Targeting final gravities?

[bernardsmith]

Coming from a wine making background where attenuation is not in our dictionary and where yeast can ferment brut dry any sap, flower or fruit based sugars how do brewers predict their target FGs? Is this based on knowledge of the grains themselves or does yeast not have any impact on the final gravity? Do you need to know how much fermentable sugars are in different kinds of crystal malts or different kinds of grains (Pilsner compared to say, two row or wheat or Caramunich, say). Are they always more or less constant? Do you need to use "calculators" and from where did/do the authors of these calculators get their data? I ask because I am currently making a traditional North African beer but I used Belle Saison yeast and my FG is about 1.000 although I used barley and teff)

 

[Yooper]

Several things go into attenuation. First, with beer, we are talking about apparent attenuation, not real attenuation like with wine, so that is a different way of looking at it. http://www.howtobrew.com/section1/chapter6-1.html has some easy explanations of that.

The next thing is the level of fermentability. Some ingredients are simply less fermentable, and even those ingredients can be manipulated to be more or less fermentable by things like mash temperature. Mash pH also plays a role in conversion and fermentability.

Software is about the worst way to predict probable FG- it just estimates a flat 75% apparent attenuation and doesn't really take into account the variables of ingredients and degrees of fermentability.

Things like yeast strain (some are notoriously low attenuations, like Windsor, or very very high like saison yeast), simple sugars, malt extract, etc, play such a huge role in attenuation that really experience is the best teacher in guestimating a likely FG.

 

[bernardsmith]

Thanks Yooper, So when someone offers a suggested FG with a recipe that they have created but have not yet tried that is a very rough ball park shot in a foggy moonless night out in the country kind of figure that may or may not have any relation to reality?

 

[mrgrimm101]

Pretty much. It will vary with things like different yeast strains, as well as temperature. It seems to me that if someone formulates a recipe with a suggested FG that they have not yet brewed and tested, they are probably plugging their ingredients into a software that gives them the suggested FG. Some softwares let you plug info about your brewing setup/process that could affect attenuation.

 

[Calder]

It will very much depend on the experience of the person creating the recipe.