Why adding Sucrose, can reduce FG

[peterpiper]

Just trying to get my head around how adding Sucrose to a recipe, can reduce the FG.

I've been tweaking a Evil Dead Red clone recipe, very hop forward but low IBU red (Irish) ale, to be a closer match to the commercial product: ABV: 6.66%; 10 IBU.
And decided to try using the Lallemand Verdant IPA yeast, limited attenuation, but good for hop forward ales.

Seemed a struggle to get a FG, toward low end (that I generally prefer) of the style guidelines.
But adding 300g Sucrose to the recipe (with no other changes), lowers the FG (as predicted by Brewfather) by two points (while increasing ABV form 5.5% to 6.3%).

Does presence of sucrose, encourage the yeast to ferment some sugars, it would otherwise have left.

 

[JockyBrewer]

Specific Gravity (SG) is just a measure of the density of a fluid relative to water.

Water has an SG of 1.000. Add some sugar in and that goes up.

But pure ethanol (alcohol) has an SG of 0.791, so as the sugar is converted to alcohol, the gravity doesn’t just fall due to the removal of sugar, but also because it’s being replaced by something less dense than water.

Simple sugar is 100% fermentable, meaning that it will only add more alcohol to the final product that lowers the FG, and no residual sugars that might raise FG.

Champagne can have an FG of 0.995!

 

[Manxnorton]

Away remeber that i brewed a cream porter twice & the FG stopped both at 1.020.
was getting worried i got a stuck ferment.
think it was Leon give me the answer.

 

[peebee]

And another thing ...

A proportion of what you extract from malt is not fermentable. Sugar is very fermentable. By adding sugar you dilute what you extract from malt. So, you also dilute the amount of malt unfermentables. Therefore, the FG can be lower!

Did you follow that? (Not sure I did).

 

[peebee]

Ah ... cracking! Apart from @JockyBrewer (sorry, but you don't want to be included in this!) you (@peterpiper) have got the forum's two most notorious loonies on the case.

What could go wrong?

 

[peterpiper]

Like this asylum, everything makes sense, and the dry red usually clocks in at 988.

 

[JockyBrewer]

Ah ... cracking! Apart from @JockyBrewer (sorry, but you don't want to be included in this!) you (@peterpiper) have got the forum's two most notorious loonies on the case.

What could go wrong?

I can only aspire to such notoriety.