Yeast starter - Airlock or foil?

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Onlooker said:
According to this article: http://www.maltosefalcons.com/tech/yeast-propagation-and-maintenance-principles-and-practices
using an airlock does indeed hinder yeast growth in a starter (cited from Ray Daniels in Figure 1). Take that for whatever you feel it's worth, but it does jibe with the theory commonly held theory.

If your crimping the foil down tightly then you're not going to allow much gas exchange. And keeping it kind of loose to allow gas exchange but keep out dust-borne bacteria could definitely allow a fruit fly infestation.

So how about an empty 3 piece airlock? That would seem to satisfy all the desired criteria. Of course you then have to have a stopper for the flask, if that's what you're using.
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I agree there must be a better solution. Current thinking is that you get the most yeast growth with a stir plate and "loosely capped" vessel, which would then allow fruit flies. Some type of filtered air could keep out both dust-borne baddies and flies. Perhaps constant aeration from an aquarium pump with no stone would act to both oxygenate AND stir the wort, without excessive foaming.
 
I use my Mr Beer with the non-airtight lid. I don't have a stir plate so I just give it a shake every time I walk by. Shaking release a lot of CO2 from solution and as it settles back the reverse flow pulls in O2. Basically, it breathes. In theory.
 
zacster said:
I use my Mr Beer with the non-airtight lid. I don't have a stir plate so I just give it a shake every time I walk by. Shaking release a lot of CO2 from solution and as it settles back the reverse flow pulls in O2. Basically, it breathes. In theory.
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Interesting uhhhhh... hypothesis. You can easily test it by installing an airlock to see if any air gets pulled in. I'm guessing you won't like the results.

But shaking alone does seem to work, or so the experts say.
 
There is no place for an airlock on a Mr Beer. I have heard it sucking in air after a good shake when it starts to settle. How much I can't say. In any case I have ended up with perfectly fine starters.
 
zacster said:
There is no place for an airlock on a Mr Beer. I have heard it sucking in air after a good shake when it starts to settle. How much I can't say. In any case I have ended up with perfectly fine starters.
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No doubt your starters are fine, but it's not due to air coming in after a shake. I just now shook up an active starter, with only a tiny bit of water in the airlock, and watched the bubbles settle. No air was coming back in, just co2 exiting, the entire time.

There are really two issues here that these popular articles fail to distinguish-- shaking versus oxygenation. Both seem to be useful (?), but shaking / stirring does not equate to oxygenation! To get oxygenation, it seems we really need to actively introduce air unless we use a loose fitting cover.
 
Shaking does oxygenate (i.e. introduce air into liquid). Not necessarily as effective as other methods, but it is a simple and adequate method. As for this tinfoil business, i'm skeptical. Seems like a sanitation no-no. Have you had success with airlocks? bc that's where i'm leaning.
 
papaoso said:
Shaking does oxygenate (i.e. introduce air into liquid). Not necessarily as effective as other methods, but it is a simple and adequate method. ...
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Shaking only oxygenates to the extent that there's oxygen in the air above it. Once yeast get going, the head space is just CO2 unless it's open enough to exchange air. So if it's only CO2, then you're not oxygenating.
 
papaoso said:
Shaking does oxygenate (i.e. introduce air into liquid). Not necessarily as effective as other methods, but it is a simple and adequate method. As for this tinfoil business, i'm skeptical. Seems like a sanitation no-no. Have you had success with airlocks? bc that's where i'm leaning.
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I've only used bubble locks and I've never had a failed starter.
 
EDIT: I made a separate thread for this experiment so that I don't derail this thread. Please see my experiment thread and give feed back!

Ok, Check this experiment that I'm going to conduct on my next batch of beer in 2 weeks.

Controls
I'm going to make two (2) one liter starters.
Both are going to be made from the same amount of yeast (i.e., I'll get two vials or two packets of the yeast that I am going to use and pitch in the 1 liter starter).
I will hand shake/swirl each starter evenly and exactly (i.e., if I swirl one jar five times, then I will also swirl the other jar 5 times, no more no less).
I will let the yeast starter work for 72 hours.

Variables
One starter will have a 3 piece bubble lock.
One starter will not have a bubble lock but will only be covered in tinfoil.

After 72 hours I will check the levels of yeast in the starter. These levels will then indicate which method produces more yeast.



Ok, so how does that sound? I don't have a two stir plates so they cannot be a part of this experiment. Are there any suggestions as to how to make this experiment better?

Also, is there a good way to measure levels of yeast? How should I go about doing that?
 
I have saved a lot of the little plastic cups that dip, etc. come in at restruants in our area and I simply sanitize one of them and set it inverted on top of the beaker. It acts as a shield, but doesn't seal it. I've always had good results with mine. I put some yeast from my fermenter this afternoon and am working on another 10 gallons of beer later this weekend with the same yeast.
 
I prefer foil, for purely practical reasons. I usually use iodophor for sanitation, but when it comes to starters, I feel safer putting the growlers / bottles I'm using in the oven just to be sure. In case there's some gunk I've missed that something could be hiding under, and to avoid any sort of rinsing or drying that might let dust particles to enter.

And of course, using foil you can seal the cap before placing them there. Having said that, I do use airlocks for time to time. Mostly to be able to monitor the progress of yeast of questionable quality, for instance when using something collected from commercial bottles or an outdated pack..
 
I use foil, but from now on during the fruit fly season ill fix a airlock on my starter because somehow they got by the foil.
 
SpeedYellow said:
I agree there must be a better solution. Current thinking is that you get the most yeast growth with a stir plate and "loosely capped" vessel, which would then allow fruit flies. Some type of filtered air could keep out both dust-borne baddies and flies. Perhaps constant aeration from an aquarium pump with no stone would act to both oxygenate AND stir the wort, without excessive foaming.
Click to expand...

My method, 24/7

100_5203.jpg


After 1 week (WYeast 2206)


Cheers,
ClaudiusB
 
Saccharomyces said:
I've seen a coffee filter used as well. Bacteria don't have legs, they need to arrive on dust particles, so as long as you use something to keep dust out you are going to be fine.
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Genius.
 
I have used foil and the foam stoppers and both work well. The foil is really all you need. If you're worried about fruit flies, put some apple cider vinegar in a bowl, cover with plastic wrap and poke a bunch of holes in it. No fruit fly will choose wort over vinegar. They go into the holes and get trapped.
 
Revvy said:
In fact I've NEVER seen anyone state this.

What WE DO SAY is the the tinfoil doesn't allow the ALREADY EXISTING OXYGEN which we put into the starter wort, to escape out the airlock, before it gets consumed by the yeast, as we want it to do. Not that more oxygen gets in. That what is in there doesn't get out.
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Not that I like to dispute Revvy but if the foil is tight enough to prevent Oxygen in the headspace from escaping, it is also going to prevent generated CO2 from escaping, causing pressure to build up until the foil is pushed off the top.

Wynne-R said:
...I have struggled to reconcile the notion of a CO2 blanket with what I know about partial pressure of mixed gases.
Click to expand...

I think with a continuously stirred (on a stir-plate) starter that turbulence at the air/liquid boundary is effectively continuously stirring the air as well. At least at the beginning before the thicker krusean forms. Which leads me to think that the air exchange with either a foam plug or a loose foil cap will increase oxygen getting to the starter.

Note: no science was performed in the formation of this opinion, just seems to make sense. :p
 
MisterGreen said:
I have used foil and the foam stoppers and both work well. The foil is really all you need. If you're worried about fruit flies, put some apple cider vinegar in a bowl, cover with plastic wrap and poke a bunch of holes in it. No fruit fly will choose wort over vinegar. They go into the holes and get trapped.
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Sweet tip
 
sanitized coffee filter rubber banded around the top of the flask/growler

allows air in/out but keeps bugs and flies out
 
Stauffbier said:
I've always used foil, and I've never had a fruit fly doing the back stroke in my starter. I see fruit flies in my house every now and then, but no issues yet.
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The above was my original response.

As of yesterday I'm now using one of them fancy shmancy foam stoppers!
 
I use a foam stopper but this thread is making me think, if the whole idea is to let air in for yeast growth...... I thought the co2 pushes out..... How is air getting in ?
 
Aschecte said:
I use a foam stopper but this thread is making me think, if the whole idea is to let air in for yeast growth...... I thought the co2 pushes out..... How is air getting in ?
Click to expand...

During active fermentation im sure no air gets in, but if there was no cover something could fall in which in turn could lead to unwanted contamination
 
Aschecte said:
I use a foam stopper but this thread is making me think, if the whole idea is to let air in for yeast growth...... I thought the co2 pushes out..... How is air getting in ?
Click to expand...

that's the point of shaking or using a stir plate, plus as pointed out earlier, the co2/air don't quite settle into perfectly separate layers
 
terrapinj said:
that's the point of shaking or using a stir plate, plus as pointed out earlier, the co2/air don't quite settle into perfectly separate layers
Click to expand...

This reenforces my point , a stir plate's only function is to keep yeast in suspension not for aeration. Shaking does introduce oxygen initially but not after fermentation has started. As far as layers co2 is denser than oxygen so it would push oxygen out. I understand about initial oxygenation of the starter the same as 5 gallons of Wort. My point still is why can't you after 4 hours or so and airlock it as no more oxygen is entering. Not arguing I just am having a hard time proving foil or other is really needed fwiw if this was true we would be putting foil and foam stoppers on our carboys and buckets for a batch.
 
Aschecte said:
This reenforces my point , a stir plate's only function is to keep yeast in suspension not for aeration. Shaking does introduce oxygen initially but not after fermentation has started. As far as layers co2 is denser than oxygen so it would push oxygen out. I understand about initial oxygenation of the starter the same as 5 gallons of Wort. My point still is why can't you after 4 hours or so and airlock it as no more oxygen is entering. Not arguing I just am having a hard time proving foil or other is really needed fwiw if this was true we would be putting foil and foam stoppers on our carboys and buckets for a batch.
Click to expand...

i don't think it's simply about keeping yeast in suspension, i don't think they need that much encouragement and you wouldn't get the massive increase in cell count from a stir plate just by keeping them agitated. my understanding is that the yeast continue to multiply as long as there is oxygen available and more cells are created on a stir plate because there is more oxygen available throughout the process.

from mr malty http://www.mrmalty.com/pitching.php
f you have O2 handy, you should add O2 to your starter or at the very least shake it every few hours to increase the amount of O2 available to the yeast. If you have a stir plate, that works even better at providing good gas exchange and yeast growth will increase (around 2 times as much yeast as a non-stirred starter).
Click to expand...
 
There's a lot more co2 produced in a 5 gallon batch than there is in a starter. My guess is that the vortex on a stir plate does indeed pull in some oxygen if foam or foil is being used. The small amount of co2 in a starter likely gets mixed up with the oxygen. Both probably get sucked down in to the vortex and get pushed out of the top of a foam stopper or foil. This is just my theory....

I have a friend who actually inserts a small oxygen wand in to his starters and hits it with intermittent burst. I aerate my starter wort by shaking it like mad before I cover it.
 
Stauffbier said:
I aerate my starter wort by shaking it like mad before I cover it.
Click to expand...

:rockin: Yep, that's what I do too. I also kinda like the interaction I get with my starter as a result of periodic shaking visits. In fact, I almost bought a stir plate but decided an O2 aeration setup was a better spend for me right now. (Since I don't mind the shakin..) I really got it for use before pitchin but maybe I'll give my starters a quick blast as well...
 
One of the large tasks for the stir plate is to degass the starter. This releases the co2 suspended in the starter and slows the yeast to continue to work. I expect keeping the yeast in suspension would improve their efficiency.

My opinion/understanding anyway.
 
I will occasionally "pour" the CO2 from the flask, since it is heavier than air, I tip the flask enough that any CO2 will come out and be replaced by room air. Then back on the stir plate. I don't know how much air exchange I get using the small plastic containers inverted on the top of the flask. I mainly want it to prevent undesireables from falling into the starter.
 
I've never made a yeast starter for beer, but my next batch I will. I plan to use cheese cloth soaked in iodine solution held on to the flask with a rubber band.

When I made grape wine in the past, I covered my primary fermenter (a rubbermaid trash can) with steel screen material (for support) and cheese cloth tied on with string. Keeps the fruit flies and foreign microbes out well enough.

I do believe that oxygen is delivered to the wort in small amounts, even though CO2 is being made, and it makes sense to me not to put an airlock on the flask. By this logic I would also guess that it may be more efficient to use not a flask, but a container with a larger mouth to maximize surface area and gas exchange. Just a thought.
 
I can't believe someone has brought this up....but why not just use the airlock without water in it???? This will solve all issues, correct? It is much more effective at keeping dust out, O2 can still get in, much easier...etc...etc...

This is what I do and I've never had a problem.
 
I make my starter in a growler. the first time I used foil and it worked great. The second time I got the great idea to use a stopper and an air lock. The stopper slid down into the growler and I lost it when I tried to pull it out by the air lock. I will stick with foil from now on.
 
Maybe a noob question, but why is it ok to let a starter have contact with air, but in fermenter an airlock is used? Seems like contamination risks are the same ?
 

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