IBUs without boiling??

HomeBrewTalk.com - Beer, Wine, Mead, & Cider Brewing Discussion Community.

Help Support Homebrew Talk:

Dennisusa

Well-Known Member
Joined
Apr 2, 2010
Messages
57
Reaction score
10
Location
Raleigh
Can anyone give me the formula for bittering effect when adding hops after the boil? All the formulas seem to require OG, Alpha content & boil duration, but adding a mountain of hops after flame-out (during the swirl) would seem to me to be adding IBU's as well. At least that's what I suspect. But without good data and a formula, how do we measure this? In the absence of hard data I'm not persuaded that with a steep time of, say, 30 minutes (during cool down from 205 to 180F) we would not be adding significant IBUs. And if it does, we ought to be able to calculate this.
 

juslod

Well-Known Member
Joined
Jun 21, 2010
Messages
206
Reaction score
6
Location
St. Augustine
If I have understood completely, the oils that add bitterness in hops are only extracted when at boiling temperatures. Just adding a bunch at flame out wouldn't add any IBUs.

May I ask why you would want to do this, anyway?
 

Golddiggie

Well-Known Member
Joined
Dec 14, 2010
Messages
12,171
Reaction score
660
Location
Living free in the 603
From my understanding, only when the hops are boiled will you extract the bittering oils from them. Otherwise you'll just get aroma, and maybe a bit of flavor...

There's a couple of chapters in Designing Great Beers going over hops... You might want to read through them so that you have a better understanding of what's going on... I'm not about to start typing it all in for you... :eek: Suffice to say, no boil temp, no bitterness from hops.

The oils/compounds that create the bitterness are not only extracted, but changed into what produces the bitterness during the boil...
 

BendBrewer

Well-Known Member
Joined
Jan 26, 2010
Messages
3,126
Reaction score
81
Location
Bend
Short answer is no, post Knock Out additions do not increase IBUs.

They add great aroma though.
 

Golddiggie

Well-Known Member
Joined
Dec 14, 2010
Messages
12,171
Reaction score
660
Location
Living free in the 603
Hey Bend... I've not dry hopped yet, but planning to on a brew started last week... Do you get ANY flavors from the dry hops (whole leaf in my case) or is it just all aroma?? I know that taste and smell are closely linked senses, so I was hoping that some would carry through into flavor...
 
OP
D

Dennisusa

Well-Known Member
Joined
Apr 2, 2010
Messages
57
Reaction score
10
Location
Raleigh
Very fair questions, Juslod.

I accept that isomerization maximization occurs with a 60-minute rolling boil (I've seen the IBU graphs that prove the alpha utilization curve), but I find it hard to believe no IBU's are added after the boil whatsoever. That just does not sound right - especially with an extended steep period. We all seem to accept this truism, but I've never seen an IBU graph that demonstrates no bittering effects without a boil. Yet tea made out of even one lonely hop petals steeped in (unboiling) hot water can be awfully bitter.

My question comes from wondering if: (a) bittering components are maximized with extended alpha isomerization during a long boil and (b) flavor/aroma components are maximized after the boil or during the secondary fermentation, what does adding hops 15 minutes before the end of boil do that would not be better accomplished by slightly more bittering hops at the beginning and slightly more aromatic hops at flame-out would not do even better?

Just asking.
 
OP
D

Dennisusa

Well-Known Member
Joined
Apr 2, 2010
Messages
57
Reaction score
10
Location
Raleigh
Humans can detect only 5 flavors: sweet, sour, bitter, salt, and umami. All other "flavors" are apparently just aromas in some combination with one or more of those five flavors (hence when you catch a cold food taste flavorless).
 

scottland

Well-Known Member
Joined
May 17, 2010
Messages
2,111
Reaction score
167
Location
Chandler
I'm going to disagree with what's been said above. You can still extract alpha acids and impart biterness in beer at temperatures below boiling. This all depends on how quickly you chill your wort, but I definitely believe that IBUs are extracted during the 160-200* range. Not as much as if it were boiling, but it happens.
 
OP
D

Dennisusa

Well-Known Member
Joined
Apr 2, 2010
Messages
57
Reaction score
10
Location
Raleigh
Thanks, Scotland, I was feeling rather lonely there. Do you have a "steep time" graph or any other hard data that measures this?
 

erikpete18

Well-Known Member
Joined
Apr 27, 2009
Messages
822
Reaction score
34
Location
Seattle
Well, since I'm bored at work, I thought I'd do a little digging since your theory makes sense. Here's an article you might be interested in http://pubs.acs.org/doi/abs/10.1021/jf0481296. In case you can't access it, the basic idea is that they took alpha acids at a variety of different concentrations, heated them to different temps, and measured the resulting effects on isomerization.

Table 1 says that to achieve 60% alpha acid to isoalpha acid conversion, you've got to boil it for 90 minutes (100C). Since I don't want to look up what the formula for isoalpha acid to IBU conversion is, let's assume that this is a pretty good reference point for a normal wort. At 90C (194F), it takes about 3.5 times as long (207 min.) to get the same conversion. Not sure if we can assume that the isomerization is linear across time, but a rough guess would be that you'd have 3.5 times less isomerization at 90C than you would at 100C.

From there, if you figure this 3.5x decrease, plus the amount of time that your wort is actually at 194F and the resulting exponential decreases as temp decreases, I think you're probably right that some of the alpha acids are still undergoing isomerization, especially if you do no-chill and let your wort chill down over time without any cooling attempt.

However, in the grand scheme of things, this likely makes up far less than 5 IBU (unless you're throwing in a pound of hops at flame-out) which is about the differential we can detect with taste. Of course, the iso-alpha acids aren't the only bittering components in hops, but that's a whole other set of experiments!
 

mb2696

Well-Known Member
Joined
Oct 13, 2009
Messages
409
Reaction score
7
Location
charlottesville, va
i do a 30 min hot whirlpool and calculate mine at around 10-15% utilization. i don't have any supporting scientific data, but the final beers seem about right in terms of bitterness.
 

mb2696

Well-Known Member
Joined
Oct 13, 2009
Messages
409
Reaction score
7
Location
charlottesville, va
also, there are many examples available, but here is one from Firestone Walker:

Another brewery that has embraced late hopping is Firestone Walker Brewing Company of Paso Robles, California. Brewmaster Matt Brynildson says, “…I brewed a flagship beer at another regional brewery where 95%+ of the IBUs were a result of whirlpool hopping.”

Brynildson goes on to say, “...The fact that there is some isomerization (about 15% in whirlpool versus 35% in the kettle) of alpha acid means that not only hop aroma and hop flavor can be achieved, but also some bittering.”

source: http://www.mrmalty.com/late_hopping.htm
 

juslod

Well-Known Member
Joined
Jun 21, 2010
Messages
206
Reaction score
6
Location
St. Augustine
It seems like you may get some bitterness extracted from hops in sub-boiling temperatures (thanks for tea reference) but it seems like utilization would be much less. Factor in the price of hops and over time I could see this being a large price increase. However, if you were aiming for a target IBU and the beer has hops at flame out you may be able to calculate this figure better if there were a formula. You could compensate early additions for the extra IBUs added at flame out since brewing software doesn't calculate it.

It sounds like it is possible (and happens) but I couldn't see it viable to only bitter from steeping due to price/quantity. :ban:
 

mb2696

Well-Known Member
Joined
Oct 13, 2009
Messages
409
Reaction score
7
Location
charlottesville, va
i agree...it's definitely not efficient bittering. i think the point is flavor and aroma, but when you have a big whirlpool addition (for big flavor and aroma), you will get significant IBUs, which you'll want to account for.

of course if you start chilling as soon as the flame is out, you probably don't get much
 
OP
D

Dennisusa

Well-Known Member
Joined
Apr 2, 2010
Messages
57
Reaction score
10
Location
Raleigh
Thanks to all for the great links and references. Most of the references offer strong support for the claim that there is significant IBU contribution during a prolonged whirlpool. But I've still found no hard data for computing isomerization during whirlpool. For the members that remain sceptical on this technique, here's an extract first appearing in Zymergy on this topic from Brynildson, a former hop chemist and brewer at Firestone Walker brewing:

“We practice a lot of late hopping on the majority of our beers. Our main goal with increasing our late hops is big hop aroma and flavor. All of our beers have at least some hops that are added at the beginning of boil for bitterness, as this also helps to keep foaming and boil over down in the kettle, but these kettle charges are minimal to allow for larger late hopping charges. I brewed a flagship beer at another regional brewery where 95%+ of the IBUs were a result of whirlpool hopping.”

“American Craft Brewers practice a number of different methods of late hopping, with one very popular method being whirlpool hopping. This is a bit of a fusion between traditional late hopping and hopback methods. Adding hops late in the whirlpool results in lower isomerization of alpha acids and good uptake of hop oils and flavor components (especially with pellet hops). The fact that there is some isomerization (about 15% in whirlpool versus 35% in the kettle) of alpha acid means that not only hop aroma and hop flavor can be achieved, but also some bittering.”

And from Mr Malty: Long time homebrewer, David Sousa brewed an IPA with Columbus hops, all at 15 minutes or later. “The results were as expected and more,” he said. “The hop flavor was huge. Another thing I noticed was an increased mouthfeel. The beer had a really nice texture in addition to a very clean hop flavor. And it doesn’t make you feel like you need to wait before you take another sip. Dry hopping, by comparison, tends to cling to the palette a bit more.”
 

rwmiscik

Well-Known Member
Joined
Jan 25, 2011
Messages
53
Reaction score
1
Location
parsippany
Humans can detect only 5 flavors: sweet, sour, bitter, salt, and umami. All other "flavors" are apparently just aromas in some combination with one or more of those five flavors (hence when you catch a cold food taste flavorless).
Well I lost my sense of smell in an accident 6 years ago and I can still taste impecably well and actually excel in picking up off flavors in my and other people's beer. The doctor's explanation was that when you temporarily lose your sense of smell food will taste flavorless like when your sick, but if you lose your sense of smell for a long time your brain learns to stop relying on your smell since its not working and it starts to rely fully on your taste buds which then builds your taste buds up lets you taste everything just as well if not better than when you could smell. :mug:
 

rycov

Well-Known Member
Joined
Feb 10, 2010
Messages
1,940
Reaction score
27
Location
conway SC.
Hey Bend... I've not dry hopped yet, but planning to on a brew started last week... Do you get ANY flavors from the dry hops (whole leaf in my case) or is it just all aroma?? I know that taste and smell are closely linked senses, so I was hoping that some would carry through into flavor...
i didn't read close, but i didn't notice this being answered directly so heres my 2 cents.

i think yeah, some. i recently dry hopped for the first time and the beer smells great but also tastes a lot better too. is this from what i smell? maybe, but in my head it comes across as a crisp fresh hop aroma AND flavor. so i don't know the science or whatever is going on behind it, but it does add atleast the perception of taste (to me anyway).:mug:
 

MalFet

/bɪər nɜrd/
Lifetime Supporter
Joined
May 31, 2010
Messages
8,632
Reaction score
1,479
Location
NYC / Kathmandu
Thanks to all for the great links and references. Most of the references offer strong support for the claim that there is significant IBU contribution during a prolonged whirlpool. But I've still found no hard data for computing isomerization during whirlpool. For the members that remain sceptical on this technique, here's an extract first appearing in Zymergy on this topic from Brynildson, a former hop chemist and brewer at Firestone Walker brewing:
Did you read erikpete18's article? It's very good, and more or less answers your question. Pretty much everyone agrees that late additions (like the kind JZ describes in the hop-bursting article you are citing) add bitterness, and all the formulas I have seen reflect that.

For example, I recently brewed the Evil Twin recipe from that page (very tasty!), and the Tinseth formula suggests I get 12 IBUs from the .25 oz 60min addition, 14 IBUs from the .5 oz 20min addition, and 23 IBUs from the 2oz 10min addition.

Likewise, the distinction is not really about pre-boil vs. post-boil, but about temperature. Acid to isoacid conversion is significant at boiling temps, negligible at room temps, and somewhere in between for every temperature in between. According to erikpete18's article, isomerization rates drop logarithmically...about 60% per every 10ºC. As your temperature drops from boiling, isomerization rates plummet.

So there really can't be a single formula that computes isomerization during whirlpool, unless it takes into account somehow rate of temperature drop. If it takes you three hours to chill, you'll get significant bitterness from whirlpool additions. If it takes you 10 minutes, you'll get next to none. It is certainly true that all the hop utilization formulas assume you are able to get your temps down quickly, and you'll need to adjust your times if you can't. The no-chill people (for example) know this from experience, and adjust their recipes accordingly.
 

pjj2ba

Look under the recliner
Lifetime Supporter
Joined
Jul 25, 2006
Messages
3,373
Reaction score
230
Location
State College
................. Of course, the iso-alpha acids aren't the only bittering components in hops, but that's a whole other set of experiments!
I'd like to see some real IBU data, not just anecdotal, hey this tastes quite bitter yet I only used late addition hops. The IBU calculator says I added XX IBUs. First off, I personally don't think IBU calculators are very accurate for very short hop additions. They are designed to work best for the 20 min. + additions. (Some day I'd love to see an aroma calculator based on oil content). Second, as erikpete said, there are other bitter things in hops. Hops have polyphenols that also contribute to the bitterness. My personal anecdotal evidence is when I have done a long dry hop (2 weeks) the beer ended up more bitter than expected. I like to dry hop for only 5 - 7 days now. So back to the IBU data. What portion of the bitterness is isomerized alpha acids and how much is from polyphenols? I bet a significant portion is from polyphenols.

I did a little search and found this for the Hop Research Council Website: (I added the underlining)

Hop Research Council
PO Box 198
Aurora, OR 97002 USA
[email protected]

INFULUENCES OF HOP COMPONENTS ON BEER QUALITY

Dr. Thomas H. Shellhammer, Nor'Wester Professor of Fermentation Science, Associate Professor of Brewing and Food Engineering, Department of Food Science and Technology, Oregon State University, Corvallis, Oregon

Hops play a significant role in beer flavor and quality. Work funded by the HRC in Dr. Shellhammer’s lab focuses on hop components that influence the bitterness quality of beer as well has beer shelf life. The quality of hop bitterness is a subtle but powerful driver of beer quality and contributes significantly to the “drinkability” of the final product.

Bitterness in beer is derived primarily from alpha acid isomerization, which occurs during wort boiling. The alpha acids represent a group of chemically similar compounds, the proportions of which vary greatly depending upon variety. The cohumulone content is varietal dependent and it is often used as a quality index in the selection of existing and new hop varieties. A direct relationship between alpha acid composition and bitter quality is speculative, and anecdotal reports indicate that varieties high in cohumulone lead to an inferior bitter quality in the finished beer. Despite the paucity of scientific evidence, cohumulone levels are still used an index for hop quality. Dr. Shellhammer’s lab has examined the influence of cohumulone level on beer bitterness quality and discovered that this factor has relatively minimal impact on bitter quality.

The influence of hop polyphenol on hop bitter intensity, bitter quality (harshness versus smoothness) and tannin astringency is also being explored by Dr. Shellhammer. In other food systems, monomers and polymers of flavanols elicit bitterness and astringency depending upon their degree of polymerization yet the sensorial effect of these compounds in beer has not been adequately determined. Dr. Shellhammer has investigated bitter quality in addition to temporal bitter parameters (intensity, duration, etc) of hop-derived polyphenols in beer and discovered that these compounds contribute significantly to beer bitterness and the quality of bitter from hop polyphenols may be varietal-dependent.

Due to their antioxidant power, hop polyphenols may also contribute positively to beer flavor stability. While the majority of the polyphenolic content of beer comes from malt, hop polyphenols contribute up to one third of the total phenolic load in beer and therefore cannot be ignored in regard to their effect on flavor stability and quality. Dr. Shellhammer’s lab has demonstrated the positive dose-response behavior of added hop polyphenols toward improving the antioxidant power of beer. This work will continue to investigate the influence of hop polyphenols on beer flavor stability.
Of course, does it really matter? If it tastes bitter, who cares if it is AA or polyphenols. However, I'm a bit of a stickler for scientific accuracy, so if it is not an IBU from AAs, then it shouldn't be called that. The anecdotal evidence seems to indicate that it is a different bitterness than that from the standard AA IBUs, so it deserves to have it's own name. It seems as though the brewing scientists think of then as separate. Hopefully the above research will lead to a better understanding of and an "IBU equivalent" term polyphenol bitterness.
 

MalFet

/bɪər nɜrd/
Lifetime Supporter
Joined
May 31, 2010
Messages
8,632
Reaction score
1,479
Location
NYC / Kathmandu
So back to the IBU data. What portion of the bitterness is isomerized alpha acids and how much is from polyphenols? I bet a significant portion is from polyphenols.
Not to get all nit-picky, but IBUs are a quantification of alpha acids, usually as measured by spectrophotometry. I certainly agree that many other things can impact the perception of bitterness, including phenols, food pairings, and even mood of the taster, but IBUs are all about the alphas baby. :mug:
 

pjj2ba

Look under the recliner
Lifetime Supporter
Joined
Jul 25, 2006
Messages
3,373
Reaction score
230
Location
State College
Perhaps I should have worded that more clearly. I should have said, "What portion of the bitterness is isomerized alpha acids (IBU's) and how much is from polyphenols". To be clear, I am saying the polyphenols taste bitter by themselves so the total bitterness of a beer is a sum of the IBUs from the AA's AND the XYZ's (name needed?) from the polyphenols. That's why I'd like to see the IBU data. Do these late hop addition beers taste a lot more bitter than the measured IBU's indicate? Which would suggest a larger role for the polyphenols in the perceived bitterness in these beers. For a normal hop schedule, the contribution of bitterness by the XYZs would be minimal. For a large late hopped beer they could be a significant portion.

The IBU calculators were developed (and thoroughly tested) years ago for use with a typical old fashioned hopping schedule. I just don't think it makes sense to use the std. IBU calculator for a massive late hopped beer. It is totally different chemistry. It needs it's own calculator - or just a lot of personal trial and error.

A couple years ago I made the Big Brew bitters recipe in honor of Michael Jackson. I can't recall the projected IBU's, other than something moderate. Well the recipe called for dry hopping in BOTH the primary and secondary. I think I ended up with 3 weeks total of dry hopping. This beer ended up way more bitter tasting than could be accounted for by the calculated IBUs for the recipe. I kinda liked it that way though!
 

MalFet

/bɪər nɜrd/
Lifetime Supporter
Joined
May 31, 2010
Messages
8,632
Reaction score
1,479
Location
NYC / Kathmandu
Perhaps I should have worded that more clearly. I should have said, "What portion of the bitterness is isomerized alpha acids (IBU's) and how much is from polyphenols". To be clear, I am saying the polyphenols taste bitter by themselves so the total bitterness of a beer is a sum of the IBUs from the AA's AND the XYZ's (name needed?) from the polyphenols. That's why I'd like to see the IBU data. Do these late hop addition beers taste a lot more bitter than the measured IBU's indicate? Which would suggest a larger role for the polyphenols in the perceived bitterness in these beers. For a normal hop schedule, the contribution of bitterness by the XYZs would be minimal. For a large late hopped beer they could be a significant portion.

The IBU calculators were developed (and thoroughly tested) years ago for use with a typical old fashioned hopping schedule. I just don't think it makes sense to use the std. IBU calculator for a massive late hopped beer. It is totally different chemistry. It needs it's own calculator - or just a lot of personal trial and error.
Right, but unfortunately it won't be possible to do an IBU + XYZ = bitterness formulation either. People have significantly different perceptual sensitivities to tannins/polyphenols, so they might contribute significantly for one person but not for another. Plus, some people perceive tannin astringency as a taste entirely separate from bitterness. Most of the macros and some of the micros measure polyphenols, but unfortunately there's no objective measure for combined "bitterness" in the way that there is for AAs or tannins. Taste panels get used sometimes, but anybody who has ever submitted beers into competitions knows how unpredictable subjective assessments are.

It'd be interesting to find a cheap way to measure and/or estimate polyphenols. My understanding is that the bulk of them actually come from the grain in most recipes. I'm still trying to convince the missus that we really need a spectrophotometer, but not even I can keep a straight face when trying to justify it. :mug:

(P.S. If you'd still like to see the IBU data, it's right there in the article erikpete18 posted.)
 

pjj2ba

Look under the recliner
Lifetime Supporter
Joined
Jul 25, 2006
Messages
3,373
Reaction score
230
Location
State College
I have access to spec's, just don't have the time, at least not while at work and I'm not so motivated to come in on the weekend to try and figure it out. If there were a published protocol then I might be tempted (as long as any reagents weren't too $$)

One could also very accurately follow starch conversion with a spec if you need some more justification :D

Now the question of tannins and bittereness is interesting. I'm a bit curious about the woodsy hops (ie Fuggle and Willamette) and what compounds contribute to those flavors. Do these hops have a higher Polyphenol content? To me, the flavor (bitterness?) of these two is very easy to pick out and really come across as woodsy, almost tea-like. I personally don't like the "flavor" in lighter, non-malty beers and only use them in darker beers where I think they fit nicely
 

MalFet

/bɪər nɜrd/
Lifetime Supporter
Joined
May 31, 2010
Messages
8,632
Reaction score
1,479
Location
NYC / Kathmandu
I have access to spec's, just don't have the time, at least not while at work and I'm not so motivated to come in on the weekend to try and figure it out. If there were a published protocol then I might be tempted (as long as any reagents weren't too $$)

One could also very accurately follow starch conversion with a spec if you need some more justification :D
Huh? Come in to work? It's a back of the envelop calculation. :ban:

Starch conversion is a much more complicated process than isomerization typically is, and likewise some of the maltster specifications (particularly conversion time) don't really go that far in real application. Other specs, particularly maximum extraction numbers, are used all the time with no problem. I suspect this experiment produced results very close to boil-kettle isomerization. At least, the Tinseth numbers match up to these pretty darn well. I guess I don't understand what you mean by "That's why I'd like to see the IBU data." What kind of data do you mean if not isomerization rates?
 

SkinnyShamrock

Well-Known Member
Joined
May 6, 2008
Messages
361
Reaction score
3
Location
Camp Hill, PA
I've been told that alcohol can act as a sort of solvent for alpha acids as well. So in theory, dry-hopping a beer will net you some bitterness. Whether it's a whole lot...that I couldn't tell you.
 

MalFet

/bɪər nɜrd/
Lifetime Supporter
Joined
May 31, 2010
Messages
8,632
Reaction score
1,479
Location
NYC / Kathmandu
SkinnyShamrock said:
I've been told that alcohol can act as a sort of solvent for alpha acids as well. So in theory, dry-hopping a beer will net you some bitterness. Whether it's a whole lot...that I couldn't tell you.
Hmm...interesting. I believe the alpha acids are already soluble, so I doubt it is acting as a solvent. Perhaps it is catalyzing the isomerization? But if that's the case, what's to prevent the alcohol from converting all of the non-isomerized acids? Any chance you have a source?
 

remilard

Well-Known Member
Joined
Nov 19, 2008
Messages
3,654
Reaction score
54
Location
Kansas City
Not to get all nit-picky, but IBUs are a quantification of alpha acids, usually as measured by spectrophotometry. I certainly agree that many other things can impact the perception of bitterness, including phenols, food pairings, and even mood of the taster, but IBUs are all about the alphas baby. :mug:
Actually IBUs are defined directly in terms of the spectrophotometric result but notably both isomerized alpha acids and oxidized beta acids will impact that result.

As for numbers, in addition to Brynildson's, Pelican Pub's Kiwanda Cream Ale is only hopped post boil. You can find the hopping rate and lab measured IBU online.
 

MalFet

/bɪər nɜrd/
Lifetime Supporter
Joined
May 31, 2010
Messages
8,632
Reaction score
1,479
Location
NYC / Kathmandu
remilard said:
Actually IBUs are defined directly in terms of the spectrophotometric result but notably both isomerized alpha acids and oxidized beta acids will impact that result.
Interesting...I'd heard conflicting things about whether the beta acids played a role in measurement, and this probably explains why.
 

rycov

Well-Known Member
Joined
Feb 10, 2010
Messages
1,940
Reaction score
27
Location
conway SC.
I've been told that alcohol can act as a sort of solvent for alpha acids as well. So in theory, dry-hopping a beer will net you some bitterness. Whether it's a whole lot...that I couldn't tell you.
i read this too. don't know if it was on here or in a book
 

devilishprune

Well-Known Member
Joined
Mar 26, 2010
Messages
1,241
Reaction score
15
Hmm...interesting. I believe the alpha acids are already soluble, so I doubt it is acting as a solvent. Perhaps it is catalyzing the isomerization? But if that's the case, what's to prevent the alcohol from converting all of the non-isomerized acids? Any chance you have a source?
I understood that iso-alpha acids are soluble in water/wort, while un-isomerized alpha acids are not. Thus, we can assume that these can be dissolved in beer during dry hopping, but I don't think it would add any bitterness because the acids need to be isomerized to contribute to bitterness, right?
 

MalFet

/bɪər nɜrd/
Lifetime Supporter
Joined
May 31, 2010
Messages
8,632
Reaction score
1,479
Location
NYC / Kathmandu
I understood that iso-alpha acids are soluble in water/wort, while un-isomerized alpha acids are not. Thus, we can assume that these can be dissolved in beer during dry hopping, but I don't think it would add any bitterness because the acids need to be isomerized to contribute to bitterness, right?
Yeah, I think I like your explanation better. I see conflicting things about alpha acid solubility (including on HBT wiki), but this book agrees with what you are saying, and it fits with anecdotal experience. My hunch is that it's not an all-or-none thing. Perhaps alphas are relatively less soluble and iso-alphas are relatively more? This would fit with the experience of the no-chillers: no-chilled beers get more bitterness from a given amount of hops, but not so much more that late additions functionally become early additions. Perhaps a small but non-zero amount of non-iso alphas goes into the no-chill cube, and then these get isomerized over the next few hours.

Then the question becomes about the relative bitterness of alphas and iso-alphas. Does isomerization lead to bitterness because isos are more soluble than non-isos (and thus more end up in the beer), because isos are inherently more bitter than non-isos, or because of both? People present different experiences about the dry-hop bitterness, and this would seem to fit with the idea that a perceived bitterness increase from dry-hopping might be due to things other than isoacids like tannins, etc.
 

devilishprune

Well-Known Member
Joined
Mar 26, 2010
Messages
1,241
Reaction score
15
Good link.

It seems to indicate that both iso-alpha acids and the alpha acids contribute to bitterness, but the alpha acids have less of a contribution because they are less soluble in wort. They ARE very soluble in hexane apparently, but hexane is less polar than ethanol so I would still suspect that dry hopping doesn't contribute MUCH bitterness, but it seems as though it's possible that it could.
 

pjj2ba

Look under the recliner
Lifetime Supporter
Joined
Jul 25, 2006
Messages
3,373
Reaction score
230
Location
State College
Native AA are not very water soluble, and apparently like to stick to any surfaces encountered during the brewing process. Heating them brings about the isomerization and improves the solubility (and get them off the sides of your boil pot)

I was just sent this pertinent reference, hopefully you can access it here.
Isomerization and Degradation Kinetics of Hop (Humulus lupulus) Acids in a Model Wort-Boiling System

There is a nice figure showing iso-AA concentration vs time at different temps. There is data for 90C, but unfortunately not a lower temp.

The person I corresponded with was of the opinion that with late, and dry hop additions, polyphenols will contribute to the overall bitterness of the beer. These would not be accounted for in any IBU calculations

The data I want to see about IBU's is to confirm whether a late hopped beer with a measured level of say 40 IBU's in fact tasted like one of say 60 IBUs (according to a skilled tasting panel). This might help to address the role of polyphenols in contributing to the bitterness. Ideally I'd like to see the IBU's measured by HPLC, as that way it is possible to distinguish between isomerized and non-isomerized AA's, which the spectrophotometer method is not very good at. Actually upon further reading, with a standard spectrophotometer, it is not possible to distinguish between not only AA vs iso-AA, but polyphenols as well as they all absorb light at the wavelength used to measure IBUs. I did come across a reference suggesting the use of fluorescence spectroscopy as this could distinguish all three and wouldn't need to use an HPLC to separate them (which takes more time)

ps. Spec, is lab shorthand for spectrophotometer. As in, "let me put this sample in the spec. and see what the absorbance is".
 

SpanishCastleAle

Well-Known Member
Joined
Jan 5, 2009
Messages
4,339
Reaction score
42
Location
Central Florida
Not sure why I missed this thread and at this point can't add much to it. But after brewing some IPAs with zero bittering hops and all hops added with 15 minutes or less in the boil, and a relatively quick chill, and getting WAY more bitterness than I expected I knew the method I was using (Tinseth) was lacking. You can tweek the numbers in the equations but unless you get a bunch of beers tested you can't be sure how 'right' they are. But just by taste you should be able to tell if you're getting closer.

If I don't do a whirlpool (and in the past I almost always haven't) then I calculate flame-out hops as 'boiled 1 minute'. Like the OP, I knew there was some amount of bitterness added but didn't know how much, so I just made it 1 minute. Doing whirlpools, I usually add a few minutes (depending on how long I whirlpool) to all late addition hops until I get to some predetermined point after flameout, then the rest just get 1 minute. I'm still tweeking a lot here but I'm not a hophead.

I was never comfortable with the assumption that dry hopping doesn't contribute any bitterness whatsoever. It may not be much but if I'm going to go to the trouble of trying to calculate IBUs I want to get as close as I can. I'm just trying to calculate bitterness contributed by the hops, regardless of whether it's from AA, iso-AA, oxidized-BA, polyphenols, etc.
 

devilishprune

Well-Known Member
Joined
Mar 26, 2010
Messages
1,241
Reaction score
15
Epic research success:

http://ir.library.oregonstate.edu/xmlui/handle/1957/3825

This is someone's master's thesis where they assessed whether or not unhopped lager with 14 ppm added alpha acids would have a difference in perceived bitterness. Note that these are NOT alpha acids; also note that the solubility limit is 14 ppm, which is much less than the 100 ppm I saw for iso-AA's in another article.

Quoted conclusion: "Alpha-acids did not contribute significantly to the bitterness of an unhopped lager as validated by a consumer panel. This is particularly important for brewers that dry-hop their beers."

So it appears that dry hops won't give you any more bitterness, even though they're soluble in beer. That isn't to say that higher temperature late additions won't though.
 

Steelers77

Vendor
Joined
Feb 25, 2009
Messages
2,179
Reaction score
128
Location
Janesville, WI
also, there are many examples available, but here is one from Firestone Walker:

Another brewery that has embraced late hopping is Firestone Walker Brewing Company of Paso Robles, California. Brewmaster Matt Brynildson says, “…I brewed a flagship beer at another regional brewery where 95%+ of the IBUs were a result of whirlpool hopping.”

Brynildson goes on to say, “...The fact that there is some isomerization (about 15% in whirlpool versus 35% in the kettle) of alpha acid means that not only hop aroma and hop flavor can be achieved, but also some bittering.”

source: http://www.mrmalty.com/late_hopping.htm
This article was also in BYO a few months back, I'm glad someone quted it.
 

MalFet

/bɪər nɜrd/
Lifetime Supporter
Joined
May 31, 2010
Messages
8,632
Reaction score
1,479
Location
NYC / Kathmandu
Native AA are not very water soluble, and apparently like to stick to any surfaces encountered during the brewing process. Heating them brings about the isomerization and improves the solubility (and get them off the sides of your boil pot)

I was just sent this pertinent reference, hopefully you can access it here.
Isomerization and Degradation Kinetics of Hop (Humulus lupulus) Acids in a Model Wort-Boiling System

There is a nice figure showing iso-AA concentration vs time at different temps. There is data for 90C, but unfortunately not a lower temp.
Heh. That's the article that erikpete18 posted at the start of this thread and that I've been shilling ever since. It's exactly that table I was talking referring to with the back of the envelop calculations. No wonder we weren't understanding each other. It would be nice if the data went lower, but it's a pretty simple logistic plot for what we've got. I suspect that the correlation will break down at some temp, but maybe not.

The person I corresponded with was of the opinion that with late, and dry hop additions, polyphenols will contribute to the overall bitterness of the beer. These would not be accounted for in any IBU calculations

The data I want to see about IBU's is to confirm whether a late hopped beer with a measured level of say 40 IBU's in fact tasted like one of say 60 IBUs (according to a skilled tasting panel). This might help to address the role of polyphenols in contributing to the bitterness. Ideally I'd like to see the IBU's measured by HPLC, as that way it is possible to distinguish between isomerized and non-isomerized AA's, which the spectrophotometer method is not very good at. Actually upon further reading, with a standard spectrophotometer, it is not possible to distinguish between not only AA vs iso-AA, but polyphenols as well as they all absorb light at the wavelength used to measure IBUs. I did come across a reference suggesting the use of fluorescence spectroscopy as this could distinguish all three and wouldn't need to use an HPLC to separate them (which takes more time)

ps. Spec, is lab shorthand for spectrophotometer. As in, "let me put this sample in the spec. and see what the absorbance is".
Ah...I'm missing the lingo. I thought you just meant "specification". I get what you mean now with regards to what kind of data you want to see. I guess where we still differ then is as to whether perceptual "bitterness" is empirically quantifiable. Tannins in particular are just one of those things that some people perceive as bitter and some people perceive as something else completely. It's like that old high school chemistry experiment where you figure out who in the class can taste quinine and who can't.

I've got nothing to back this but anecdotal evidence, of course. To me, tannins just taste bitter, and I could probably lump polyphenols and iso-alpha counts together to quantify bitterness. My wife the wine drinker pulls them out as something else completely. I do some coffee importing/exporting and we run into the same issue there. The various chemical quantifications are of limited value in describing the properties of beans, but all of the attempts to quantify taste-panel findings have always fallen flat thanks to the idiosyncratic palates of even well-trained tasters.
 

MalFet

/bɪər nɜrd/
Lifetime Supporter
Joined
May 31, 2010
Messages
8,632
Reaction score
1,479
Location
NYC / Kathmandu
Epic research success:

http://ir.library.oregonstate.edu/xmlui/handle/1957/3825

This is someone's master's thesis where they assessed whether or not unhopped lager with 14 ppm added alpha acids would have a difference in perceived bitterness. Note that these are NOT alpha acids; also note that the solubility limit is 14 ppm, which is much less than the 100 ppm I saw for iso-AA's in another article.

Quoted conclusion: "Alpha-acids did not contribute significantly to the bitterness of an unhopped lager as validated by a consumer panel. This is particularly important for brewers that dry-hop their beers."

So it appears that dry hops won't give you any more bitterness, even though they're soluble in beer. That isn't to say that higher temperature late additions won't though.
Excellent stuff. I'm still reading through it, but this already clarifies a few things.

* Vanilla alphas are significantly less soluble than iso-alphas, but their solubility is still high enough to be consequential (the numbers here should be able to help no-chill brewers predictably adjust their recipes).

* Non-iso alpha acids are themselves completely non-bitter.

* If dry hopping increases bitterness, it's not because of solubilized alpha acids (though I still wonder if isomerization can happen at room temperature, albeit slowly).
 

SpanishCastleAle

Well-Known Member
Joined
Jan 5, 2009
Messages
4,339
Reaction score
42
Location
Central Florida
* If dry hopping increases bitterness, it's not because of solubilized alpha acids (though I still wonder if isomerization can happen at room temperature, albeit slowly).
Haven't read that link but still curious, could the alcohol aid in isomerization? Or in any other way make dry hopping add some level of bitterness (even if it's from polyphenols).
 

Latest posts

Top