The “What beer is made from” series is deep dive into beer’s four main ingredients and their impact on its flavour. New to the series? Start here.
It’s time to talk about hops. What are hops I hear you ask?
Hops are the plant that gives beer its bitterness. (They also contribute to beer’s aroma & flavour, too.)
Often called the “spice” of beer, hops give beer bitterness, aroma and flavour.
But they also play a few other key roles, like helping to support a beer’s head of foam and preventing beer from spoiling by inhibiting the growth of bacteria. (This is actually why hops were first used by brewers, as they gave their beers a longer shelf life.)
Hop plants are tall climbing bines that produce small cones with delicate leaves surrounding a resinous core. (Check out the video above for visuals.)
And it’s inside this resinous core where hops’ 2 key components are found: their bittering alpha acids and aromatic essential oils.
Bittering alpha acids
In order to impart bitterness, hops need to be boiled.
Why? Their bittering alpha acids don’t dissolve particularly well. But during the boil, a structural change takes place, forming iso-alpha acids, which can dissolve into beer.
A typical boil usually takes between 60–90 minutes; the longer the hops are boiled, the more bitterness is extracted.
Why is bitterness important in beer? It balances out malt’s sweetness and gives beer a refreshing edge.
Measuring a beer’s dissolved iso-alpha acid content gives us a way to communicate its bitterness level on a scale called IBU, or International Bitterness Units.
It’s important to keep in mind, however, that IBU is a measure of bitterness alone. It doesn’t take into account the level of malt sweetness in a beer, which can impact the beer’s perceived bitterness – 50 IBU will taste very different in an English barleywine versus a best bitter, for example, as bitterness tastes stronger in a weaker beer.
Hops don’t only contribute bitterness though. They also influence beer’s aroma and flavour.
Aromatic essential oils
As hops’ aromatic compounds, the essential oils, are very volatile they dissipate quickly during the boil.
To focus on this aspect of hops’ character – the “spice” – hops will be added late in the boil, just after the boil or once the liquid has cooled completely after fermentation.
Hops added late in the boil, typically the last 15 to 30 minutes, are often called “flavour additions”, as the hops contribute both a bitter taste and bold aroma.
Adding hops after fermentation is process called dry-hopping. It brings out intense hop aroma, but at very high levels, it can make the beer taste slightly grassy and a bit astringent from tannins in the hops.
(Fun fact: the letters DDH on a beer mean that it’s been double dry hopped, or dry hopped twice.)
There are hundreds of different hop varietals, but most hops are classified into one of three groups: bittering, aroma or dual purpose.
- Bittering hops, are used primarily for their high alpha acid content and are added early in the boil.
- Aromas hops are prized for their essential oils and are added late.
- Dual-purpose hops, as the name suggests, bring the best of both.
Hops can be added to a brew in a variety of formats, from whole cones, to pellets, extracts and oils.
Each has its own advantages and disadvantages:
- Whole cone hops are most traditional: the hops are harvested, dried and packaged into big bales. These dried hops are then added directly into the brew. While they deliver a big aroma hit, they can soak up a lot of beer, leading to waste.
- Pelletized hops are dried hops that have been ground up and compacted into small pellets. As there’s less plant material, there’s often less beer absorption and waste. Plus, they save on storage space. But the processing they’re put through can reduce their aroma contribution slightly.
- Finally, extracts or oils have no hop material; they are shelf-stable liquid extracts that directly impart hop bitterness or flavour.
What form is used largely depends on when they’re added into the brew and what flavour impact the brewer is aiming to achieve.
We’ve now talked about the impact of when and how hops are added, but where hops are grown can also have a significant influence on the aromas and flavours they express.
Hops require a certain amount of sunlight per day, so they tend to grow best in specific climates between the 35th and 55th parallel.
This narrow latitude band includes the noted hop-growing regions of Germany, the Czech Republic, the UK and the Pacific Northwest in the USA; along with Australia and New Zealand in the southern hemisphere.
Within each of these regions, hops develop unique aroma and flavour profiles influenced by soil type, rainfall levels, climate and more.
Here’s an idea of how hop traits vary by region:
- German and Czech hops, including those known as noble hops, like Saaz, are described as being floral, spicy/peppery, and perfumy.
- UK-grown hops have herbal and woodsy aromas. Classic examples include Fuggles and East Kent Goldings.
- Finally, US and new world hops from Australia and New Zealand, like Cascade and Galaxy, can burst with aromas and flavours of citrus, tropical fruit, resin and pine.
Historically, brewers would have been limited to the hops that grew locally, hence why certain hop profiles are considered characteristic for certain beer styles.
While both beers have similar levels of bitterness, an English IPA has floral, peppery and orange-like aromas from it’s traditional English hops. While an American IPA tastes more like grapefruit, pine, resin or tropical fruit from the American hops it contains.
As you can see, hop choice can have a big impact on a beer’s flavour profile.
And these days, new hop varietals are continually being developed to introduce even more unique aromas and flavours to beer – everything from melon and berry, to white wine and coconut.
Clearly hops have come quite far from their early use as a preservative! Not only contributing to beer’s bitterness, but it’s aroma and flavour, too.
Now, I know I’ve said in this series that beer is typically made with four ingredients – malt, water, yeast and hops – but that doesn’t stop brewers from adding extra ingredients to change their beer’s flavour, texture or strength.
To close out this series, it’s time to learn more about some of the other ingredients that can used in a brew.