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The process of heating the wort to 100 deg. C or higher, causing the wort to boil. Hops are most often added during the wort boil.

Boiling is an important part of the beer-making process. It accomplishes several main tasks:

  1. Sanitizes the wort.
  2. Extracts bitterness, flavor and aroma from the hops.
  3. Denatures any remaining enzymes from the mash, fixing the proportions of wort sugars.
  4. Concentrates the wort by boiling off water.
  5. Allows for coagulation and removal of excess (often undesirable) protein and polyphenol compounds from the wort.
  6. Drives off S-Methyl Methionine (SMM), a natural component of malt, which is the precursor to Dimethyl Sulfide (DMS), a sulfur compound produced during fermentation of beer that has the aroma of cooked or creamed corn.

Hops added at different points provide different qualities:

  • Adding hops early in the boil (typically 60 to 90 minutes before flame-out) extracts bitterness from the hops by isomerizing certain hop resins (mostly alpha-acids).

  • Adding hops later in the boil (typically 15 or less minutes left) extract flavors from the hops.

  • Adding hops extremely late in the boil (typically with 5 or less minutes left) extracts hop aromas.