Breeding starters

[Matilda]

Hey y’all,
Just wondered what people do to recycle yeast?
I had to remove some wine from a dj as the froth had erupted
Anyway, made me think... if I only returned half of the litre I removed I’d have a viable starter left for next run?
How would I best keep that starter going? If I stop feeding it, it’ll go dormant and might be harder to get going again.
If I keep feeding it, it’ll reach its limit and stop...
I thought about maybe removing half of the starter, topping up with a bit of water, and then adding sugar?
Wondered what you lot do/recommend?
Thanks

 

[stz]

Yeast management has the right way and ... other ways!

Ideally you crop yeast at a point around high krausen/after 24 hours/at 50% of fermentation (experience tends to lead here) off of something which is certainly less than 6% and repitch as soon as possible. Before use assess viability and perform a cell count to determine a constant pitch rate. It should be chilled to compact, the balm ale almost completely poured off, kept chilled and used within a few days. Viability loss on storage can be decreased by keeping it under a layer of distilled water, but you don't really want to keep it longer than a week. With a good flocculant strain cell density can be as high as 3*10^9 per ml.

With top cropping and open vessels this is quite easy ... with a bottom cropping strain you'd dump loose material from the bottom and collect comparatively quite a lot or you'd transfer it straight over to fresh wort staggering your brews. Chilling helps to compact it down, but to store a bottom cropping strain in the required amounts is best with something like a yeast brink. You end up needing more slurry because it has a lower cell density. Standard bottom cropping is usually lager, the point to crop is much later, like a week in. Some kviek is bottom cropped, I've no experience of it except at home where I store and prop off starters each time, pioneers are on their own in a commercial brewery!

Sealed vessels and top cropping introduce other challenges. Tend to take yeast a little later in the fermentation when bottom cropping a top cropping strain, it is a bit of a compromise, some strains flocc out lovely, some need a gentle chill, others are awful and almost a waste of time to crop, again calling for a brink, cropping little and often. The later you leave it the more yeast is dead, but the more yeast has dropped. Tank time needs to be accommodated for. It becomes a game of how long can I leave this because it is eating into my dry hop time and do I have the time to slightly chill it to crash the yeast and extend the dry hopping time to accommodate for the lower temperature. It influences the decision on what strains are desirable to use. It can be enough to make you use fresh yeast all the time, but the additional cost, especially externally propagated wet can limit creative options when brewing.

Brewing is often about finding budget solutions though, so we'll do stuff like brew a weaker beer where the dry hop doesn't matter so much which we can crop to death alongside a stronger beer with the same yeast which is all about the dry hop, contact time, settlement and running off. The weaker brew allows us to keep the culture going while we've no intention of cropping the bigger beer and will proceed to dry hop much sooner. Even better if I can cost the yeast into a complimentary brew and then use the now 'free' yeast in another beer which now has a bigger budget for ingredients!

When reusing it over successive generations your aeration and/or oxygenation must be on point to sustain a constant heath and performance of the culture. After a while genetic drift (debatable, impact is strain dependent) can introduce undesirable characteristics and you should renew the culture. At any point, but also after a while you can pick up a few unwanted organisms which over successive generations reach a level where they introduce undesirable characteristics and again, call for renewal. In the meantime acid washing can extend the time on the second problem. House cultures can have an acceptable level of contamination as part of the charm because it never shows up under typical time frames.

In reality though you can do almost anything depending on your spirit of adventure and aversion to risk! What would I do in your shoes? I tend to build a starter for all the yeast I use at home. I reserve typically 2 vials of from the starter and use one to build the next. I'll typically reserve 2 vials of this one and I'll work through them in sequence. This way I've got a back up and I'm limiting genetic drift. They keep pretty well in the fridge, I've not had a failure to reanimate yet, but I tend to keep them no longer than 6 months. I also weigh if it is worth keeping a culture or if an older culture is worth using when presented with other options. I have access to quite a few yeasts via work and if I don't want to use any of the 3-4 strains on the go there then I'll prop some. I've also constant access to wort which helps.

 

[Hoddy]

Bang on to what @stz says.

My process is to start the collection of a 500ml collection bottle from my FS after fermentation is complete. Because i only have the ability to bottom crop i make sure i get a mixture of the most, mid and least flocc'ed yeast (top, middle and bottom from the cone) from collection to make sure i avoid as much genetic drift as possible. (if you only ever take from one stratification you are genetically selecting a certain cell which will mean you will lose the overall yeast character after time as you are selecting a specific cell type)

I then wash that yeast to remove as much trub as i can (using three 2L flasks with sterile water to remove the heavy particles) and then before storage i will acid wash the harvested yeast every other time with phosphoric acid.

I store my yeast in my bank (home fridge) stored in strong spring top jars and then usually just dump the whole jar into a 1.7L (1.036) starter a few days before needing it to be pitched. I don't go for the vitality starter option i prefer to see the yeast has multiplied and is fully stored up on nutrients ready for the adaption phase (lag) after pitching.

I usually have 5 or 6 yeasts in my bank at any one time. American ale, Kevik, London Ale III, Vermont (yeast bay wet strain), French Saison, Californian Common and the Lallemand New England Dried Yeast Strain are in the bank ATM.

As said before its all about finding the methods, costs and processes that suit you and your skill/budget.

I dont do the split vial thing like @stz does but that is a great idea and i might consider that one in future.

 

[Matilda]

Thanks all, this is a bit more technical than I was hoping/expecting.

I was simply hoping to transfer a pint of the last brew into a DJ, add some water, nutrient and sugar and wait for bubbles...

Is that unrealistic?

 

[Hoddy]

Thanks all, this is a bit more technical than I was hoping/expecting.

I was simply hoping to transfer a pint of the last brew into a DJ, add some water, nutrient and sugar and wait for bubbles...

Is that unrealistic?

Hate to burst your bubble. But yes, totally unrealistic.

 

[Matilda]

Hate to burst your bubble. But yes, totally unrealistic.

How so? I’ve made wine this way before? Using a pint of active wine and must and slowly adding wine ingredients to build up a stronger colony seems like it’d work fine... I know it works...
I was wondering if anyone had found new ways to get a good starter that I hadn’t thought of.
Thanks

 

[Hoddy]

How so? I’ve made wine this way before? Using a pint of active wine and must and slowly adding wine ingredients to build up a stronger colony seems like it’d work fine... I know it works...
I was wondering if anyone had found new ways to get a good starter that I hadn’t thought of.
Thanks

Why not try it and report back how it goes?

 

[stz]

Yeah like I said in my long winded waffle ... there is the right way and ... other ways. Other ways if they work work just fine too.

From a technical perspective yeast propagation is different to fermentation. When you are trying to create more yeast you need more cells as healthy as. If you keep feeding a jar of yeast you eventually create a saturated colony with a not insignificant amount of alcohol and a mixture of different generations, dead, dying and so on. Most of it is no good to you. You've also got really wonky control over the amount of oxygen in the medium which heavily influences the yeasts ability to reproduce and be strong enough to handle whatever fermentation is to follow.

Ideally you take yeast in the growth phase and transfer it (discarding the spent medium and dead yeast) to a greater quantity of fresh medium and you repeat this step again and again. That way the yeast is always in the growth phase, under optimum conditions, the medium never becomes overtly hostile and you are constantly increasing the quantity of healthy cells. Once you've got enough healthy cells sky is the limit on what you do with them.

Again, back to your opening post. There is nothing wrong with at the high point of fermentation taking a litre or two of actively fermenting wine and using it to start the next batch. Obviously you'll be soon making an awful lot of wine. But this is what professionals do. But if you wait until the end or if you want to store that litre or two for a later date? It is probably best to chill it, discard the liquid portion once it settles out and then use that slurry later on to create a fresh starter following the principles of creating a starter. The stored yeast is of an unknown viability and condition, you can't really 'keep it going' by 'feeding' it.

An active fermentation isn't a colony of yeast at 100% viability and 'health' working away that can be kept alive by feeding it with more food. It is basically a colony that due to oxygen, free fatty acids and a few other essential nutrients undergoes a population boom on pitch. This population pretty much undergoes genocide once those things run out and it becomes a game of 'I hope my fermentation completes before all the yeast is dead'. The yeast you pitch doesn't finish the fermentation, ideally it has a 2.2 daughters before dying as the oxygen runs out. The daughters grow up tough in a hostile part of town and get on to the business of having a few daughters of their own and doing the bulk of the work surviving in an anaerobic environment. They produce a lot of waste products (ethanol) as a result. By the time the food is exhausted and the latest generation turns to what sources of energy remain (cleaning up) grandmother and mother are dead or soon to die.

When you harvest for a fresh fermentation you don't need the dead generations. You don't want the straggling daughters who never got enough free fatty acids when starting out in life and are into some really weird stuff. You don't need the knackard dying mothers. You want to grow up sufficient cells from the initial generation during the ideal population boom when conditions are excellent.

Again, what works is what works. But I'd create a starter. Pitch most of it. Reserve some of it. Use what I've reserved to make a starter for the next time. That way you are always using yeast in the growth phase.

Also man this is wine right? Wine yeast is generally super cheap and generic. I used to buy a few hundred grams for a couple of quid. Unless you've access to some rare stuff I wouldn't sweat wine yeast long term storage.