Yeast viability

[Ian_68]

Ok. I've just tried at least 4 different yeast pitching rate calculators in readiness to make a starter yeast for 22l of cal common, est OG 1.052 with one pack of White Labs WLP810 (MFG 16th Jun 2019). The problem is, i'm getting different yeast viability % ranging from 29% up to 92%. Why is this and what would be the most accurate calc to use?

Cheers

Ian

 

[JonBrew]

I'd suggest you pick a yeast pitch calculator and stick with it. I like this one:
http://www.brewunited.com/yeast_calculator.php.

It calculates your viability to be 47% which sounds about right to me. 29% is very low and 92% would be very high given the age of the pack of yeast.

You get discrepancies between different calculators because their are different schools of thought on estimating yeast cell death rate (and growth rate) - the footnotes on the above calculator help to explain that. I suspect a linear model has been used to get that figure of 29%.

 

[Ian_68]

Thanks Jon.

So would you recommend smaller starters, mutiple steps or less steps, larger starters.

I have a 5 litre demijon i could use for a 4 litre starter with 404g of DME. What do you reckon?

Thanks

 

[JonBrew]

Thanks Jon.

So would you recommend smaller starters, mutiple steps or less steps, larger starters.

I have a 5 litre demijon i could use for a 4 litre starter with 404g of DME. What do you reckon?

Thanks

Assuming you're doing the manually shaken method, for best results, I'd suggest doing a 1L starter at SG 1.037 (with 100g DME) then step it up to 2L, same SG (200g DME). If you have time you'd be best to cold crash an rack off the starter beer in-between steps but if time is tight you'd be fine to just add one on top of the other.

If you plan to make using liquid yeast a regular thing a stir plate and Erlenmeyer flask would be a great investment and will cut down the need for stepped starters. You can make a stir plate yourself quite easily which is what I did. Guide below:

https://www.thehomebrewforum.co.uk/threads/how-to-build-a-stir-plate-for-less-than-ten-quid.65471/

 

[Linalmeemow]

I've always used the Mr Malty calculator and have never had any pitching rate issues.

This weekend I had a bit of nightmare - got my mash on for a biggish IPA then found that Geterbrewed had forgotten to put in the yeast I ordered. All I had in was about a pint and a half of BRY97 slurry from another IPA in March. I didn't want to risk leaving the wort while I sourced more yeast or made up a starter so I pitched the whole jar of slurry. I put the yeast data into the Mr Malty calculator and with the harvest date for the slurry it reckoned i needed 750ml, pretty much exactly what I ended up pitching. By yesterday evening it was bubbling away as heartily as any fermentation I've ever had, so hopefully it'll turn out OK.