If you’re reading this, I can probably assume you have a passing knowledge of beer and are therefore vaguely familiar with what hops are and what their role in beer is. So, here’s a slightly more in depth (albeit still very brief) look at hops and how brewers use them.
Hops primarily have two functions in brewing; the first is for bitterness, the second is for flavour and aroma. Both of these functions come from using the hops at different stages of the brewing process, and in different ways to yield different results.
Hops have been cultivated for centuries to be used in beer, but still can also be found growing wild too (I’ve even seen some growing in an abandoned house’s front garden in South London before). Today, there are over one hundred hop varieties, each promising its own unique set of characteristics. The reason why hops impart the traits that brewers seek comes from underneath their little green leaves (bract). There are tiny sacs (see below) that resemble pollen called lupulin glands that are filled with oils and acids. Using hops in a brewery is therefore simply a process of bursting those little sacs to access what’s inside. Simple enough for the most part however, depending on a wide range of factors, how and when a brewer does this can have drastically different outcomes on the final beer.
The acids (notably alpha acids) impart bitterness into beer when added to the wort (unfermented beer) above temperatures of 79°C. The closer to boiling this temperature is, and the longer the hops are held at this temperature, the more the alpha acids are isomerised and will thus be perceivable as bitterness. Not only this, but different varieties of hops have different amounts of alpha acids in them (ranging from around 2% w/w to over 20% w/w). Brewers add hops to wort when it is boiling to get bitterness from the hops as the hot temperature most efficiently extracts bitterness. The physical movement of a boiling liquid helps burts the lupulin glands too.
The oils in the lupulin glands are where the flavour and aroma comes from. There are many types of oil to be found in hops, each with its own flavour and aroma. When you are seeking out a beer with a certain hop, you are essentially looking for the combination of oils that one particular hop promises. Unlike the acids, the oils don’t need to be heated to be extracted and dissolved into the beer; in fact at high temperatures the oils can be driven away from the beer. So, when a brewer adds hops to hot wort, there is a balancing act between how much bitterness is needed, and how many flavours and aromas are needed to be retained. For this reason, there are normally multiple additions when the wort is being boiled. As consumers’ appetites for hoppy beers have grown, breweries now often implement an addition after the wort has been boiled and cooled a little, (called a whirlpool or flameout addition depending on the method). This is so more hoppy notes can be packed into the beer without making the beer overly bitter.
If a brewer wants to solely add flavour and aroma with a minimal bitterness contribution, the best way to do it is via dry hopping. Dry hopping is not dry at all, it is simply the process of throwing hops directly into fermenting or recently fermented beer. This is normally done between 12-20°C depending on the brewery, and can be as simple as throwing a bucket load into a fermenting vessel, or it can be done with far more sophisticated machinery. To assist with bursting the lupulin glands, hops are often processed into pellets; one of the many benefits of pellets is the oils are exposed and more easily dissolved into beer.
Brewers are always trying to develop new techniques and methods to get the most out of their hops. In recent years, there has been an emergence of double dry hop beers (DHH - although there isn’t a consensus on what this really means) which is just yet another evolution of the humble pale ale but exposed to more dry hopping. Having said that, peak dry hopping levels have begun to hit a plateau of effectiveness as brewers realise that the diminishing returns mean that simply throwing more hops isn’t always worth it.
Maybe we all got mad with hop power, and now the dust has settled, consumers and brewers alike are starting to see the wisdom in controlled dry hopping amounts. Or maybe the future of hoppy beer rests on new hop varieties and new techniques that are yet to be discovered.
Further reading:
https://appellationbeer.com/blog/