Actual IBU calculations?

[HoppyJake]

I've been been brewing all-grain for about a year now and I can't for the life of me figure out why my IBU's always seem to be on the low side of what I have calculated for my recipes. I use BeerTools and have always treated it as "this is exactly what the beer will be" program. The gravity is always spot on (simple enough calculation), but the IBU's always seem off.

I've tried different water (tap, filtered, spring). I've tried more vigorous boils (helps). I've dried my beers out to 1.010. I don't use hop socks. But the end result is always a beer with more to be desired in the way of bitterness.

I know that AA%'s in hops change year to year, and I must admit that I've never actually changed the %'s in BeerTools- but I cant imagine that these changes would turn a 100 IBU recipe to a 50 IBU recipe.

I'm wondering how realistic IBU calculating is for home brewers? I've read that some people double their hop usage to 200 IBU+ in their recipes to obtain a 100 IBU result. I even saw a pliny clone on here that calculated out to over 200 IBU. Before I go out and spend a ton of money on hops, I want to hear what others think.

 

[Nateo]

You should definitely be adjusting your hops based on the AA% the retailer gives you. Hops vary quite a bit. One crop may be 13%, another may be 10%. The difference may seem small, but the 13% hop is actually about 33% more bitter than the 10% hop, relatively speaking. So small differences in AA% could make a big difference in perceived bitterness. A 33% difference could turn a 100 IBU beer into a 66 IBU beer.

Another issue is the kettle utilization of your particular kettle. That's something you'd have to brew a batch and send it into a lab to truly figure out, but generally for small batches you can assume 100% utilization.

I don't remember what formula Beertools uses, but I'd use Tinseth's. Take a look at this: http://users.rcn.com/thor.dnai/dboard/dbnewsl/t9509d.htm

Also, the 200 IBU beer is a myth. Beertools and such use simple formulas to calculate bitterness, assuming that each bit of AA% added increases IBUs by the same amount. Meaning if 10oz gives you 100 IBU, then 20oz MUST give you 200 IBU. The formulas will tell you that there is no limit to IBUs if you just keep dumping in hops.

In reality there is an upper bound to IBU that hops are able to provide in wort. I don't know if there have been any definitive studies, but among pro brewers it's generally thought to be around 120 IBU. Pliny the Elder "only" has 100 IBUs. Avery's Maharaja "only" has 102 IBUs, and so on. I've never seen or heard of a beer that has been tested at a lab have more than 110 IBUs.

One more thing, I believe hop utilization drops with higher concentration of wort, so the big beers that you're most likely to want high IBUs in will require more hops per IBU than a lower gravity beer. I think beertools takes that into account, but I'm not sure.

 

[jfowler1]

In reality there is an upper bound to IBU that hops are able to provide in wort. I don't know if there have been any definitive studies, but among pro brewers it's generally thought to be around 120 IBU. Pliny the Elder "only" has 100 IBUs.

Nateo did a good job of explaining already, but there is a little more to the story that I'll add.

First of all, I have heard that the taste ceiling for IBU's is 100. Once you get above that, the changes are undetectable. However, a measured 100 IBU's is basically unheard of.

All of the formulas we use are complete BS. They do a horrible job of calculating actual IBU's. However, they do a great job of giving a consistent calculation....it is just consistently wrong. Just look at them as a tool for future recipe adjustments. In other words, if you are making a pale ale that is calculated to "45" IBU's, and it is too bitter for your taste, you can use the calculation to reduce the next batch to "40" IBU's, and the beer may be more to your liking. But the chances of that beer actually being 40 IBU's is really slim.

In fact, an experiment was done measuring the actual IBU's in several hob-bombs. Listen to the IIPA show in Jamil's style series. He talks about a trip he took where a blind tasting was done on about a dozen commercial Double IPA's. Pliny was in fact one of the beers evaluated. Don't quote me, but I recall that despite a recipe calculation above 200 IBU's, the beer was measured in a lab to be under 70 IBU's. Personally, I found that shocking, but it really drives home the point that the formulas are no indication of the actual IBU's in the beer.

The formulas give us a common language to speak in, and with experience, you will learn what a calculated "30/40/100" IBU's tastes like, but the calculations themselves are no more accurate than a broken clock.

There are adjustments you can make to your water that will give the hops a little more bite, but before you screw around with your water, you may want to start with simple adjustments to your hop bills. If your "40" IBU's is not bitter/hoppy enough for your taste, bump it to "50" and re-brew.

Joe

 

[broadbill]

+1 to everything that's been said.

I was also trying to play the IBU calculation game (Tinseth vs. Rager? Utilization? Why are my numbers close on a small beer, but way off on a hoppy beer?).

My plan is to say FU to Tinseth/Rager and all that rest, do the IBU calcuations as it is outlined in Ray Daniel's book, and use that as a metric of more hoppy/less hoppy and use that to dial in recipes.

My experience is that if you are following a recipe designed to be home-brewed, and you are using the same amount of hops at a similar %AA...you are going to get close to where the hoppiness is supposed to be. Scale up/down in re-brews for personal taste.

 

[HoppyJake]

Thanks guys. Very informative.

 

[Dog House Brew]

I read Nathan Smith had his beer tested at Whitelabs after it won the NHA contest in IIPA. A Pliny type clone with a mountain of hops. Calculated well abouve 100 IBU................test 26 IBU. In order to get the same hoppiness of commercial scale Imperial IPA, I think it would be more calculated at 200 than their calculation of 100. When I started jacking up my numbers during calculations, I started getting more in line with what I wanted. I have beers calculated in the mid 60's and they are hop-less.

 

[badhabit]

Same subject different thought..... if you are, don't use conditioning hops boiled less than 10 minutes in your calculation for IBU's. You can see the chart regarding utlization on this site by typing hops utlization chart. Not sure how your software treats conditioning hops???

 

[HoppyJake]

I want to know what is so different about brewing on a small homebrew scale than on a commercial scale that allows for so much variation in achieved IBU's. I know there are variables in homebrewing that are not computer automated... but really where are we loosing all this bitterness?

Maybe if the answer was known than people wouldn't be wasting money on doubling their hop schedules.

 

[bullinachinashop]

Adjusting your water can help clean up the bittering and make the IBU's more or less pronounced based on beer style.

 

[Nateo]

I want to know what is so different about brewing on a small homebrew scale than on a commercial scale that allows for so much variation in achieved IBU's. I know there are variables in homebrewing that are not computer automated... but really where are we loosing all this bitterness?

On small batches (<20gal), hop utilization is about 100%. Large batches are much higher. Some breweries use alpha acid extract for bittering also.

When Widmer was just starting out, and their recipes were basically homebrew recipes scaled up to pro size, they sent a batch of their hefeweizen to a lab for analysis. They were shocked to find their hefe had over 40 IBU, when they were targeting somewhere in the 20s. So batch size makes a big difference.