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aroma vs boil

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pcollins

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New forum member and haven't been able to find the answer to this question on the forum:

Aroma vs Boil for the hop additions seems to be somewhat arbitrary. If I add hops at 60 minutes they are boiling for that duration and are bittering but if I add hops at 5 minutes they are aroma hops but still boiling for those 5 minutes. Despite the function of the hop additions it changes the IBU calculation dramatically. In my recipes are all hops boiling hops?

Thanks for your time.
 
The hop oils isomerize, or the molecules rearrange themselves, over time. 

The longer you boil the more isomerization occurs. 

The boil volatizes off the aromatics over time while creating more bitter compounds. 

Late edition hops do isomerize some and do add some bittering as well as some of the aromatics volatize and disperse.  Even those added after the flame is off add some bittering just not much. 

There is a point of diminishing return around 80 or 90 minutes where the rate of isomerization really trails off. 

All calculation assume or state a hop utilization efficiency. 

Higher gravity beers have a lower efficiency and therefore need more hops in the long boil period. 

Dry hopping have very, very little effect on bittering and the fragile aromatics stick around in the beer for several months.  They too fade with time.  Usually after 3 months they are on a rapid decline.

When I brew, I use hop sacks.  The boil hops are removed when I shut off the flame as theya re intended to be there 60 or 80 minutes.  The late edition hops stay in t'til the end.  I feel like I have better control of the hops this way.  I am probably just fooling myself that it matters.

 
Excellent explanation, Jomebrew!

Now, as it applies to BeerSmith... Maybe it's just semantics on my part but when you add hops at the beginning of the boil they are functioning as "Bittering" hops. When you add hops closer to the end of the boil they are functioning as "Aroma" hops. In BeerSmith the calculations for those two functions are vastly different and I'm wondering if "semantically" and for calculation purposes ALL my hops added during the boil--regardless of how long they're boiled for--are bittering hops.

I do add hops for FWH and flameout. There is a function in BeerSmith allowing for FWH calculation so I'm wondering if in BeerSmith "Aroma" is considered flameout or whirlpool, i.e., post boil hop additions.

Thoughts?
 
Late edition hops contribute some to bittering but more to aroma and flavor.  It could be said all hop additions are aroma and flavor however slight.  The community at large refers to hops in the same way Beersmith 2 does.  At least among those I see and talk to.  Beersmith is keeping continuity of thought while taking into consideration the utilization of the hops for bittering calculations.

A handy way to visualize the hop utilization is John Palmers chart from How  to Brew http://www.howtobrew.com/section1/chapter5-5.html

Also, Glen Tinseth (recently on a Beersmith Podcast and very interesting at that) has pages on realbeer too. http://www.realbeer.com/hops/research.html
 
Hi,
  Just to clarify - in BeerSmith "aroma" hops generally refers to hops added at flame-out - they are assumed to add no bitterness to the beer, but instead are added to preserve delicate hop aroma oils which boil off easily.

  Boil hops are anything boiled - if you only boil it for 10 minutes, BeerSmith will do the IBU estimate correctly and calculate the IBU contribution - even if it is small.

  I'm of the opinion that if you want to maximize aroma for a given addition, minimizing the boil time is important as most of the aromatic oils boil off very quickly (as little as a few minutes).  Many brewers add aroma hops at flame out (after the boil), in a hop back device or use them for dry hopping.

Brad
 
Thank you, Brad. That's the clarification I was looking for.
 
So, as thick headed as I am, this says to me that all late hops regardless of time, other than knockout need to be entered as boil to recieve a bitterness value? I have have been entering thme as aroma and was twerked because i was getting no BU's for my trouble!
 
That is true.  I'm considering other options for "whirlpool" or "hopback" or "steeped" hops which do make a slight IBU contribution.  Isomerization is a continuous process, and can happen at lower temperatures albeit at a much slower rate than it does in the boil. 

The challenge has been finding a good formula to estimate it as I've found little hard research in this area.  If anyone has some good academic references let me know!

Brad
 
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