Yeast starter - Airlock or foil?

[chuckstout]

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.

Sweet tip

 

[steelersrbrun]

Sweet tip

That's what she said.

 

[terrapinj]

sanitized coffee filter rubber banded around the top of the flask/growler

allows air in/out but keeps bugs and flies out

 

[redketchup]

I use a half gallon growler with airlock... The best

 

[Nagorg]

I use a half gallon growler with foil. So far so good and no fruit flies!

 

[Stauffbier]

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.

The above was my original response.

As of yesterday I'm now using one of them fancy shmancy foam stoppers!

 

[Aschecte]

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 ?

 

[chuckstout]

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 ?

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

 

[terrapinj]

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 ?

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

 

[Aschecte]

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

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.

 

[terrapinj]

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.

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).

 

[Stauffbier]

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.

 

[Nagorg]

I aerate my starter wort by shaking it like mad before I cover it.

: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...

 

[mavrick1903]

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.

 

[Tom-R2]

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.

 

[Pezzonovante11]

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.

 

[ANewrBrewr]

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.

 

[Onlooker]

I can't believe someone has brought this up....but why not just use the airlock without water in it????

Umm, actually, I did.

Me: "So how about an empty 3 piece airlock? That would seem to satisfy all the desired criteria."
https://www.homebrewtalk.com/f163/yeast-starter-airlock-foil-155763/index2.html#post4330362

I agree that it's puzzling why more haven't come to that conclusion. I use it when I make a big 1 gal starter in a jug.

 

[ODG34]

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.

 

[beerluvva]

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 ?

 

[ANewrBrewr]

Good looking out "Onlooker" I didn't see your post at first.

Here is a pic of what I use. My LHBS just got these new caps for gallon jars that screw on, but have a hole in the middle for an airlock. As mentioned before I simply don't add the water in the airlock and it works great for my starters!

 

[ANewrBrewr]

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 ?

Not an expert, but I would assume that a starter has such high volumes of active yeast that if anything makes it to the liquid it would not be strong enough to propagate amongst all the good guys Also while the yeast is actively working it is producing a great deal of CO2 that is forming a constant flow up and out. For the "germs" to get in it would be like trying run through a marathon backwards...too crowded chances are you wouldn't make it very far. Believe it or not some people actually still do open vessel brewing (aside from sours of course).

 

[Pezzonovante11]

To add my .02 to the above: not only is air infection risk, but oxidation as well.

As I understand it, you want oxygen in the beginning while the yeast are propagating. The yeast use it up during this stage. Later, when the yeast finish multiplying, it isn't necessary. Not only that, if there is excessive oxygen present, the product will oxidize and taste "stale." That's why kegged beer pushed out with an air pump tastes bad so quickly vs. CO2.

Back to fermentation for a minute. Has anyone done an experiment comparing airlock vs. open yeast starter? I have to wonder if there isn't plenty of oxygen in the headspace (depending on the amount of headspace present, of course) for the yeast. I mean, we have to be talking about microliters of oxygen that these yeast consume, right? Are we fooling ourselves leaving off the airlock? How much air really transfers? Maybe the stir plate is a matter of increased contact area and not so much increased oxygen in the vessel. I'll bet some really smart people here could attempt to calculate that out. Any volunteers?

Boy, I think I am a true homebrewer now. I really like to mentally masturbate over this stuff :cross:

 

[Caveman3141]

I've made many starters in an old gallon milk jug and just setting the lid loosely over the top. I've never had a problem doing this. Remember, you're just making beer. It can be as complicated as you want but it can also be as simple as you want.

 

[mattd017]

If I had to guess the idea behind a stir plate I'd venture this:
Gas has a lot of liquidity to it. My thought is that as the wort vortexes, that movement transfers to the air above it (CO2), and causes the air to vortex. As it vortexes, it will push the vortexing CO2 up the walls of the flask and out, and will suck more air (from the lightly capped top) down the middle of the flask's opening. The new air, laden with O2, will be sucked down into the vortex, causing air exchange across the surface. Thus, increasing the dissolved O2.
My basis: Take vinegar and oil and pour it into a flask. Let it sit on the stir plate and watch as the two different and completely phobic liquids get drawn down into the vortex and mixed.

This is just from my basic understanding of chemistry/physics. I have no idea if it's true.

 

[Onlooker]

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 ?

It's not about contamination. With a starter you also want to protect against contamination by having some kind of cover that won't allow dust particles, etc. to get in. That's how bacteria or wild yeast can be transported. Another threat is fruit flies as they carry the very potent acetobacter bacteria that will ruin your starter. That's where the empty air lock can be quite helpful; or the foam stopper as well.

But for a starter you want gas exchange to take place so that oxygen can be made available for the yeast which enables more and healthier yeast growth. We don't want that with our fermenting beer as that can cause oxidation and the resultant off flavors. Whereas we don't care what the starter "beer" tastes like.

 

[Joebrew892]

Sorry I know this thread is ~7 years old, but I'm just getting into brewing and I'm confused by the airlock conundrum. Why can't I use an airlock, but not put any liquid in it, so it in essence becomes a two way valve? Wouldn't this be the same as using foil?

 

[ScrewyBrewer]

Definitely foil. The idea is that nasties, that can contaminate your starter, can't climb. With that said simply covering the top of the flask with sanitized aluminum foil is enough to allow oxygen to enter the spinning wort, without fear of contamination. Plus it's a whole lot easier to do.

 

[lzotarelli]

Here some interesting article... http://braukaiser.com/blog/blog/2013/03/19/access-to-air-and-its-effect-on-yeast-growth-in-starters/