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 Post subject: Yeast starter calculator
PostPosted: Wed Sep 28, 2016 8:21 am 

Joined: Wed Dec 17, 2014 9:03 am
Posts: 77
I found this yeast starter calculator today which is based on a lot of actual empirical research, and which has graphs plotting how many cells there are at each hour since the start, so you know when your starter will be ready and you can plan when to start the starter so it's ready to pitch on brewday or so you can crash it and pour off the fermented wort.

http://www.woodlandbrew.com/2015/02/sta ... lator.html

There is a lot of other interesting info on there as well, I found his procedure for counting yeast cells really easy to follow and the photos are handy as well. I set the yeast to S-04 in the Rate Wizard tab and although I'm using Wyeast1968 it started to flocculate heavily at the same time the graph showed the number of live cells begin to flatten out, so I think it can have value for other yeasts as well as the Safale dried ones the calculator has in it.


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 Post subject: Re: Yeast starter calculator
PostPosted: Wed Sep 28, 2016 1:07 pm 
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Thanks Angus, it looks like a lot of work has gone into that and it helps to understand the growth characteristics of yeast.

As a note of caution though I think brewers can sometimes rely too much on what yeast starter calculators tell them. If enough nutrients, oxygen and sugar is available to even a small *healthy* yeast pitch it should grow adequately to achieve full attenuation, with only a small difference in the time taken. There are some thought provoking posts here:

https://www.homebrewersassociation.org/forum/index.php?topic=22055.15
and here

https://www.experimentalbrew.com/blogs/saccharomyces/yeast-cultures-are-nuclear-weapons

from the same guy (S. Cerevisae) who is a bit of a yeast guru.

His approach rejects stir plate starters in favour of shaken starters in a vessel with a lot of head space to ensure adequate oxygenation of the starter. The other key point is to pitch the starter at high krausen before the yeast go into a quiescent phase and become harder to wake up.

I use this approach now (for liquid and slurry yeasts) and it works well. If a wort is <1050 and the liquid yeast is fresh i usually just pitch, again with good results. The only times I have had poor fermentation has been with dry yeasts (Mauribrew 514 and Mangrove Jack "workhorse") which have failed to ferment out fully - despite following rehydration routines.

Cheers
Steve

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 Post subject: Re: Yeast starter calculator
PostPosted: Wed Sep 28, 2016 7:24 pm 

Joined: Wed Dec 17, 2014 9:03 am
Posts: 77
Very interesting articles there mate. I have read about the importance of yeast health in several places, Chris White stresses the importance of healthy yeast in his book "Yeast". I might try using a 1L shaken starter in my 5L flask next time, and see what kind of cell count I get after 24 hours, just out of interest. I wonder what the effect of spinning a small starter very fast on the stir plate would be, so it draws bubbles of air into the liquid when the vortex hits the stir bar? Probably still not as much oxygen available as in a flask full of bubbles.

Either way, having a starter ready to pitch after 24 hours seems to be the way to go to pitch while the yeast is in the exponential phase.


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 Post subject: Re: Yeast starter calculator
PostPosted: Wed Sep 28, 2016 7:37 pm 
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Location: Bristol
The downside to pitching the starter at 'high krausen' is that you pitch a litre or so of shit wort into your beer. Not so significant in 60 litres, but I'd be concerned in 20 litres.

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 Post subject: Re: Yeast starter calculator
PostPosted: Thu Sep 29, 2016 4:55 pm 

Joined: Wed Dec 17, 2014 9:03 am
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If you crashed it at high krausen you could pour off the bad flavoured fermented beer and pitch the yeast still in the exponential phase. I might try this.


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 Post subject: Re: Yeast starter calculator
PostPosted: Thu Sep 29, 2016 7:54 pm 
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Location: Bristol
That might work. Remember to equalise the temperature before pitching.

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 Post subject: Re: Yeast starter calculator
PostPosted: Fri Sep 30, 2016 4:17 pm 
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Joined: Thu Apr 22, 2010 8:49 pm
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RogerP wrote:
The downside to pitching the starter at 'high krausen' is that you pitch a litre or so of shit wort into your beer. Not so significant in 60 litres, but I'd be concerned in 20 litres.


S. cerevisae contends that starter wort smells foul when from stirplate starters because of inadequate oxygenation and shear stress arising from the stirring. Shaken not stirred starters don't suffer this way. There's a logic to that but I haven't seen any evidence. However I pitch a whole litre of starter at high krausen into my worts (normally 16 Litres) and have noticed no off flavours.

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 Post subject: Re: Yeast starter calculator
PostPosted: Mon Oct 10, 2016 1:33 pm 
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The brulospher has just done an exBeeriment on the issue of decanting starters vs pitching the whole volume. No statistically significant effect detected.

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 Post subject: Re: Yeast starter calculator
PostPosted: Mon Oct 10, 2016 2:01 pm 
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steve crawshaw wrote:
The brulospher has just done an exBeeriment on the issue of decanting starters vs pitching the whole volume. No statistically significant effect detected.


It's reassuring and whilst I'm no statistician, for 8 out of 20 tasters able to tell the difference seems significant to me, yet he doesn't think so.

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 Post subject: Re: Yeast starter calculator
PostPosted: Sat Oct 22, 2016 8:41 am 

Joined: Thu Aug 01, 2013 11:23 am
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RogerP wrote:
The downside to pitching the starter at 'high krausen' is that you pitch a litre or so of shit wort into your beer. Not so significant in 60 litres, but I'd be concerned in 20 litres.


Apart from when I've used liquid yeast, I've only ever pitched my starters at high Krausen in the 20 litre batches I make. I pull off a litre of the wort I'm making and set that aside to cool, add my dried yeast and shake it for 5 minutes and leave it overnight. As far as I'm concerned that's going to be the same quality added to the rest of the wort.

Am I missing something?


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