Horticulture

Smelling the Forest (or the Funk) From the Glass

Finally. The week concludes with the mellifluous sound of the pull-back of the metal tab, the tilt of the glass, and the perfumed liquid cascading from one vessel to the next. Deep inhalations prior to imbibing. Ah, the stimulating fragrance from a heavily terpenated (apparently, it is a word) elixir.

You already know that terpenes are staunch contributors to the organoleptic explosion imparted by all of those hazy, juicy, resinous India pale ales (IPAs) so common in today’s craft beer industry. And you may know that myrcene and humulene dominate hop terpene profiles. Much like their cannabis cousins, however, there are many varieties of hops available, and these differ not only in their acid contents (what drives up the International Bittering Units, or IBUs), but also in their terpene profiles, the result of which is a wonderful cornucopia of different notes from pine trees and oranges to the exquisite cattiness of Citra or Simcoe hops or the musty funk of Vic Secret, something I personally cherish. And much like cannabis, it’s been said that 80-90% of the flavor perception of beer begins in the nose. [1]

Terpenes are produced within the lupulin glands of the hop cones. [2] Dried hops often contain 0.5-3% essential oil. [3] Approximately 50 to 80% of hop essential oil is comprised of the monoterpenes α– and β-pinene, myrcene, and limonene, and the sesquiterpenes including α-humulene, β-farnesene, β-caryophyllene, α– and β-selinene, and γ-muurolene. [4] There is also an oxygenated fraction of the essential oil that can include the terpenoids linalool, geraniol, caryophyllene oxide, and farnesol.

With all those lovely terpenes, not to mention a litany of other antioxidant polyphenols, it’s not surprising that hops have been used medicinally for over 2,000 years. [5] Hops are especially known for their anti-microbial properties. In 1158, for example, a German botanist suggested adding hops to other beverages to increase their shelf life. [4] Perhaps this earlier finding marked where Bow Brewery and the East India Trading Company began the tantalizing tradition of adding hops into beers destined for the Far Eastern shores of India. [6] Traditional beers suffered from microbial infestation, obviously making them undrinkable by the displaced British soldiers and other patrons far away from home. These hop additions prevented the microbes from proliferating, and thus, the IPA, thankfully, was born.

Hops are also known for their sedative properties, perhaps from the monoterpenoid myrcene. [7] In fact, the combination of hop extract and valerian presents a common herbal sleeping aid. [8]

American hops are known for being fruity and citrusy, whereas German and Czech hops are known for their spice from sesquiterpenes like α-humulene, β-farnesene, β-caryophyllene. Citra hops, for example, contain higher concentrations of linalool and geraniol, and provide grapefruit, lychee, lime, and passion fruit flavors. [9] During fermentation, geraniol transforms into β-citronellol; this chemical conversion is thought to provide the characteristic lime flavor the hops are known to impart. Researchers measured a higher concentration of linalool in the beer compared to geraniol or β-citronellol; however, additions of geraniol (15 μg/L) and β-citronellol (20 μg/L) enhanced the fruity or citrusy flavors when in the same matrix as the linalool, showing the synergistic nature of the terpenes.

Geraniol is a Citra hop cultivar-specific terpene, and in varieties containing low amounts of geraniol (German aroma hops), β-citronellol concentrations are concomitantly low. The aforementioned sesquiterpene β-farnesene is characteristic of Saaz hops, and their genetic variations. [4] The Australian Galaxy hops contain elevated levels of alpha­– and beta-selinene, but the dominant spicier, woodsy aspects stem from myrcene and alpha-humulene. [10] In Super Pride hops, however, also from Australia, these terpenes comprised nearly 36% of the essential oil, which resulted in these hops revealing more herbal notes.

The point and the beauty of knowing all of this lay in being able to not only craft beer with designed aroma and flavor profiles, but also in being able to enhance certain attributes of your beer with supplemental terpene additions, from dry-hop additions to adding in specific, isolated hop essential oils. Plus, like most things involving terpenes, it’s just cool science, since we can readily relate experimentally from using our organoleptic capabilities. So, the next time you’re deciding what IPA to get, just like you may gravitate to specific cannabis cultivars once you’ve imbibed their bouquets, consider the hops used in creating the beer’s sensory attributes. I’ll bet if you accessed the terpene profiles, there’d be some common themes. And the next time you see Vic Secret on a menu, or Nelson Sauvin hops, as in my all-time favorite beer pictured herein (Nobody’s Robot from Dancing Gnome), get it, especially if you’re into a little musty funk.

Image Credit: Andrew Witchey, Brewmaster, Dancing Gnome Brewing

References

[1] Wolfe, P. “A Study of Factors Affecting the Extraction of Flavor When Dry Hopping Beer”, Oregon State University, Master’s Thesis, 2012. [journal impact factor = N/A; cited by 29]

 

[2] Briggs D. et al. Brewing science and practice, 2004, London: CRC Press. p 900. [journal impact factor = N/A; cited by 669]

 

[3] Eri, S. et al. “Direct Thermal Desorption−Gas Chromatography and Gas Chromatography−Mass Spectrometry Profiling of Hop (Humulus lupulus L.) Essential Oils in Support of Varietal Characterization”, Journal of Agricultural and Food Chemistry, 2000, Volume 48: 1140–1149. [journal impact factor = 3.154; cited by 85]

 

[4] Karabin, M. et al. “Biologically Active Compounds from Hops and Prospects for Their Use”, Comprehensive Reviews in Food Science and Food Safety, 2016, Volume 15: 542-567. [journal impact factor = 8.738; cited by 33]

 

[5] Koetter U. and Biendl M. “Hops (Humulus lupulus): A review of its historic and medicinal uses”, HerbalGram, 2010, Volume 87: 44–57. [journal impact factor = N/A; cited by 23]

 

[6] Bostwick, W. “How the India Pale Ale Got Its Name: A look to the hoppy brew’s past brings us to the revolution in craft beer today”, Smithsonian.com, 2015, Accessed July 16, 2019.

 

[7] Russo, E. “Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects”, British Journal of Pharmacology, 2011, Volume 163: Pages 1344–1364. [journal impact factor = 6.81; cited by 397]

 

[8] Dimpfel W. and Suter A. “Sleep improving effects of a single dose administration of a valerian/hops fluid extract”, Eur J Med Res, 2008, Volume 13(5): 200–4. [journal impact factor = 1.414; cited by 6]

 

[9] Takoi, K. et al. “The Contribution of Geraniol Metabolism to the Citrus Flavour of Beer: Synergy of Geraniol and β-Citronellol Under Coexistence with Excess Linalool”, J. Inst. Brew., 2010, Volume 116(3): Pages 251–260. [journal impact factor = 0.994; cited by 48]

 

[10] Whittock, S. and Koutoulis, A. “The aroma potential of Australian hops”, Institute of Brewing and Distilling Asia Pacific Section 31st Asia Pacific Convention, Surfers Paradise, Australia. [journal impact factor = N/A; cited by 1]

About the author

Jason S. Lupoi, Ph.D.

Jason S. Lupoi, Ph.D.

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