Image of the Month: Hops Flower Over 7 million liters of beer are consumed, endless parades are held, delicious specialty foods are consumed, and traditional lederhosen are worn; these are only a few highlights of Oktoberfest, one of the world’s largest festivals. Originating in Bavaria, Germany, the festival also includes rides, bands, brewery tents and of course, commencement by tapping of the first beer keg by the mayor of Munich. What started out in 1810 as the celebration of a royal wedding in Munich, the festival is now celebrated annually and even internationally with multiple countries having their own versions of the festival. Interestingly, one little cone-shaped flower makes this 16 day festival possible. In celebration of Oktoberfest, we decided to explore the importance of the vital hop flowers.
Although hops are largely known for contributing a bitter taste to beer, hops do much more. Hops impart citrus, floral and other fruity flavors to beer, as well as increase the shelf life of beer due to their antibacterial properties. Despite their desired characteristics, hops were not utilized for the first 9000 years of beer brewing. The insoluble bitterness of hops may have made them undesirable to early brewers. Once it was discovered that long boiling periods converts the insoluble hop chemicals to a soluble form and reveals an array of flavors, hop gardens became increasingly popular. The use of hops for dyes, and hop stems for ropes soon minimized; hops were utilized and specifically bred for beer production. Hops now provide varying arrays of bitterness for beer that complement the sweetness of the malt to create refreshing flavors.
The hop flower, Humulus lupulus, is a cone-shaped flower with multiple leaf-like structures known as bracts. Underneath the bracts lie lupulin glands which produce the resins and essential oils that give beer their distinctive taste, aroma, and contributes a preservative effect. Two main acids in hop resins are alpha acids and beta acids. The heat-induced chemical reactions of these acids contribute to the bittering of beer, as well as the antiseptic nature, eliminating growth of undesired bacteria and aiding in the growth of the desired yeast. Once water is boiled with a malted syrup and optional steeped grains, a wort (sugar syrup) is generated. The wort mixture must be cooled down as quickly as possible to avoid oxidation damage and undesirable flavors. Only after this, the solution is transferred to a fermenting vessel where yeast is added to convert wort sugars into alcohol. Unwanted byproducts are eliminated from this mixture by the use of an airlock.
Two main types of hops are Bittering and Aroma, along with two other additions called flavoring and dry hopping. Bittering hops have a greater amount of alpha acids and are added to the boil for approximately one hour. As the boiling time increases, alpha acids isomerize and the beer becomes progressively bitter. The volatile nature of the essential oils in the bittering hops cause loss in their aroma during the long boil. Aroma hops are lower in the alpha acid content and are added towards the last 15 minutes of the boil. Aroma hops, also known as finishing hops, generally impart preferred flavors and aromas to beer. Flavoring hops, another variety of hops, can be added midway through the boil for a specific balance between bitterness and aroma. Hops can also be added to the fermentation vessel during the late portion of fermentation; this is typically known as dry hopping. Dry hopping provides further aromas to the ultimate beer product. The individuality of a particular brew can be attributed to adding various varieties of hops at different times during the boil. Hops are available in numerous varieties including mild, spicy, floral or piney.
The scan above allows us to visualize the minute details behind the bracts of the infamous hops flower and thus further appreciate the complex and precise chemistry behind beer-making and Oktoberfest.
A History . (2015). Retrieved from Oktoberfest Beer Festivals:
Cornell, M. (2009, November 20). A short history of hops. Retrieved from Zythophile: http://zythophile.co.uk/2009/11/20/a
Hops: Anatomy and Chemistry 101. (n.d.). Retrieved from Multiple Organisms:
Indiana Hops Industry on the Rise . (n.d.). Retrieved from Tow Yard Brewing : http://towyardbrewing.com/indiana-hops-
Katz, J. (2014, March 20). Beer. Retrieved from Food Republic: http://www.foodrepublic.com/2014/03/20/beer-geekery-13
-things-you-probably-never-knew-about-hops/ Palmer, J. (1999). How to Brew. Boulder, CO: Brewers Publications.