Hops are one of the four basic ingredients in beer, the others being water, barley and yeast. Of course brewers are free to use a varied array of ingredients but these four are the backbone of brewing. Hops, however, are a relatively new ingredient in beer making.
The oldest evidence of brewing goes back to approximately 9,000 years ago but it is not until the year 822 that we get the first evidence of hops being used for beer production. This comes from the Abbot of a Benedictine monastery near Amiens in France writing a list of rules governing how the abbey should be run and the how the collection of sufficient wild hops should be arranged. It is not for another 300 years before we see any evidence of widespread use of hops with commercial hop cultivation beginning in Germany in the 12th and 13th century. Before hops were adopted, many other plants were used to flavour and bitter beer such as bog myrtle or yarrow. Beers bittered and flavoured in this way was usually called gruit.
Hops are the flower of the hop plant, Humulus lupulus, these hop flowers or ‘cones’ have waxy lupulin glands that contain the alpha acids responsible for the bitterness, required to offset the sweetness of malt sugars, and oils that lends all those wonderful hoppy aromas and flavours to beer. The reason hops took so long to become a key ingredient in beer production is probably due to the time and energy required to bring these characters out in the beer. In general hops are boiled for an hour or more for this to occur.
The amount of bitterness hops impart to the finished beer is determined by when they are added to the boil. Hops added at the start of the boil will impart more bitterness while those added at the end of the process will add more flavour and aroma. The amount of bitterness imparted and the aroma profile is also massively determined by the climate and the variety. Different hops varieties produce different flavour and aromas. From the traditional ‘noble hops’ of central Europe with their floral and slightly peppery or spicy character to new world hops with intense citrus, pine needle and grapefruit. At the turn of the last century there were perhaps a dozen different hop varieties in widespread use, now there are well over a hundred. In the 20th century growers and institutions began experimenting with breeding programs to create new varieties of hops (the now ubiquitous Cascade hop was first released in 1971) and now each year seems to bring with it a new hop. Hops have come along way.