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Old 11-16-2010, 09:04 PM   #1
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Default Why can't Beersmith figure out final gravity?

It seems like no matter what recipe I do the final gravity is always estimated near 1.016.

Mash at a very low temp, add a very attenuative yeast to the recipe, choose light body mash/sparge options - it doesn't make a difference.

Anyone else notice this?

Not a huge deal, I just estimate on my own, but would be nice if their estimate was at least somewhat close.

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Old 11-16-2010, 09:06 PM   #2
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I think there are just too many factors that play into it. Any guess is just going to be as wrong as a static 1.016, so....

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Old 11-16-2010, 09:12 PM   #3
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There is no way to calculate the fermentability of a wort based on mash temps. IIUC, BS rudimentarily estimates final sg based on OG and yeast attenuation.

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Old 11-16-2010, 09:16 PM   #4
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Gotcha, makes sense on OG/yeast attenuation.

I'm building a Delirium Tremens recipe based off of jkarp's recipe and was trying to calculate it out (shooting for as low FG as possible).

A little off topic, but what's the lowest I can mash at, say 148? Shooting for maximum ferment-ability from a 90 minute single stage infusion mash.

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Old 11-16-2010, 09:26 PM   #5
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Limit of Attenuation

The limit of attenuation is the sum of all the sugars, that the yeast is able to ferment, expressed as a percentage of the total extract content. Since ale yeasts (saccharomyces cerevisiae) can only ferment maltotriose to a third and lager yeasts (saccharomyces uvarum) can ferment that wort sugar completely, lager yeasts will show a slightly higher limit of attenuation for the same wort.
Other than this the limit of attenuation of a given wort does not depend on the yeast strain. It is solely set by the mashing process. All yeasts are able to ferment all the fermentable sugars (save for the lager - ale difference mentioned above) in a given wort. This fact is taken advantage of in a [forced ferment test]. The forced ferment test uses a sample of wort and pitches it with a large amount of yeast. To ensure complete fermentation this sample is kept warm and the yeast is regularly roused (shaking or stirring). Once the fermentation is complete the apparent extract is measured and the limit of attenuation for that wort can be calculated.
[edit] Yeast Strain Differences in Attenuation

If there are no limit-of-attenuation differences between the different yeast strains, why are there more and less attenuative yeast strains available?
Though yeast strains are able to ferment all the sugars in the beer, they usually don't get to. In contrast to a forced ferment test, beer is generally fermented at lower temperatures, with smaller pitching rates and without constant rousing. Because of that the yeast will not get a chance to ferment all fermentable sugars in the wort. Flocculation will cause it to drop to the bottom or collect on the surface where it doesn't have as much contact with the sugars anymore. Because of nutrient depletion and or high alcohol levels cells die before they get a chance to ferment every last bit of sugar in the wort. The result is left over fermentable sugars that play an important role in the character of the finished beer. The closer a beer's attenuation is to its limit the drier and less sweet it will taste. When looking at the attenuation ranges given for commercial yeast you will notice that the less flocculating a yeast is, the more attenuative it will be. This makes sense as the poorly flocculating yeasts will remain in contact with the wort for a longer time. The beech wood aging process used by Anheuser-Bush to brew Budweiser does exactly that without relying on poor flocculation alone; it maximizes the contact area between beer and yeast.

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Old 11-16-2010, 09:32 PM   #6
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Quote:
Originally Posted by DrinkNoH2O View Post
Gotcha, makes sense on OG/yeast attenuation.

I'm building a Delirium Tremens recipe based off of jkarp's recipe and was trying to calculate it out (shooting for as low FG as possible).

A little off topic, but what's the lowest I can mash at, say 148? Shooting for maximum ferment-ability from a 90 minute single stage infusion mash.
Beta optimum Ranges are from 130 to 150 at pH 5 to 5.5
Alpha optimum ranges are 150 to 160 at pH 5.3 to 5.8

IIRC.

I think there is some limited Alpha at 140 but I am not sure how much.
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Old 11-16-2010, 09:42 PM   #7
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Quote:
Originally Posted by GilaMinumBeer View Post
Beta optimum Ranges are from 130 to 150 at pH 5 to 5.5
Alpha optimum ranges are 150 to 160 at pH 5.3 to 5.8

IIRC.

I think there is some limited Alpha at 140 but I am not sure how much.
Maybe I'll shoot for 151. With my 10 gallon Rubbermaid cooler I typically lose about 2 degrees during a 90 minute mash.
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Old 11-16-2010, 11:15 PM   #8
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Mapleroots.... very nice description!

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Old 11-16-2010, 11:34 PM   #9
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Mash long. I.e., hours.


If you look at the graphs on Kaiser's site, you'll see that fermentability improves appreciably with time, especially at low temps (because at higher temps the beta amalyse is being denatured and becomes useless after a short while).

In fact, Mapleroot's text is pulled straight from Kaiser's site. I think. Love that site.

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Old 11-16-2010, 11:37 PM   #10
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Quote:
Originally Posted by DrinkNoH2O View Post
Gotcha, makes sense on OG/yeast attenuation.

I'm building a Delirium Tremens recipe based off of jkarp's recipe and was trying to calculate it out (shooting for as low FG as possible).

A little off topic, but what's the lowest I can mash at, say 148? Shooting for maximum ferment-ability from a 90 minute single stage infusion mash.
Quote:
Originally Posted by DrinkNoH2O View Post
Maybe I'll shoot for 151. With my 10 gallon Rubbermaid cooler I typically lose about 2 degrees during a 90 minute mash.
If you want a more fermentable wort, I'd go with 147-148. I mashed a rye IPA at 147, and got a 1.007 result! A triple would be great at 1.006-1.007.
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