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Old 12-30-2008, 01:19 PM   #1
phidelt844
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Default Quick question on reusing yeast cake

I have a hefe I fermented at low 60s, and I want to reuse the yeast cake to try the same recipe in the upper 60s to compare flavor. However, I really don't feel like bottling and brewing on the same day. Is it all right to bottle and leave the yeast cake with a small amount of beer on top for a day or two, or is it recommended to immediatly throw a new batch on the yeast cake? Thanks

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Old 12-30-2008, 01:53 PM   #2
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Originally Posted by phidelt844 View Post
I have a hefe I fermented at low 60s, and I want to reuse the yeast cake to try the same recipe in the upper 60s to compare flavor. However, I really don't feel like bottling and brewing on the same day. Is it all right to bottle and leave the yeast cake with a small amount of beer on top for a day or two, or is it recommended to immediatly throw a new batch on the yeast cake? Thanks
Yes, in fact, you may store yeast for a period of time with proper handling and sanitation. See here: http://www.homebrewtalk.com/f13/yeas...strated-41768/
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Old 12-30-2008, 01:56 PM   #3
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I think a day or 2 and you should be fine. However, how did you pitch the first batch? Because it might be difficult to compare the differences in flavor profiles with higher fermentation temp since you're way over-pitching the second batch. Pitching rates will affect flavor profiles, especially with a hefe, so you're kind of adding in another variable. If you just want to compare differences from fermentation temp pitch both batches the exact same way.

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Old 12-30-2008, 02:07 PM   #4
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Usually it's best to immediately knock out onto a cake, if you choose to use that method.

I suggest, however, that you harvest some of the cake. It's easy, and it permits you to both clean your fermenter and pitch the right amount of yeast - using the entire cake is way too much.

First, clean and sanitize several glass jars. Mason jars work best, but I've used apple juice jugs, as well as Nantucket Nectars bottles. As long as they're glass with relatively tight-fitting lids, you're all right.

Second, remove the finished beer, leaving as little beer behind in the vessel.

Third, carefully skim the yeast bed with a sanitized stainless-steel spoon - a large soup-spoon works okay for this, though a bit time-consuming compared to a serving spoon - and scoop the harvested yeast into the jar/bottle.

Fourth, cap the bottle(s) and refrigerate. Since you're only going to be waiting a few days, the more technical stuff involved in yeast harvesting isn't really worth worrying about. You don't need to wash it, you don't need to do cell counts - you just need to get enough yeast out of the fermenter to pitch into your next batch.

To determine the appropriate amount of yeast to pitch, consult the Mr Malty Pitching Calculator. Before doing that, read JZ's essay on calculating how much yeast to pitch.

Cheers!

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Old 01-02-2009, 02:01 AM   #5
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Originally Posted by NQ3X View Post
Usually it's best to immediately knock out onto a cake, if you choose to use that method.

I suggest, however, that you harvest some of the cake. It's easy, and it permits you to both clean your fermenter and pitch the right amount of yeast - using the entire cake is way too much.

First, clean and sanitize several glass jars. Mason jars work best, but I've used apple juice jugs, as well as Nantucket Nectars bottles. As long as they're glass with relatively tight-fitting lids, you're all right.

Second, remove the finished beer, leaving as little beer behind in the vessel.

Third, carefully skim the yeast bed with a sanitized stainless-steel spoon - a large soup-spoon works okay for this, though a bit time-consuming compared to a serving spoon - and scoop the harvested yeast into the jar/bottle.

Fourth, cap the bottle(s) and refrigerate. Since you're only going to be waiting a few days, the more technical stuff involved in yeast harvesting isn't really worth worrying about. You don't need to wash it, you don't need to do cell counts - you just need to get enough yeast out of the fermenter to pitch into your next batch.

To determine the appropriate amount of yeast to pitch, consult the Mr Malty Pitching Calculator. Before doing that, read JZ's essay on calculating how much yeast to pitch.

Cheers!
Whats the longest you can keep the yeast like this before it goes bad?

If I drop new wort right after bottling and its the same style can I just drop it on the whole yeast slurry or do I still have to calculate and clean out the vessel?

How many times can you reuse the yeast this way?

I am planning to make Belgian Wit on regular basis and as well as Hefe, for other brews I think I will use dry yeast. I dont mind making back to back batches of the same style.
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Old 01-02-2009, 03:28 AM   #6
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Look the current science is now leaning away from yeast washing.
I have harvested about 5 lots of yeast cakes and my method is simple.
Buy a 2 liter PET bottle of water, drunk use or throw out the water.
Bottle beer, leave some beer over the yeast cake and give the fermenter a good shake until all the cake is suspended in the beer.
Drain into 2 liter pet bottle, squeeze out the air and refrigerate overnight, the yeast settles to the bottom beer on top.
The rest is up to you, you can drain off the beer and add sterile water (can's see why though). You can transfer to a smaller bottle.
I've heard shelf life is around 3 months, i've never had mine that long but i have some currently at the 1 month stage that i will be using later.
To reuse just take it out of the fridge and let it warm to room temp, you only want to pitch a small amount though, usually pitch about 200mls.

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Old 01-02-2009, 03:54 PM   #7
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Originally Posted by Pivzavod View Post
Whats the longest you can keep the yeast like this before it goes bad?
Stored under beer, harvested yeast loses about 10% viability immediately, and 25% viability per 7 days thereafter. (Note: Those are very rough ballpark figures; the only reliable method of determining viability is cell-counting with a haemocytometer and methylene blue stain.) I wouldn't wait more than two weeks.

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If I drop new wort right after bottling and its the same style can I just drop it on the whole yeast slurry or do I still have to calculate and clean out the vessel?
You can just knock out into the just-emptied fermenter. I don't recommend that practice because it's overpitching and just icky. It takes such little time to harvest the yeast and clean the vessel that it smacks of laziness to just dump fresh wort into the old fermenter.

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How many times can you reuse the yeast this way?
Practically speaking, a dozen generations, so long as care is taken when harvesting and pitching. That's according to the yeast labs and my personal experience in commercial and amateur settings.

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I am planning to make Belgian Wit on regular basis and as well as Hefe, for other brews I think I will use dry yeast. I dont mind making back to back batches of the same style.
If you're brewing beers in which ester development is crucial - like Wit and Hefe - you really, really don't want to knock out onto the cake or otherwise over-pitch. Over-pitching results in suppression of ester development, which happens during the reproductive phase of the yeast's life cycle. If you pitch too much yeast (or knock out onto a cake), the yeast never need to multiply, so esters aren't formed. That spells disaster with Belgian yeast of any kind or classic Hefeweizen yeast.

Cheers!

Bob
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Old 01-02-2009, 04:03 PM   #8
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If you are not going to use your yeast cake for a few days I would recommend keeping it cold.

When there is not a lot of liquid on it it gets warm. This allows the remaining beer and yeast to turn and start to smell like nail polish remover.

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Old 01-02-2009, 10:11 PM   #9
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Thanks Bob.

I guess when the time comes I will do more research about how much I should pitch from a cleaned yeast cake. After I bottle batch #1 I will collect the yeast cake with as little beer as possible. Hops should not be a problem because I will use a strainer when transferring from pot. I will put it in a glass bottle and keep in the fridge and let the yeast settle down. I will then get rid of the liquid and replace it with boiled, cooled water and will measure the amount needed to pitch and pitch it to wort of batch #2. As far as reusing I think I will stick to 10 times max per each yeast.

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