yeast culture technique critique

So I tried to do a yeast wash a couple days ago and the mason jars I put them in were the small half pint ones. I figured one of these will not be enough to start a fermentation so I plan on doing a starter culture a couple days before the next brew day.

I like the idea of building a stir plate for the culture but I was thinking, if the whole point is to aerate the culture and provide some turbulence in the water could I rig up something with my aquarium pump that bubbles into the culture (filtered air of course). Is there any issues with this?

I was just about to post a similar question. One issue I can think of is that you are pumping unfiltered, unsanitized air into your sensitive culture. I'm a little afraid of contamination. I also wondered about setting a timer for on 5 minutes, off 5 minutes, or something to that effect. This might control the bubbling over that might (hopefully) occur!

I'm planning on trying this unless I hear otherwise, so I'll let you know!

I believe that the purpose is aeration, but also keeping the yeast in contact with the nutrients and in the reproduction phase. I personally wouldn't bubble anything but pure oxygen through a starter for the exact reasons mentioned.

And blue, you should always make a starter with your washed yeast. If you dont' know if your culture is viable and ready to be pitched, it doesn't matter what quanity is there, ya dig?

If you are going to re-brew within a few weeks, you can wash the entire cake and store it in one big jar. Then you don't need a starter, since you know you have plenty of viable yeast.

I save my yeast in four half pint jars. There are probably 50-100 million cells per jar, with a 20% per month mortality rate, similar to a Wyeast smack pack. Use the Mr. Malty pitching calc to figure out what size starter you need; input the harvest date as the manufactured on date. A 1L to 1.5L is probably sufficient for most batches. I tend to error on the side of overpitching when I'm not sure... I hit my starters with pure O2 until I get 1" of foam, and I shake them every few hours for a few days to keep the yeast in suspension. I use the "intermittent shaking" setting on the calc. If the calc shows I need over 1.5L I would just use two jars and make a smaller starter, since your yeast is getting old at that point anyway...

So I've got a few supplies. Most importantly is a .2um air filter that has hose attachments on either side to pump in filtered air. The problem I have come up with is that I need an air in spot and an air out that can handle a big krausen in the starter. I'm thinking maybe a bung that I could run a hose in and an airlock to fit on a 2 liter pop bottle? or a 1 gallon glass jug? Would a plastic milk jug work?

blue, I'm way, way less experienced than most on here (present company included), but you might learn from my mistakes...

I set up a starter w/ aeration 2 days ago. I just used an old (but clean) 2 quart plastic bottle with an aquarium pump and diffuser. I drilled a hole in the plastic screw-on cap to snugly fit the air line, then punched a bunch of tiny holes right in the cap. Sanitized everything with iodine solution.

The bubbler goes on 20 minutes, then off 20 minutes.

The problems (so far) are these: the shape of the bottle is not ideal (flat bottom). Even with the bubbler going, there are yeast cells that settle out. I would rather be using something like an upside down 2-liter bottle. Then I could just stick the end of the airline right at the bottom and that would keep them all suspended.

My other problem is that my increase in volume is way too big -- I'm going from a very small population of yeast to a very large one. From what I've read that's not desireable and stresses out the yeast. But, it doesn't sound like you should have this problem if you have a whole jar of washed yeast.

I'll keep you updated as the experiment progresses!

Just my opinion but it would seem that the tinkering and cleaning required for an air bubble aeration system is not going to be worth the result. I could understand if you were talking about constructing something like a bioreactor to grow yeast on a commercial or brewpub scale but even if you were going to do two 10 gallon batches you are really better off just using a shallow flat bottomed glass container and stir plate. As long as your solution dept is fairly shallow you will have excellent oxygen penetration with the stirplate.

I think a design based on this would be a good answer to tthose issues [ame=http://www.youtube.com/watch?v=7uNkHPuGaqo]YouTube - Do-it-Yourself: Brine Shrimp (artemia) Hatchery[/ame] . (Something like this would be much easier than building a stir-plate. Just add a filter on air in, and design a good air out point.)

Esarkipato, I wont need a starter for a month or so, but I think using a 2 liter bottle as a mini conical is a great idea then put a hole in the bottom (top of the device) of the 2 liter and put in an airlock of sort as the air/out point. The added benefit is that you could drain the completed culture (if your not pitching at high krausen) out of the "air in tube."

For yeast numbers, I've got some washed yeast in 10mL tubes and then mini jars in 125ml (half pint) jars, I am expecting to have to do 2 steps on the 10ml tubes. But if you let the first culture complete, then drop all the yeast out by putting them in the fridge, drain off the spent wort and add fresh wort as the second culture?

Blue, that's funny....you found my other hobby....fish tanks. Lots of cross-over to this one actually with the chemistry, biology, and sanitation practices! That's where I got the idea to do my current yeast culturing experiment.

better off just using a shallow flat bottomed glass container and stir plate.

Click to expand...

I agree.....but I'm not about to go buy a stir plate, or spend time making one. You have to understand that I'm not in this as a professional, just a hobbyist. As such, I'm not willing to spend lots of time/money doing things just right and being overly careful with sanitation. I know that dealing with yeast cultures is probably not the best realm to explore without having sanitation as the primary focus, but I'm giving it a shot.

My "experiment" is going pretty well so far....the sediment/slurry on the bottom is growing, and fermentation is taking place. Unfortunately, it doesn't smell like 2 hearted yet

Cool. That's a DIY Sea Monkies!

AT the risk of continuing to hijack your thread, blue800.....

Update: I eventually ended up with quite a bit of dormant yeast at the bottom of my wort mixture. I brewed last night, and just super-cooled a quart of the wort to pitch onto the yeast for an hour or two. I tried constantly aerating this, but it bubbled over too soon!

After pitching into the wort, it was fermenting vigorously in 16 hours or shorter. So far, so good.

ON TOPIC: how did your starter turn out?

My starter worked well. I did not get that nice conical design I was going for (maybe something to work up to). I did fit the aquarium pump through an air filter (like you can get at northern brewer I believe) through the cap and into the bottom of a 2-liter bottle, with aluminum foil covering everything. I had a 10mL culture tube from some washed yeast...about 4 weeks old now and pitched that into about 500 ml starter wort that should have been about 1.040 with spraymalt light DME. This worked very well, when I stepped it up to ~1.2L (as recommended by Mr Malty) though the bubbles caused leakage from the top, and I unhooked the air pump and swirled it every time I walked by. I cold crashed it this morning and had about an inch of yeast in the bottom
The air exited from the hole I cut in the bottle lid since I couldn't get a good seal with anything I had laying around the house. In retrospect I would really like to figure out that mini-conical system so I don't have to pitch all that spent wort...it didn't smell very good, can't add to much to the beer.
If I ever get around to designing it, I'll post some pics.

update edit: I had signs of fermentation at ~11hrs...possibly earlier.