Harvested Yeast - Should it look like this?

[Oyarsa]

Last beer I made I harvested the yeast. I left some wort, poured it into two jars (only partially filled the second jar), and put it in the fridge. The jars were sanitized, but I didn't sanitize the inside top of the fermenter before pouring it out.

I've read there should be three layers, but looking at pictures in articles, I still can't really tell what it should look like...

Does this look right? What should I do prior to using it? Is there any way to test the yeast for contamination prior to using it?

 

[SoCal-Doug]

The "3 layers" people talk about are definitely there. The greenish diaper pie looking schmutz on the bottom is your trub, hops and other gack. Then there is a very thin layer of white yeast cells. Then the clear beer is on top of that.

What you might consider doing is... Mix up real good, what you take out of the fermenter and put it in a large jar. Watch for the unwanted gack to settle a bit while the fluid on top is still hazy and cloudy (basically 2 layers, crap on the bottom, suspended yeast on top). Once this happens, carefully pour only the hazy liquid into another jar and save it. Discard anything that settled first. After settling overnight, you should wind up with only a tiny layer of yuck, then a thin layer of white yeast, and beer on the top.

What you keep, should remain viable (meaning enough live yeast to be useable) for a few weeks. But you should do a starter with it before pitching it into another batch.

 

[Oyarsa]

I think I was expecting the yeast layer to be larger. It also looks to me like the yeast layer is still mixed a bit with the trub.

I've never made a yeast starter before (this coming from only my second batch of beer), but plan to for the next batch. If I use this yeast, how would you recommend making the starter? Pour off the wort and make a starter with the yeast and trub? Try separating the yeast and trub? Just use whole thing, wort and all?

 

[SoCal-Doug]

The yeast layer is very small compared to everything else. Actually, most of the yeast layer you'll see is dead yeast. Keep in mind those things are literally microscopic critters. 50 or 100 billion of them still don't add up to much.

For a starter, you can make some wort with DME (dry malt extract) and water, to a gravity of about 1.040. Maybe a quart of it. Heat it up, dissolve it, boil it for about 10 minutes (gets rid of chlorine and sterilizes it). Let it cool to room temp (seal it shut so no bad things get in, like airborne wild yeast from a local fruit tree or something).

Using your saved yeast... Carefully pour off (discard) about 90% of that liquid (don't disturb the white layer), then mix it up real good and pour it into your new wort. Put an airlock on it, or plastic and a rubber band, or something, so CO2 can get out but air can't get in. It'll foam up in a couple days, then after 3-4 days you should have a good yeast batch ready for making beer. Give it a shake/swirly a few times a day.

There are ways you could separate out more yeast and less trub, but mixing it up and pouring off the suspended yeast after some of the trub settles. Might not be worth it this time. That's best done fresh from the fermenter.

You can also google up or youtube "making a yeast starter" as well as "yeast washing" or "reusing yeast". There's a zillion ways to skin those cats.

 

[Oyarsa]

Thanks for the advice.

Out of curiosity, why do so many people use an erlenmeyer flask? Aside from being able to heat the wort in it, is there any other particular benefit, or would a 1 gallon fermenter work?

 

[beerlover77]

Flasks have a flat bottom perfect for a stirplate and a narrow top, easy to foil over. All the one gallon fermentors I own have a punted bottom which makes it impossible to keep a stir bar spinning

 

[SoCal-Doug]

(1) you can feel like a microbiology lab nerd
(2) rubber stoppers are made to fit them and airlocks go right into the stopper hole
(3) you can put them on a hot plate or flame without shattering them
(4) fairly cheap and readily available
(5) volume graduated on the side
(6) flat bottom to work with magnetic pill's for stirring

Any old jug/bottle/container will work. Stick with glass though. But don't try to put non-lab glass on a stove, or pour boiling liquid into it