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Wort Cooling
Formation of Cold Break
As the clear hot wort is cooled, the previously invisible coagulum loses its solubility and precipitates. The precipitate is referred to as the cold break and begins forming at about 60ºC (4). The cold break mostly consists of protein-polyphenol (tannin) complexes, whereas the hot break is mostly proteinaceous. The cold break also has a higher level of carbohydrates (primarily beta-glucans) than the hot break (7). Highly modified malts yield a higher percentage of polyphenols in cold trub than do less-modified malts, while under-modified malts yield more protein and beta-glucans and relatively fewer polyphenols (1).
It is essential that the cold break be precipitated as much as possible, which is done by a very rapid cooling. The wort must be force-cooled to below 10ºC to secure a satisfactory break, and it precipitates best at 0 to 5ºC. Complete precipitation of polyphenol/proteins to achieve a brilliantly clear beer is achieved by cooling the wort until it becomes slushy. Many brewers have found that following this procedure greatly reduces the need for clarification. A long, slow cooling does not give a good cold break because more protein is trapped in suspension; this gives rise to a finer trub, chill haze, and harsh, sulfur-like aftertastes in the beer. Coarse trub is essential for good separation and good beer stability. In addition, a rapid cooling will minimize the development of dimethyl sulfide (DMS), which is more likely, to form when using lager malt. If the wort is reheated, cold trub will go back into solution, forming a chill haze.
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