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Old 05-01-2012, 03:49 AM   #1
alestateyall
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Default Mathematical model for hop flavor and aroma?

Is there a mathematical model for hop aroma and flavor in beer?

I think I understand the basic relationships:

1. More hops equals more flavor and aroma
2. Later hop additions increase hop aroma and flavor
3. Dry hops increases hop aroma

I currently have 2 beers on tap:

Beer 1: OG 1.044, grain bill 2-row & caramel malts (9%), 1oz citra @ 15 min, 0.5oz citra @ 0 min, 0.5 oz citra dry hop 7 days

Beer 2: OG 1.058, grain bill 2-row, wheat (8%), Munich (8%), 0.5 oz Simcoe @ 30 min, 1 oz Simcoe @ 15 min, 1 oz Simcoe 5 min, 0.5 oz Simcoe @ 0 min, 1 oz Simcoe dry hop 7 days

Beer 1 has great hop aroma and flavor

Beer 2 has OK hop flavor and not much aroma

I would expect more aroma and more hop flavor from beer 2 but that is the opposite of what I got.

Maybe this is expected with Simcoe vs. Citra. Alternatively, maybe the bigger gravity mutes the hop flavor and aroma profile.

My question is are there numbers or equations that would help me predict this?

Thanks!

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Old 05-01-2012, 06:40 AM   #2
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doublepost sry!

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Old 05-01-2012, 06:41 AM   #3
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A large factor is the size of your boil. I'd bet money your first boil had a larger volume than your second. You can throw in all the hops you want but a given volume of water will only dissolve AA so readily.

I'd recommend http://www.beersmith.com/ it's a paid program but there's a 21 day free trial. It has all those mathematical equations you requested built into it, plus a database of values for most of the commercial hops/grains available as well as a rough price gauge for when your planning a recipe.

Also, later hops = aroma,
early hops = flavor because the boil releases the Alpha Acids that give you the flavor.

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Old 05-01-2012, 12:48 PM   #4
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The boils for the 2 beers were both full boils. Both were about 7 gallons before boiling.

Are you saying Beersmith has equations for hop aroma and flavor? Lots of programs have an equation for hop utilization (Tinseth or Rager) which is used to predict bitterness.

Thanks.

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Old 05-01-2012, 12:52 PM   #5
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Apparently you are aware that there are several models for bitterness as a function of hop amount, hop alpha acid content, wort strength and boil time. Search Rager, Tinseth... with bitterness. These work, but not that well because the perception of bitterness is tied to the amounts of isomerized hop acids in the beer and it is possible to roughly estimate the amount of those from the parameters listed above. These models do not consider wort pH, however, and that also has an effect.

Bitterness is pretty much bitterness (though there is fine bitterness and coarse bitterness) but when it comes to flavor and aroma there are many more dimensions: fruity (several fruits), citrusy, spicy, floral, piney, earthy, licorice like... One could try multiple experiments where drinkers perceived flavors and aromas were tied to certain compounds (licorice to ethyl hexanoate, for example), many hops cultivars anaylyzed for their content of these compounds and all that data stirred up into a big principal components analysis (PCA) but the task would be daunting and not something that would be of practical use to brewers. I don't doubt that some of the things I'm suggesting here have already been done and can be found buried in the literature.

Practically speaking, control of aromas and flavors is done through the brewers knowledge of which hops cultivars present what flavors and how to handle these hops in order to avoid volatilizing the essential oils that are responsible for the aromas and flavors the oils deliver. Another approach is to obtain (either by purchase or extraction) these essential oils and then dose them into the finished beer to taste.

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Old 05-01-2012, 02:56 PM   #6
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I've not seen a formula for aroma and flavor, just for bitterness. It certainly would be nice.

I've toyed with the idea of making a rough estimate of the oil content in my house IPA recipe and then trying a different combination of hops that gives me the same oil profile. The problem is most of the data on hop oils gives a range of content so it is not that accurate. For this to really work, you would need more accurate oil values, akin to what we get for AA percentages.

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Old 05-01-2012, 03:51 PM   #7
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Everything with Hops is a guess, there are a few standard equations out there that some people have come up with. I tend to use Tinseth's model, Rager and some other's are out there. Here are the equations for IBUS:

IBUs=AAU*Utilization*74.9/Volume
Utilization = BTF*Bigness Factor
Bigness Factor (SG of boil determination) = (1.65*(.000125^(PreBoilSG-1))
BTF (length of boil determination) = (1-(2.71828^(-.04*BoilTimeMinutes))/4.15(this can be adjusted to mimic your kettle efficiency and dial in the equation (the 4.15 number))
AAU (Alpha Acid Units) = Weight(oz)*(AA(alpha acid percentage)*100) eg: 2 oz hops with 4.5 AA (2*(.045*100))= 9 (tettnang)

The 4.15 number as mentioned above in the BTF Factor, can be adjusted to adjust for your Kettle's efficiency. Every boil has a different gravity, different chemical interactions, different boil, etc..but this will get you in the ball park. A lot of people use Rager's equations as well, but those are the ones I use in my spreadsheet.

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Old 05-01-2012, 03:51 PM   #8
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Do you know which oils contribute to aroma and flavor? In my case on the Simcoe versus Citra comparison there is data like this available:

http://www.hopunion.com/17_HopVarieties.cfm?p3=open

The oil contents are generalized but that would be a start.

Thanks.

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Old 05-01-2012, 03:54 PM   #9
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Quote:
Originally Posted by dbhokie View Post
Everything with Hops is a guess, there are a few standard equations out there that some people have come up with. I tend to use Tinseth's model, Rager and some other's are out there. Here are the equations for IBUS:

IBUs=AAU*Utilization*74.9/Volume
Utilization = BTF*Bigness Factor
Bigness Factor (SG of boil determination) = (1.65*(.000125^(PreBoilSG-1))
BTF (length of boil determination) = (1-(2.71828^(-.04*BoilTimeMinutes))/4.15(this can be adjusted to mimic your kettle efficiency and dial in the equation (the 4.15 number))
AAU (Alpha Acid Units) = Weight(oz)*(AA(alpha acid percentage)*100) eg: 2 oz hops with 4.5 AA (2*(.045*100))= 9 (tettnang)
Thanks, but, I am not asking about bitterness. I am asking about a mathematical model for aroma and flavor (not bitterness flavor, maybe best put has flavor from hop oils).
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Old 05-01-2012, 04:05 PM   #10
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No, but I would think if you came up with a subjective flavor profile (the flavors they convey may be perceived different to different people, From my generic understanding the isomerization of the Beta Acids are what convey your "aroma's" and flavor. They do not isomerize during an extended boil, which is why they tend to convey bitterness then. There are a few major types of these oils, and if you could establish a spreadsheet imparting a table with the different base oils, and a cross-reference to your associated taste, you could come up with some equations for them I suppose.

EDIT: Although to ensure accuracy of your calculations with your setup, you would need some lab equipment to measure the oil levels, A great cook though, doesn't measure chemical flavor profiles with lab equipment at the end, it could be done, I suppose, but it would take more equipment than I have to get it right, that's for sure.

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