Hop Science 101: IPAs and NEIPAs

[Pappers_]

Post Page

Last week we had a virtual BJCP beer tasting workshop, a continuation of our in-person workshops, led by Jeff Whelpley and me. Over twenty folks participated and we tasted Burnt City Brewing’s The Dankening (NEIPA) and Around the Bend’s Villainous (American IPA). Both breweries are a part of the District Brew Yards.

Before getting into the tasting portion of the workshop, to help us understand some of the significant differences between IPAs and NEIPAs, I spent a few minutes going over some basics of hop science. Here are my notes:

Notes for BJCP NEIPA and IPA Tasting Workshop
Intro to Hop Science as it Relates to IPAs and NEIPAs

Resources
John Paul Maye, Ph.D., researcher, technical director at Hopsteiner
Stan Heironymous, journalist and author

1. Hops contribute:
   • Alpha acids
   • Essential oils
2. When alpha acids are isomerized, they provide the traditional bitterness to beers
   • Isomerization is a chemical reaction where one molecule is transformed into another by rearranging its atoms
   • When it undergoes isomerization, the alpha acid humulone is converted into iso-humulone, the compound that gives the bracing bitterness we associate with American IPAs
   • Heat is the catalyst for this reaction – we boil the alpha acids from hops and they become iso-alpha acids
   • No boil hops in NEIPAs, no isomerization, no iso-humulone or iso-alpha acids = reduced bitterness
3. Oils – focus on three kinds
   • Hydrocarbons – specifically myrcene – highly volatile, not very soluble, only perceived when added late in the boil or in dry hopping; myrcene is the most prominent oil in most hop varieties – 50% in Cascase and Simcoe for example
   • Oxygenated Hydrocarbons – more soluble than myrcene and aromatic, includes the compounds geraniol, linolool and citronellol and hundreds more
   • Thiols (sulfur compounds) – very small part of the hops oils but we have a very low perception threshold for them, so thiols can have a significant impact on aroma; thiol compounds have linked to aromas like passion fruit, tropical fruit and sauvignon blanc grapes – typical NEIPA aromas
4. American IPAs
   • Rely on isomerized alpha acids, specifically iso-humulone, for bitterness
   • Rely on essential oils (hydrocarbons and oxygenated hydrocarbons), from dry hopping for aromas
   • The chemistry associated with these beers seems to be well-researched and established
5. NEIPA
   • Hop chemistry in NEIPAs is less well understood and our understanding is evolving
   • Bitterness does not come as much from iso-humulone or isomerized alpha acids because of the emphasis on late hop additions
   • Bitterness comes more from alpha acids and humulone, not iso-alpha acids or iso-humolone
   • Analysis shows a much higher presence of alpha acids and humulone in NEIPAs than in IPAs, but lower levels of iso-alpha acids and iso-humulone, which makes sense because of the lack of boil hops
   • Humulone does provide bitterness but at a lower level, about 60% of the intensity compared to iso-humulone; the bitterness also has a different character, sometimes described as softer
6. Biotransformation
   • NEIPAs rely on dry hopping during active fermentation, unlike IPAs where dry hopping is traditionally done post-fermentation
   • Biotransformation refers to essential oils, specifically oxygenated hydrocarbons like geraniol, linolool and citronellol, being transformed by the yeast and fermentation
   • During biotransformation, yeast metabolize the oxygenated oils into compounds that are floral and fruity – what we describe as juicy
7. Hops and Haze
   • NEIPA haze does not come from yeast, but rather from protein; many NEIPA grain bills have up to 50% high protein grist, such as oats or wheat
   • Some hop compounds, such as alpha acids, myrcene, and beta acids, are kept in solution by protein haze
   • The haze acts as a carrier, solubilizing the hop compounds, protecting them
   • Haze is not stable and when turbidity lessens and the beer clarifies, the hop compounds in solution dissipate
8. Synergy and Masking
   • Combining hops and hopping processes are complex in part because of the concepts of synergy and masking
   • Synergy = two or more compounds interact to create a sensory perception that is different from either independently
   • Masking = a compound suppresses our ability to perceive another compound

 

[Transamguy77]

Thanks for sharing, that’s good info all in one place.

 

[RPh_Guy]

Thiols (sulfur compounds) – very small part of the hops oils but we have a very low perception threshold for them, so thiols can have a significant impact on aroma; thiol compounds have linked to aromas like passion fruit, tropical fruit and sauvignon blanc grapes – typical NEIPA aromas

I want to point out that using copper in your brew system will reduce or eliminate these compounds, especially from any hops added before using a copper chiller.

NEIPA haze does not come from yeast, but rather from protein

Does none of the haze come from hop polyphenols?

 

[VikeMan]

Does none of the haze come from hop polyphenols?

It certainly does.

 

[kevink]

Many of the statements about NEIPAs have been disproven years ago.

 

[stickyfinger]

aren’t all IPAs NEIPAs today? ha ha ha. i’ve forgotten what other IPAs even taste like.

 

[Pappers_]

Many of the statements about NEIPAs have been disproven years ago.

Which exactly? John Paul Maye's study is recent and I heard Stan Hieronymous speak on many of these points less than four months ago.

 

[Pappers_]

I want to point out that using copper in your brew system will reduce or eliminate these compounds, especially from any hops added before using a copper chiller.


Does none of the haze come from hop polyphenols?

I did not know that about copper, very interesting.

As I understand it, yes. But what Maye was getting at was that in his lab analysis of commercial examples of the NEIPA style, the haze was not from suspended yeast but mostly protein. He did not address hop polyphenols, that I saw or remember. His overall point was that the protein haze was not just a visual aspect of the NEIPA, but because it held the aroma compounds, compared to clearer beers.

I don't know a ton about polyphenols, but they also come from malt, correct? And they lend a roughness to the mouthfeel, if I'm remembering correctly.

 

[VikeMan]

As I understand it, yes. But what Maye was getting at was that in his lab analysis of commercial examples of the NEIPA style, the haze was not from suspended yeast but mostly protein. He did not address hop polyphenols, that I saw or remember.

Maye's study showed that the haze was caused by proteins and polyphenols. You can read the abstract here... MBAA TQ 2018 - Hidden Secrets of the New England IPA

 

[Clyde McCoy]

Do you mind providing citations for the claims below? Most of the top producers of this style are not dry hopping during active fermentation (or they are dry hopping at the very tail end of fermentation, after harvesting yeast, not unlike traditional IPAs).

Biotransformation

• NEIPAs rely on dry hopping during active fermentation, unlike IPAs where dry hopping is traditionally done post-fermentation
• Biotransformation refers to essential oils, specifically oxygenated hydrocarbons like geraniol, linolool and citronellol, being transformed by the yeast and fermentation
• During biotransformation, yeast metabolize the oxygenated oils into compounds that are floral and fruity – what we describe as juicy

 

[stickyfinger]

yeah, Janish’s IPA book makes a very strong case for post fermentation dry hopping in NEIPA and many breweries use it if for no other reason than to reuse yeast but also to reduce hop burn and astringency.

 

[VikeMan]

Do you mind providing citations for the claims below? Most of the top producers of this style are not dry hopping during active fermentation.

Biotransformation

• NEIPAs rely on dry hopping during active fermentation, unlike IPAs where dry hopping is traditionally done post-fermentation
• Biotransformation refers to essential oils, specifically oxygenated hydrocarbons like geraniol, linolool and citronellol, being transformed by the yeast and fermentation
• During biotransformation, yeast metabolize the oxygenated oils into compounds that are floral and fruity – what we describe as juicy

Point one is debatable. Points 2 and 3 are covered very thoroughly in Scott Janish's book The New IPA: Scientific Guide to Hop Aroma and Flavor.

 

[Clyde McCoy]

Point one is debatable. Points 2 and 3 are covered very thoroughly in Scott Janish's book The New IPA: Scientific Guide to Hop Aroma and Flavor.

I've been meaning to check this book out.

But I will say, these claims strike me as dubious. Alchemist, Other Half, Monkish, Alvarado Street, Cellarmaker, Russian River (Happy Hops isn't hazy but its flavor profile is NEIPAish), and Lawson's, among many others, harvest yeast before dry hopping.

I think there are many, many ways to make a great IPA, but the claim that "NEIPAs rely on dry hopping during active fermentation," is strongly overstated IMO.

 

[Pappers_]

Do you mind providing citations for the claims below? Most of the top producers of this style are not dry hopping during active fermentation (or they are dry hopping at the very tail end of fermentation, after harvesting yeast, not unlike traditional IPAs).

Biotransformation

• NEIPAs rely on dry hopping during active fermentation, unlike IPAs where dry hopping is traditionally done post-fermentation
• Biotransformation refers to essential oils, specifically oxygenated hydrocarbons like geraniol, linolool and citronellol, being transformed by the yeast and fermentation
• During biotransformation, yeast metabolize the oxygenated oils into compounds that are floral and fruity – what we describe as juicy

I see your point. I'm familiar with NEIPA brewers here in Chicago who add hops towards the latter end of fermentation. But if that isn't prevalent, I stand corrected.

I think our understanding of biotransformation is developing or growing, but with that being said, I think the very brief summary I shared with the workshop is up to date and accurate, but not at all comprehensive. My source for this was Hieronymous, who himself is reporting from others.

If this two sentence summary of our understanding of biotransformation are inaccurate, please let me know.

Again, the context of this was a brief, 5 minute, spoken introduction as part of a tasting workshop. Brief, summarized, accurate and relevent to the distinctions between the two styles we were tasting - that was my goal.

 

[stickyfinger]

i think just saying some people use bio transformation and some don’t is fine. that is true of west coast ipa or NEIPA.

 

[Pappers_]

i think just saying some people use bio transformation and some don’t is fine. that is true of west coast ipa or NEIPA.

I got that. But you don"t have an issue with the two sentences summarizing what biotransformation is, correct? Or am I misunderstanding you?

 

[stickyfinger]

that’s close i think. it’s linalool. i don’t remember the details on which oils get converted to which.

 

[Clyde McCoy]

I got that. But you don"t have an issue with the two sentences summarizing what biotransformation is, correct? Or am I misunderstanding you?

I need to read more on the academic research on this subject, but I think this is one of the most cited studies on biotransformation: Biotransformation of hop aroma terpenoids by ale and lager yeasts

The authors culture ale and lager yeast in the presence of syrup. They feed Geraniol and Linalool and then do gas chromatography–mass spectrometry.

Here's another relevant study: https://pubs.acs.org/doi/pdf/10.1021/jf1000524

https://www.researchgate.net/profil...Brewers-Yeast-in-Dry-Hopped-Wort-and-Beer.pdf
Tendency was shown that higher temperatures at primary fermentation cause increased releases of aroma compounds into the gas phase, which was observed on model fermentations in previous studies. The reversible uptake of β-myrcene by yeast cells, identified in separate test series, was determined as being a highly effective factor decreasing amounts in beer systems. In bottled beers 100 million cells/ml led to decreased amounts of about 98–99 %. It was shown that solvent systems with similar properties to beers (5 % and 10 % ethanolic solution) are inadequate for re-dissolving compounds attached to yeasts. The absorbed amount in yeast therefore cannot contribute to the flavor of beer. Incomplete recovered amounts of β-myrcene even in pure ethanol suspensions indicate that there are strong bonds between yeast cells and the odor compound. Linalool, on the other hand, was not affected by the test conditions used.

With the help of the bubbling water column used for these brewing tests, releases of aroma compounds into the gas phase were confirmed.

no linalool could be detected, which is attributed to the excellent dissolution of this substance in beer

 

[VirginiaHops1]

Who says you even need active fermentation dry hops for biotrans. A big whirlpool(which most NEIPAs employ) will leave plenty of compounds in the wort for whatever supposedly happens during biotransformation.

 

[day_trippr]

Perhaps - but perhaps the warmer WP temperature does something to those fractions/compounds that degrades or even dissipates them, or simply changes the way yeast might affect them later...

Cheers!

 

[VirginiaHops1]

I would give that theory more credence if I noticed that active fermentation dry hopping had some profound impact on my NEIPAs flavor, vs crashing the yeast then doing a big dry hop. But I haven't.

One thing active fermentation dry hopping does do is allow the brewer to minimize O2, if their processes don't allow that after fermentation is complete. So alot of people preferring that method could be doing so simply because their beer is less oxidized, and not because of some enhanced chemical reaction. There's another theory for you

 

[day_trippr]

[shrug] Still, the folks that came up with the idea still do it, presumably for justifiable cause in their minds...

Cheers!

 

[VikeMan]

A big whirlpool(which most NEIPAs employ) will leave plenty of compounds in the wort for whatever supposedly happens during biotransformation.

I don't want to read too much into the word "supposedly," but studies have shown that it happens. (Scott Janish's book makes a good starting point for reading about this, because he cites the studies.) But I think it's fair enough to question how desirable, noticeable, or cost effective it is.

 

[VirginiaHops1]

I don't want to read too much into the word "supposedly," but studies have shown that it happens. (Scott Janish's book makes a good starting point for reading about this, because he cites the studies.) But I think it's fair enough to question how desirable, noticeable, or cost effective it is.

I've seen some of the research. I wasn't doubting something is happening, just that whatever is going on is still not well understood. Hence, why there is still so much discussion about best practices.

 

[Wayne1]

Here is Dr. Maye's webinar on:
Hidden Secrets of the NEIPA

 

[day_trippr]

[...]One thing active fermentation dry hopping does do is allow the brewer to minimize O2, if their processes don't allow that after fermentation is complete. So alot of people preferring that method could be doing so simply because their beer is less oxidized, and not because of some enhanced chemical reaction. There's another theory for you

Except I believe most neipas follow the "bio-hops" with a conventional dry hop.
All of mine do...

Cheers!

 

[couchsending]

Except I believe most neipas follow the "bio-hops" with a conventional dry hop.
All of mine do...

Cheers!

It depends but I would say most of the best ones don’t... unless the hopping load is incredibly high then there are times when a dry hop added at the tail end of fermentation can be beneficial.

There is plenty of “biotransformation” going on all throughout fermentation. All the oils released into the wort during a WP or end of boil addition are being biotransformed by yeast during fermentation (if your yeast strain has the ability to do so).

Sure you can add hops during fermentation and certain compounds will be “biotransformed” however you also run the risk of:

A: Blowing off quite a few of those compounds with Co2 created during fermentation as yell as yeast dragging them out of the beer when they flocc.

B: Creating potential off flavors and aromas caused by extended contact with yeast and hops especially at elevated fermentation temps. Alpha acids can coat yeast cell walls and cause them to explode, releasing their guts into your beer and forming mercaptans. They are rather prevalent in a lot of beers where people are adding a significant hop load during fermentation. Too me they’re disgusting. Some people have different thresholds of perception to them.

C: IMHO creating more “muddy” hop flavors and aromas.

Waiting until after fermentation has come to and end, and either yeast has flocced on its own or soft crashing to drop a significant amount of yeast, then adding dry hops (if you can keep O2 at bay) will result in a much more expressive beer flavorwise and aroma wise. You will get better bang for your buck from the hops. Hop flavor and aroma will be more defined and will IMHO last longer. I also think haze has more stability when adding hops this way. You add “fruity/juicy” hops you’ll get “fruity/juicy” beer. You don’t need “biotransformation”.

If you listen to the Pros that have been making this style the longest. The ones that just make “IPA” that happens to the hazy. The ones that have made this “style” probably thousands of times. They will tell you they’ve tried everything when it comes to dry hopping and have all settled on adding hops after fermentation has completed. I think there’s still some debate on dry hopping at warmer fermentation type temps or colder but generally almost all additions should be done after fermentation has completed.

If you want more “fruity” expression just ferment it warmer. A lot of places ferment both Conan and LAIII at 72 or higher.

 

[ScrewyBrewer]

I prefer to eliminate bittering hop additions in favor of a big whirlpool hop addition, followed by a good sized dry hop addition at the tail end of active fermentation.

 

[VirginiaHops1]

Except I believe most neipas follow the "bio-hops" with a conventional dry hop.
All of mine do...

Cheers!

I've gotten kind of lazy about it lately being quarantined, but for awhile I was listening to a lot of podcasts while in my car or working out. From what I heard, I wouldn't say "most". It was probably like 50/50(rough estimate) of the hazy makers who did fermentation dry hops vs those who did not. And several of the most highly regarded were in the latter group. I'd have to check my notes but I think Monkish and Lawson don't do it. So this isn't some awesome tried and true process the pros have all adopted and us mouthbreather homebrewers haven't caught onto.

My biggest takeaway from listening to all the podcasts honestly was that there were many different methods being used by these guys making great hazys, and I wasn't going to find the blueprint. I was going to need to just experiment and figure out what worked for me on my system.