OnTap Magazine

O  nce all brewers aspired to create crystal-clear beers, free of haze or sediment. Wheat beers and Lambics aside, clarity was a sign of quality. A cloudy beer was considered contaminated, poorly brewed or kept, or simply a mistake. The late 90s was a time of great bitterness – a craze to create ever more off-the-scale bitter beers leading to IPAs in the early 2010s getting juicier. Bitterness was dialled down and later additions of hops with tropical fruit aromas and flavours produced beers that were all the rage. Vermonters from the US northeast coast started crafting juice bombs – beers that were not just hazy, but positively opaque. Demand for new fruity aromatic hop varieties surged as the NEIPA - New England-style IPA - craze exploded. Today’s haze-craze beers are intentionally cloudy by design and although this deliberate haze contributes to the overall taste and mouthfeel, it does affect the beer’s colloidal stability and, consequently, its shelf life. WHAT IS COLLOIDAL STABILITY? Over time the complexes formed by the interaction between proline-rich haze sensitive proteins and polyphenols (tannoids) increase in size and begin to create a visible colloidal haze in packaged and stored beer. The colloidal stability of a beer is the period until the haze value or turbidity becomes unacceptable. As the haze value increases, the colloidal stability decreases, and the beer’s shelf-life is greatly reduced. Hazy beers can present challenges, especially for craft breweries without cellar conditioning facilities, or those lacking filtration kit. Dry hopped hazy IPAs that have not had sufficient cold-conditioning risk developing hop bite or hop burn, an unpleasant spicy bitter astringency that can develop when organic hop material remains in suspension in the beer. These hazy beers have a limited shelf-life and, ideally, should be consumed fresh. Nineteenth century improvements in brewing science, following Louis Pasteur’s work on yeast, flocculation, and refrigeration, at the same time as glass replaced pewter and earthenware as the preferred material for drinking vessels, made beer clarity the focus of brewing attention, such that bright beer became the norm. Yet there is nothing wrong with unfiltered beer. Wheat and oats - known to make beer hazy - have long been used by brewers. Adding yeast to unfinished beer and practices such as kräusening, also contribute deliberate cloudiness. Effectively, haze is turbidity caused by the reflection of light from small particles suspended in a liquid. In beer these particles are typically proteins, polyphenols (also called tannins or tannoids) and yeast, but can also be bacteria, in the case of biological haze, or finings, stabilisers and clarifiers if applied in excess and not adequately removed. The primary cause of colloidal, or non-biological haze, is proteins and polyphenols from malt and hops joining to form complexes large enough to cause visible turbidity. Whilst yeast cells can affect beer clarity, they tend to drop out of suspension over time and are also easily removed by chilling, filtration or by centrifugation. Proteins are important for foam formation and mouthfeel, but also influence haze formation and the beer’s colloidal stability. Proteins originate from brewing cereals as the product of the enzymatic (proteolysis) and chemical modifications that occur during malting and brewing. Polyphenols in the form of tannins, phenolic acids, flavones, xanthohumol and prenylflavonoids, are derived from malt and hops. They influence beer flavour, astringency, and mouthfeel, and have a positive effect on preventing oxidation but can negatively impact colloidal and foam stability which will shorten a beer’s shelf-life. Colloidal haze manifests in two ways: chill haze and permanent haze. Chill haze is reversible since it solubilises and disappears as the beer is warmed to room temperature. Whereas permanent haze, as the name suggests, is there all the time and can develop from chill haze. Here the proteins and polyphenols become covalently bonded producing insoluble complexes. Repeated cycles of warming and cooling over extended ageing periods create an irreversible haze which significantly shortens a beer’s storage life. Other constituents of haze include residual starch, cell wall components such as beta-glucans, and pentosans from barley malt, wheat, and oats, hop resins, and melanoidins formed when sugars and amino acids are heated in thepresenceofmoisture. Less common causes of haze include biological haze caused by bacterial infection and dead bacterial cells, suspended yeast or yeast autolysis through damage or stress, and oxalates in the beer from calcium deficient wort. SO, WHAT EXACTLY IS HAZE AND IS THERE GOOD AND BAD HAZE? COLLOIDAL HAZE OTHER HAZES ontapmag.co.za | Autumn 2024 | 19