When is that yeast active on the stir-plate...?

I've been trying to figure out when my yeasts are active on the stirplate. Some of them are pretty obvious (Wyeast 1968 comes to mind), but others, it's like watching paint dry (minus the fumes).

One thing I've noticed, though, is that I always seem to get some condensation on the (in)sides of my flasks after a day or so.

I started 2 flasks, about the same volume, on 2 stir-plates. This morning, one flask had condensation, the other didn't (yet).

Is this a decent sign of yeast activity?

M_C

when yeast relases CO2 it also goes through an exothemic reaction, releasing heat. So, to me, I think this is a definite sign of yeast activity.

hopsalot said:

when yeast relases CO2 it also goes through an exothemic reaction, releasing heat. So, to me, I think this is a definite sign of yeast activity.

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All right, that's good to know. Now if I don't see condensation after 24-48 hours, I know my yeast is kaput.

M_C

I got condensation with straight water when I was testing my homemade stir plate.
As I have only made my first yeast starter, I was wondering the same question.

FWIW, mine looked like the starter on the right in this video.
[ame]http://www.youtube.com/user/jpboileau#p/a/u/1/WvrUkqWAwYs[/ame]

Misplaced_Canuck said:

All right, that's good to know. Now if I don't see condensation after 24-48 hours, I know my yeast is kaput.

M_C

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not necessarily, are you getting a cake at the bottom of the one without condensation?

hopsalot said:

not necessarily, are you getting a cake at the bottom of the one without condensation?

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Well with the stir-plate active, I don't think that anything is sticking to the bottom

M_C

Misplaced_Canuck said:

All right, that's good to know. Now if I don't see condensation after 24-48 hours, I know my yeast is kaput.

M_C

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I made a small starter from a WLP300 vial that was over a year outdated. It took almost 4 days to gets started. I stepped it up a second time before use. If there is any question about the yeast's viability, just be patient.

ChandlerBang said:

I made a small starter from a WLP300 vial that was over a year outdated. It took almost 4 days to gets started. I stepped it up a second time before use. If there is any question about the yeast's viability, just be patient.

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Tell me about it. I have a Wyeast 1007 that has pre-puffed (partially, on its own), and at 40 hours it's not active. We'll see where it goes. It did create condensation but it's not active.

M_C

I can usually tell because it starts getting milky lookin and you can smell the c02 .. You dont want your starters to go more than 24 hours according to white labs theres a video on here somebody posted about it

bv805 said:

I can usually tell because it starts getting milky lookin and you can smell the c02 .. You dont want your starters to go more than 24 hours according to white labs theres a video on here somebody posted about it

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I know the video you refer to however they are talking there about a typical case. Where you are looking at extremely fatigued yeast or unknown quality/quantity of yeast you have to step out side the regular practices.

I usually will leave my starters on the stir plate until they show a milky color change. This means that the yeast are trying to flocculate out and have done most of what they are going to do. The time this will take will vary and from my experiments it seems to be related to how big a step you are doing and the strain of yeast.

So if you a doing a healthy vial/smackpack into a 1-2L starter it will only take a few hrs to show signs and maybe 12-18hrs to be done. However if you are stepping from a slant or a very harshly treated vial/smakpack where the cell count is very low it will take a lot longer to finish as the sugar/nutirent:cell count ratio is much greater they have more room to expand. Some day I will test this theory with putting a single cell colony into a 1L flask (that has been pressure cooked) and see how long it takes to finish the starter, that might be a while as I have packed my stir plates, flasks and brew stuff for my move... Hawaii to Gettysburg PA no brewing for two months.

The amount of yeast in a given volume of starter is determined by the amount of sugar/O2/nutrient level, as long as they have those component I think they will keep growing. Now we cannot just make a 1.090 starter (as that will weaken the yeast) or push the nutrient levels too high (some compounds that are needed for yeast growth could become toxic at higher levels). So if we were to use a constant step up or constant vial to starter volume ratio you could get a more consistent time frame but as you really don't have any idea how healthy your purchased yeast is (one of the reasons for doing a starter in the first place) I guess we will just have to play the wait and see game. I take the lag time of my starters (if using my normal step up routine) as an indication of yeast health.

Clem

bv805 said:

I can usually tell because it starts getting milky lookin and you can smell the c02

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You must have a good nose if you can smell CO2

Clementine said:

Hawaii to Gettysburg PA no brewing for two months.

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Dude, why?

el_caro said:

You must have a good nose if you can smell CO2

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Have you ever stuck your face into a keg that you just released the pressure on and popped the top? CO2 doesn't have an oder, but it kind of burns the nose a bit.

:rockin:n

ChandlerBang said:

Dude, why?

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Wife got a job in Pa and she is getting out of the navy. It was either that or we were going to go to Australia or Japan. Although my first choice was Australia her job paid more so Gettysburg it is.


Clem

el_caro said:

You must have a good nose if you can smell CO2

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Once you learn the smell, you never forget it.

Well my starter of Wyeast 1007 was a dud. After 3 days on the stir plate and 2 days off the plate at room temperature, no yeast smell. I will taste it tonight to see if it's still sweet or not.

JP

Misplaced_Canuck said:

Well my starter of Wyeast 1007 was a dud. After 3 days on the stir plate and 2 days off the plate at room temperature, no yeast smell. I will taste it tonight to see if it's still sweet or not.

JP

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Yep, tasted it last night. DUD. Note to self: Don't leave a wyeast smack pack in the car at 100F+. Oops.

M_C

I had a minute silence for your fallen friends...

Clem

The fallen friends death turned into a success. I reboiled the starter briefly, cooled, and pitched a healthy vial of Wyeast 1028.

I now have fermentation. I finally figured that if the fermentation is active, there will be tiny bubbles swirling around when on the stir-plate. I had to turn off the stirrer briefly and I saw the bubbles rising.

M_C