Frozen Yeast/Slurry

[Elbow]

I followed the mini mash recipe for Grain and Grape Pilsner from their website recently, nice drop! I used a Wyeast liquid, Danish 2042. I was intending to do another batch straight after and pour the fresh wort onto the yeast slurry/cake left from the last batch. However, I never got a chance and instead poured the slurry into sterilised plastic drinks containers and put them in the freezer. In all I got about 2 litres of slurry. There was probably lots of hops in there as well as I dry racked around 20g of Saaz as per the recipe (I didn't rack to secondary due to time constraints).

Can I defrost this and use again? If so, is it the same as making a yeast starter? I am intending to do another Pils.

[warra48]

What you propose is usually fine.
I've never put the slurry into the freezer, so I don't know how much of the yeast will survive that treatment.
I think the prevailing wisdom id to store it in the fridge.
I guess if you use it to build a new starter, you'll know.

[billybushcook]

I guess if you use it to build a new starter, you'll know.

+1
If you defrost it slowly (ambient temp) then build a starter with some sort of sugar, you will soon know if it is still a viable yeast, that is, if it comes to life in a reasonably short time with a bit of aeration,

Cheers, Mick.

[Elbow]

No worries,

It was actually split between two bottles, one a 1.5 ltr and the other 1/2 ltr. I might defrost (slowly ) the little one first and try making a starter from that.

Thanks for the advice guys.

[Trough Lolly]

G'day Elbow,
Unless you plan on conducting some pretty advanced yeast management processes, I would not freeze your slurry, especially if you plan on making another Pils in the near future (ie, the next month or so). By now, you should have some clearish liquid above the settled slurry that you can decant and dispose of when you next use it A few hundred mls of the settled slurry is more than enough to kickstart the next batch of pils that you're after and that slurry in a clean environment will easily last for the next few weeks, in the fridge.

Freezing yeast is possible but you need to have the yeast in the right media to begin with, otherwise you will do a lot of damage to the yeast cell walls which will in turn result in undesirable flavour outcomes when you next use it. Just keep the slurry in a sealed bottle and it will remain viable in the fridge for at least the next few weeks, no probs. Keep an eye on the bottle - lager yeast is still quite possibly active in the fridge and you don't want to make a bottle bomb, do you? Just ease the cap every week or so, or when the bottle walls feel quite tight...I'm assuming you've used a PET bottle, not glass?

Cheers,
TL

[Elbow]

Hi TL,

It's actually already frozen (PET), was going to defrost the smaller bottle today and make attempt my first yeast starter in preparation for another Pils in a couple of days. Once it's defrosted, should I dispose of the clear stuff on top?

[drsmurto]

If its frozen solid you have done some serious damage to your yeast. As TL mentioned, the cell walls would have been damaged so the number of viable yeast has been greatly reduced.

You should never freeze yeast in water, glycol is the preferred medium.

Pour off the beer, add some starter to it and see what happens but if it was my yeast, i would be ditching it.

[Elbow]

Bugger!

As mentioned before, I basically ran out of time as I was heading overseas for a month and was not sure whether the slurry would be ok in the fridge for that length of time.

Ah well, chalk this one off to inexperience.

[drsmurto]

Yeast slurry will be fine in the fridge for a month or 2.

Have a read of this thread - Linky

Cheers
DrSmurto

[Anna]

DrSmurto - I had a look at your instructions in the "Yeast Harvesting" sticky and thought I might give it a go, as I just hate washing all that lovely slurry down the drain. Question: How much of the harvested slurry do you need for a fresh brew? (K&K) I'm currently using SA-23. One of the posts above says 100 ml or so - is that really enough? Do you just pour the harvested slurry on the top of the new wort and mix in?

[drsmurto]

DrSmurto - I had a look at your instructions in the "Yeast Harvesting" sticky and thought I might give it a go, as I just hate washing all that lovely slurry down the drain. Question: How much of the harvested slurry do you need for a fresh brew? (K&K) I'm currently using SA-23. One of the posts above says 100 ml or so - is that really enough? Do you just pour the harvested slurry on the top of the new wort and mix in?

I would normally use ~1 cup of slurry in a new batch. Since this is a lager yeast i assume you are pitching the yeast into the wort once the temp is ~20C or below and allowing it to cool to the desired fermentation temp of 12C?

If the harvested slurry is fresh then yes, just mix it in with your new wort.

If the slurry has been in your fridge for more than a week i like to fire it up first to make sure its viable. Since it is a large amount of yeast you don't need to increase the number of yeast present, just get them active so i would add a 500mL starter.

Or alternatively, you could make up your new wort and pour ~500mL of it into a flask/jar containing your yeast slurry and let it sit for an hour. When you see signs of activity, pitch that into your fermenter.

You should also make sure that your wort is adequately aerated. A sanitised spoon (assuming you use the white plastic spoon that came with the kit) and a rapid mix to 'froth' up your wort and you're done! I would do this regardless of how fresh the yeast is.

Provided your sanitation regime is up to scratch you can repeat this process a few times.

Have fun
DrSmurto

p.s. once you get confident doing this you can move up to liquid yeasts.

[Anna]

You should also make sure that your wort is adequately aerated. A sanitised spoon (assuming you use the white plastic spoon that came with the kit) and a rapid mix to 'froth' up your wort and you're done! I would do this regardless of how fresh the yeast is.

Thanks once again Doc! You are so very helpful. Do you mean 'froth up' the new wort before or after the yeast slurry is added? (Sorry to be so pedantic....)

PS: Are you really a doctor?

[drsmurto]

Either way works fine Anna, i tend to aerate the wort before adding the yeast.

Cheers
DrSmurto

p.s. depends what you mean by real?