Just picture this… you’re out at a bar with a few of your friends for happy hour (back when there wasn’t a pandemic happening) and one of them says “mmm my beer has such great hoppy aroma”. Do you nod your head and pretend you know exactly what hops are because you don’t want to be THAT friend that seems clueless? Well if that’s you, have no fear! This article brought to you today will explain the basics of what hops are and why they make beer so magical, unique and awesome.
What are hops anyways? Hops are the flowers of the plant Humulus lupuslus L, which belongs to the family of Cannabinaceae, which also happens to include plants such as cannabis. However, hops do not have any of the crazy properties we usually associate with cannabis (no, you cannot get high from hops). Instead, hops are responsible for many functional properties of beer. Out of all the major ingredients of beer, hops are mostly known to provide the characteristic bitterness of beer, as well as functioning as a preservation method by increasing microbiological stability and increasing the stability of foam. These are all properties that are very important aspects to the modern-day beer that we all know and love.
The composition of hops is fairly complex, which can be seen by how they contain up to 1,000 different organic compounds from many different chemical classes. The main constituents of hops include resins, essential oils and polyphenols. The resin part of the hops is responsible for most of the bitterness compounds, while the essential oil and polyphenols are more responsible for the other flavors and aromas associated with hops. Besides adding a bitter flavor to hops, they can also impart a wide range of other flavors and aromas which can range from floral and fruity to spicy, herbal and woody characteristics. Since there are many varieties of hops that can be grown and processed in many different methods, this means that there are endless possibilities as to how brewers can use hops to craft their own unique desired flavors in their beer.
Although there are many varieties of hops that can be grown, there are two main categories of hops. They can generally be classified as bittering hops or aroma hops, however sometimes hops can be both too. What’s the difference between them? Well bittering hops are usually higher in alpha-acids (aka the main compound responsible for bitterness) but generally lower in other refined flavors and aromas. Meanwhile aroma hops are the opposite, where they are usually lower in alpha-acids and higher in flavors and aromas.
However, when alpha-acids are originally found in the hops flower, they don’t actually have too much of a bitter flavor to them. This characteristic bitterness is developed when hops are added to the wort mixture which is then boiled during the brewing process. This reaction is called isomerization, which converts the alpha-acids to iso-alpha-acids, which are one of the main bitter compounds in beer. Another commonly used name for this compound is isohumulone.
As mentioned already, there are so many different compounds found in hops that make it so complex. This is a great thing which leads to so many possibilities of beer flavors, however it also means that a lot can go wrong during the brewing or beer storage stages which can lead to unpleasant flavors being formed. A big part of the brewer or food scientist’s job is to reduce the amount of undesirable off-flavors produced in the product so that it can reach the consumer in the highest quality possible. Generally, the major contributing factors that lead to the development of off-flavors in beer includes exposure to oxygen, high temperatures and light. When this happens, it will lead to a cascade of chemical reactions that produces unwanted compounds. An example of this is the production of diacetyl or butanedione, which gives an unwanted butter flavor due to contamination by wild yeast or bacteria which reacts with hop compounds. Another example is when a skunk flavor is developed due to a light source converting the iso-alpha-acids to 3-methy-but-2-ene-1-thiol (MBT). So make sure you keep your beer cold and away from direct light sources!
All in all, because of hops, we have beer… an awesome, bitter, hoppy and flavorful beverage that we all love.
Written by: Fiona Kao (U4 Concurrent Food Science/Nutrition Student)
References:
Buiatti S (2010). Beer in health and disease prevention: Beer Composition Overview.Amsterdam: Elsevier/Academic Press. (2009). https://doi.org/10.1016/B978-0-12-373891-2.00020-1
https://beerandbrewing.com/dictionary/VnEcZ72c86/
Bamforth C and Lentini A (2013). Beer: A quality perspective: The flavor instability of beer.Burlington, MA: Academic.
Wunderlich S and Werner B (2009). Beer in health and disease prevention: Overview of Manufacturing Beer: Ingredients, Processes and Quality Criteria. Amsterdam: Elsevier/Academic Press. (2009). https://doi.org/10.1016/B978-0-12-373891-2.00001-8