I’m not the biggest fan of hop puns. The incredible proliferation of hoppy beer-producing small breweries over the past several years has led to a flood of me-too beer names all clamoring to incorporate “hops” in some awkward fashion. So imagine the horror I felt when attending a symposium where Tim Kostelecky of Barth-Haas, one of the world’s largest hop suppliers, switched to a powerpoint slide listing just about every hop pun name in use. Kostelecky was delivering a presentation on hop varieties to a group of brewers who had converged on Paso Robles this past June. Brewers from as far away as Minnesota (Surly), Indiana (Three Floyds), Michigan (Bell’s), and even Europe (Birificio Italiano, Brasserie de la Senne) were in attendance, along with a collection of Californian brewers. We were eager to learn about new varieties, techniques, and scientific research, as well as discuss our own experiences. Yet as much as I wanted to roll my eyes at the puns, Kostelecky’s infectious enthusiasm for all things hop-related gave him a pass.
Barth-Haas works with growers all over the world to process and deliver hops to brewers large and small, and they also develop new varieties. Technical Manager Georg Drexler flew in from Germany for the symposium, and kicked things off with a presentation and discussion of brewing techniques for emphasizing hop flavor and aroma. Whirlpool and dry hopping have been widely practiced in the American brewing industry for years now, though these techniques have been less widely adopted in Europe, and Germany especially. Up until very recently it was believed that the German Reinheistgebot, also called the “Beer Purity Law,” forbid adding hops after the end of the wort boil, but a recent reinterpetation of the law now allows dry hopping with whole hop products, though not with hop extracts, which can still only be added to boiling wort.
When wort – the malt-sugar solution that is fermented to make beer – is boiled, brewers typically add hops at least two times: once at the beginning of the boil (usually 60-90 minutes in duration) to attain a high amount of isomerization of alpha acids, which adds bitterness to beer, and again near the end of the boil time to provide more essential oil retention, which provides the characteristic flavor and aroma of hops. By the end of theboil, most of the essential oil from the bittering hop addition has been boiled off, and you are left with mostly just the bitterness from the iso-alpha acids in the hops, which have been made soluble by the heat of the boil.
When the wort boil ends, brewers typically whirlpool the wort, either by pumping the wort tangentially back into the kettle, or pumping it into a special whirlpool vessel. The centrifugal forces in the whirlpool cause the solid matter to form a cone in the center, allowing the liquid to be pumped off the side of the vessel. This post-boil step has become a popular time to add more hops in the search for bigger and better hop aroma, as the lack of boiling action allows more essential oil to remain. The wort is usually only a couple of degrees below boiling at this point, and you still lose some lighter oils to vaporization, especially myrcene, which is a big part of the aroma of many IPAs. At the symposium, Drexler went over new research that suggests lower whirlpool temperatures increase oil retention and overall hop aroma. Some brewers, especially homebrewers, are trying this by lowering the temperature to about 170-180 degrees and then adding their hops before resting for about 20-30 minutes and cooling to yeast-pitching temperature. This reduced temperature can be accomplished by either recirculating some of the wort through the heat exchanger and back into the kettle/whirlpool, running and immersion chiller for a short amount of time, or brewing to a slightly higher gravity and blending in some cold water at the end of the boil.
While dry hopping remains the most effective way to get a big hop aroma in a beer, Drexler stressed that hop-focused beers lack complexity when not also given a generous dose of late-boil or whirlpool hops. Hop varieties will always lend a different aroma when added to hot wort than to fermented beer, even with intensity controlled for. The biological interactions of fermenting yeast have the capability to change aromatic compounds from hops, creating wholly different aromas than were present in the wort before fermentation. Some of these compounds, like glycosides, are combinations of hop and malt compounds that are bonded during wort boiling and then cleaved into new compounds by the yeast during fermentation.
At the Bräu Beviale industry convention in Germany in 2011, Barth-Haas conducted taste tests with several single-hop beers, including dry hopped and non-dry hopped versions with German Tradition, American Citra, and New Zealand Nelson Sauvin. Theresults showed marked differences in aromatic impression between the two versions of each variety. The dry hopped Citra beer was the most preferred, while the non-dry hopped Citra beer was fourth, behind the non-dry hopped Tradition beer in second and dry hopped Tradition beer in third. These results can be interpreted in different ways, but they seem to confirm that the big oil profiles being developed in American hops are best expressed through dry hopping, while the noble and noble-derivative hops of Germany best show their classic hop aroma when added to the boil. Poor Nelson Sauvin was relegated to last and second to last place with the dry hopped and non-dry hopped versions, respectively. I suspect that many brewers are still not on board with thepowerful tropical, grassy, and white wine aromas it lends to beer.
While brewers typically dry hop their beers for periods of several days to a couple of weeks, new research suggests that the main hop oils reach their peak concentration in beer in a much shorter amount of time. A 2011 study by Peter Wolfe at Oregon State University tested extraction rates for various hop oils using both whole-cone and pelletized Cascades from that year’s harvest. While pellets generally led to better extraction, peak concentration of most oils was reached in under six hours, suggesting that much shorter dry hop times are possible. The tests were done at 23 degrees Celsius, which is warmer than what most brewers dry hop at, but Wolfe concluded that even at cold temperatures, extraction doesn’t take more than a day.
New hop varieties were a big topic at the symposium, with some of the most exciting new ones surprisingly coming from Germany. The Hüll hop research center has released four new varieties in the last couple of years, all targeted at the bigger, fruitier aromas ofthe newer hops from the US, Australia, and New Zealand. Polaris is a high alpha hop with the highest levels yet of any variety (19-23%), and a correspondingly high oil content. Its aroma is described as floral and minty, with “ice candy” being a popular descriptor. Mandarina Bavaria is a mid-alpha hop (7-10%) with a very fruity aroma of tangerine, pear, orange, and lime. The Barth-Haas guys were very excited about this one and see it as a German answer to American hops like Citra and Amarillo. Hallertau Blanc is another mid-alpha (9-12%) hop that is similar to the popular Nelson Sauvin from New Zealand, with an aroma of tropical fruit, grass, white wine, gooseberry, and grapefruit. Hüll Melon rounds out the new group of German hops, with a lower alpha content of 6.9-7.5%, but a very fruity aroma with a distinct honeydew melon quality.
While Germany is making waves with its new releases, mostly due to how different they are compared to older varieties from the country, New American variety Mosaic was released in larger quantities this past harvest after some limited availability as HBC 369 previously. Mosaic is a high alpha variety (11-13.5%) that is a cross between Simcoe and a Nugget-derived male plant. Its aroma is floral and fruity with the character of tropical fruit, berry, citrus, and pine. Lots of American brewers are experimenting with Mosaic right now so it should be relatively easy to find an IPA or pale ale with it.
Sam Tierney is a brewer with Firestone Walker Brewing Co. in Paso Robles, CA.