Yeast

[thesteve]

Can anyone advise how important the quantity of yeast is in all grain brews?

I prefer to do smaller batch brewing so I end up with maybe 10 litres of beer in the end but the packets of yeast normally cover bigger batches so I only use part of the packet.

Is this important or what would be the result of just chucking in the whole lot? Is it likely to have a good effect, bad effect or make no difference at all?

 

[The Baron]

There are a few experts on cell count for yeasts on this forum I personally do not bother too much as I know that I do not under or overpitch through experience and only use dried yeast or slurry from a previous brew anyway I would say that you are safe using a full packet in a 10ltr brew but one of the experts will confirm what is and isn't correct. I think you are erring on slightly overpitching at a full packet but as I said it should be ok

 

[Sadfield]

From Wyeasts website:

A low pitch rate can lead to:

• Excess levels of diacetyl
• Increase in higher/fusel alcohol formation
• Increase in ester formation
• Increase in volatile sulfur compounds
• High terminal gravities
• Stuck fermentations
• Increased risk of infection

High pitch rates can lead to:

• Very low ester production
• Very fast fermentations
• Thin or lacking body/mouthfeel
• Autolysis (Yeasty flavors due to lysing of cells)

Better to over pitch than under pitch. However, if using dry yeast, use what you need and seal the pack and store in a container in the fridge for use in the next brew.

 

[MyQul]

I do 10L brews too. Usually about 5g should do you. But use this yeast calc to calculate the exact amount

http://www.mrmalty.com/calc/calc.html

If you pitch too much yeast you can get over attenuation as there is more yeast to do the work

 

[Clint]

Why can it over attenuate? Why does it not just use up the sugars present and what it's able to then stop?

 

[MyQul]

Why can it over attenuate? Why does it not just use up the sugars present and what it's able to then stop?

Not sure tbh. I'd have to look in my yeast book (Im at work at the mo)

 

[Sadfield]

Why can it over attenuate? Why does it not just use up the sugars present and what it's able to then stop?

Good question. Less of a growth phase is needed, therefore less of the sugar in the wort is used fuel yeast growth. Instead it is converted into alcohol. More alcohol results in higher attenuation and a thinner beer.