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The Language of Hops: How to Assess Hop Flavor in Hops and Beer

Tim Kostelecky

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Georg Drexler,1 Elisabeth Wiesen,1 Mark Zunkel,1 Sebastian Hinz,1 Alicia Muñoz Insa,1
Victor Algazzali,2 Tim Kostelecky,2 and Christina Schönberger1
1. Joh. Barth & Sohn GmbH & Co. KG, Nuremberg, Germany
2. John I. Haas Inc., Yakima, WA, U.S.A.

ABSTRACT

Hops are the soul of beer, yet not easy to characterize in terms of flavor expression. The aim of this work was to improve the way of describing the flavor of raw hops and hops in beer. In the last 10 years, the hop usage in brewing has changed tremendously. Before then, a subtle to moderate hop aroma achieved with kettle additions was standard. Now, with the importance of dry hopping and the addition of high amounts for hop aroma in the brewing process in general, the need for a uniform hop sensory language is apparent. Many of the new “flavor hop” varieties such as Citra®, Mosaic®, Galaxy™, Mandarina Bavaria, Monroe, or Relax do not allow an accurate evaluation with, for example, only five descriptors, as was done for a long time. If one uses only citrus, floral, hoppy, fruity, and herbal as descriptors, this nowadays is not enough information to assess the aroma and flavor of these intense hop varieties. With the help of flavorists and beer sommeliers, we have developed a tasting scheme for hops and hoppy beers that works with defining intensities for 12 aroma categories and identifying specific aroma attributes. This tasting scheme results in a defined aroma profile for the relevant hop variety or beer. It is meant to help speak the same language about hops so that an easier comparison of hop varieties and hoppy beers in a sensory context is possible.

Keywords: Hops, Flavor, Language of hops, Sensory evaluation, Aroma categorization

 

Differences of Hop Flavors in Raw Hops and Beer

It is well known that the brewing process has a significant influence on the aroma and flavor expression of a hop variety in beer. The main influencing parameters are time and amount of dosage, yeast strain, fermentation parameters, contact time (for dry hopping), and the filtration process. Even the raw hops show different aromas from year to year or batch to batch owing to different growing conditions. These are mainly soil, temperature, precipitation, occurrence of pests and diseases, time of harvest, hop drying and processing, and of course hop and hop product storage. In a previous study, it was shown that only a few days of variation in time of harvest can cause significant differences in hop aroma and taste in a dry-hopped lager (1). The more intense the flavor impact of a hop variety is, and the larger the hop dosing into the beer, the more easily one can detect differences. So it is recommended not only to look at the aroma profile of raw hops but also to evaluate the hop flavors in beer—and, if possible, not only a beer but the beer into which the hops of choice shall be dosed! This means more work but is crucial to get all the relevant information.

Definitions: Aroma and Flavor

Aroma
• Aroma is any property detected by the olfactory system.
• Olfaction is the sensation caused by volatile compounds reaching the olfactory epithelium.
• Odor (=aroma) thresholds can be defined as the lowest concentration of a compound in a certain matrix that is sufficient for recognition.
• Recognition of an odor is the comparison of sensory contacts from the surroundings with similar ones kept and stored in memory.
• Introduction of an odorant above a certain threshold triggers a response to the stimulus (4).

Flavor
• Flavor is the sensation realized when a food or beverage is placed in the mouth, and the overall sensation of flavor is the result of a combination of responses to receptors present on the tongue and in the mouth, throat, and nose (7).
• Flavor is the complex combination of the olfactory, gustatory, and trigeminal sensations perceived during tasting (3).

Aroma Categorization

In other sectors, such as in the wine and food industry, it is common to talk about aromas and flavors with a kind of special language to describe these flavors. But it is difficult to state what the correct number of aroma classes is. Even centuries ago, there were researchers looking at suitable aroma and flavor categorization (6):
• Linnaeus in 1756 was the first to propose a classification of odors based on named plants.
• Henning in 1915 made a system of six aroma classes, for each of which several examples were quoted.
• Crocker and Henderson in 1927 came up with only four classes, including a numerical system for describing these odors.
• Amoore in 1952 used a system with seven odor classes.
• Schutz in 1964 came up with a system consisting of nine aroma classes.
• Wright and Michaels in 1964 used eight aroma classes.
• Zwaardemaker in 1895 used 30 aroma classes.
• Harper in 1968 and Dravnieks in 1978 proposed 44 aroma classes.

It is obvious that it depends on the kind of food you are looking at, or if it is about food in general. There will be no categorization that works for everything.

To set up a suitable aroma categorization for hops, we were supported by a professional perfumer, Frank Rittler. For flavor description and the development of new perfumes, he uses 16 categories (including some examples) (5):
• Floral (rose, terpineol, geranium, jasmine)
• Chypre (patchouli, bergamot)
• Fougère (lavender, tonka bean)
• Ozonic (calone/methylbenzodioxepinone, sea breeze)
• Oriental (vanillin, labdanum)
• Woody (cedar wood, sandalwood, Timberol®)
• Spicy (cinnamon bark, nutmeg, pepper)
• Mint (spearmint, peppermint)
• Herbal (rosemary, mugwort, basil, tarragon)
• Green (galbanum oil, violet leaves, hexenol)
• Gourmande (diacetyl, coffee, Siam benzoin)
• Fruity (benzaldehyde, passion fruit, lychee)
• Citrus (lime, clementine, lemon, lemon grass)
• Camphoraceous (isobornyl acetate, eucalyptus)
• Animalistic (galaxolide, civet)
• Aldehydic (aldehyde C10)

This existing categorization was the basis for us to develop a new one, reworked and adjusted to hop flavors. The number of categories was reduced from 16 to 12. Figure 1 shows these main categories, together with one example for each of a hop variety. These hop varieties are good representatives of and show strong flavors that fit well into the relevant category; for example, the hop variety Mandarina Bavaria has intense citrus flavors.

Descriptors and Further Attributes

The main descriptors already help us define the main aromas and flavors of hop varieties. For a more detailed description, it is necessary to take a closer look at further attributes present in the flavor (Fig. 2). At first glance, there are some attributes that do not remind someone of hops; however, all of these were found in one or more hop varieties available. Intensities of these attributes are rated on a scale of 0–10.

For beer evaluation, additionally other specified attributes can be useful information to describe the overall quality of a hop variety. These attributes are as follows, rated on a 0–10 scale (except ranking and IBU):
• The overall intensity of the hop aroma
• The overall quality of the hop aroma
• The overall intensity of the bitterness
• The overall quality of the bitterness
• Estimated Bitterness Units (IBU)
• Harmony: whether the hop flavor and bitterness fit for this beer
• Quality of body and mouthfeel
• If the tasting is about a comparison of different hop varieties, a ranking that gives additional information is recommended.

The results gained by this kind of hop evaluation can contribute to beer quality in various ways. It may help in new product development to identify a suitable hop variety that fits the flavor profile in the final beer set as one of the targets. Related to this, using a common language for the description of hop variety properties supports a comparison of different beers or different hop varieties used in the same or similar beers or beer styles.

Another significant advantage of a uniform and comprehensive flavor assessment is the possibility of describing beer taste and aroma (including the abovementioned parameters of bitterness, harmony, body, and mouthfeel) in a detailed, more effective way; this can be important with regard to flavor consistency from batch to batch. Because no instrumental methods exist that effectively represent sensory hop flavor in beer, sensory analyses are still the means of choice for hop descriptors and their impact on the beer profile. Complex and costly gas chromatographic methods exist, but they are suitable only for identifying and quantifying single or certain groups of compounds that are not necessarily representative of sensory flavor effects.

The results gained by this new method of hop evaluation can be presented in the form of spider graphs, as text, or some combination—it depends whether one prefers information at a glance or a comprehensive and detailed description (Figs. 3 and 4).

Conclusions

More hoppy beers and new intense hop varieties prompt a more detailed evaluation and description of hop aroma and flavor, both in raw hops and in beers. Setting up this new aroma categorization provides new and more effective hop flavor descriptive options. An important advantage of this new scheme is that a common language is established that enables everyone to describe hop aroma the same way.
Those who are interested in learning how to evaluate and describe hop aroma in beers should consider attending our Hopsessed seminars. Hopsessed is the sensory teaching program of the Barth-Haas Group, set up as part of the Hops Academy.

ACKNOWLEDGMENTS

Many thanks to Frank Rittler and to colleagues on the Technical Sales Support Team.

 

REFERENCES
1. Drexler, G., Bailey, B., Schönberger, C., Gahr, A., Newman, R., Pöschl,
M., and Geiger, E. (2010). The influence of hop harvest date on flavor
stability in dry-hopped beers. Tech. Q. Master Brew. Assoc. Am.
doi:10.1094/TQ-47-1-0219-01
2. Drexler, G., Algazzali, V., Kostelecky, T., Schoenberger, C., Wiesen, E.,
and Zunkel, M. (2016). The language of hops. Poster 171, World Brewing
Congress, Denver, CO. www.mbaa.com/meetings/archive/2016/
Proceedings/Pages/171.aspx
3. International Organization for Standardization. (2008). Sensory analysis—
Vocabulary. ISO 5492:2008. ISO: Geneva, Switzerland.
4. Jelen, H. (2011). Food Flavors: Chemical, Sensory and Technological
Properties. CRC Press: Boca Raton, FL.
5. Rittler, F. (2016). In-house Hop Aroma Workshop. www.thenose.de
6. Theimer, E. T., ed. (2012). Fragrance Chemistry: The Science of the
Sense of Smell. Academic Press: Cambridge, MA.
7. Woods, M. P. (1998). Taste and flavour perception. Proc. Nutr. Soc.
57:603-607.

Corresponding author Georg Drexler graduated from the Technical University Munich Weihenstephan as an engineer in brewing. He was hired in early 2008 by Joh. Barth & Sohn, a member of the Barth- Haas Group, as a technical manager, where he focuses on providing technical support to breweries regarding hop products and their applications. Georg Drexler also lecturers at the Barth-Haas Hops Academy, where hop enthusiasts can increase their knowledge about hops—whatever they are interested in.

Based on a poster presented at the World Brewing Congress (2).

E-mail: Georg.Drexler@johbarth.de

http://dx.doi.org/10.1094/TQ-54-1-0143-01
© 2017 Master Brewers Association of the Americas