Yeast attenuation

[paulpj26]

It's not particular important but I'm trying to understand why yeast has a certain percentage of attenuation? what I mean is why does a certain yeast have an attenuation percentage of 75% and another 70%, surely if their are fermentables to be fermented wouldn't it ferment that out? (or does it).

Does it have something to do with a yeast being more alcohol tolerant than another yeast?

:wha:

Hope that makes sense :thumb:

 

[markp]

My understanding, is that there are so termed unfermentable sugars in the wort....sugars that the yeast can't metabolise or take a long time to metabolise.
These 'unfermentables' do though obviously contribute to the gravity readings and give the beer it's relative sweetness.

So you have an amount of sugar showing on the OG reading and the residual unfermentable sugars (FG); from this you work out the attenuation.

Hope that makes sense.

 

[paulpj26]

My understanding, is that there are so termed unfermentable sugars in the wort....sugars that the yeast can't metabolise or take a long time to metabolise.
These 'unfermentables' do though obviously contribute to the gravity readings and give the beer it's relative sweetness.

So you have an amount of sugar showing on the OG reading and the residual unfermentable sugars (FG); from this you work out the attenuation.

Hope that makes sense.

Yes these are dextrin sugars Mark.

What I'm saying is that you could have 2 worts exactly the same (in terms of fermentability) and put two different yeast in it with different attenuation percentages and get different levels of alcohol in each one. I'm trying to understand why this is.
: :thumb:

 

[Good Ed]

Aleman must be busy, we'll have to wait for his sage advice

 

[paulpj26]

Perhaps i'm getting confused :hmm: :lol:

 

[ano]

Simply put, different strokes for different folks, some strains are more able to ferment the dextrinous sugars than others, for the same reason a spaniel looks different to a labrador. Even dextrins are fermentable (just not very), that's why it's easier to leave a high OG beer to bottle condition without priming sugar.

 

[paulpj26]

Thanks for your replies guys :thumb: :

 

[TheMumbler]

Differences in attenuation are because different yeast strains differ in their ability to ferment maltotriose, one of the fermentable sugars present in wort. Or at least that is what it says in Yeast.