re-pitch

[lcguy]

I've never re-pitched yeast, so please don't wire brush me too bad.

I do partial grain brewing in 5 gal batches.

I saved a pint of yeast/slurry from my last brew session (2 months) ago and put it in a sanitized jar in the refrigerator.

Can I still use this in my next batch? If so, how do I go about starting it to add to my next batch of wort? Thanks.

 

[Burquebrewer]

Two months is a little bit of a long time to store a slurry in the fridge, but if your sanitation is tight, it may be fine. I'd start by smelling the yeast to ensure it is still good. I, personally, would also make a starter with it to ensure it is still viable.

As long as the starter ferments, and nothing smells funny, I'd pitch either the entire starter at day two or let it ride for three to four days then refrigerate it overnight, decant the wort on top, and pitch the slurry from the starter.

 

[flars]

At two months old you will need a starter for the harvested yeast. This thread on harvesting and repitching will give you a lot of information, or at least enough for another question.
https://www.homebrewtalk.com/showthread.php?t=579350

A picture of your harvested yeast would help to show how much hop debris and yeast is in the jar.

Edit: I estimate 2 billion to 4 billion cells per milliliter depending upon the strain of yeast. I don't have any hop debris in my harvested yeast.

 

[LLBeanJ]

I'll be the contrarian here and say the yeast is still perfectly fine to direct-pitch even at 2 months old, assuming you have enough for your batch size and OG. I'd assume ~1B cells/ml (so about 450B cells) and maybe deduct 20% for lost viability due to age, which would put you in the neighborhood of 360B cells. To use, just get your wort to pitching temp, sanitize the outside of the jar (I just dunk it in a bucket o' Starsan) and dump it in. I like to give it all a stir after pitching, but you don't have to.

 

[beermanpete]

To add to what Burquebrewer said: I would also taste the beer sitting on top of your yeast. It should taste clean and like the beer you made with the yeast. Any sour taste indicates an infection.

 

[lcguy]

Thanks for everyone's feedback. I have NEVER repitched; always bought new yeast. Plus, I have not brewed much in the past 3 or 4 years, so I'm just getting back into it. So, I appreciate your feedback. I'll take a look tonight, crack the top open, take a smell and taste and maybe a pic.

If I choose to repitch, I'm guessing I'd add some DME and let sit at room temperature for a day or so? Also, I assume I'd poor off the beer on top and just retain the yeast at the bottom. Again, sorry for the amateur questions. I'm sure these have been answered a million times on other threads, so feel free to ignore and I'll search around a bit.

 

[LLBeanJ]

If I choose to repitch, I'm guessing I'd add some DME and let sit at room temperature for a day or so? Also, I assume I'd poor off the beer on top and just retain the yeast at the bottom. Again, sorry for the amateur questions. I'm sure these have been answered a million times on other threads, so feel free to ignore and I'll search around a bit.

No DME unless you're making a starter. Otherwise, sanitize the outside of the jar, give it a good shake to mix it all up, remove the lid, and dump contents into the fermenter (assuming you have enough slurry to hit the required cell count).

 

[flars]

Thanks for everyone's feedback. I have NEVER repitched; always bought new yeast. Plus, I have not brewed much in the past 3 or 4 years, so I'm just getting back into it. So, I appreciate your feedback. I'll take a look tonight, crack the top open, take a smell and taste and maybe a pic.

If I choose to repitch, I'm guessing I'd add some DME and let sit at room temperature for a day or so? Also, I assume I'd poor off the beer on top and just retain the yeast at the bottom. Again, sorry for the amateur questions. I'm sure these have been answered a million times on other threads, so feel free to ignore and I'll search around a bit.

This will be a flat oxidized beer full of yeast you will tasting. It won't be good. Use a sanitized spoon for the taste sample if you do it. A picture will be good for helping to estimate cells per ml. At the least a vitality starter will be needed.

 

[lcguy]

Thoughts. Look ok?

 

[LLBeanJ]

Looks fine, but I'd definitely give it a smell test before pitching.

I would say you have about 125ml of thick slurry or if you shook it all up about 400ml of thin slurry. Based on this, I'd estimate you have about 250B cells in there, assuming the thick slurry contains 2B/ml. Adjusting viability down for age (loss of 10%/month), it's more like ~200B viable cells. Now that you have some sort of guestimated cell count to work with, the determination as to whether you need to make a starter or can direct-pitch as-is will depend on batch size and OG of the recipe. If it's close, but a little short, a vitality starter as suggested by above by flars wouldn't be a bad idea. If it's significantly short (>25%), I'd make a starter.