Stepping up and pitching yeast starters

[Bum]

Why is it you think that the yeast doesn't need to grow in your fermenter?

[Planner]

See sticky

Had a read of DrS instructions on starting and splitting Wyeast packs, I've got my first pack happily sitting in the fridge door at present and have a question.
Does the pack need to be bought up to room temp to smack? and I'm guessing it should be kept at pitching temp while it swells.

[billybushcook]

Why is it you think that the yeast doesn't need to grow in your fermenter?

Because youvé just spent several days building up the numbers prior to pitching.
That & the fact that the starter youvé just prepared & got fermenting ready to attack more sugars, is going to have to revert back to it's multiplication phase again.........Why not make the buggers crack on with fermentation?

Edit: Sorry planner, I wasn't ignoring your post, I just havn't had allot of experience with smack packs, only two infact.
My thoughts are, that you are right, you can smack it at a low temp if you wish but it will probably not activate until it comes up to a suitable temp, after all, smacking it is just combining the yeast with some nutrient & sugars which starts a small fermentation like a starter.

Mick.

[rotten]

Gday planner.
My first smackpack was only a few days ago. I read instructions, forum suggestions, wy-yeast net info. In the end i decided to just let yeast do it's thing. I took it out of fridge while mashing, smacked 1/2 hour before i pitched into 15c wort, and waited 3 days for ferment to start, shaking fermentor after 2. I will if I have time make a small starter or at least let it swell next time, it needs to be 20c at least I think.
Might help, or might not. Moral is it still worked!!
Cheers

[speedie]

would anyone like too comment on how your lovingly yeast culture which has been isolated from atmosphere became oxidised?

[Bum]

Deliberately over-aerating steps for a starter is a practice commonly employed by some brewers. Apparently it does the brew no harm so long as no oxidised starter beer is pitched.

Or so I've been lead to believe. Not my practice.

[bullfrog]

I was thinking the same thing as Speedie, sans the pompous attitude however.

I suppose we're talking about starter vessels that are being rigorously shaken constantly, well after the point where the yeasties should be in an anaerobic state, or perhaps a similar effect happening on a stir-plate that is set to "cyclone" level. After all, every piece of instruction on creating starters that I've ever read say something along the lines of "shake the bejesus out of it until your arm is sore then do it some more. Repeat this every time you walk past the starter vessel."

Whenever I make a starter I pour off the starter beer but not for reasons of oxidisation in the starter, just because if I had wanted DME in the brew, then it would have been in the recipe to begin with.

EDIT: Bum beat me to it.

[warra48]

would anyone like too comment on how your lovingly yeast culture which has been isolated from atmosphere became oxidised?

Using a stir plate, or an airtube from a pump, can hardly be considered "isolated from atmosphere".
Many brewers use those techniques to encourage maximum yeast growth.
I always assumed yeast needs oxygen to grow, and the growing bit is the primary objective of a starter.
Am I missing something here?

[billybushcook]

Why is it you think that the yeast doesn't need to grow in your fermenter?

Because youvé just spent several days building up the numbers prior to pitching.
That & the fact that the starter youvé just prepared & got fermenting ready to attack more sugars, is going to have to revert back to it's multiplication phase again.........Why not make the buggers crack on with fermentation?

Mick.

Been think'n about this over night (yes it did hurt )
& looking at it from another angle.

It makes more sense to build up cell numbers on a stir plate by regularily replenishing the wort without letting it go into fermentation, earate the wort (beer) in the fermenter & pitch straight off the stir plate so the little guys are still actively multiplying & not getting thrust to & fro, from phase to phase & back again.

It's all just a question of the same process but controlling when to let the yeast switch from reproductive mode to fermentation.

My thoughts on adding an actively fermenting, ample numbered starter to an un-earated wort to get a quicker start up are exactly the same two phases but fermentation begins in the starter & in theory at least, should continue as soon as it hits the freshly prepared wort.

If this is true.
Then it should be easy to observe this in a flask by building up a starter, take it off the stir plate & letting it go into fermentation, then once fully active, gently add some more fresh wort which has not been earated. If I'm right it should keep fermenting.

By the same Token, If i added earated wort, it should stop fermenting & go back into reproductive mode.

I can feel an experiment coming on

Mick.

[drsmurto]

Using a stir plate does not prevent fermentation. The physical act of stirring ensures the yeast doesn't flocculate out too quickly, it's not too aerate the wort as you have only a limited supply of oxygen dissolved in the starter and in the atmosphere above the liquid. Unless you have a very violent stirring with a huge vortex you are causing enough splashing to aerate. You don't make a starter without some sort of lid/airlock so the supply of oxygen is finite.

As for Speedies comment about oxidation, i may be missing the point but the first stage in the fermentation cycle is adaptation/growth which requires oxygen. You cannot over aerate your wort as oxygen has a limited solubility of something in the order of 10-20 ppm. Whilst continuous stirring has the potential for oxidising the wort it is normally a small percentage of the total wort overall and if you choose to tip the 'beer' off and pitch only the yeast slurry then this is further reduced.

I can see how the concept of continual addition of oxygen would increase the cell count but i recall reading a paper where a graph was plotted that suggested the increase in cell count in a continuously aerated wort versus continuous stirring wasn't large, certainly not the same increase you see when going from not stirring to stirring. The problem you face also is how do you tell when the yeast switches from growth to fermentation?

I tend to reuse yeastcakes and top crop more these days than make starters other than the initial step from a smackpack.

As for the comment about the temperature of the pack when smacking - i take it out of the fridge and immediately smack it. Once the inner package is broken i shake it to mix the contents and leave it somewhere warm (20+C) and allow it to swell. A fresh pack can be ready to burst in less than 30 mins whereas others have taken 3 days. You dont have to wait for it to swell up if you are going to use it in a starter. If you plan on direct pitching it i would wait for it to swell and would only do this if the pack was fresh (<1 month from manufacture date).

Think of a starter as an insurance policy. You may not need it but the risks of not making one are higher. The few infections i have had due to yeast health are the times when i have not heeded my own advice and taken the lazy approach.

If you pitch a large, healthy, active amount of yeast into your freshly aerated wort then half the battle is won.

These are just my thoughts/experience, not to be taken as gospel.

[Bum]

You cannot over aerate your wort

Poor choice of words on my part. I just thought "deliberately oxidising" would cause an unnecessary tangent to occur and explaining the process of regularly agitating the starter would send me away from the point I wanted to make. Apologies to anyone I might have mislead.

[billybushcook]

oxygen has a limited solubility of something in the order of 10-20 ppm. .

I know that Water can hold higher levels of disolved Oxygen at lower temps,
Does this mean that the levels only vary by 10 ppm across a broad temp range Doc?

Mick.

[drsmurto]

oxygen has a limited solubility of something in the order of 10-20 ppm. .

I know that Water can hold higher levels of disolved Oxygen at lower temps,
Does this mean that the levels only vary by 10 ppm across a broad temp range Doc?

Mick.

No, as you cool down the temperature the solubility of any gas in a liquid increases. As you increase the temperature the gas will come out of solution unless your system is sealed like a keg.

The 10-20ppm is from memory, i know its very low compared to CO2 but don't quote me on the exact numbers.

[speedie]

Mr start dude is that, Boyle’s ,Charles or Daltons law that you are referring too!
P1=t1=v1

[speedie]

There is a distinct difference from oxidized too oxygenated
Picture you cut an apple in half leave it to atmosphere
The result would be that the exposed surface browns due to oxidation
When we put air or pure oxygen into wort this is referred to as oxygenation
Which is essential to yeast growth?
Chemical the wall (membrane) needs it for growth
Think of it this way
When the boil takes place it drives oxygen out of solution basically rendering it free of oxygen
We put it back and whalla
Pacman produced beer!

[Tipsy]

Mr start dude

Who's this Mr start dude of which you speak, speedie?

[earle]

Imaginary friend perhaps?

[bullfrog]

I don't think anybody is confused as to the differences between oxygenation and oxidisation, Speedie. The latter occurs when oxygen is dissolved back into solution after the yeast enter an anaerobic state, so will definitely happen if people are vigorously shaking their starter vessel after that point. I don't understand where you were trying to take your argument.

[squirt in the turns]

So I stepped up my recultered CPA yeast starter to 2L earlier in the week. It had pretty much fermented out yesterday, so I put it in the fridge last night and poured off the beer this evening. This is what I've got now:


It's a pretty thin layer over the bottom of a 2L conical flask. As stated before, I've only ever used dry yeast, so I have no idea if that's enough cells or not. It doesn't look like much. It's coming up to room temp now. Should I just pitch it (I've got my CSA clone in a no chill cube ready to go)? Or am I better off adding another 2L of wort?

(edited because I did the image link wrong)

[speedie]

Squirt you are on the right track with your culture but as a word of warning don’t decant off the residual fluid in your culture vessel until you are ready to use it
It is a better practice to leave the yeast covered with brew!
Also I would not have put it the fridge overnight just keep it near your ferment temperature

As a suggestion use a small ID diameter tube to siphon off the liquid when ready then pitch your slurry

And by the looks of your yeast paste there will be heaps for a 22 litre batch
Good luck with your brew
speedie