A Craft Beer & Brewing Magazine® reader recently asked us the following question:
What are the differences among bittering, flavor, and whirlpool hops? How can a homebrewer do a whirlpool addition?
As little as 5 years ago, brewers primarily used three types of hops additions for making beer: bittering, flavor, and dry hopping. Bittering additions were added early in the boil to provide the bulk of the bitterness needed to balance the beer. Flavor additions were done late in the boil, usually at 20, 15, 10, or 5 minutes from the end of the boil. These were intended to provide more flavor and aroma than boil additions. And finally dry hops were added late in fermentation, not to provide bitterness but to add fresh hops aroma to the beer.
Over the past few years, our knowledge of hops aroma oils and how they contribute to beer aroma and flavor has expanded dramatically. Scientists have isolated dozens of hops oils including myrcene, linalool, gerianol, caryophyllene, humulene, and farnesene. We’ve also learned that these aromatic oils are extremely volatile, which means the bulk of the oils will boil away in as little as 10–15 minutes in the boil. The net result is that we now understand that boiling hops, even for a short period, does not preserve the flavor and aroma we most want to preserve in beer. The former “flavor” additions don’t add much flavor; they primarily contribute bitterness, which of course can be more efficiently done with a bittering addition. Whirlpool and dry-hop additions done below boiling temperatures do a much better job of preserving desirable hops oils.
The net result of this new knowledge is that modern hops schedules for hoppy brews such as IPAs consist of bittering, whirlpool, and dry-hop additions, but not flavor additions. The boil/bitterness addition provides the bulk of the bitterness, and the whirlpool and dry-hop additions preserve the critical aromatic oils.
Whirlpool additions are usually added shortly after flame-out while the wort is still hot (typically at 168–194°F/75–90°C). On a commercial system, these are done in the “whirlpool” system after the boil, which helps separate the wort from hops and grain materials. Homebrewers also commonly refer to “whirlpool” hops as hops added to the wort after the boil but before the wort is chilled. A homebrewer would typically add whirlpool hops to the kettle and let them steep for 10–20 minutes before the wort is chilled and transferred to a fermentor.