Hops Under the Microscope

Written by Josh Charig

31 January 2022

Ever since the craft beer boom exploded into our bars and pubs, IPAs and its variations have taken over taps as beer drinkers demand more bold flavours. This pushed the humble hop to rockstar status.

With such a wide range of flavours – from citrus fruits, to wood, to herbal and more – it’s no wonder hops took centre stage. This one ingredient gives brewers so much creative freedom not just from the dozens of varieties, but quantities, when they are added, and in what combination. 

So how does a brewer choose the right one for their beers? It’s quite simple to Google search varieties and see a list of flavour descriptors, but taste is so subjective and often there are discrepancies between different flavour descriptions.

To solve this, hop varieties have data sheets which detail their contents and if we know what we’re looking for, we can get an idea of the characteristics of a certain variety. There’s usually around 20-25 data points which might seem like a lot to consider, but it also includes information about how they grow. When looking at a data sheet, remember that hops (Humulus Lupulus) are a perennial plant which has one growing season per year, and the season’s weather can affect the makeup of the plant.

This is an introduction to a data sheet, and should give a basic understanding of what to look for and what it means. Entire articles can be written about each of the points below, but we’ll save that for another time. 


Alpha acids (AA): This can be seen as potential bitterness. Measured as a percentage of the total weight of the hop, the higher the AA% the more bitterness it can impart to the beer. I say potential, because there are some other factors which affect bitterness, such as time in the boil, boil vigour, water chemistry etc.

Beta acid (BA): Whereas alpha acids add bitterness almost instantly, beta acids take a while to break down and will add bitterness over time. Beers which are stored for a long time and oxidise will lose bitterness imparted from AA. When BAs oxidise, they can add bitterness, however they can also add a harshness to the beer.

Cohumulone: One of the acids which comprise alpha acids, this measures the harshness of the bitterness, and generally speaking the lower the cohumulone the better. It’s measured as a percentage of AAs. One reason Magnum has become such a widely used bittering hop is because it has relatively high AA%, with relatively low cohumulone levels.


Total oil composition: quite simply this is the total amount of oils in the hop measured in ml per 100g. There are up to 1000 different oils present in hops, but we’re interested in just a few of them.

Myrcene: this is what causes that “hoppy” smell in beer. Usually the most “dominant” of the hop oils in both percentage (around 50-80% of total oils) and in aroma. American “C” type hops usually have higher amounts of myrcene and as it’s utilised in the brew will lead to strong citrus and floral flavours. It is very volatile though and won’t survive too long in the boil.

Humulene: this is the spicy and woody aroma, and is found in greater quantities in noble and some British hops. It’s also highly volatile and doesn’t dissolve easily into liquid so not much of it will end up in the final beer. It’s measured as a percentage of total hop oils. Humulene evaporates at 99°C.

Caryophyllene: usually up to about 8% of essential oils, so less than myrcene and humulene, it imparts a black pepper, herbal and spice flavour. Whilst similar in flavour to humulene it’s less volatile, evaporating at 127°C, so is more likely to last longer in the boil.

Farnesene: again found in smaller quantities, farnesene imparts a floral flavour, along with some citrus and woody flavours. It can evaporate at 95°C so may not survive a rolling boil for too long.


Different companies and different growers will put other information on their data sheets and there is no standardised sheet all companies use. There’s usually growing data, something to consider as a homebrewer is whether the plant is high or low yield, the latter could end up being more expensive in times of short supply, or farmers give up growing low yielding crops for more commercially viable high yield varieties. Hops with more pest and disease resistance are more likely to survive years where these become an issue.

Hopefully this will help you choose hops more effectively. We encourage you to experiment with as wide a range as possible as well as learn more about the contents of hops and their rockstar qualities.

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