Secondary Fermentation

[floydmeddler]

Hi all,

Have a query - Why is it OK to leave beer in your secondary fermenter for anything up to 4 months when at the bottom, there is clearly sediment aka dead yeast etc; the very reason why it can't be kept in primary? Surely that sediment must be damaging to the beer in secondary just like it is in primary? Yes? No?

Cheers,

Floyd

 

[buttersd70]

Floyd
I presume you are referring to cold conditioning, or lagering, as opposed to secondary fermentation (which is different. In secondary fermentation, active fermentation is still occuring, and there is unfermented sugars available for the yeast.)

For a single stage fermentation that is then racked to another vessel for cold conditioning, all the dead yeast is left behind in primary. So what you have is live yeast in suspension. That is then chilled, causing the yeast to flocculate out, and drop to the bottom. It is the cold that causes the yeast to drop, not the fact that the yeast has died. So it is still live, viable yeast (granted, there will be a certain amount of dead matter come through in there, but that will be minimal). Also, due to the cold, that yeast will be (relatively) innactive. Autolysis (the yeast consuming itself) is less likely to occur in these cold conditions.

For those that have done a short period secondary fermentation (ie racking prior to the conclusion of primary fermentation, and allowing fermentation to continue in the secondary vessel), a determination is made as to whether or not it is necessary to rack a second time into a clean vessel for cold conditioning, and in a practical sense, this is rarely done. It mainly comes down to how much dead yeast has dropped in the secondary prior to chilling (which comes down to how long it is in secondary fermentation stage, and how much sugar was left for the yeast to consume). For the small amount from a 24-48hr secondary that drops out dead on the bottom, the contamination risk of the second transfer is (often considered) higher than the risk of leaving it on the (small amount) of trub. So it comes down to a numbers game.

 

[matti]

The yeast is past the initial fermentation stages once you rack to secondary so the chances that it will have go at cannibalising is less likely.
Also one should lower the temperature once final gravity has been reached so the yeast goes to sleep.

When brewing lager the yeast works very very slowly still at 3-7 degrees. Yeast are lazy and converts easy sugar 1st then the the harder sugar last. The yeast that remain active are few and not very strong, so providing you have racked off the all the dead yeast from primary fermentation the yeast that drops out of suspension in secondary can do little harm if done correctly.
I.e. No aeration, keep cool and dark.

I've got refer to literature for a better explanation.
MAtti

 

[floydmeddler]

Two fantastic responses. Cheers brewers!

Floyd