If you haven’t had a craft beer in the last four years or so, you may not be aware that the Hazy IPA is all the rage. Walk into any craft beer bar today and you will find at least one, but more likely, an entire flight of hazy beer options. In an abrupt face from years of clarity, turbidity is being embraced as never before.
For decades the stamp of approval for many brewers was a nice translucent product, signifying full removal of yeast, and proper conditioning time. This became a virtual necessity to overcome the stigma associated with “back-yard brew”. Only those “in-the-know” were accepting of a few hazy styles, such as the witbier or hefeweizen.
Over the years many people have solicited advice on a variety of topics, but the irony of time is cyclical. At early entry into this industry, I remember having several discussions on hefeweizen and attempting to maintain a stable haze during distribution. Slowly, conversations shifted to lager-like clarity for dry hopped or fruited pale ales, and today we are back to haze stability, albeit primarily in IPAs this time. Not so subtly, the goal posts have moved from colored seltzer water to a glass of orange juice.
Haze (n.) is the optimal descriptor in both primary definitions as it is an obscuration caused by fine particulate, as well as causing a state of mental confusion. In order to combat the latter we will attempt to explain the former. Whether you are “pro” or “anti” haze is irrelevant for the purpose of this discussion. The goal here is conceptual learning, allowing you to implement the information for your own purposes. In a real sense, our perception of haze is the scattering of light by reflection.
Fine particulate is a fairly general term, but in beer this has come to represent two basic categories. With an average size of 3-5 microns per cell, yeast (S. cerevisiae) dispersed in suspension, is the largest impact to clarity. Charged particles including yeast will slowly bind together and, as the mass increases, so will the rate of sedimentation. A single yeast cell may drop about 18cm per day while a group of six cells may drop 72cm per day. Flocculation of yeast is dependent on genetics, but can also be influenced by calcium content, temperature, and mass of individual yeast cells. Once yeast has dropped below about 1 million cells per ml in suspension, you should have no significant visual impact from the yeast. At this point, any visible haze is likely to be light diffusion caused by fine particulate, probably between 2 - 0.5 microns in size. While aftermarket enzymes are available to combat these complexes post production, preventative actions can be taken during the mash and lauter procedures to avoid or encourage haze forming compounds from the beginning.
To avoid getting too deep into Stoke’s Law, Reynolds numbers, or Brownian motion, we will attempt to keep this simple. The smaller a particle is, the longer it will stay in suspension. If it is small enough, it will become colloidal, meaning it is dispersed throughout the substrate homogeneously and will not drop out, filter, or centrifuge. The primary source of these colloidal dispersions are polypeptide-polyphenol complexes formed late in production. It is therefore advisable to remove as much peptide-phenol reactive material as possible through hot and cold break.
Over the course of production, both peptides and phenols are expressed in the wort. They come from both malt and hops, and can be significantly influenced by the yeast. Individually, peptides and phenols are not visible as they are too small for the naked eye. Even as they begin to polymerize, or link together, they will be too small to see directly.
Catechin, as a monomer, is small enough to bind with protein complexes without forming a visible haze. As simple flavinoids (such as catechin) oxidize and begin to polymerize, they become large enough to cross-link proteins. At an intermediate state, you may experience a reversible chill haze. This occurs when there are few protein-polyphenol cross-links and the warming of the liquid allows the agglomerations to be re-solubilized temporarily. As further oxidation and polymerization of the flavinoids continues into tannoids, the size of the agglomerated molecules increases, leading to a permanent haze condition, or sedimentation in the product container.
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