Ah, that sweaty scent ...
BY GEOFF GRIGGS
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In last week's column I mentioned Emerson's JP, a beer brewed by Dunedin brewer Richard Emerson as a tribute to his friend and colleague, Otago University brewing scientist, Professor Jean-Pierre Dufour.
The Belgium-born professor passed away in 2007, but writing about him reminded me of an interesting exercise he ran a few years ago. As part of her course work one of Professor Dufour's students had the task of identifying and then creating a vocabulary to describe the aromas and flavours of different hop varieties. To this end she sourced samples of different hops from Germany, England and New Zealand and then arranged for a group of brewers and hop growers to visit Dunedin to spend a day analysing them. I was fortunate enough to be invited to join the panel.
I remember the day very clearly. Having assembled in a classroom at the university we were presented with a series of tiny glass vials. Hop oils are highly volatile and intensely bitter so the samples were dissolved in a liquid medium for us to sniff, but not taste. Sealed with a tight-fitting cap, each vial was identified only by a number. It was our job to sniff each sample in turn and write down the three adjectives which best described what we were sensing.
It was a demanding day's work but the results were most interesting. When the identities of the samples were revealed we found that in almost every case the most identifiable similarities between samples were associated with where they were grown.
Without exception we found samples we had described as "sweaty", "earthy" or "peppery" came from the United Kingdom, while those with a fragrant, woody or polish-like character the words "cedar" and "sandalwood" kept popping up originated in Germany. Meanwhile, New Zealand hops shared a "grassy" or "herbaceous" character not dissimilar to that found in many Kiwi white wines.
The Dunedin research continued along with similar work in Australia and a subsequent report published in the Journal of Agricultural and Food Chemistry said the aromas came from a class of chemicals called terpenes. Wikipedia describes terpenes as "a large and varied class of hydrocarbons, produced primarily by a wide variety of plants", and it is known that they are responsible for the unique aromas of many foods, beverages and perfumes.
The report concluded that five particular terpenes were most prevalent in hops: geraniol, which is named after geranium flowers and has a floral scent; linalool, which is also found in mint, cinnamon and rosewood and has a floral and spicy scent; eugenol, which has a spicy, clove-like aroma; beta-ionone, which has a complex woody and fruity scent; and caryophyllene, which is found in black pepper.
If you want to experience for yourself the differences between hops from different countries, here are a few suggestions for beers that exemplify their regional characteristics: Three Boys Pils or Emerson's Pilsner (New Zealand hops); Fuller's ESB, Fullers IPA or Greene King Abbot Ale (English hops); Epic Pale Ale or Little Creatures Pale Ale (American hops) and Radeberger Pilsner (German hops).
Bearing in mind hop aromas and flavours are the first to suffer as a beer ages, I suggest you try to source the freshest examples possible. Happy tasting! Cheers!
- The Marlborough Express
