Author Topic: IBU Calculations - Tinseth vs. Rager  (Read 20709 times)

Offline philm63

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IBU Calculations - Tinseth vs. Rager
« on: September 08, 2012, 06:43:28 PM »
There are threads going back a ways on this forum with various bits and pieces of this topic which I still find confusing. I know BS2 defaults to the Tinseth model, while some recipes found on-line or in magazines use Rager.

Is one "better" than the other, or is it meaningless to assign "better" or "worse" to either one? From what I've been able to gather, there are varying opinions regarding the accuracy of each, and folks are using both with good success, but I'd like to get a fresh take on this, and here's my MO:

I was thinking of changing the Hop Utilization Factor in my Equipment Profile to tweak how my IBUs are calculated as I was assuming, based on a recent brew, that I was under-hopping, but was advised it would likely be better to leave that set at the default 100% and just add more hops next time (there are plenty of reasons why this was good advice).

But then I got to thinking about the models used to make the IBU calculations; why does BS2 use Tinseth as its default? Is there something that appealed to the software developers or is it simply a more accurate way of calculating IBUs?
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Offline MaltLicker

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Re: IBU Calculations - Tinseth vs. Rager
« Reply #1 on: September 09, 2012, 11:39:30 AM »
Tinseth is the most recent model to come out, and is based on the most empirical data, I think.  Most "experts" seem to agree it's probably the most reliably accurate. 

Rager (I believe) was the default in ProMash, which many of today's "thought leaders" used since days of old.  JZ, for one, in BCS. 

If you're trying to emulate a recipe, you have to know what they used for your replication math to work out, and then you can switch, and make the adjustment. 

I lobbied Brad hard to make BS2 allow us to show both IBU figures on the screen at once, which he did with the 12 fields we can choose for the main screen.  I thought this would eliminate the idea that one is the "truth" since all utilization models are just 'best guesses' much like hurricane forecasters have multiple models and then they overlay them all to get a consensus model for the TV audience. 

For brewing consistency, I think it best to pick one model and then calibrate your tastes to those numbers until you find what IBUs you like in your [style.]

Offline chiller_AUS

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Re: IBU Calculations - Tinseth vs. Rager
« Reply #2 on: January 09, 2013, 05:17:42 PM »
I realise this is now considered an old post but one aspect mentioned by the OP is worth reviewing.

When I first began testing BeerSmith back in about 2003 one of the most useful but often least used or appreciated options in equipment setup was/is the ability to influence how your system presents you with a perceived bitterness or simply the hop ulilisation %. Unless you have access to a brewing lab you are relying on how the particular algorithm in BS handles the hop data you give it, and it does an excellent and consitent job, "and" the other lab is the one we all have, your own built in lab, your taste buds.

It is said that we can only start to detect IBU changes of around 3 - 5 ibu so that already account for the seeming difference between Raeger and Tinseth. Both systems, without lab analysis are complety accurate for your system. The laboratory tool for your system is your sensory system or wife or someone you know has a good understanding of bitterness.
Where actual bitterness results from your software are most important is in the low to mid bitterness level beers. It is in these beers that we can tell more easily if a beer is under or over hopped. Mega hopped beers to a large degree are far less affected by small variations in the IBU's returned by either formula.

One point to remember is that the beer is as bitter as the beer is so if I use Tinseth or Raeger and brew a 1.050 beer and use 30 gms of hops it will always give you whatever [in real bitterness] "X" ibu's in the beer from those hops even if one formula says 30 ibus and the other says 35 ibu's. 30 grams of hops is going to give a particular ibu level independent of the formula used. The most important thing is to stick with one formula and don't chop and change.

Your final "lab test" is your tongue or the tongues of friends or judges if you enter competitions. If you have very poor perception of bitterness requirements for differing styles of beers or you are new to home brewing stick with the formula and utilisation BeerSmith provides until you have a good handle on how hops work in a beer. To educate your tongue find a medium to low bittered beer on the commercial market that states the ibu level and brew a beer with ibus as close as you can get to that. It should teach you that commercial beers are often not as bitter tasting as you think for the ibu's stated and that home brewers very often over bitter their beer by quite a significant margin compared to a commercial counterpart. BeerSmith is a very professional piece of software because it doesn't assume all systems are the same. In your equipment settings you can alter the hop utilisation of your system to match your perception of bitterness regardless of the formula you use. Examine a beer you have already brewed. The Hop utilisation factor is a percentage increase or decrease you can set. If your beer is too bitter increase the utilisation % but don't alter the amount of hops you used in that beer and then observe the ibus returned by the software. Repeat the changes until the ibus returned are about your bitterness perceptions. This is a quite subjective but eventually you will nail it down for your system. Use the new utilisation % for the next brew. You will notice that you use more or less hops depending on how you altered the utilisation %. Fine tune over a couple of brews and soon you will have your system giving you more accurate to your palate hop bitterness levels.

There is a very basic issue with bitterness in that many people don't account for a change in AA% for the new bag of hops they have purchased and they are often very slap dash in weighing the hops. Spend the money and get a very accurate set of scales. I don't use ounces but my scales measure accurately in 1/10 of a gram. No big deal for low alpha hops but if you are using some of the newer 15 -17% AA hops small errors in a low to mid bittered beer will cause you much grief.

As an example I changed pots about 8 years ago and started using a high output gas burner compared to an electric heat wand and my next couple of beers were too bitter [by to my taste about 10% at least] compared to those brewed previously. BeerSmith allowed me to adjust the hop utilisation percentage and my next beer was very close to what I perceived the bitterness to be.

If you are fine tuning your system only change one thing at a time and keep reasonable records of what you have done.

BeerSmith is a superb tool for brewing and in reality does just about everything for you. It does require you to know your system and give it accurate data though.