Margins of error for pitching yeast.

[TheRedDarren]

Hello.
Having just got into culturing my own yeast supplies has led me onto thinking more about pitching rates.
I will be using a calculator for the first few times until I get my eye in but I was wondering what sort of margins for error there are in pitching.

I guess the liquid yeast phials I use are sold at the lower end of the correct amount for a 23l @ 1040 ish brew, if only for profitable reasons.

If I were to double this amount after culturing up my own, would this be too much?
I'm not so bothered about using just enough so I can make my yeast last longer, I just want good beer.
Having split a few of the White labs phials I've now got an abundance of good yeast, so much so that I probably can't use it all in small amounts.

I've just discovered that under pitching can stress the yeast and cause a solvent type flavour, can over pitching cause similar issues?
Or should I take a small amount a make a starter every time?

Thanks in advance.

 

[clibit]

If you have split a yeast by growing a big starter and stored them in the fridge, you should make a starter for each brew. The viability of yeast reduces with time, a fresh starter enables you to more accurately estimate the amount pitched and means you pitch healthy active yeast. You can wing it, but your beer can suffer if you do. It's the most important ingredient in many ways.

 

[TheRedDarren]

Ok cool, so I make a litre of wort at 1040, then I measure out the amount of yeast to inoculate it?
Or just chuck in one of the portions split from the original?

What is the danger with over pitching?

 

[clibit]

Just chuck on one of your portions. Read this...

http://byo.com/grains/item/1717-yeast-pitching-rates-advance-homebrewing

 

[TheRedDarren]

Ok will do, thanks mate.

The only reservation I have (should have mentioned this earlier!) I followed the homebrew-tripod method that Myqul linked to another thread, but I split it into 6 instead of 12 portions. Should I half these portions back to the correct quantity?

 

[MyQul]

Ideally of course you want to pitch the "correct" amount of yeast for your OG/brew length.

However if your going to do one or 'tother under pitching is far worse than over pitching. Afaik from reading/researches

Under pitching: Stuck brews. Off flavours - however some 'off flavours' are actually desirable. e.g. Esters are considered off flavours in clean tasting styles of beer

Over pitching: Over attenuation. More bitter flavour to final beer than planned

Here's a nice article with an 'overpitching vs under pitching' experiement

http://sciencebrewer.com/2012/03/02/pitching-rate-experiment-part-deux-results/

Again afaik you've got to really be going some as a home brewer to overpitch. Remember plenty of people just pitch new wort onto a previous yeast cake with little negative effect (it's bad practice to do this but people still do it - although it can have benefits e.g. say you want to make a barley wine. People often make a batch of low OG beer so they can pitch the barely wine onto the low OG yeast cake.

It's also much better to pitch healthier yeast than more yeast. I take advantage of this to be lazy. I never actually bother measuring how much yeast I've got. I just make eye ball how much yeast I've got and pitch based on previous experience. I also make sure my wort is very well aerated and pitch at high krausen. High krausen is when the yeast it at it's healthiest. So if I happen to unknowingly underpitch, these two things help me get away with it. It's not something I tell other people to do but it works for me

 

[MyQul]

Ok will do, thanks mate.

The only reservation I have (should have mentioned this earlier!) I followed the homebrew-tripod method that Myqul linked to another thread, but I split it into 6 instead of 12 portions. Should I half these portions back to the correct quantity?

No. The amount difference wont be that much. Yeast growing isnt linear e.g. if you put x amount of yeast into 1L of starter then put double the amount into another 1L you wont get 4 x the amount of the first lot. You can test this yourself on a yeast calc.

 

[TheRedDarren]

Ideally of course you want to pitch the "correct" amount of yeast for your OG/brew length.

However if your going to do one or 'tother under pitching is far worse than over pitching. Afaik from reading/researches

Under pitching: Stuck brews. Off flavours - however some 'off flavours' are actually desirable. e.g. Esters are considered off flavours in clean tasting styles of beer

Over pitching: Over attenuation. More bitter flavour to final beer than planned

Here's a nice article with an 'overpitching vs under pitching' experiement

http://sciencebrewer.com/2012/03/02/pitching-rate-experiment-part-deux-results/

Again afaik you've got to really be going some as a home brewer to overpitch. Remember plenty of people just pitch new wort onto a previous yeast cake with little negative effect (it's bad practice to do this but people still do it - although it can have benefits e.g. say you want to make a barley wine. People often make a batch of low OG beer so they can pitch the barely wine onto the low OG yeast cake.

It's also much better to pitch healthier yeast than more yeast. I take advantage of this to be lazy. I never actually bother measuring how much yeast I've got. I just make eye ball how much yeast I've got and pitch based on previous experience. I also make sure my wort is very well aerated and pitch at high krausen. High krausen is when the yeast it at it's healthiest. So if I happen to unknowingly underpitch, these two things help me get away with it. It's not something I tell other people to do but it works for me

Fantastic, thanks dude.