Yeast use Critique needed

[Kelbor]

I have been keeping a yeast strain alive for about eight ferments and I want to make sure Im getting the most out of it.

I started with a liquid package and grew it into a 14 cup sized bomb (a bit less then a gallon). I used 12 cups of this in my two fermenters and the last two I threw into another 12 cups of wort (wort is LME @ 1/2 cup per 2 cups water, boiled ten minutes). An example of my schedule is to mash in corn on friday at 3:00pm, I take my yeast out of the fridge then. By saturday evening/night I have completed the mashing and inoculate the batch. On sunday morning I put the gallon of yeast bomb-to-be in the fridge.

Im plagued with a few questions; The question I have is would it be better to just save a quart in the fridge instead of a gallon and then grow that to size the day before I inoculate? Also Im unsure on how long to let X amount of yeast feed in Y amount of liquid before putting them up for hibernation of the week. The other thing Im wondering is when the point of most population is in my bomb (so I can use it at its prime) - I assume its when it becomes super fizzy but am not sure.

Thanks!

[Coyote]

What are you making?

Everything I do I just toss the bakers yeast on top

Coyote

[MitchyBourbon]

Sounds like what you are doing is growing a series of starters and reserving a portion each time to make the next starter. This probably is not the best way to maintain a strain long term, it certainly is a lot better than harvesting spent yeast from the bottom of your fermenter. A slightly better method would be to grow a starter, remove most of the liquid and divide into vials that can be sealed and stored in your fridge. Then when it's time to ferment your next mash, just take out a vial and grow a starter. When growing a starter you want to be careful not to create an environment where the yeast create alcohol. The starters purpose is to grow yeast not to make alcohol. You only want to use a small amount of sugar or DME or whatever to grow a starter.

Yes, you will know the starter is active if it is foaming. Sometimes it won't foam much, but if you look closely you can see the liquid churning up and down in the container. When you see physical activity it is a good time to pitch.

What kind of equipment are you using? Do you have a stir plate or microscope? You will want some way of estimating yeast counts.

At some point you may want to try re - propagating your strain from a single yeast cell. I do this from time to time if I feel one of my strains has gone weak or even contaminated.

[Kelbor]

Coyote - i have used bakers yeast in the past (and will again Im sure as it is a great yeast) but this is a more expensive English Wyeast that cost me like 7bucks for one smack pack ....thus propagating to save $$.

Mitchy B- Thanks for the tip/recommendation. Vials would be a better way to NOT introduce bacteria and would insure a much more consistent strain...
I do realize that every time I save some of my larger starter bomb I increase my risks. I'll have to check on sources for good, sterile vials.

How long will a strain of yeast last in the fridge in on of these sealed vials? I do not have a stir plate or microscope. I realize these would be cool to have and really useful but at my level of expertise I would not gain much from them. As for the stirring - I just kinda give her a swirl every time I walk past my yeast jug. I do maintain a clean and sterile as possible environment (star-san, while not the most effective means, is my friend).

[Coyote]

Yeast strain - how long will it last?

My sourdough has been documented at over 125 years
Way before refer's

Coyote

[T-Pee]

What's wrong with saving yeast from the trub if it's going to be used in the same recipe wash?

For the time being I've settled on three ferments...UJSSM w/baker's, an apple juice w/EC-1118 and a Birdwatcher's w/C-1118. I was hoping to re-propagate the washes from the respective trub for consistency. Dumb idea?

tp

[MitchyBourbon]

Sealed in a vial it will last several months. But if it does go weak, you just take a small amount and grow it up to about a liter. Even better if you propagate in a petri dish from a single healthy cell. But that's a lot of work.

[Kelbor]

T-P,
I think saving yeast from trub works just fine as long as you dont push generation after generation. A few should be fine. The problem arises from small contaminations that might get in there. At first they are not noticable because there are still so many good yeast cells but through time, those bad yeasts or bacterias will reproduce just as the good ones - essentially shifting the balance in their favor. The other negative I've heard of is that the good and healthy yeast is racked off and put in the still while the trub on the bottom is the dead and sick yeast. There is good yeast there but a larger % of not so great yeast. It is the equivalent of modern day big game hunting - killing off all the truly magnificent beast and letting the runts reproduce gives you a weakened overall population.

[Kelbor]

hmmm...

http://www.ebay.com/itm/50-Brand-New-La ... 4897.l5658" onclick="window.open(this.href);return false;" rel="nofollow

[T-Pee]

But...but...what about the UJSSM process where generation after generation after generation is dropped right on top of the same yeast cake?

tp

[MitchyBourbon]

As far as harvesting yeast goes, the best yeast does not come at the end of fermentation. All the yeast is on the bottom of the fermenter. If you scrape off the top you will get yeast that was the last to settle, this yeast will tend to resist flockulation. If you take the yeast from the very bottom you get yeast that flock late too early. The yeast you want would be in the middle, but how are you going to get it? Even if you did get it, it's not going to be all that healthy. Yeast exposed to more than 4 % alcohol are not good candidates for harvesting. Breweries and distilleries harvest yeast but they use equipment most here don't have. They use conical fermenters that allow them to harvest yeast at any time during the fermentation process.

Reference: Yeast The Practical Guide to Beer fermentation.

[T-Pee]

Makes sense, I think. But it's ok to reuse the trub at the bottom and drop another ferment on top ala UJSSM? My intent is to do just that with an apple wash after racking off the wine for distillation and making another.

tp

[MitchyBourbon]

But...but...what about the UJSSM process where generation after generation after generation is dropped right on top of the same yeast cake?

tp

The UJSSM process uses all the yeast, the good the bad and the ugly. Each generation there will be a certain percentage of the population that remains healthy enough, but that percentage gets smaller each time. Sooner or later there won't be enough healthy yeast to get the job done.

But it's ok to reuse the trub at the bottom and drop another ferment on top ala UJSSM?

tp

Yes it will work just fine. Until, well until it can't.

[T-Pee]

My 7th generation UJSSM just finished its ferment. It's been known to go 20 generations and beyond.
Where do you start fresh? The one after things get wonky somehow?

tp

[MitchyBourbon]

My 7th generation UJSSM just finished its ferment. It's been known to go 20 generations and beyond.
Where do you start fresh? The one after things get wonky somehow?

tp

I don't really know, I have only tried UJSSM once. I took it to gen 4. But I didn't stop cuz the yeast was weak, I just decided to go back to my bourbon.

[MitchyBourbon]

I think I have posted this a few times but it's worth saying again since Kelbor has hit upon this on his own, I think.

The best method of re-using yeast is to re-use it before you use it. Sorry if that sounds like double talk. Na, I'm not sorry. What I mean is that by making a starter that is bigger than you need, you can set some aside for the next batch. When that time comes along you pull out your starter, grow it some and repeat the process.

So why is this a superior method? Done right a starter will not produce much alcohol. Done right it will produce mostly new healthy yeast that have not been stressed out by high gravity wort or high levels of alcohol. In order to achieve this you must provide the proper environment. I use a stir plate, this provides a constant source of oxygen. I make a very low density wort that i feed to the yeast as needed. In a plastic 2 liter bottle fill with water, add 5.2 ph buffer, add 7 table spoons DME. This produces an SG of 1.015. The oxygen and low density wort prevents the yeast from making much alcohol.

[Kelbor]

Thanks Mitchy - that is a bit lower of a SG then I've read. It seems the rule I see repeated a few time is 1/2 cup DME to 2 cups water. Boil for ten minutes and then cool in an ice bath. Shake the shake out of it and then pitch your yeast. The yeast I've been using still seems pretty happy, smells good, and gets the job done but I plan on trying new yeast here soon and will definitely store many small bottles from day one for later use rather then building up each time and saving a percentage of the bulk starter bomb. (note to self - order those plastic test tubes..)