Figuring out FG with Promash

I can't seem to find a way to estimate a Final Gravity using the Promash Sortware, does it do that? Is there another way for me to estimate it?

A simple way to estimate FG is to use the yeast's attenuation figures. Or you could just use 1/4 of the OG, since most yeast's attenuate to 75% or so.

FG points = (1 - attenuation) * OG points

12 = (1 - 0.75) * 48

I believe that's how promash does it. I think it will estimate it for you in the fermentation section of the brew session.

Does it take into account the gravity points gained from unfermentable sugars, though? For instance, if I add a half-pound of lactose to the boil, my OG will go up significantly; however, my FG will go up just as significantly. Regardless of the attenuation my yeast will get, it will never ferment those sugars.

Right?

Isn't the same true for dextrose/cara-pils/etc.?

sonvolt said:

Does it take into account the gravity points gained from unfermentable sugars, though? For instance, if I add a half-pound of lactose to the boil, my OG will go up significantly; however, my FG will go up just as significantly. Regardless of the attenuation my yeast will get, it will never ferment those sugars.

Right?

Isn't the same true for dextrose/cara-pils/etc.?

Click to expand...

You're right but I don't think promash takes that into account, you could experiment easily. I think it just takes the attenuation of the particular strain and multiplies it by your OG.

sonvolt said:

Does it take into account the gravity points gained from unfermentable sugars, though? For instance, if I add a half-pound of lactose to the boil, my OG will go up significantly; however, my FG will go up just as significantly. Regardless of the attenuation my yeast will get, it will never ferment those sugars.

Right?

Isn't the same true for dextrose/cara-pils/etc.?

Click to expand...

Right. And some sugars are more fermentable: like honey and sucrose.

And some mashing procedures make more (or less) fermentable worts than others.

And so on...it's always mostly a guess predicting FG.

I believe ProMash does take into account non-fermentables. If you go into the grain database and pick say Pale Malt 2 Row and hit edit you'll see the gravity potential (1.036) and the other field % yield. I'd suspect this is how they derive at your estimated FG based on the yield %?

2-row gravity potential: 1.036 - % yield: 76.40
Carpils gravity potential: 1.033 - % yield: 69.91

All speculation but the help talked a bit about it. What'da think?

% yield is related to the potential SG and is a measure of how much of a malt's mass may be converted to sugar at a given grind. So this doesn't tell the FG story in Promash, either, unfortunately.

I'm pretty sure Promash just uses the yeast's attenuation to calculate the FG based on OG. You can make a recipe with nothing but crystal or roast barley and it will calculate an FG based on the yeast's attenuation.

Calculating the FG is where the brewers' art comes in

What about Beersmith, does it have this same flaw? Seems to be a pretty fundamental problem, doesn't it?

EDIT: Seems to be the case, just did a "recipe" with 10lbs of lactose and Nottingham yeast, says OG should be 1070 and FG 1017. Damn!

Due to the fact that there are so many factors that affect the attenuation of the beer (starting with the age of the grain all the way to the health of the yeast) there is no reliable way to calculate the attenuation that you will get. Using the yeast attenuation to estimate the FG of your beer may get you within 2-4 gravity points of the actual FG assuming that your wort's fermentability somewhat matches the fermentability of the wort that was used to determine the yeast's attenuation.

The only solution is to brew a certain recipe multiple times and play around with the mash schedule (saccrification rest temp and length in particular). If you want to know the exact limit of attenuation of your wort after it has been brewed and before it is done fermenting you can make a fast ferment test by fermenting a sample of the wort with lots of yeast at warm temps.

Kai