The Art and Science of Hazy Beer

Hazy IPA lit up craft beer nearly two decades ago now. The brewers who cultivated its original brand of intense juicy flavors and aromas, and paired them with its distinctive glowy turbidity, brought on a craze for haze that has lasted, despite — or perhaps in part because of — its controversy. Methods for brewing hazy beers and understanding more about persistent, stable, colloidal haze developed over time, and first by those brewers who experimented.

Especially surprising to its critics (who previously only knew haze as a fault in beer) its technical difficulty, and the nuance of what makes good haze so good, began to emerge. Brewers experimented to refine techniques, observing cause and effect. Then those in the lab started to help consider new issues that all of this brought up. 

The strain most people were using with hazies was British V. Analog strains are known across the industry as London Ale III, 1318, London Fog, Foggy London, etc. It was proving to be a large factor in a successful haze strategy, but exactly how it was helping to create haze had not yet been considered. This is how it started — and how it’s going now — according to Laura Burns, Director of R&D at Omega Yeast. 

Read on to hear about it in Laura’s words below:

How it started

In 2019, I [Laura] joined Omega Yeast to lead the R&D department. One of the earliest projects I initiated was an examination of the different effects of dry hop timing on various fermentation outcomes. One of Omega Yeast’s research scientists and I set up a series of flask fermentations. We had intended to be poking around factors related to hop creep, but, nearly immediately, we came across a striking phenomenon: flasks in the series with some strains ranged from super bright to massively hazy, with changes in dry hop timing alone. 

Many factors are known to impact haze, so, to narrow in on what yeast’s role was here, we developed a protocol of controls, like using the same 2‑row base malt wort across flasks, and keeping the pitch rate, fermentation temperatures and sampling methods consistent.

How it’s going

In order to get to know more about the mechanism in yeast that was behind the haze-positive phenotype (the appearance of haze under certain conditions), we started a couple of breeding projects, that generated hybrid strains.

We crossed British V with a haze-neutral strain to see what would happen with the resulting strains’ haze abilities.

To our surprise, hybrid offspring were split between haze-positive and haze-neutral strains. The pattern of inheritance suggested that the haze-positive phenotype was dominant, and linked to a specific gene. From there we set off on our quest to find that gene, the gene responsible for haze.

We had some signs that it would be pretty straightforward, but it ended up being way more complicated than we had anticipated. The project went down a deep hole of genetics and long-read sequencing data that led us to a gene with a previously unknown function. We named it HZY1.

The HZY1 gene is prone to mutations that involve repetitive DNA resulting in versions of the gene that are anywhere from 580 base pairs to more than 2500. And within any given strain, we found up to 5 different versions of the HZY1 gene. So it wasn’t a straightforward answer which version causes haze, but there was a strong correlation between longer versions of the HZY1 gene and the haze-positive phenotype.

Haze-neutral and haze positive are more of a spectrum than a binary. Haze-positive strains are strong enough in haze-determining influence that they’d be good in a strategy for haze generation. Neutral strains, not so. They are so relatively ineffective at haze contribution that it would be extremely hard to build a successful haze strategy on their backs. 

Some contribute a small degree of haze (think the small amounts of haze in most dry-hopped beers), just not significant amounts. That means when the HZY1 gene is disrupted in every brewing strain we have tested — haze positive or haze neutral — the resulting dry-hopped beers are less hazy.

Uncovering the HZY1 gene was super cool, but it doesn’t directly answer how yeast causes haze in beer, just that both yeast — and more specifically, this gene — are definitely involved. Though we may not know yet exactly how, we have some good hints: 

From looking at the DNA sequence itself, we can see that the HZY1 gene encodes a secreted glycoprotein that is anchored to the cell surface. This is very similar to the FLO genes that encode the cell surface proteins that lead to flocculation, for example..

The HZY1 gene is heavily glycosylated, meaning it’s coated with sugars, and we can detect the Hzy1 glycoprotein in the haze particles that form after dry hopping with haze-positive yeast. 

While at this point, we can confidently say that stable haze shouldn’t rely on yeast cells in suspension, we can see that yeast-derived Hzy1 glycoprotein is doing the trick.

Even if you don’t make hazy beer, you should still care. This haze research isn’t all about making hazies; it has helped us understand a lot about avoiding haze, too: the brewing strains you use have a version of HZY1 that either leads to a small amount of haze or a large amount of haze. 

If you want to make a dry-hopped beer that has brilliant clarity, chances are good that getting rid of HZY1 in your house strain will make that easier. 

We still have more to learn, but we ultimately hope to make the execution of hazy and non-hazy beer more of a science, so that we can provide brewers with more tips, yeast options, and predictability when designing their IPA brands.

If you want a deeper dive into the research, check out our paper.

Laura’s comments above were generated first for the Colorado Brewers Guild as part of their educational content series. Check out their other content, and support your local brewing guilds.