A Look at Studies and Experimental Brew

While I can’t say for certain what is causing the haze in NEIPAs, I can say that this is a good-faith effort that has been ongoing for many months, incorporating both brewing experiments as well as hours of reading through the brewing literature to find potential haze forming clues. As of now, it makes the most sense to me that the haze mainly boils down to two key factors: proteins and polyphenols. After discussing the research on proteins and polyphenols below, I did an experimental brew to try and put the information to the test by intentionally brewing a clear NEIPA using 17% oat flour!

Typical haze example of a NEIPA I recently brewed.

Protein and Polyphenol Reaction

It’s been understood in brewing for some time that one of the main causes for beer turbidity levels are associated with the interaction between polyphenols and proteins. Specifically, haze-active proteins that bind to polyphenols contain an amino acid called proline.1 When polymerized (oxidized) polyphenols react with proteins, the bindings between protein and polyphenols are irreversible, resulting in a permanent haze.2 So, the greater the concentration of proteins and polyphenols, the greater the chance of permanent haze.

About 80% of the polyphenols in beer has generally been said to originate from the malt and the other 20% from the hops.3 I would assume that the ratio of polyphenols coming from hops has gone up in recent years as the whirlpool and dry hop additions continue to increase. However, the malt polyphenols have likely stayed about the same or in some cases also increased as some brewers choose to use high protein malts in their NEIPAs. So, if the hopping rate increases (increased polyphenols) and so too does the protein-rich malts, the likelihood of haze from the protein/polyphenol reaction could also increase.

Having had the fortune of tasting at least a hundred different samples of NEIPAs over the past few years, both commercial and homebrew, my biggest recurring complaint in some of the beers is a harsh finish. I think it’s best described as a vegetal bitterness that I would compare to taking a sample straight off of a tank loaded with dry hops. The astringency of the finish in some of these beers, likely caused by an excessive amount of polyphenols, is a result of both the process and the ingredients and may play a role in the haze too.

To put a finer point on this claim, one study found that upon the addition of polyphenols to a base beer, the authors found a haze would form despite seeing 25% of the polyphenolic material dropping out of solution when the additions were on the high end (up to 200 mg/L). This seems to indicate to me that the majority of the polyphenols from dry hopping are likely hanging around in the finished beer because during dry hopping 50-60% of the total polyphenols can find their way into solution.4 Sensory analysis of the higher polyphenol beers in the study also had higher marks for harsh, medicinal, and metallic tastes.5 These descriptors seem to align to my comments above about NEIPAs that may be a victim of over-hopping.

To my palate, what makes a great NEIPA is a smooth and delicate body while simultaneously having an incredible amount of both hop flavor and aroma without a biting bitterness from both the isomerized alpha-acids from the boil or derived either via humulinones or polyphenols from the cold-side via dry hopping. This is a difficult balancing act as you want to add enough hops during the whirlpool for flavor and bitterness, while also leaving room for large dry hop aroma additions. My personal experience has shown that both the whirlpool and dry hopping is necessary as one can’t be compensated by the other. For example, in one beer I chose to skip all hot-side additions, including the whirlpool and instead did a huge dry hop addition (10 ounces per 5 gallons) which resulted in beer lacking both hop aroma and flavor but instead had a lot of vegetal-like bitterness. One hop researcher suggested to me that it’s possible when introducing a lot of dry hops to beer like that, you could potentially be removing beneficial hop compounds via absorption through the hop leafy material as the hops fall and settle out to the bottom of the vessel, suggesting there is a point where less may be more.

This post is about haze though, so I need to get back on track, but I’ll try to make a connection here between haze and vegetal-bitterness. If haze increases as the polyphenols from dry hopping increases, it should be then that two beers made exactly the same, except for different dry hopping regimes (one with more hop material and the other with less) should have a noticeably different appearance. I put this thought process to the test when I brewed two identical beers but altered the dry hopping where one beer received four ounces of Mosaic pellets and the other just two ounces of Mosaic lupulin powder. This is a great test for this theory because lupulin powder has the leafy plant material removed, including polyphenols, where the pellets do not. This could potentially then reduce both the haze contribution by having fewer polyphenols in the beer to potentially bind with proteins as well as reduce the vegetal bitterness that can happen from excessive pellet hopping.

Mosaic Lupulin Powder | Mosaic Pellets

As you can see from the experiment results above, the lupulin powder beer on the left is noticeably less murky than the pellet hopped beer on the right, despite everything else being the same in the two beers. The lupulin hopped beer has more of a nice hop sheen compared to the pellet beer, which looks much more orange juice-like. In terms of this experiment, it does appear then that as the polyphenol concentration increased the haze factor also increased. I should also point out that these two beers also had 22% malted wheat in the grist, which is a high protein malt (more on that below). In terms of the vegetal bite, the pellet hopped beer clearly had more of it than the lupulin powder beer.

Early Dry Hopping

A common practice when brewing NEIPAs is to dry hop early into fermentation (sometimes as early as brew day) to encourage a process called bioflavoring, which is essentially the interaction between the active fermenting yeast and hop compounds. I’ll sidestep the research on bioflavoring for now, but this early dry hopping may be important as it relates to the protein/polyphenol reaction leading to haze. A study that looked at how the protein content in beer changes during active fermentation examined two different strains (WLP001 and KVL011). They found that with both strains, the protein content decreased during fermentation. Likely either degraded proteolytically by yeast or precipitating out with the yeast slurry. Specifically, WLP001 had a decrease of 16% and KVL001 decreased 42%.6

I wonder then if dry hopping early into fermentation is creating a situation where brewers are exposing the extracted polyphenols from the hops to a higher amount of available active proteins in the wort, essentially increasing this polyphenol and protein environment leading permanent haze. It’s also interesting to think that as the experiment above showed, different strains may be leaving more proteins in the finished beer than others. I’m curious if the same study was done with the common NEIPA strains if fewer proteins would be degraded during fermentation by the yeast, which would enhance this protein/polyphenol theory. I wonder too if more proteins are left in the finished beer if this would also play a role in the full mouthfeel of the style. As a side note, I don’t think the mouthfeel is the result purely of dextrins, which I concluded in a recent article.

High Protein (Malted) Grist

I understand the BJCP is currently considering language to create the new official category for New England IPAs, which I hope doesn’t ultimately slow the fun experimentation I’ve seen with the style. Without any specific requirements as to what should or shouldn’t be in the beer at this time, I like to brew them with plenty of protein-rich malts as a part of the grist, which the paragraphs below explain why the malted aspect of grains like wheat may be another factor leading to haze.

A study looking at the haze of beer brewed from a control of 100% malted barley compared to two beers with either 20% and 40% of the malted barley was replaced with unmalted wheat found that the higher the addition of unmalted wheat, the less permanent haze. The beer with 40% unmalted wheat had significantly less permanent haze than the beer with 100% barley. The authors also tested a number of polyphenols in the beer and found that the higher the percentage of unmalted wheat in the beer, the less amount of measured polyphenols were in the beer.7 Do you see a pattern of protein/polyphenol concentration in NEIPAs starting to form?

So what exactly is going on here, if the protein concentration increases when using unmalted wheat, shouldn’t this also increase the chances of haze in the final beer? The authors speculate that due to higher proteolytic activity in malt (breakdown of proteins) the barley proteins are more degraded leading to smaller proteins. The idea is the smaller proteins leads to smaller particles that are more likely to remain in suspension.

It appears that total gluten levels in unmalted wheat may be responsible for this phenomenon of increased proteins leading to fewer polyphenols and clearer beer. Gluten is essentially the general name given to the group of proteins found in wheat and when these proteins are not degraded during malting, they are represented in beer in larger fractions. When a grist is high in unmalted wheat these non-degraded proteins are larger with a higher molecular weight, which means they can more easily precipitate or bind together and drop out of the beer. This is compared to smaller gluten proteins which are more likely to remain in solution from malted wheat. This is backed up by a study that found that the haze intensity of wheat beer depends on the concentration of gluten. At lower gluten levels, the haze increases and at higher gluten levels, a decrease in beer haze is found because gluten proteins have a polyphenol-removing effect.8

This information seems to conclude that using a high percentage of unmalted wheat for example, could slightly help clear up the murkiness in a NEIPA (if that’s a goal), but also reduce the polyphenol content (because gluten proteins have a polyphenol-removing effect), which might not be a bad thing considering the large amount of polyphenols that will also be added during dry hopping. Remember, polyphenols can have a harsh, medicinal, and metallic tastes in large concentrations.

Experimental Brew

Rather than just spit out literature claims to make a case for why NEIPAs may be hazy, I wanted to try and test the protein/polyphenol information and purposely brew a NEIPA that is NOT hazy.

To do this, I tried to keep the process as close to typical for the style as I normally do, that is high chloride water (in this case all chloride) high mash temperature, both malted wheat and oats in the mash, and a very flocculant English yeast strain. I think it’s worth mentioning that most of the NEIPA strains used are advertised as being highly flocculating yeasts, that is they tend to clump together and drop out of beer increasing clarity, which is not happening in these beers! The biggest difference between this experimental beer and what I typically do for the style is 1) dry hopping immediately after or near the tail end of fermentation and 2) substituting the flaked oats with oat flour.

Why Oat Flour?

The choice to use oat flour in a beer I’m hoping clears up is partly influenced by the research and partly a subtle poke to the idea that flour is used in brewing only for generating intentional haze. The mantra for the style is that the haze happens via the process and not by artificially creating haze, like dumping flour into the boil. So, by using lots of flour in this beer, but potentially getting a clear(er) beer, hopefully, I can help show how using flour (during the mash) is not a haze factor as many may think and potentially might have the opposite effect.

Oat flour is made by milling whole grain oat groats9 which is different from quick flaked oats which undergo further processing. Flaked oats undergo kiln toasting and are steamed before being rolled into flakes10, which I wonder might potentially degrade the proteins in the oats similar to malted vs. unmalted wheat (no hard proof on this). Even though oat flour hasn’t been subject to the heat, you don’t have to do a cereal mash as the gelatinization temperature of oat flour was found in the study discussed below to be around 134°F (56°C).

One big benefit to using flour in a mash is the potential for improved efficiency because the flour is essentially a finely milled grain. In my case with this beer, I had six more gravity points than I typically get when using a similar amount of flaked oats instead of flour. As the amount of flour goes up in a mash tun so does the likelihood of a stuck sparge. I avoid this problem by a brew bag liner in my mash tun, which worked, but I did have to maneuver the bag a little to get things flowing at one point (the bag sometimes gets sucked into the cooler valve).

In a study which brewed and analyzed beers made from worts ranging from 10-90% oat flour in the grist showed that not only do high oat flour beers show good fermentability and extract potential, they also had other aspects that might make them good choices for NEIPAs. One such finding was that as the oat flour percentage increased in the beer, the color of the beer decreased. Specifically, when 20% or more of the barley was replaced with oat flour the drop in color was significant going from 12.8 EBC units (20% oat flour) to 8.0 EBC units (90% oat flour). In terms of SRM values, this would be like going from a 6.5 SRM to a 4.0 SRM. In my case for this beer, perhaps a slightly lighter beer will be easier to see through. A Brulosophy experiment also found that a NEIPA brewed with oats was noticeably lighter in color than one brewed without.

As a quick note regarding brewing lighter SRM beers with the NEIPA style, I highly recommend shooting for a low color for one main reason, preventing your hazy beer from looking like dirty dishwater. As you can see from the two images below of previous NEIPAs I’ve brewed, the first beer used 40% raw oat groats and the second had 26% millet as part of the grist (which has been found to produce darker beers than barley beers11 Which one would you rather drink?!

40% Oats Beer

Millet Beer (not oxidized!)

Another haze clearing potential with the oat flour found in the study is that when high amounts of barley was replaced with oat flour, they found larger amounts of unmodified high-molecular-weight proteins were brought into solution and were “extensively degraded by endogenous malt proteases or precipitated during the mashing process.” I understand that to essentially mean that these heavy proteins are dropping out resulting in less final proteins in the finished beer, which of course may result in less protein/polyphenol reactions leading to haze.12

One last thing on oats, a study that examined unmalted oats (not flour) looked at the impact of replacing barley with oats and the impact on total polyphenol content in the beer from the grain. The authors found that as the oats increased as a percentage of the grist, the polyphenols decreased. Specifically, when 20% barley was swapped with unmalted oats there was a 30% reduction in polyphenols and when 40% barley was swapped with unmalted oats there was a 45% reduction in polyphenols.13Combining the two studies, you can see that brewing with oat flour could decrease the total protein in the beer and decrease the total polyphenols, hopefully leading to less permanent haze due to the binding of the two. For those sensitive to high polyphenol beers, perhaps large amounts of oats might also be a way to still dry hop heavily but with less of the harshness due to lower amount of polyphenols being contributed from the malt.


Original Gravity: 1.057
Final Gravity: 1.010
ABV: 6.2%
Water: 100% Reverse Osmosis treated with 1.50 grams/gallon calcium chloride

65% Briess 2-Row
17% Bob’s Red Mill Oat Flour
18% Malted Red Wheat
(Acidulated malt added as needed for mash pH of 5.35)

10 grams Columbus @ 60 minutes
30 grams Eureka for a 15-minute whirlpool @185°F
30 grams Columbus for a 15-minute whirlpool @185°F

WLP030 Thames Valley Ale Yeast @68°F

Dry Hops:
Day 3 of Fermentation: 56 grams Eureka and 28 grams Nelson Sauvin
Day 10 of Fermentation: 28 grams Eureka and 28 grams Nelson Sauvin (purging the headspace with 5 psi while dropping in the hops and left the keg under pressure)
Day 14: Kegged from fermenting 10-gallon keg to 5-gallon serving keg with C02 under pressure with 28 grams Eureka, 28 grams Nelson Sauvin, and 28 grams Columbus (left at room temperature overnight under pressure shaking the keg periodically to speed up extraction)


First of all, this is the first time I’ve used WLP030, which is a White Labs Vault strain I’ve been waiting for which they describe as “very flocculant strain for all things English. Great for porters, stouts and ESBs. Lower ester production than most English strains but creates a bigger mouthfeel than most cleaner strains.14 The description seems to hit most of the NEIPA points. It turns out this strain is incredibly aggressive! In fact, I made a starter the night before brew day and woke up the next day paranoid the yeast was dead because there was no activity in the starter and throughout the brew day I still didn’t see any activity. It turns out the starter completely finished fermenting in less than 8 hours.

One of the main variables I wanted to test in this beers is dry hopping after fermentation to see if that had an effect on clarity, which to my surprise was at day three of fermentation with this strain! I’m curious if this was unique to me or if others have experienced extremely fast fermentations with WLP030? If this is typical for the strain than it is definitely a great yeast to get a beer from grain to glass in about a week if that’s a goal.

Well, in terms of clarity, I actually brewed hoppy beer I can see through! Granted, this isn’t the kind of clarity you’d see in something like a Pilsner, but compared to a typical NEIPA that can be almost murky, this is definitely much clearer.! The picture below is after about a month in the keg, it was slightly hazier during the first few weeks but did begin to drop (semi) clear, which I’ve never had happen in other NEIPAs I’ve brewed. It does appear that trying to reduce the total protein in the beer combined with dry hopping after fermentation does appear to produce a less murky beer, perhaps giving weight to the protein/polyphenol theory. I’m curious what this would have looked like if I would have used just lupulin powder or even a 50/50 split with powder and pellets to reduce the polyphenol content and potentially having an even clearer beer. Likewise, with the research saying that malted grains might negatively impact clarity, I’m curious what swapping the malted wheat portion of the grist with flaked wheat would have done. With WLP030, you might have to add your hops on brew day to get the murky haze look of most NEIPAs because of how aggressive it is.

Here’s another picture in a glass that shows off clarity better.

In terms of taste and aroma, which almost seems irrelevant to this post, the beer is no surprise, extremely dank. Eureka, Nelson, and Columbus combine to produce a very green and dank, slightly sweaty and oniony aroma. I’m sure this aroma bouquet might be a turnoff to some, but I was curious what combining such dank hops might do in combination. It’s not my favorite combo and likely not one I’ll be using at Sapwood Cellars. The beer could definitely use a more fruit-forward variety to cut down on the greenness of the trio. There’s a bit of a cherry note struggling to come through, but overall just a dank sweaty beer. There is also a little too much of that vegetal bitterness I complained about earlier in the post, it seems that (at least with these hops) eight ounces of loose dry hops in a 5-gallon batch may be too much for my tastes.

Final Thoughts

  • When polymerized (oxidized) polyphenols react with proteins, the bindings between protein and polyphenols are irreversible, resulting in a permanent haze.
  • Dry hopping will likely result in approximately 50-60% of the total polyphenols from the hops finding their way into the beer.
  • Sensory analysis of high polyphenol beers had high marks for harsh, medicinal, and metallic tastes.
  • Lupulin powder is a great way to introduce desired hop compounds without the polyphenols and vegetal matter of pellets, potentially giving beer greater clarity.
  • Dry hopping early during active fermentation may result in more haze, potentially because polyphenols are reacting to a greater concentration of proteins while fermentation is in the early stages.
  • The higher the percentage of unmalted wheat in the beer, the fewer measured polyphenols, likely from gluten proteins removing them.
  • When a grist is high in unmalted wheat these non-degraded proteins are larger with a higher molecular weight, which means they can more easily precipitate or bind together and drop out of the beer.
  • Mashes high in oats will likely have fewer polyphenols, lighter color, and more precipitated proteins.
  • Since this was the first time using WLP030, I’m curious how the results would compare to a more traditional NEIPA strain like 1318 in terms of clarity.
  • I’m certainly not trying to say proteins and polyphenols are the only contributor to haze in NEIPAs, but it does seem logical that it’s a major factor. I’m open to other variables contributing as well, like yeast in suspension, but I haven’t seen any literature yet that would explain why dry hopping during early fermentation would cause this. I look forward to learning more as the style continues to grow and is tested!


  1. Asano, K., Shinagawa, K., and Hashimoto, N. Characterization of haze-forming proteins of beer and their roles in chill haze formation. J. Am. Soc. Brew. Chem. 40:147-154, 1982.
  2. L. Mélotte, INBR, UcL, XIIIth J. DE CLERCK CHAIR, September 2008
  3. Knorr, F., Brauindustrie, 1977,62, 1017.
  4. Forster, A., & Gahr, A. (2013) On the fate of certain hop substances during dry hopping. Brewing Science, 66, 93-103.
  5. S. (2008). Bitterness-Modifying Properties of Hop Polyphenols Extracted from Spent Hop Material. Journal of the American Society of Brewing Chemists. doi:10.1094/asbcj-2008-0619-01
  6. Berner, T., Jacobsen, S., & Arneborg, N. (2013). The impact of different ale brewer’s yeast strains on the proteome of immature beer. BMC Microbiology, 13(1), 215. doi:10.1186/1471-2180-13-215
  7. Depraetere, S. A., Delvaux, F., Coghe, S., & Delvaux, F. R. (2004). Wheat Variety and Barley Malt Properties: Influence on Haze Intensity and Foam Stability of Wheat Beer. Journal of the Institute of Brewing, 110(3), 200-206. doi:10.1002/j.2050-0416.2004.tb00203.x
  8. Ambiguous Impact of Wheat Gluten Proteins on the Colloidal Haze of Wheat Beers. (2003). Journal of the American Society of Brewing Chemists. doi:10.1094/asbcj-61-0063)
  9. http://www.bobsredmill.com/whole-grain-oat-flour.html
  10. https://en.wikipedia.org/wiki/Rolled_oats
  11. Agu, R. C. (1995). Comparative study of experimental beers brewed from millet, sorghum and barley malts. Process Biochemistry, 30(4), 311-315. doi:10.1016/0032-9592(95)87039-3
  12. Schnitzenbaumer, B., Kaspar, J., Titze, J., & Arendt, E. K. (2013). Implementation of commercial oat and sorghum flours in brewing. European Food Research and Technology, 238(3), 515-525. doi:10.1007/s00217-013-2129-0
  13. Schnitzenbaumer, B., & Arendt, E. K. (2013). A comparative study of oat (Avena sativa) cultivars as brewing adjuncts. European Food Research and Technology, 236(6), 1015-1025. doi:10.1007/s00217-013-1965-2
  14. https://www.whitelabs.com/yeast-vault
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