Culturing Proper Job Yeast.

[Little Rock Brewing]

I knew I'd be back for advice!
So I made 1 litre of wort from DME, boiled for 15 mins, added a bit of yeast nutrient, cooled and tipped into a 2 litre plastic bottle.
I tipped the dregs from my one and only bottle of PJ in and shook it up.

My question is - how often should I be shaking it, or if at all?
To my mind all I've done is made a 1 litre brew (minus hops) instead of 23 litres.
I don't keep shaking or stirring my FVs, so why do I read that I have to keep agitating this?

Obviously I don't have a stirrer plate.
I'd have thought all this agitation would just cause oxidation?

 

[Agentgonzo]

My question is - how often should I be shaking it, or if at all?

Every time you go past it. Try to do it at least once an hour, but you don't need to be mega-diligent about it (ie, don't feel you need to set alarms through the night or sleep next to it).

I don't keep shaking or stirring my FVs, so why do I read that I have to keep agitating this?

In the presence of oxygen and glucose, yeast will grow and multiply. You need this at the start of your brew to make lots of healthy yeast. Once the oxygen has been depleted, the yeast will stop multiplying and just ferment out your wort. You want this in your normal brew because you don't want too much yeast (also fermentation gives you the expressive yeast flavours whereas (I think) the growth phase doesn't, or at least not as much.

But this isn't a normal brew. You're not trying to make a beer, you're trying to grow yeast. So as the yeast uses up the oxygen in your starter, you want to continue to shake it to add oxygen back in so that the yeast can continue growing.

I'd have thought all this agitation would just cause oxidation?

Oxidation problems occur after fermentation has finished. Someone more educated than me will probably give the explanation, but I think that oxidation problems are because the sugars have been used up and the yeast will (in the presence of oxygen and absence of glucose) convert ethanol into ethanoic acid (vinegar) and other reactions. However, in the presence of both glucose and oxygen, yeast will convert it to CO2 and the yeast will grow.

 

[Little Rock Brewing]

Thanks AG for a great reply!
Glad I brought it to work with me, for constant care.

 

[An Ankoù]

I knew I'd be back for advice!
So I made 1 litre of wort from DME, boiled for 15 mins, added a bit of yeast nutrient, cooled and tipped into a 2 litre plastic bottle.
I tipped the dregs from my one and only bottle of PJ in and shook it up.

My question is - how often should I be shaking it, or if at all?
To my mind all I've done is made a 1 litre brew (minus hops) instead of 23 litres.
I don't keep shaking or stirring my FVs, so why do I read that I have to keep agitating this?

Obviously I don't have a stirrer plate.
I'd have thought all this agitation would just cause oxidation?

While I agree with most of what agentgonzo says, above, I think it's the physical action of swirling that accelerates the multiplication of the yeast. A stir plate doesn't oxygenated the wort, after all.
I think, perhaps, that swirling encourages budding and separation of the new yeast cells from the parent. A good swirl, then, not a violent shaking is what's called for.
When the foam starts to form, let the gas out and crush the PET bottle so there's room for new CO2. Don't Introduce new air as this may also introduce infection.

 

[Little Rock Brewing]

Great stuff An Ankou.
That all makes perfect sense.
Cheers!

 

[Cheshire Cat]

Swinging is always good to make things reproduce just like in the swinging 60’s.

 

[RoomWithABrew]

Its the wort that you want with oxygen in to encourage yeast multiplication.
Shaking or a stir plate moves the surface and so gets more wort exposed to the air. Much like force carbonating a keg you shake it and the co2 gets in quicker than just letting it sit quietly with high pressure above it.
Oxidation will occur of the beer formed, you are going to cool the starter once finished to drop the yeast and the.n pour off the oxidised beer to leave just a little to make a pourable slurry to pitch.
I would have started with a few hundred ml of wort at about 1.030 that the yeast can start in and reduce the chance of infection getting in when the cell count is low.
Then cool and pour off the little amount of used wort and then add one to 1.5 litre of 1.040 to make your pitchable starter.

 

[Little Rock Brewing]

Thanks for that RWAB.
I was wondering if i'd need to "feed" it with more wort. Sounds like sourdough!

Got some activity today and the bottle is pressurised.

 

[UKSkydiver]

Got some activity today and the bottle is pressurised.

Pretty sure you'll need to release that, so unscrew the cap a quarter turn so that the CO2 can escape.

And whilst I'm here, some articles on the Shaken Not Stirred method for your delectation , which for no other reason than logic, if not science based proof, make sense to me.

https://hornbrewing.com/blog/2019/03/21/shaken-not-stirred-starter-illustrated-steps/
https://www.experimentalbrew.com/blogs/saccharomyces/shaken-not-stirred-stir-plate-myth-buster
And a very long thread here:
https://www.homebrewersassociation.org/forum/index.php?topic=24447.0

 

[Little Rock Brewing]

Cheers, loads to read and I'm supposed to be working!!

 

[Agentgonzo]

Pretty sure you'll need to release that, so unscrew the cap a quarter turn so that the CO2 can escape.

You definitely want to unscrew the cap (leave it on as loosely as you can). You want to allow oxygen to enter into the bottle to help the yeast grow and you want to let the CO2 out as it inhibits yeast growth.

 

[Little Rock Brewing]

Will do, it's right by my side!

 

[An Ankoù]

Cheers, loads to read and I'm supposed to be working!!

Me too, but I'll read it all later on.
Bottom line, my culture is made in 600ml wort at OG 1040 in a 1 litre conical flask. A doubled over piece of aluminium foil is secured over the mouth with an elastic band. The flask gets a swirl every time I walk past. It's normally ready to pitch on the third day. I don't "build" the culture to a bigger volume in a bigger flask, rather i pitch first time onto a 10 to 12 litre batch thus: building the yeast into enough for several full-size brews, saving on build time by producing something drinkable, testing the yeast to see if it tastes ok or is infected or is most likely a bottling yeast.
I've never added new wort to the culture, obviously there's sufficient oxygen in the headspace air for encourage the growth of healthy yeast. If there wasn't, it wouldn't work. I should add that lag time is short and the yeast can usually be seen to be colonising the surface of the beer within hours. BUT, it's important to let the yeast grow fully into the culture medium and I tend to pitch as the head and growth are dying down.

EDIT:
I read the articles. lost the will to live on the third one. Bottom line, there's no need to invest in a stir plate. Line under the bottom line, nearly all this stuff is about building bigger pitches from smack packs. I think recovering yeast from a bottle can be a much more delicate matter. Trying to recover yeast from a filtered beer (I successfully cultured Adnams dual-strain from a party keg of Ghost Ship) is even more haphazard (second attempt failed- it was closer to its SBD). My advice is don't obsess about getting lots of air into the bottle- it's an unecessary risk of introducing infection.

 

[RoomWithABrew]

You could squeeze the bottle to expel the CO2 and then when it releases it will pull more air in.
I just put a sterile tinfoil cap on my erlenmayer flask to allow gas exchange.

Yes I would build the starter a bit more once you see it not bubbling cool it a bit and then spray neck of bottle with star san, pour off the " oxidised " beer. Taste if you want an experience.
Then add more wort with nutrient at the the correct temp. You want to try and get more volume in there as yeast cells need space to keep growing in numbers, hence the fresh wort and a step up of volume.
Also plan to have a sterile container that you can save some in come brew days so you have something to build from next time.
Also plan to top harvest the yeast and save some of that in a different sterile vessel.

 

[Little Rock Brewing]

Thanks for the advice RWAB.
It does seem to be slowing up a bit now, so will probably give it a wort change tonight. Hopefully it'll be ready by Sunday.
If not, i'll wait.
I do a lot of top cropping of yeast so will definitely get some of this for future use.

 

[Northern_Brewer]

You definitely want to unscrew the cap (leave it on as loosely as you can). You want to allow oxygen to enter into the bottle to help the yeast grow and you want to let the CO2 out as it inhibits yeast growth.

I wouldn't do this - in the real world the effects are marginal, and your real worry is infection. As long as you don't leave the bottle so long it explodes, it can be sealed tight. When I'm growing up yeast I do it in knock-off Schott bottles and keep the lids tight, I'll vent them every time I shake them between days 2-4 or whenever it's actively bubbling, otherwise once a day is fine.

It is good practice to step up volumes rather than giving them 1 litre straight away and give them something gentle to start with - I'll make up 6g DME in 120ml (ie 5% DME, around 1.020) , tip the dregs into about 10-20 ml of that and then add the remainder 2-3 days later, then in another 2-3 days step up to 500ml of 10% DME (~1.040).

Rather than boil it I pressure-cook it for 20 minutes in my Instant Pot clone - make sure you don't seal bottle tops on tight when you pressure cook!!! - having added a hop cone/pellet or two just to discourage nasties.

You're not worried about flavour or oxidation at this stage, just maximising the amount of happy yeast with the minimum of contaminants.

 

[Agentgonzo]

I wouldn't do this - in the real world the effects are marginal, and your real worry is infection

Interesting. Advice for culturing yeast in conical flasks is just to cover in tin foil. That won't be air tight - so what's different between a loose bottle cap that is bad and loose tin foil that is recommended? (It's been over a decade since I cultured yeast)

 

[Northern_Brewer]

Interesting. Advice for culturing yeast in conical flasks is just to cover in tin foil. That won't be air tight - so what's different between a loose bottle cap that is bad and loose tin foil that is recommended? (It's been over a decade since I cultured yeast)

Anything that's loose is a risk for nasties getting in. Personally I wouldn't recommend just loose tin foil - when I was culturing yeast "professionally" flasks were autoclaved with a foam bung in place, and then "capped" with some foil just to keep the water out during autoclaving. And then they were left overnight on an enclosed shaker which kept any passing bugs out. But we were inoculating reasonable amounts of happy yeast (not a few dregs that have been sat on Tesco's shelves for 6 months in beer) and only overnight. We might occasionally just use foil if we were out of bungs, but it was never first choice.

 

[Twogunrocky]

I wouldn't do this - in the real world the effects are marginal, and your real worry is infection. As long as you don't leave the bottle so long it explodes, it can be sealed tight. When I'm growing up yeast I do it in knock-off Schott bottles and keep the lids tight, I'll vent them every time I shake them between days 2-4 or whenever it's actively bubbling, otherwise once a day is fine.

It is good practice to step up volumes rather than giving them 1 litre straight away and give them something gentle to start with - I'll make up 6g DME in 120ml (ie 5% DME, around 1.020) , tip the dregs into about 10-20 ml of that and then add the remainder 2-3 days later, then in another 2-3 days step up to 500ml of 10% DME (~1.040).

Rather than boil it I pressure-cook it for 20 minutes in my Instant Pot clone - make sure you don't seal bottle tops on tight when you pressure cook!!! - having added a hop cone/pellet or two just to discourage nasties.

You're not worried about flavour or oxidation at this stage, just maximising the amount of happy yeast with the minimum of contaminants.

So would you say that an Erlenmeyer flask with a bung & airlock would be acceptable for building starters up?
Only ask as I just ordered a bung & airlock for my flask a couple of days ago, but recent reading was leading me to believe oxygen needed to enter the flask, thus negating it.

I didn't think a continuous supply of oxygen was essential for yeast growth, I mean once the fv is full of CO2 there isn't any getting in right, So why would a starter be any different?

 

[Agentgonzo]

, I mean once the fv is full of CO2 there isn't any getting in right, So why would a starter be any different?

Once oxygen is depleted, yeast move from the growth phase into the fermentation phase and stop multiplying. But if you're trying to actively grow yeast, you want them to have as much oxygen as they can get