Yeast and Haze

The last two decades have witnessed a sea change in brewer and beer consumer perception of haze. In the US especially, craft beer drinkers have come to appreciate and even expect to see haze in beer. There is even evidence that haze contributes to the aromatic qualities of hoppy beer by solubilizing hydrophobic components of hops. In some beer cultures, however, haze is viewed as the enemy. 

For example, patrons in English pubs have been known to send back a cloudy pint drawn from a cask, and German lager brewers often strive to achieve brilliant clarity without filtration for most of their beers. 

Much of our understanding of beer haze revolves around chill haze and permanent haze.

Now that we are looking closely at haze, rather than trying to excise it, how do we embrace and perfect it?

When we talk about the haze in hazy IPA, we’re referring to something closer to the permanent variety of haze— that milky haze that seems to magically appear when buckets of hops are added to the fermentor during fermentation. One popular belief is that this type of beer haze occurs as a result of interactions between malt proteins and hop polyphenols. It’s truly a​“Goldilocks” scenario: if the protein-polyphenol complexes become too large, you get colloidal instability, or what look like fish food flakes swirling around, creating a snow globe effect and resulting in sludge at the bottom of the can. If the protein-polyphenol complexes are too small, they won’t obstruct light and the haze will be minimal. 

Brewers have explored all sorts of methods for manipulating haze, and much of this focus has been on what can be contributed from malt and hops. For malt, increasing protein content by using wheat and other high-protein adjuncts, as well as beta-glucan content from oats, have proved to be a part of the haze equation. Dry hopping is another piece, with the leading theory being that hop polyphenols play an important role in haze development, which is one reason why we tend to associate styles like NEIPAs with haze.

There’s lots of talk about how ingredients and process can affect haze, but we want to focus on how yeast can affect haze. Our go-to terminology includes ​“haze-positive” to signify strains that could be used to promote haze in a beer recipe and ​“haze-neutral” for strains that don’t seem to have much, if any, effect on haze. We got here by running experiments using various strains and subjecting samples to dry hopping at different intervals: knockout, day 1, day 2, and so on all the way up to day 7. 

Key points from these experiments: 

• Earlier dry hop timing could be a method of removing haze. Flasks with knockout dry hops tended to clear up the sample (and this is true for both haze-positive and hazeneutral strains). 
• Mid-to-late dry hopping promotes haze, in combination with haze-positive strains. Certain varieties of hops create more haze than others (Galaxy, for example). 
• Haze is NOT related to flocculation there are examples of low flocculating yeast that are haze-positive and some that are haze-neutral. In other words, the haze in hazy IPA is not a result of yeast in suspension. 
• More dry hops means more haze. The amount of haze was correlated with the size of the dry hop load.

These strains can be made to deliver consistent high levels of haze pretty easily (haze-positive):

• British Ale I
• British Ale V
• East Coast Ale
• Hefeweizen Ale I
• Irish Ale
• Kolsch I
• Kolsch II
• Voss Kveik
• Scottish Ale
• West Coast Ale II
• Point Loma (aka West Coast Ale III)

Beers made with these strains need coaxing to get a final beer with a good hazy outcome (haze-neutral), including relying on haze from other sources:

• Bayern Lager
• Extra Special (aka British Ale VIII)
• DIPA Ale (aka Conan)
• French Saison
• German Lager I
• Lutra Kveik
• Tropical IPA
• West Coast Ale I (Chico)

Late-fermentation dry hopping will definitely help promote haze. Timing your dry hop to be at the tail end of fermentation — when the yeast is still pretty active — can also be a strategy for mitigating hop creep.