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What are hops?

"The hop and the grape" is a phrase which describes the two main families of fermented alcoholic drinks, beer and wine. While the relationship between grapes and wine is plain to see from the colour and flavour, hops play a more complex role in craft brewing. We thought we'd briefly describe what they are and how they influence the brew.

Hops used in beer making are a flower of the plant called the common hop, or Humulus lupulus to give the scientific name. The plant is a cousin of the cannabis plant, but the flowers themselves play no part in the narcotic properties of beer – that's entirely down to the alcohol formed during the brewing process. 

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What do hops do in beer?

Making beer is a scientific process involving four main ingredients (water, malt, hops and yeast). With those four ingredients, hundreds of flavours, colours, ABVs (measures of alcoholic strength) and mouth feels can be created in the brew. The flavour is adjusted by changing the proportions of ingredients, time spent on different processes, temperature, the point at which ingredients are introduced, the variety of grain and hops, where the water is from, and the type of yeast used.

With that said, the hops themselves play the most significant part in the flavour. In this, they have two main effects: bitterness and overall flavour. Because when they are boiled they create soluble alpha and beta acids that become part of the brew, they are responsible for the bitter taste (along with the alcohol). Bitterness is measured in International Bittering Units (IBU); the IBU will often be indicated on craft ale but not usually on mainstream beers. The flavour comes from the unique blend of oils present in each unique variety – extra hops can be added after the boiling process to flavour the beer without adding bitterness. Finally, they have a role in the stability of the finished product as the acids act as a preservative.

Even with this immense range of permutations from four main ingredients, there's still plenty of opportunity to introduce other flavours through additives, be they herbs, spices, minerals, sugars, fruits or any other edible additive. It's why you could drink a different beer every day of your life and never experience the same flavour twice.

How to make beer from hops

Making beer is a multi-stage process, which we've simplified into a brief guide below.


Dried grains (usually barley, wheat or oats) are malted, which means they are steeped in water until they germinate. The germination creates enzymes that will break down the starch in the grain and allow subsequent processes, but the brewer doesn't want the grain to start growing, so they stop the process by heating and drying the mixture. (Not all brewers do their own malting – buying malt is possible.)


The next stage is mashing. Mashing is where the malt is added to warm water, activating the enzymes. They produce a thick, sugary liquid known as wort. The liquid wort is then filtered away from the mash, which is used in the next step. 


In stage three, the hops are added to the wort, and it's all boiled. Boiling the hops makes the sweet wort bitter, although extra ones can be added to the wort after it has cooled down to give more flavour.


The next stage is fermentation. Yeast is added to the wort and quickly starts feeding on the sugars, producing two essential chemicals: alcohol and carbon dioxide. Using additives in this stage gives a signature flavour. In general, ales need a cool ferment for a short time, while lagers need a cold but longer ferment.


The final stages are filtration and storage. Filtration removes the particles, but over-filtration can make the beer too clean for many tastes. Craft beer tends to have less filtration to keep more of the colour and give a pleasant mouthfeel, while mass-market beers tend to be heavily filtered. Finally, the beer is stored in casks, kegs, bottles or cans to be sold and consumed.

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Types of hops

Just as wine has dozens of varieties of grapes, so beer has a wealth of hop varieties to choose from. They can be divided into two types: old world and new world. The old world ones are those from Europe cultivated for centuries. They are subtly bitter and aromatic. New world hops are those grown and cultivated more recently, especially in the Americas. By contrast, they have big flavours and are often compared to strong citrus fruits like grapefruit.

Some of the best known and most widely used hops are Citra, Cascade, Mosaic, Amarillo, Magnum, Centennial, Chinook, Simcoe and Nelson Sauvin. Describing the notes and flavours of just these would run to thousands of words, but they represent a small sample of all the hops used by breweries worldwide. To complicate things further, they are often blended and used at different stages of the recipe to perfect the flavour. Brewdog's Punk IPA, for example, contains Ahtanum, Amarillo, Cascade, Chinook, Nelson Sauvin and Simcoe. These distinct ingredients, alongside Brewdog's unique process, result in an IPA that's good enough to launch a global brewery from its humble Scottish roots.

Every ingredient is essential for a great beer, but the hops give the beer its uniqueness, despite representing a tiny percentage of the final volume. It's a magnificent, complex flower to which every brewery owes its existence. 

Of course no learning process is complete without some hands on experience. So take a look  at BrewDogs great range of craft beer options and taste how hops can make a difference.