Stir Plate Starter

[Jimmy]

So I did my second step of my step-up starter yesterday and I'm wondering if it's normal to not see any visible sign of fermentation with a stir plate starter? There was no krausen and no foam, just cloudy wort..is this normal because of the stir plate keeping everything mixed together and gassing off any co2 that is produced?

[GillettBreweryCnslt]

This'll be good to know, as I'm building a stir-plate right now!

[mr x]

I'm not sure as I never do that.

[Jimmy]

I'm not sure as I never do that.

You never use a stir plate?

[mr x]

I was assuming you dumped fresh wort into the fermented wort.

[KMcK]

I've never used a stir plate (for brewing), but even with three litre starters in colourless glass jars there's very little action to be seen on the surface because of the small volume. If you want to to know if it's working treat it like a brew and take gravity readings and even taste a sample.

[Jimmy]

Is there any way to estimate how much yeast is in this? This whole starter thing seems so variable and subjective to me...

IMAG0382.jpg

[Stusbrews]

Use a smaller/taller vessel to get a better guesstimate? A 2L juice jug works for me(even has graduations!)

[Tony L]

Given the amount of wort you have compared to the amount of yeast, it looks to me like you have
about the same amount I get from my starters without a stir plate. I have a home made stir plate
that I don't use because it throws the bar even though I adjust the speed.

Looks like healthy yeast to me, given the colour.

[henry]

When you pitch the yeast from a packet into the wort it won't begin fermenting the starter wort. The yeast will consume some of the nutrients in the wort, use the available sugar in the wort and begin the process of reproduction. This is important because you want the yeast to multiply, at least double, in population before you pitch that yeast into your batch. Even then, the yeast will acclimatise to their new surroundings, and multiply again before you see any "active" fermentation.

So to answer your question, wort that gets cloudier is a good thing.

The stir bar also helps evacuate any CO2 in the starter so you won't see any krausen at all.

[wortly]

[quote="Jimmy"]Is there any way to estimate how much yeast is in this? This whole starter thing seems so variable and subjective to me...


Yep. Neubauer chamber or a hemacytometer (same thing) and a microscope.

[sleepyjamie]

when you guys are making a yeast starter from a previous top crop/wash i assume you use the "previous slurry" tab from the mr malty calculator? and if so im guessing you measure the required yeast when it has been crash cooled?

[Jayme]

The purpose of the constant stirring is to pull in oxygen - although CO2 is driven off too, that's more a side effect. This why you don't want to drink starter wort - it's oxidized to the max (also why when you pitch, your starter volume should be less than 10% to avoid off flavours). It is perfectly normal not to have krausen due to this. Think of what you do to stop a boil over - you stir like a mofo to break surface tension. So by constantly stirring you're not only creating gas exchange, but also breaking the surface tension. For the cell count, a hemocytometer is the way to tell. I have one and a microscope but just haven't had the chance to get it all set up (hopefully by the fall). At the moment, I rely on the mrmalty.com pitching calculator to ballpark my initial count of viable cells and then also use it to calculate approximate cell growth (there is a nice option to choose your starter method which then selects the correct growth curve - stir plate being the steepest curve). Bear in mind, Nash has said this estimate of viability neither matters nor is an accurate calculation. I however, believe in Jamil's research as it claims to be based on real world numbers. FWIW, Gavin is a Microbiologist and has found almost all of Jamil's work on yeast to be academically sound. At some point this fall when life gets less busy again, I do intend to start doing cell counts and staining for viability. I will be sure to post results somewhere on how close our numbers agree with the mrmalty.com calculations.