Is MY Starter Junk?

[Harleybrews]

I am pretty sure I already know the answer but I will ask for you opinions anyway. I have been building up a starter for a Maibock brew this weekend. I came home today to find my 1500 ml starter (on a stir plate) had foamed out the stopper thru 1 foot of blow off tubing and clogged up my hepa filter. The rubber stopper had popped out of the flask leaving the opening in the erlenmeyer flask about 1/4 of the way open and the yeast exposed to the ambient air. I am hoping someone will validate me hope that the fermenting wort had enough co2 blowing out that i may have avoiding possible contamination.
1; Is this yeast usable for brewing?
2; is my hepa filter useless now that it has been clogged.?

[Speyedr]

Relax, and have a home brew!

As long as it was still fermenting you're OK. The fermentation will generate enough CO2 to keep out the nasties. Just clean everything up with sanitizer, or better yet, alcohol, and close it back up again.

Keep in mind that krausen is a really good source of yeast, so if you lost a lot of the krausen, some of the yeast went with it. You may or may not want to add a little more wort to the starter. If you were going to step it up again the just do that.

Finally, you gotta ask WHY the starter went into fermentation. The main reason you use a stirplate is to provide O2 for growth. If you have a blow off tube installed and no source of O2, then your yeast grew as much as they could and then once all the O2 was gone, went into fermentation mode. In the future I'd say ditch the blow off tube and just put foil or a foam stopper on the flask. Also, time your starters so that you are either stepping up every 18 - 24hrs, or you are chilling after 18-24hrs to drop the yeast out. If you leave it on the stirplate longer it will ferment. You really want to try to avoid having a starter ferment out if you can. Save it for your batch.

As for your filter, if it;'s one of those disc jobbies from B3 or the like, then you can try to clean it, but it's probably hosed.


Good luck, and you'll be OK.

[Harleybrews]

thanks for the repy spyder. I just wanted to address your comments about the blow off tube. the point of what i hoped to accomplish was to provide some measure of filtered air for the starter. I attached the filter to the tube which was inserted into the stopper hole. I figured, when the vortex pulled in O2 at least it would pass thru the filter, not intending that the starter would be active enough to clog the filter. I was thinking that simply covering the flask with foil would not stop air borne nasties from being sucked into the starter? Is my theory bogus?

[Speyedr]

It was a good idea but it sounds like not enough O2 got in, 'cause the yeast usually doesn't ferment unless deprived of O2. At least that's how I understand it. Fermentation is anaerobic, and not as efficient as aerobic respiration. Given the choice the yeast should chose aerobic, or growth.

I use a foam stopper on my flasks, but I have done the foil too with no problem. I wouldn't worry about it. The airborne nasties fall down, they don't fly up. As long as you don't have an insect problem where bugs will literally crawl into your beer, this just isn't an issue.

[bub]

your theory is bogus... the air really won't be sucked in, and once fermentation starts air will actually be pushed out... the air that is in the flask just kinda recirculates untill you add more liquid and create a pressure difference, otherwise it is kinda stagnant, but there is plenty of air in there for the yeast as long as the wort is circulating.
BUB

[Harleybrews]

Bub and Speyedr, I guess i am not understanding how a stir plate works. I was thinking that O2 was constantly pulled into the solution buy the vortex and thus providing a continual supply of o2. Are you both saying that the air in the head space is what is mixed around and feeding the yeast?
Bub just to follow up. If air is not pulled in how come people don't just put an air lock on the starter vessel? I thought the foil every one seems to cover with allowed for to be mixed in.
Guys I am not doubting your information just a bit confused on the stir plate subject.
thanks for your responses.

[bub]

I have seen airlocks on stirplates, BTW none of this is scientific, I may be full of shit... but what I understand is the foil or foam stopper allows diffusion, the foil prevents nasties because they are too heavy to fall then get "sucked" up the inch or so that it takes. Also many people start their starters while a bit warm and they tend to cool creating a vacuum, not good to have an airlock on a vacuum. There is a physics thing to explain the fact that the air intake (what little there is) under the foil is an extremely low pressure due to the sizing of the intake or something and this prevents sucking "heavy" things up in there. Feel free to do whatever you are comfortable with, but "extreme measures" really aren't necessary. If you were doing yeast slants for long term storage or selling a shitload of yeast I would do it differently but then you should have a clean room etc at that point.
sorry for the train of thought theatre, I'm a bit frazzled.
BUB

[Speyedr]

I'm no yeast expert. I'm just going off of all the stuff I've learned here. I can't say for sure if any air goes in and out. Logically though, I would think that the turbulence created by stirring up a vortex will cause some air exchange with the outside air, but I have no data to back that up.

Now if you add a small ID tube and a Heppa Filter, you're going to need more suction to pull air in and more pressure to push it out. In that case I don't think you will get any exchange.

However, that is not necessarily going to cause fermentation by itself. If you pitch enough wort for growth into that O2 rich environment then the yeast will grow and, then again the yeast should just start to ferment it out if you pitch too little.

My starters used to ferment out all the time. Once I started using the pitching calc on Mrmalty.com, and sticking to the 18-24hr growth window I've been able to keep it from fermenting, which uses up it's reserves, or so they say. So, pitch enough wort and you shouldn't have much fermentation.

As for the foaming, you can also use that Foam Control stuff from B3:
http://morebeer.com/product.html?product_id=15464. They also sell it under other names at other stores. I use it when I make starters to keep from boiling over. I also use it when I boil my batches for the same reason. If you put a drop or two into your starters it should help with blow-off as well. As a sidenote, I also don't add hops to my starters. They can create nucleation sites for foam.