I have a re-pitch of yeast from a previous batch of beer that has been sitting in a glass jar in my fridge for about 21 days now, maybe longer. I know in a perfect world I should have used that yeast within 7 days.

Can I still use this yeast?

What about making a starter, rinsing the yeast and pitching the slurry into the starter to wake it up? Worth my efforts or cut my losses?


thanks


Kevin

You should be fine using the yeast directly as long as it's not a wheat beer yeast. The pitching rate calculator on mrmalty.com shows that at 3 weeks your're still around 82% viability.

What would it matter if it was a wheat beer??

Probably added the wheat beer caveat since Jamil and others have found that bavarian wheat yeasts lose their viability much quicker than other strains.

Ah thats right... I do remember that now that you said that. But a Cal Ale yeast pitched into a wheat beer wont matter as far as viability goes though right?

It also is going to depend on what beer it came out of... if it was a beer that stressed the yeast out, they are going to be in poorer shape and my not do well in your second beer...

Before you consider using this yeast, make sure the beer you previously made with the yeast turned out fine and doesn't have any off flavors or infections. If any yeast off flavors are present in your previous batch of beer they will be compounded if you re-pitch that yeast for your next fermentation. Perhaps make a starter with some of it, smell it and taste a small portion of the decanted wort to see if there is a clean yeast flavor the coincides with the flavor profile of that particular strain.

Also is this yeast pulled from Primary or Secondary fermentation?

It just so happens that I have been listening to the White Labs 2009 episode of the Session at work today. Here are a few more things I can relay over to you from The Brothers White. If this sounds similar to your process then you probably have yeast that will ferment relatively well.

After racking your beer off the yeast, protein and hop sediment, use the remaining liquid/beer in your carboy/bucket to swirl your yeast and detach any of the sticky yeast particles that may be clinging onto the bottom of your fermentation vessel.

Put this mixture into a sanitized seal-able container in your fridge and let it settle out for a day. Make sure to vent the gas out of the container 2-3 times a day for the first few days because the yeast are still producing gas and the pressure of this gas is more harmful in such a small environment. Basically the yeast can kill itself off in that gaseous environment. If you use aluminum foil as a lid you are likely fine because the gas can escape but if you used a jar with a screw lid you will need to vent off that gas. If you open your sealed container a few days later and you hear a huge hiss (like the sound of opening a carbonated beverage for the first time) and you smell a ton of gas, your yeast may be in rough shape.

After 2 days in the fridge pour off some of the liquid on top and strive for a 50/50 mixture of yeast slurry and liquid. Use this 50/50 mix for your next batch.

For an easier way to get a larger and healthier yeast slurry, above all else Chris recommends top cropping during the first 2-3 days of fermentation. Typically after a month healthy yeast that has been harvested has less than 50% viability. The thing to keep in mind is that during fermentation the amount of yeast cells is 4-5x as large so even with less than 50% viability in your slurry you still have a lot of good yeast but you also have a lot of bad yeast.

Hope this helps