Wort Cooling, Clarification, Aeration(book excerpts)
Before the wort can be added to the fermenter it must be cooled to the temperature at which fermentation will start when yeast is pitched. Both the boiling and cooling stages are accompanied by precipitation of solid materials. These are referred to as “hot” and “cold break,” respectively, or “trub,” the German for sediment or clouding. Trub is a heterogeneous complex formed from a coagulation reaction between wort proteins and other nitrogenous components with polyphenols. Wort cooling is accomplished with the use of heat exchangers with high heat transfer efficiency. Typically, the wort is preferably cooled to a temperature of 5 to 15 degrees C (41–59°F) for bottom-fermented beers and to 15 to 18 degrees C (59–64°F) for top-fermented beers before yeast is added to start fermentation. The cool down from boiling must occur aseptically and in a timely manner. As the clear hot wort is cooled, the previously invisible coagulum loses its solubility and precipitates which needs to be removed. Though opinions vary among brewers as to whether or not it is necessary to remove cold break. The wort is then aerated in preparation for the addition of yeast and subsequent fermentation.
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