Hops are a vine type plant native to North America, Europe and Asia. It is a highly oiled plant closely related to hemp. Hops were first used in beer production in 11th century replacing other bitter herbs like dandelion, marigold and heather. The number of varieties has grown to over 100 now due to extensive breeding programs to increase bittering compounds and resistance to disease.hops on bins

The female plant (or bine) produces cones which contain all the flavour and aroma compounds. Hops have natural preservative qualities helping to protect the beer against unwanted bacteria and this is what made them attractive to early brewers.   

How do they grow?

Hops can grow up to 30 foot tall in one season if they are supported and are generally grown on stringed supports. These supports can then be lowered at harvest time so that the cone from the tall vines can be removed. There are some smaller dwarf varieties which only grow a few feet tall but these will  require more space. They are perennial which means they grow year after year in the summer and die back to the crown in winter.

The main, modern, hop growing regions are America, New Zealand, England, Germany, Czech Republic, China, Poland and Australia. Each region has a variety of different hops but each tends to have quite similar characteristics. 

Traditionally hops were harvested by hand. This required a huge amount of manual labour and would be a cause for a large social event. In England people would travel to the region on special enlisted trains and buses. The whole family would then spend several weeks picking hops and staying in special hop-picker huts.

Modern processing is done mechanically but there are still special celebrations and excitement at hop harvest.

Many breweries brew with the undried green hops to celebrate the new harvest. Green hops should only be used for aroma and late additions as the alpha content is unknown and generally you use 5 – 7 times the amount.

Once picked the hops are dried and then vacuum packed and processed by hop merchants.

Using hops in beer.

Hops contain two resins, which are used in brewing: Alpha and Beta acid compounds.

The quantity of Alpha Acid (usually labelled as %) measures the potential bitterness that can be extracted from the hops. These humulone resins are not soluble in water so require boiling to isomerise them. The longer the boil time the more resins will be dissolved and the greater the final bitterness. Most brewers look for hops with low levels of Cohumulone as this is believed to give a harsher bitterness than other resins so hops like Magnum with high alpha and low Cohumulone levels are favoured.

Beta acid compounds are used to give aroma and they are not isomerised during boiling. They contain very volatile essential oils which are driven off by the steam leaving the boil and therefore tend to be added in the final minutes of the boil or after it’s complete. Dry hopping is also a commonly used method for adding these delicate compounds to the beer.

Brewers add hops at differing intervals during the boil to give the beer different character. Hops added early in the boil time will give bitterness balancing out alcohol flavours to give smoothness to the beer. These bittering hops will give almost no aroma or defining flavour just a bitter flavour. These are usually added at the start of the boil.

Hops are then added later to give flavour and aroma. These tend to be added in the final 30 minutes in several additions depending on the desired character. Another method of adding aroma and flavour is a process called first wort hopping (FWH). This is a very old traditional method which uses a proportion of the aroma hops but adds them into the run off from the mash tun. While the wort is transferring into the boiler, the hops steep and oxidise which allows some of the beta acid compounds to dissolve into the wort rather than being driven off. In blind tests beers produced using this method were found to have a more smooth bitterness and aroma so its definitely worth experimenting with this. Some bitterness is also extracted from these hops but its equivalent to boiling for around 20 minutes rather than the actual longer boil time.

Different types of hops.

Historically hop types were split into two categories, bittering hops and aroma hops. Bittering hops are high in alpha acid but lower in beta while aroma are the opposite. Nowadays due to breeding more and more hop varieties are suitable for both. These are known as dual purpose so the definition of use is becoming less clear.

Although recipes often call for a certain type of hop there are many very similar varieties so often hops can be substituted. There is also a school of thought that dictates that any hop can be used in the bittering as it makes little difference to the overall beer as it simply adds bitterness. If you are substituting alternative hops in the boil then differing alpha acids will need to be accounted for. Beers are usually measured in International Bitterness Units, IBU, which donates how bitter the beer, is. The easiest way to do this is to download some brewing software, which will handle all the calculations for you.

There is a simple formula for determining the weight of hops in grams required to brew to a specified IBU value. This formula assumes a 20% hop utilisation. Some brewers may better this utilisation so adjustments may be necessary.  

the following formula.


Example: You decide to brew 25 litres of Bitter at IBU 35 using Fuggles with an alpha acid content of 5.6%. The calculation is as follows:

(35 x 25 = 875) divided by (5.6 x 2 = 11.2) = 78 grams

The internationally recognised standard for measuring bitterness in beer is the International Bittering Unit, IBU. Most beers fall between IBU 25 and IBU 65 although lots of modern craft brewers are pushing things way beyond this.

Hops react with light and air making them deteriorate relatively quickly. This is also why beers need to be stored in brown/green bottles to avoid the hop particles reacting with light. When this happens it is known as light struck and will cause strong undesirable aromas.

Reputable suppliers will always sell hops in light protective, vacuum sealed packets. In these packets the hops will last for a couple of years but once opened and exposed to air they will dry out and loose the delicate essential oils.

They are usually packed in 100g quantities and many beers require several different varieties so most brewers end up with lots of left over half used packs. If you don’t have the facilities to re vacuum pack them then simply put them in the freezer. This will help maintain the hop character then simply use direct from frozen as required.