This guide was written by The Homebrew Forum member, ‘Oblivious’. It’s a superbly simple ‘how to’ guide which tells you how to harvest yeast for brewing.
You can find the original thread here.

How to harvest yeast for brewing

This is my method of yeast harvesting, this was done for my last brew a Saison with WLP550

After racking the beer to the keg pour the remaining liquid, trub and yeast into a sterilized container. I find one around 2 liters to be a good size. Place the full container in the fridge for a few hours.

Harvesting yeast

The trub being heavier, will settle out faster than the live yeast. It is the liquid part we are interested in as this will have a greater concentration of viable yeast. Pour this liquid off into a new sterilized container, this can be of a smaller than the first and place in the fridge over night.

Reusing yeast

As the liquid we placed in the container is yeast rich, we want to harvest the sediment in this container. Decant of the majority of the liquid and transfer the rest includin the sediment to your storage vessel, I use sterilized 50ml tubes.

Yeast Sediment

Yeast harvesting

Decant off the majority of the liquid and pour the yeast in to your selected container. I find there is enough yeast  in each of these tubes to pitch into a starter for a month or so. Over that it I would add two of the tubes to a starter.

Yeast Vials

What do we do in these situations? Panic.

“Is it ruined?! What if it’s infected? I must tip it all away down the sink because I messed up and ruined my beer! ”

What should we do in these situations?

RDWHAHB!

RDWHAHB!

Or in laymans terms: Relax, Don’t Worry, Have A Home-Brew!

There’s very little you can do to completely ruin a batch of beer. I once heard a veteran brewer give a panicking newbie the sound advice, “Unless you actually defacated into the fermentation vessel, your beer is going to be just fine.”

Whatever you do, do NOT dump a batch of beer. See how it turns out, and if it’s undrinkable after the full brewing process (after 3 weeks in the bottle!) you are then still not permitted to dump the batch. Beer gets better in time, and the yeast know what they’re doing. Besides, even if you do have an infected batch, it won’t do you any harm! No pathogens can survive in beer, due to the PH level. Even if your beer tastes like a small animal died in it, all it will do is give you an ‘icky tummy’.

So before you tip away that beer you ‘ruined’, give the yeast a chance to do their thing and clean up after your mistakes!

RDWHAHB!
- Brewingtips.com Staff

Thanks to www.rooftopbrew.net for this fantastic ABV Calculator.
- Brewing-tips.com

It is important to note that Diacetyl can also be produced by bacterial infection of the wort during fermentation, so the first step in reducing diacetyl levels in your beer is good sanitation.

Diacetyl Molecular Structure

Fortunately, diacetyl is reabsorbed by the yeast during the end of primary fermentation. This can only happen however at regular fermentation temperatures – If you are largering a beer, you will need to raise the temperature of the fermenting beer to room temperature for a few days after primary fermentation; this is called a diacetyl rest. If you are brewing an ale, your beer should be fermenting at the correct temperatures already; to reduce diacetyl levels simply leave the beer in primary fermentation until the buttery taste and aroma has subsided.

For more information about Diacetyl and how to get rid of it, check out these useful links:

http://beerme.com/diacetyl.php

http://en.wikipedia.org/wiki/Diacetyl
Thanks for reading,
Brewing Tips Staff.