1.016 or 1.012 ?!

[hector]

Hi there !

Lets assume that I have a wort with the O.G. 1.050 .

Also assume that 45 points are from fermentables and 5 points are from unfermentables .

The yeast strain I use has the apparent attenuation of 75% .

What F.G. should I expect after the fermentation ?

1.016 OR 1.012 ?!

I mean , 75% of 45 or 75% of 50 ?!

Hector

 

[beerkrump]

If it truely unfermentable, then you would get 45 - (45*0.75) + 5, or your 1.016.

 

[hector]

If it truely unfermentable, then you would get 45 - (45*0.75) + 5, or your 1.016.

O.G. = 1.050

F.G. = 1.016

So , ABV is 3.5% . But , I'd like to have a beer with at least 4% Alcohol .

Should I brew with a higher O.G. ?!

Hector

 

[DSmith]

1.050 -> 1.016 is 4.5% ABV (3.5 ABW).
1.050 -> 1.012 is 5.0% ABV (3.9 ABW).

Either of these attenuation senarios may make a great beer.

A lower mash temperature will increase fermentability and it's possible to attenuate use a yeast that's specified as 75% attenuation and get 85%.

In addition, proper amount of yeast and stable fermenation temperature (maybe with slight temperature rise at end) will ensure attenuation.

 

[ResumeMan]

Keep in mind that all wort contains some proportion of unfermentables (I don't know how much). That's the main reason why yeast doesn't attenuate 100%, and therefore the presence of unfermentables is "built in" to the expected attenuation.

Also "unfermentable" is not a fixed characteristic either. Some yeast strains can ferment certain sugars (like maltotriose) to a greater or lesser extent, and others can't, which helps explain the differences among attenuation of various yeast strains.

To answer your question...um, I don't know. It depends on what these "unfermentables" are, and how fermentable the "fermentables" actually are.

 

[944play]

HBT Wiki has a very helpful article on attenuation:
https://www.homebrewtalk.com/wiki/index.php/Understanding_Attenuation