ibu values
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They are all ways to estimate the amount of bittering the hops provide when they are boiled.
Average assumes a 'fixed' percentage utilisation somewhere between 20% (too low) and 30% (too high) for the duration of the boil and assumes that late hops provide no bittering.
Rager assumes that alpha acid utilisation is a 2nd or 3rd order reaction (Typical of a sigmoid type rate curve . . . shallow foot . . .steep middle point . . . . shallow head) . . . allows you to estimate the bittering contribution of your late hops.
Tinseth, is an experimental derived formula 'proving' that utilisation is a 1st order or pseudo first order reaction. rapid utilisation initially tailing off with time. I feel that this is the most likely as it reflects the fact that initially alpha acids are produced rapidly and then as time goes on there is a balance between isomerisation with forms the iso alpha acids and the destruction of the iso alpha acids. . . . It also balances with what I found in my old systems pretty well.
Average is OK for a rough and ready estimate, rager way over emphasises bitterness, and Tinseth comes pretty close (more or less) . . .Which is the correct one to use . . . take your pick, but whatever you do stick with it, chopping and changing will wildly affect your beer quality. I personally chose Tinseths as I know that it comes pretty close to what I see on my system. The only way to be sure is to brew a 1.050 beer with a single hop addition (With a hop of measured alpha content), and then take samples every 5 minutes for 2 hours cooling the samples rapidly, before sending these off to Brewlab for IBU measurement (at 13 quid a time) . . . You can then amend the Tinseth Fudge factors to accurately reflect what is happening in you kettle.
Graham Wheeler uses a 'simplified' Tinseth approach in the Beer Engine which I have discussed with him in the past and again I like this approach . . .there is too much going on in the boil to really predict 'accurately' what is going on the best we can do is to come up with an approximation, and as long as we quote the method used then other brewers can take that into account when converting a recipe for their system. THBF recipe engine uses Tinseth AFAIK.
Average assumes a 'fixed' percentage utilisation somewhere between 20% (too low) and 30% (too high) for the duration of the boil and assumes that late hops provide no bittering.
Rager assumes that alpha acid utilisation is a 2nd or 3rd order reaction (Typical of a sigmoid type rate curve . . . shallow foot . . .steep middle point . . . . shallow head) . . . allows you to estimate the bittering contribution of your late hops.
Tinseth, is an experimental derived formula 'proving' that utilisation is a 1st order or pseudo first order reaction. rapid utilisation initially tailing off with time. I feel that this is the most likely as it reflects the fact that initially alpha acids are produced rapidly and then as time goes on there is a balance between isomerisation with forms the iso alpha acids and the destruction of the iso alpha acids. . . . It also balances with what I found in my old systems pretty well.
Average is OK for a rough and ready estimate, rager way over emphasises bitterness, and Tinseth comes pretty close (more or less) . . .Which is the correct one to use . . . take your pick, but whatever you do stick with it, chopping and changing will wildly affect your beer quality. I personally chose Tinseths as I know that it comes pretty close to what I see on my system. The only way to be sure is to brew a 1.050 beer with a single hop addition (With a hop of measured alpha content), and then take samples every 5 minutes for 2 hours cooling the samples rapidly, before sending these off to Brewlab for IBU measurement (at 13 quid a time) . . . You can then amend the Tinseth Fudge factors to accurately reflect what is happening in you kettle.
Graham Wheeler uses a 'simplified' Tinseth approach in the Beer Engine which I have discussed with him in the past and again I like this approach . . .there is too much going on in the boil to really predict 'accurately' what is going on the best we can do is to come up with an approximation, and as long as we quote the method used then other brewers can take that into account when converting a recipe for their system. THBF recipe engine uses Tinseth AFAIK.
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