Harvesting yeast from Primary

Reading this thread has got me thinking...

Is it possible to harvest yeast directly from Primary?

By that I mean:

1. Take about a bottle's worth (call it 450ml) of beer from primary just after the majority of fermentation is complete
2. Seal the bottle (cap it)
3. Stick it in the fridge for 3 - 4 weeks until next brew
4. Create a starter with some DME + the bottled harvest

Would this be ok for re-using yeast in future batches?

I'm thinking of taking the harvest roughly 1 week into primary. I usually leave the beer in primary for just shy of a month.

This would work, but I'd worry about capping a bottle of actively fermenting beer, even though it's going in the fridge. I think a better approach would be: after racking off the yeast/dregs from the primary, just pour some slurry into a sanitized jar. I like honey jars for this, because they have a wide mouth. Put some saran wrap over the top & screw on the lid. This is not airtight enough to explode the jar, but it's sealed well enough for your purposes. Go ahead and keep it for 4 weeks - it will wake up just fine. Doing an acid yeast wash is the preferred method, but if you just want to get one more batch from it, and your primary was infection free, this will work.

Thanks!

I have a jar sitting around that I'm going to do just that to! Going ot boil the jar and lid first though.

You could also just sanitize the jar and lid in StarSan or Iodophor. No need to boil (same effect as sanitizer).

khiddy said:

You could also just sanitize the jar and lid in StarSan or Iodophor. No need to boil (same effect as sanitizer).

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Because you're dealing with such a small cell count of yeast and the possibility of contamination, I'd boil both the jar and the lid to sterilize.

flyangler18 said:

Because you're dealing with such a small cell count of yeast and the possibility of contamination, I'd boil both the jar and the lid to sterilize.

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But the point is that a huge cell count is harvested. I'd tend to agree with Khiddy that sanitizing is enough (that's how I've done it), but there's certainly no harm in boiling...

I think it's better to actually rinse the yeast, commonly called "washing yeast." This will get them in a solution with a minimal amount of nutrients and oxygen, thereby discouraging any metabolic activity on their part. They'll hibernate more readily, and when reawakened will be in better health than just straight up saving slurry.

Read the sticky about washing yeast, and listen to every Brew Strong episode about repitching and washing yeast. Trust me, these procedures sound so much harder than they are. Just listen to everyone else's procedures, then look at what equipment you have and make a plan of action. You'll be really excited and proud about the step your homebrewing is taking when you have 3 or 4 bottles of cultured yeast in your fridge.

I use swing-top bottles to store harvested yeast. Once I get 'em in the bottle, I pop the top once after two days of storage to release any pressure in case the yeast were up to something. You don't even have to really open the bottle - just crack it open to release a tiny amount of gas.