this explanation on various sites, always attributed to Chris White (lol even on he Wyeast site they attributed Dr White)


Stationary phase of yeast growth- 3-10 days:
At this point, yeast growth slows down, and yeast enter into a stationary phase of growth. Most of the flavor and aroma compounds have been produced, which include fusel alcohols, esters, and sulfur compounds. The beer is called "green beer" because it does not yet have the acceptable balance of flavors.

Beer is matured in the stationary phase of growth, also known as the conditioning phase. Yeast reabsorb diacytyl that was produced during fermentation, and hydrogen sulfide escapes from the top of the fermentor as a gas. The krausen falls, and yeast begin to settle out, or "flocculate". It is important to check the degree of attenuation at this point to confirm that the yeast has completed fermentation. Some strains of yeast will begin to flocculate out before terminal gravity has been reached, and need to be "roused" back into solution.

Professional breweries will cool the contents of the fermentor gradually to 35-40F, which will force most of the yeast to flocculate. Most homebrewers do not have the facilities to do this, so they must wait for the fermentor to "clear". If the homebrew is to be bottled, flocculation can be allowed to complete in the bottles.

Bamforth says that chilling to 30 Farenheit/-1 celsius is actually dramatically much more efficient than 0 or +1/2 celsius and all breweries should try chill at -1 Celsius. Isn't there any problem to leave the yeast to drop out only once in the bottle, isn't it better to use gelatin or try to chill for 2/3 days?