Dry hopping is the process of adding hops to the primary fermenter, the maturation tank, or the casked beer to increase the aroma and hop character of the finished beer. Some brewers believe dry hopping should not be done during primary fermentation because of the risk of contaminating the beer with microorganisms. Dry hopping adds no bitterness to the beer, and any lingering bitterness will dissipate in a few weeks. This is because alpha acids are only slightly soluble in cold beer. It should also be mentioned that a beer that has been dry hopped is also usually late hopped in the kettle. British brewers use this method to give a special hop character to cask-conditioned ales.
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