OG, Attenuation, Dry vs Sweet

[Clarke]

I am trying to wrap my head around this so bear with me if I am off track…

Let’s say I brew a beer and get an OG of 1.060, per my hydrometer, I can say I will get a potential alcohol of 7.8%

But not really, this presumes the yeast will attenuate 100% of the sugar. Most yeast, at least the 10 or so I quickly spot checked, will attenuate with-in a range, 75% being about the average. So it is safe to say I may get an alcohol percentage of about 5.85%.

But not really, this presumes a 100% of the sugar is fermentable. The yeast will only attenuate 75% of the fermentable sugar which is not calculated in the OG reading because OG includes both fermentable and none fermentable sugars, right? And now to complicate things, depending on mash temperature we can achieve more or less fermentable and un-fermentable sugars.

The way I am starting to see this is:

1.060 mashed at the low end of the temp rage with:
Low attenuating yeast will provide a dry/sweet beer
High attenuating yeast will provide a dry/dry beer

1.060 mashed at the high end of the temp rage with:
Low attenuating yeast will provide a sweet/sweet beer
High attenuating yeast will provide sweet/dry beer

Is my logic on track and is there a way to measure the amount of fermentable vs none fermentable sugar due to mash temp?

 

[pdietert]

This is fairly correct but there are other things that impact sweetness/dryness. This is why brewing is both science and art.

Software can help measure these.

 

[WoodlandBrew]

You've got it mostly right. The sugar that the yeast will ferment is called fermentable. For nearly all strains used in beer this contains single chain sugars like fuctose and glucose, two chain sugars like sucrose, dextrose, and maltose and three chain sugars like matotriose. It doesn't ferment longer chain sugars like maltodextrin.

When you measure the gravity of the wort at 1.060 you are measuring all of the sugars including the unfermentable sugars such as maltodextrin. The attenuation is dependent on the yeasts ability to ferment different sugars and the composition of the wort.

more details here:
http://www.woodlandbrew.com/2013/02/wort-sugars.html

As for mash temperature, essentially the closer you mash to 150°F the more fermentable the wort will be meaning there are more short chain sugars and less long chain sugars and other carbohydrates.

more details here:
http://www.woodlandbrew.com/2013/01/measured-mash-temperature-effects.html

 

[Yooper]

You've got it mostly right. The sugar that the yeast will ferment is called fermentable. For nearly all strains used in beer this contains single chain sugars like fuctose and glucose, two chain sugars like sucrose, dextrose, and maltose and three chain sugars like matotriose. It doesn't ferment longer chain sugars like maltodextrin.

When you measure the gravity of the wort at 1.060 you are measuring all of the sugars including the unfermentable sugars such as maltodextrin. The attenuation is dependent on the yeasts ability to ferment different sugars and the composition of the wort.

more details here:
http://www.woodlandbrew.com/2013/02/wort-sugars.html

As for mash temperature, essentially the closer you mash to 150°F the more fermentable the wort will be meaning there are more short chain sugars and less long chain sugars and other carbohydrates.

more details here:
http://www.woodlandbrew.com/2013/01/measured-mash-temperature-effects.html

That's all good info.

Something else to keep in mind is that a key of a good beer is balance. For example, a beer with a FG of 1.020 may or may not be sweet.

Let's say that you made a 1.040 beer that finished at 1.020. It has 75 IBUs, though. That means that the beer won't be sweet- it will be bitter.

Another beer that is 1.040 finished at 1.020- with 12 IBUs. That beer will be a bit sweet in the finish.

Also, the ingredients play a large role. If sweet crystal malts are used, the beer will be perceptibly sweeter in the finish and taste, while if something like a roast malt may mean less sweetness in the finished beer.

While OG/FG do play a role in the level of sweetness, much more important is the IBU/SG ratio, and the ingredients.

 

[catdaddy66]

That is great info that I can use right away on all future batches. In general I was using the OG/FG figures for both ABV and dry/sweet character. Didn't really pay as much attention to the change from hop usage and ingredients balance, but did note character of each individual ingredient.

What is SG in the ratio above (IBU/SG)?


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[Yooper]

That is great info that I can use right away on all future batches. In general I was using the OG/FG figures for both ABV and dry/sweet character. Didn't really pay as much attention to the change from hop usage and ingredients balance, but did note character of each individual ingredient.

What is SG in the ratio above (IBU/SG)?


Sent from my iPhone using Home Brew

Oh, man- I'm having couple beers and you want MATH?!?!

Ok, then. Let's see.

In the example of OG 1.040 and 75 IBUs, that is a ratio of 1.9!

For a beer of 1.040 and 12 IBUs, that is a ratio of .300.

The tale is not always told by IBUs, that's why the IBU/SG ratio is important.

For example, a barleywine may have 75 IBUs, but with an OG of 1.095, that won't be a bitter beer. It's really all about balance.

 

[catdaddy66]

Oh, man- I'm having couple beers and you want MATH?!?!



Ok, then. Let's see.



In the example of OG 1.040 and 75 IBUs, that is a ratio of 1.9!



For a beer of 1.040 and 12 IBUs, that is a ratio of .300.



The tale is not always told by IBUs, that's why the IBU/SG ratio is important.



For example, a barleywine may have 75 IBUs, but with an OG of 1.095, that won't be a bitter beer. It's really all about balance.

Damn, Yooper! I'm sorry, I didn't want the calculations but only what the letters 'S' and 'G' stand for..,

I know IBU is for international bittering units, OG is original gravity, FG is final gravity... What is SG? Starting Gravity...?


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[Yooper]

LOL.

SG= specific gravity. OG is actually the proper term, as it is the original specific gravity we're working with, but SG just means "specific gravity".

 

[Clarke]

http://www.woodlandbrew.com/2013/01/measured-mash-temperature-effects.html

Woodland, Thanks for the link, I think this is what I was looking for.