Ingredient basics: Hops
An introduction to hops
Hey brew fans,
The next ingredient I will be discussing is hops – the sexy bit. Hops have made a massive impact on beer, especially over the last decade being at the forefront of the ‘craft beer revolution’. An influx of varieties from all over the globe, primarily from warmer climates, has taken the industry by storm. Flavours of tropical fruit, citrus, pine and resin have become some of the most prevalent within popular beers today. But it’s not just the huge flavour and aroma impact that we have hops to thank for, they also benefit the beer in a number of other key ways. So, let’s get into this introduction to hops, looking at what they are, where they come from and their impact.
What are hops?
Hops are the flowers of a common perennial plant that, similarly to grape vines, grows on tall trellises that the ‘bines’ (rather than ‘vines’) wrap themselves around and climb as they grow. The hop plant, Humulus lupulus, is within the Cannabaceae family alongside the (you guessed it) cannabis plant. In fact, both cannabis and hops share some of the same aroma and bittering compounds. This particular aroma is usually termed as ‘dank’ within craft beer jargon. When we refer to hops, especially as brewers, we’re most likely referring to the ‘hop cone’, rather than the plant itself. The hop cone (AKA the strobilus) is the flowering part of the plant, and this is where all the compounds beneficial to brewing are found. At the base of the cone are the lupulin glands which are made up of a sticky yellow powder, similar in appearance to pollen. These lupulin glands contain the essential oils and resins that brewers most desire from the plant – more on these later. The hop plant is dioecious, meaning that they have male and female flowers on separate plants. It is only the female plant that is used within brewing – sorry lads. The male plant is unable to grow cones but produces a large number of seeds, which can be detrimental to beer. Seeds have a high fatty acid content, the presence of which can cause issues with foam and flavour stability in the final product.
Where are they found?
As I mentioned earlier, hops grown in warmer climates have greatly impacted the craft beer scene. American varieties such as Citra, Mosaic and Amarillo have become some of the most popular hops used today. In recent years we’ve also seen Australian and New Zealand hops used in many hazy/pale styles, giving a bright, zesty burst of fruit. But much like barley, hops are grown in all corners of the globe – even in colder parts. Here in England, we have a rich history of hop growing – especially in the South East. Hops were first grown in the UK in the counties of Sussex, Surrey, Kent and Suffolk. This is where a large portion of today’s UK varieties are still grown, alongside the West Midlands. You may have come across wild hops growing in hedgerows or along fences. Popular British varieties include Fuggles, Brambling Cross, East Kent Goldings and First Gold to name a few. Whereas hops grown in warm climates tend to deliver bold flavours and aromas of citrus, stone fruit and pine, the varieties grown in areas with less sun usually have a more moderate flavour range. British varieties give aromas of milder fruit and earthy and herbaceous notes. Other countries producing large quantities of hops include Germany, the Czech Republic, France, China, Poland and many more.
Wild hops I found growing outside my local!
A quick history of hops
It’s fair to say that in modern times hops are seen as an essential ingredient in almost every beer style. But this wasn’t always the case. Before the widespread use of hops in beer, most were made using a mixture of herbs called ‘gruit’ to give bitterness and flavour. This may have included heather, mugwort, yarrow and horehound to name a few. The first recorded use of hops within beer was in AD822 by the abbot of a Benedictine monastery in Picardy, France. The abbot had outlined the rules for running the abbey which included collecting wild hops to be used in brewing. It wasn’t until the 13th century that hops began to take over from the widespread use of gruit to flavour beer. The use of hops was even the determining factor between the terms ‘beer’ and ‘ale’. The former being produced with hops and the latter without. One big contributor leading to hops’ ubiquitous use in brewing was the discovery of their antibacterial properties. Brewers began to realise that with the use of hops their beers would have a longer shelf life. This was supposedly the origin story behind the infamous IPA. As the story goes, barrels of beer being sent from Britain to India were unable to make the arduous journey without spoiling. Also, the beloved dark porters of London were not as well-enjoyed in the hot Indian sun. This gave birth to the production of paler beers, with much higher hopping rates by the Bow Brewery, resulting in a pale, bitter, high-ABV beer able to withstand the long voyage due to the increased antibacterial properties of the hops. Unfortunately, there’s no real evidence to support this story, and some believe pale ales would have been produced before this period. But what we do know is that some of the compounds present in hops inhibit the growth of certain bacteria, making for an effective natural preservative.
How we use hops
Traditionally, hops were most commonly used in their dried, whole-cone form. Over time growers have found ways to process these cones in order to more effectively concentrate the components important in brewing. The most commonly used type of hop today is the pellet. A variety of different pellets are available but all share the same idea. The whole cones are dried, hammer milled and compacted into small pellets, containing more of the compounds we desire.
The compounds that have the biggest influence are those found within the hops’ lupulin glands – the resins and essential oils.
The resins:
These are broken down into two categories – soft and hard. We’ll just focus on the soft resins as these are the main contributor to the bitterness found in beer. The soft resins are made up of the α- and β-acids. Now, α-acids in their natural state are not that bitter, but it is how the hops are used within the brewing process that unlocks their full potential. The use of hops in brewing is broadly categorised in two ways, either as ‘bittering’ additions or as ‘aroma’ additions. Most commonly hops are added to the kettle (or copper) during the boil stage, i.e. after the grains and water have been mixed together in order to produce wort. When hops are added at this stage, it causes the α-acids present in the hop to isomerise, which changes the α-acids into isomerised-α-acids, making them more soluble and around 10 times more bitter. The longer these hops are boiled, the more of these bitter isomerized-α-acids are produced.
The essential oils:
The components responsible for the aroma characteristics of beer are the essential oils. These volatile compounds make up a very small percentage of the total hop cone, at around 0.5-3% of the total weight but impart a huge range of flavours and aromas. These sensitive oils can easily be lost, especially in the boil as they will be volatilized and driven off. Hence the use of hops later in the process, and at cooler temperatures in order to retain these compounds. Different varieties will have varying levels of α-acids and essential oils, making some more suitable than others depending on the desired outcome. For example, the use of a hop with very favourable aroma potential would be wasted if used at the beginning of the boil, as all aroma compounds will be lost. Whereas a variety with a high α-acid content, and little in the way of aroma compounds, would be best utilised as an early boil addition for its bitterness. To maximise the aroma of a beer, brewers can use the process of ‘dry-hopping’ to add hops during, or post-fermentation directly to the fermentation vessel with minimal levels of bitterness extracted. The small amount of bitterness imparted here is not due to the iso-α-acids, as obviously the temperatures are too low, but instead the α-acids become oxidised. In this method, brewers are able to retain a huge amount of aroma. Good examples of this would be found in beers that have been ‘double dry-hopped’ (DDH).
Effects on beer
We have talked about the main effects that hops have on our perception of how our beers taste and smell. We’ve also seen how hops help our beer to keep fresher for longer. This is through the effects of the α- and β-acids and their ability to inhibit the growth of certain gram-positive bacteria. One effect we have not touched on is their ability to improve the visual aspect of beer. The α-acids found in beer can also contribute to enhancing the frothy head on top of our favourite pint. The hydrophobic α-acids help to hold the foam structure together, enhancing foam stability. Thus they help to create great-tasting beer that lasts longer and looks the part too. No wonder the industry has gone hop-mad!
In the next post, I will finalise this ingredient basics series with an article on yeast. But feel free to let me know of any topics you would like to me cover in the future.
All the best,
Will