# Coopers Yeast Starter - Green Apple Smell?



## Jimmeh (6/3/11)

Hello all

I've cultured up some Coopers Pale Ale yeast and all seems well except it has a distict green apple smell. Is it acetaldehyde? My stir plate stopped over night which may have contributed.
Has anyone experienced this smell with a coopers starter and should I be concerned?

Cheers

Jim


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## Maxt (6/3/11)

Jimmeh said:


> Hello all
> 
> I've cultured up some Coopers Pale Ale yeast and all seems well except it has a distict green apple smell. Is it acetaldehyde? My stir plate stopped over night which may have contributed.
> Has anyone experienced this smell with a coopers starter and should I be concerned?
> ...



I cultured my first Cooper's recently and had the same concerns, but reasoned it was just the yeast profile.


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## fergi (6/3/11)

i reculture coopers yeast a lot, quite often i have had funky smells from it, not sure why, i always have a taste of it, little bit onto a teaspoon and if it tastes good it probably is good,any funny tastes though and i would ditch it.
fergi


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## mwd (6/3/11)

When I recultured Coopers yeast from Vintage it smelt yeasty as in bakers yeast. I don't think I would use it if it had the apple smell though.
Good excuse to go and buy another 6 tallies of CSA.


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## Jimmeh (6/3/11)

Tropical_Brews said:


> When I recultured Coopers yeast from Vintage it smelt yeasty as in bakers yeast. I don't think I would use it if it had the apple smell though.
> Good excuse to go and buy another 6 tallies of CSA.



I do get some of that yeasty bready smell but there's some green apple as well :unsure:


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## mwd (6/3/11)

Jimmeh said:


> I do get some of that yeasty bready smell but there's some green apple as well :unsure:



Don't really know what to suggest but could try doubling up on the starter with some more DME and see if the smell is still evident.
If the liqour does not taste cidery then it may be fine to go. Would be painful to waste a batch for the sake of a bit of yeast.


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## felten (6/3/11)

nothing wrong with acetaldehyde in your starter, a healthy ferment will convert it all into ethanol by the end of fermentation.


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## Jimmeh (6/3/11)

Yet to taste it, will do now.

Thanks for the advice lads!

Jim


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## pyrosx (22/1/12)

Last time I attempted a CPA yeast reculture, I noticed this sour smell... I found this thread, and thought "seems okay, i'll just pitch it".

The beer ended up with the same green apple sour smell - it wasn't massive, and it did dissipate within a minure or so, but it wasn't ideal. (Ultimately, I masked the smell completely with 20g of amarillo in the keg... but that's a different story)

So, as I approach my second attempt, i'm looking for a more "scientific" approach to the reculture process... rather than the "1L of starter should be okay" approach.

I'm aware of the Mr Malty pitching rate calculator, but can't figure out how to make it apply to the reculture situation... possibly dialing in the right numbers on the "slurry" section - but I don't know what these numbers should be.

Is there any other way of even roughly determining the amount of yeast cells available after a reculture process?


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## [email protected] (22/1/12)

pyrosx said:


> Last time I attempted a CPA yeast reculture, I noticed this sour smell... I found this thread, and thought "seems okay, i'll just pitch it".
> 
> The beer ended up with the same green apple sour smell - it wasn't massive, and it did dissipate within a minure or so, but it wasn't ideal. (Ultimately, I masked the smell completely with 20g of amarillo in the keg... but that's a different story)
> 
> ...



When i culture up from a bottle, i go 100ml, 500ml, 1 - 2L.
I let the end starter ferment out and clear on its own at ferment temps.
I then decant the spent wort and wash the yeast, so i end up with a fairly clean sample of yeast.
I transfer this to a jar with known measurements, using the slurry calculator on Mr malty estimate how much yeast cells i have. Its up to you to determine the density of your slurry, thick yeast or thin slurry on the sliding bar, the default setting should serve you well.

Edit: So if you have 60ml of thick clean slurry @ 2.5billion cells / ml, you may have around 150billion cells.
Then minus the non yeast percentage i think default is 15%, minus your harvest day what ever that is


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## pyrosx (22/1/12)

Beer4U said:


> When i culture up from a bottle, i go 100ml, 500ml, 1 - 2L.
> I let the end starter ferment out and clear on its own at ferment temps.
> I then decant the spent wort and wash the yeast, so i end up with a fairly clean sample of yeast.
> I transfer this to a jar with known measurements, using the slurry calculator on Mr malty estimate how much yeast cells i have. Its up to you to determine the density of your slurry, thick yeast or thin slurry on the sliding bar, the default setting should serve you well.
> ...



Sounds good, thanks for that.

While i'm on the subject of the green apple smell - I believe it's acetaldehyde? Am I right in also believing that it's generally the result of a stressed starter? I think I started the dregs with too much starter last time....?


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## [email protected] (22/1/12)

pyrosx said:


> Sounds good, thanks for that.
> 
> While i'm on the subject of the green apple smell - I believe it's acetaldehyde? Am I right in also believing that it's generally the result of a stressed starter? I think I started the dregs with too much starter last time....?



Yeah prob stressed the yeast, start small, plan ahead and take the time it takes to get a good healthy yeast population up.


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## Ironsides (22/1/12)

Disclamer: I'm not a scientist.

I have however been trained in wine tasting, and spent a few years working as a cellar hand. I believe that it is Acetaldehyde caused by oxidation in the starter. Its the same thing that gives Fino Sherry the green apple smell. Not sure if it would harm the finished beer, but I dont think its an infection and if its diluted in enough wort might be undectectable.


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