Colloidal Haze, a type of non-biological haze in beer. Haze in beer can be formed by either of two main factors: biological (bacteria and yeast) or non-biological agents. Non-biological haze can be amorphous (e.g., starch based) or colloidal. Colloidal systems refer to the presence of one substance suspended within another. Beer colloidal haze is generally the result of protein molecules within the beer joining with polyphenols to form molecules large enough to cause turbidity. Colloidal haze can be a chill haze that is present at 0°C (32°F), but solubilizes and disappears at 20°C (68°F), or it can be a permanent haze that is constantly present in the beer. Colloidal haze is considered a quality problem in pilsner beers, which are expected to be brilliantly clear, but a very desirable aspect of Belgian-style white beers. Two strategies can be employed by a brewer to control colloidal haze: decrease the protein level in the beer or decrease the polyphenol content in the beer. There is much more protein than polyphenol in beer. The most common method of physical stabilization is to decrease the protein level by treating the beer with silica gel, which binds with protein and removes it during filtration of the beer. See silica gel. One drawback to silica gel is that it may remove proteins that are responsible for head stabilization; this effect can lead to poor foam formation and retention. Alternatively, removal of polyphenols can also be achieved by the use of polyvinyl polypyrrolidone (PVPP). See pvpp. PVPP is also removed, along with the haze-causing polyphenols, during filtration. However, PVPP is expensive, so recent years have seen an increase in filtration aids that combine silica gel and PVPP at a lower cost. Hazes caused by dry hopping are also colloidal hazes and are caused by polyphenols from the hops combining with protein, oxygen or heavy metals. Dry hop hazes can be difficult to remove, and many craft breweries practicing dry hopping do not bother to make the attempt because colloidal haze has no effect upon beer flavor.

See also clarity, dry hopping, haze, and polyphenols.