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Hop Notes PDF Print
Contributed by Hubert Hanghofer   
May 05, 1999 at 12:00 AM

Apart from bittering, hop is capable of imparting aromatic flavors to the final beer. Balancing bittering and aromatic effect is adjusted by the hop boil time. Determining bittering compounds in the final beer are the iso-alpha acids, formed during the wort boil from primary insoluble alpha acids (AA) of the hop resin. Brewers call this process Alpha Acid Utilization. The longer a hopping is being boiled the more iso-AA are dissolved, imparting more bitterness to the beer.

If hop boil time is short or hopping is done right after the end of boil, utilization is low, but a high share of volatile aromatic compounds (hop oils) remains in the wort. Thus hop flavors are perceptible in the final beer. Only selected fine (expensive) Aroma Hops give the required spectrum of flavors! High alpha Bittering Hops are only suitable for basic bittering (long boil). Some beers don't require hop aroma (Stout, Lambic, some wheats) -so hoppings are done near the beginning of the boil. Unfortunately many brewers sacrifice hop flavors in their lagers these days -for profit, I think.

Conclusion:
  1. To adjust bittering it's of great importance to balance the hoppings to the AA rating and exactly keep to the hop boil time!
  2. To obtain a hop aroma that is typically for a certain beer style it's important to use a suitable aroma hop. For brewing my domestic recipes I'm recommending to use one of these varieties: Tettnang, Spalt Select, Hallertauer (particularly Hersbrucker Spätlese), Perle, Saaz, Malling ...and for my friends in USA.: Mount Hood (Thanks to Tom Daniels for sending me some samples. -Excellent hop, clean aroma).
  3. Some aroma hops have an AA rating >5% and thus may even be used for basic bittering. Compared to bittering hops, this gives a cleaner bitter in many cases. Further advantages for homebrewers are that little AA additions can be measured out more precisely and that fewer hop varieties are needed. This in turn may compensate higher alpha rated pricing when buying bigger quantities.
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