First Wort Hop Additions IBU calculations

I was doing some research on this topic and it seems that your default FWH utilization factor of +10% might be way off.  According to this article, http://brewery.org/library/1stwort.html there is an avg. 10% increase in the IBU's over and beyond what you would get for a 20 minute boil of the same hop, but not +10% for the 60 min boil.  I think that most users are entering 60min boil for the FWH (since we are truely boiling them for 60min.) and this irroneously increases the IBU's calculated.  I figured that the FWH utilization factor should be -33.5%.  If you enter 2 identical hops at the same weight, 1 set for a 20min boil and the other for a 60min FWH,  the 60min FWH should come out only 10% higher in IBU's than the 20 min boil.  Changing the FWH utilization to -33.5% will compensate for this correctly.  There is no way that you get 110% utilization from the hops that you FWH at 60 min. compared to the normal 60min boil hop. 

One other easy way to correct for this, which has been mentioned in other forums, is to just use your default +10% FWH utilization and just enter 20 min. for the boil time when entering the FWH addition to your recipe.  Same effect but not accurate in the boil times.

Thanks,
Samsonite

Samsonite,
  I have seen the 1995 article, but it is a summary of the original article here:  http://www.franklinbrew.org/brewinfo/brauweltfwh.html

  The original article provides some interesting insights.  While it unfortunately does not provide the original hop schedule in its entirety, it does provide experimental levels for the original brews as well as rough hops amounts and schedule.

  For brew A, we see that the overall bitterness of the FWH brew (by EBC) is 6.35% higher than the non-FWH.  Brew B has a whopping 28.1% increase in bitterness for the FWH case.  In both cases, late addition hops were moved forward to FWH additions.  For A, 34% of the hops was moved forward while for B approximately 53% of hops was moved forward.  Both were low alpha hops (Tettnang or Saaz) - likely in the 4 to 4.5% alpha range.

  Looking at case B, lets make some very rough assumptions:
  - For simplicity, lets make it a 5 gal brew, 6 gal boil at roughly 1.045 OG (which can be backed out from the numbers given)
  - Assume the hops all Tettnang at 4%, and that the original recipe had 50% of the hops boiled for 20 min, moved forward to be the FWH
  - Again for simplicity lets use 1 oz boiled for 80 min, 1 oz added for 20 min as the baseline

  Using the hop calculator (Tinseth), I get:
    1)  25.6 IBU for the original recipe with half the hops at 20 min, half at 80 min boil (recall that FWH measured should add 28.1% to this number by the EBC measure)
    2) 32.5 IBU for the original recipe with all of the hops (2 oz) boiled for the full 80 min (no FWH adjustment) -- 26.9% above the baseline case
    3) 35.8 IBU if I use a FWH adjustment of 10% -- 39.8% above the baseline case
    4) 21.6 IBU if I use a FWH adjustment of -33.5% as you suggest - or 15.6% BELOW the baseline case
    5) Alternately if I add 110% of the 20 min contribution (per your rule of thumb) I get about 26.5 IBUs -- 3.5% above the baseline

Looking at the actual experimental results, it is interesting to note that case (2) above comes closest to the original case, indicating that leaving the FWH in for the whole boil does not significantly change its contribution to overall bitterness.  This does make some sense - the alpha acids in the hops do not disappear when we FWH, and in fact assuming you leave the FWH in the wort (i.e. it is NOT a mash hop but a FWH) those alpha acids will be extracted during the boil.

  I also ran the numbers for case A, which is a substantially lower increase in finished EBC alpha (about 6%) even though the wort isomorized is much higher in the FWH (13% higher).  Again, the zero FWH addition comes closest in the IBU increase to the experimental results, though it is slightly high for this case.  Your recommended setting of -33.5% FWH adjustment comes in low by some 28% from the measured EBC value.

  Unfortunately, we only have two experimental data points with a very large variation (22% difference in EBC values and a little smaller if we look at the Wort values) between batches A and B.

  However, overall I would say a FWH setting of around zero to -5% would hit the midpoint of these two data points.  The BeerSmith default of 10% is probably on the high side, but a setting of -33.5% is way too low.  The hops are boiled the full time, plus steeped for some time, so it does make sense that their contribution would be around the value of a full boil hops.

  I would love to see some actual IBU data from some more FWH brews.  I know I have made a large number of FWH only brews with great success, and they have not been unbalanced.

VR
Brad

Brad,  that is how i ran the numbers too.  However, i got 4.3 and 17.1% for the differences between the reference beer and experimental beer, not 6.35 and 28.1% like you did.??  Beer A was 37.9 (ref) and 39.6(exp) EBC and Beer B was 27.2 and 32.8 EBC.  Where did you come up with your numbers?  Even your percentages for your simulation are off.  25.6 is 21.2% less than 32.5....not 26.9.  The numbers can make a big difference here.

The avg. of my two numbers is 10%.....meaning that if you only move the 20min hop addition to a FWH situation (exaclty what they did), keeping the total hops weight as well as the percentage for each addition the same, one should only show a 10% increase in the total EBC's when using the FWH.  Some say that a FWH adds about the same IBU's to a batch as does a 20min boil of the same amount...in this case the research is saying 10% higher though.  Looking at their research, it appears that there are distinct changes happening in the ratios of isomerized to non-isomerized acids.  Maybe this is the reason for the IBU's not being that much higher in a FWH.  Of course, there will be more AA in the boil for a longer time to isomerize so it is obvious that the IBU's will increase in some amount, however, according to their research and my numbers, it should only be 10% higher than a normal 20 min aroma boil.  Steeping these hops obviously starts a different pattern of chemical reactions that has aprox. 15-20 min. to take place which could significantly alter the way the AA are isomerized during boil.  IOW, not all of the original AA's are available for isomerization after FWH in the boil.  Just my thoughts.  Some of the Promash guys are using -40 in their calculations for FWH utilization. 

When i enter 1.045 OG 5 gal and 1oz (4%) 80min and 1oz 20 min. i get 26.5IBU's.  If i change that 1oz at 20min to a FWH for 80min boil, the IBU's should be approx. 10% higher which would be 29.15 IBU's.  In order to get to this number, you will have to change the FWH utilization to -27 in this case.

This is obviously a numbers game and your great software has really helped me to learn and look deeper into all of this.  Thanks.

samsonite