stirring a yeast starter

Thu Jan 26, 2017 8:43 am

Hola! I have made 2 starters on my stir plate and both were bad. Let me tell you what I did and tell me where I screwed up.

1. cleaned my 2 liter flask with PBW
2. covered with foil and sanitized with starsan for an hour.
3. 2 cups H2O to 1/2 cup DME
4. boiled the shit out of it
5. cooled it in the sink
6. pitched yeast
7. turned on stir plate

I am thinking that maybe I stirred it at too high a rate and sucked in some outside air with bugs maybe. I have used foil in the past with no stir plate and had good results. I am at a loss. Should I have flamed the flask edge or something? grrrrrrr!!!!
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Re: stirring a yeast starter

Thu Jan 26, 2017 12:42 pm

I use a stir plate for starters, but I don't run it fast enough to suck air into the solution. But I don't think that's the problem.

Fruit flies are attracted to yeast starters, and can crawl up under the foil cap if it's too short or loose.

My recipe for yeast starter is 100g DME per liter, and I can't translate to cups per cup.

What does the contamination look like, and/or why do you think the starter is bad.

Charlie
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Re: stirring a yeast starter

Thu Jan 26, 2017 1:32 pm

Charlie wrote:I use a stir plate for starters, but I don't run it fast enough to suck air into the solution. But I don't think that's the problem.

Fruit flies are attracted to yeast starters, and can crawl up under the foil cap if it's too short or loose.

My recipe for yeast starter is 100g DME per liter, and I can't translate to cups per cup.

What does the contamination look like, and/or why do you think the starter is bad.

Charlie


It smelled sour which is a sign to me it was bad. Maybe it wasn't bad. It wasn't horribly sour smelling but it had a sour note. It could have been my best starter yet and I tossed it. Ooooh the pain.
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Re: stirring a yeast starter

Thu Jan 26, 2017 3:27 pm

Measure out 6 oz DME to 2 quarts distilled water. Add 1/4 tsp yeast nutrient. I usually do this first step in a saucepan on stove to be sure it is all thoroughly mixed and dissolved well over low heat.

Transfer to my 2 L + erlenmeyer flask with a funnel and bring to boil. I will also add 1-2 drops fermcap-S (foam inhibitor) to stop boil-over.

Boil for 10 minutes with last 4-5 minutes getting a piece of foil over the top to sanitize from heat.

After boil, transfer to ice bath and cool to 70-75F. Add liquid yeast (from pouch that has been sanitized and opened with sanitized scissors) with sanitized funnel and add sanitized stir bar.

Put on stir plate and away you go!
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Re: stirring a yeast starter

Fri Jan 27, 2017 7:57 am

SoCal Surfer wrote:
Charlie wrote:I use a stir plate for starters, but I don't run it fast enough to suck air into the solution. But I don't think that's the problem.

Fruit flies are attracted to yeast starters, and can crawl up under the foil cap if it's too short or loose.

My recipe for yeast starter is 100g DME per liter, and I can't translate to cups per cup.

What does the contamination look like, and/or why do you think the starter is bad.

Charlie


It smelled sour which is a sign to me it was bad. Maybe it wasn't bad. It wasn't horribly sour smelling but it had a sour note. It could have been my best starter yet and I tossed it. Ooooh the pain.

Every starter I've made has a sour taste after growth. It doesn't taste like the finished beer that it makes. As far as I know, this is normal and a byproduct of the growth metabolism in an aerobic environment.
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Re: stirring a yeast starter

Fri Jan 27, 2017 8:29 am

SoCal Surfer wrote:It smelled sour which is a sign to me it was bad. Maybe it wasn't bad. It wasn't horribly sour smelling but it had a sour note. It could have been my best starter yet and I tossed it. Ooooh the pain.


Early on I noticed that my starters (mostly 001 and 007) smelled sour, but the club's yeast guru assured me that was normal. I have come to rely more on appearance than odor as a sign of the culture's health, but I have never had a bad starter that I know of.

Starters are the first link in the chain, and I take a lot of care to maintain a pure culture. Everything is sterilized in a pressure canner for at least 15 minutes. Even the scissors I use to cut the yeast package are sterilized. Maybe that's overkill, but I treat it as a game, and I play to win.

Charlie
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Re: stirring a yeast starter

Sat Jan 28, 2017 7:03 am

Here is another data point, for what it is worth:

Like others, I have also gotten a sour note to the finished starter. I think I have seen this more with lager yeasts (2308, 2124) than I have with ales (1968 mostly), but it has been there. It hasn't ever translated to a problem.

As method goes, this is what I do:

Clean flask with soap and water and a brush and rinse, maybe PBW
I don't bother to starsan it (heat will do the job later)
Put on a scale set to grams

Add 150g of DME
Add a couple grams of nutrient
Fill the flask to the 1.5L mark with water
Shake to mix
Put on stove and boil for 10 minutes with foil cap
Put in a cold water bath and let it cool (65F to 75F, I'm not super particular)
Toss in the sanitized stir bar and pitch in the yeast

Set the stir plate to a modest speed, enough so things are stirring and there is a dimple in the surface. Let it run for 24hr and then shut it off and put it in the fridge.

On brew day:
In the morning I decant off the spent beer and add a bit of fresh wort (often from some 2nd runnings of my mash that I boiled for a few minutes and cooled). I let that come to life and then pitch the whole thing, which usually occurs at about the same time I run the wort into the fermentor, which works out perfectly.
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Re: stirring a yeast starter

Sat Jan 28, 2017 8:16 pm

NateBrews wrote:Put on a scale set to grams
Add 150g of DME
Add a couple grams of nutrient
Fill the flask to the 1.5L mark with water
Shake to mix
Put on stove and boil for 10 minutes with foil cap
Put in a cold water bath and let it cool (65F to 75F, I'm not super particular)
Toss in the sanitized stir bar and pitch in the yeast


A couple of points to streamline your procedure:

1. I find that it's better to dribble the DME into the stirred water, and avoid clumps that take forever to break up.
2. For a 2L starter I add 200g to 1500 ml of water, and then qs to 2L rather than guess at the final volume.
3. If you throw the stir bar in the flask before you boil it the stir bar will be sanitized with the rest of the solution (rather than having to sanitize it separately).
4. I never, ever, put a flask of boiling wort into an ice bath! Yes, it will work. Sometimes. And other times your flask will shatter wasting equipment, supplies and time. I cool my flasks on the counter top until they are comfortable to the touch before I put them in the water bath. It only takes 45 minutes or so, and when I'm in brew mode that's no time at all.

At the medical center there is a thing called "Central Services", and they do sterilization of equipment and other stuff either by autoclave or ethylene oxide (for plastic stuff that can't stand the heat). The durable stuff, like surgical equipment, comes back in pouches similar to the mylar barrier bags you get with bulk hops. So I ran some of the equipment I use in yeast propagation through the autoclave in one of those mylar bags, and guess what: It works! They wrinkle up a bit, but don't go to pieces. I'm gonna do that until something better comes along.

Charlie
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