The Hop Core
Resins
Split into alpha and beta acids called humulones and lupulones. These affect flavour, shelf life and head retention among other things.
Humulones
Become bitter when boiled. The rate at which they change depends on the length and speed of the boil – all part of the brewer’s art. There are six different alpha acids in all hop strains. They all impart a different quality of bitterness from harsh to soft.
Lupulones
Tasteless and don’t affect the flavour.
However, they have strong antimicrobial and antibacterial qualities. Hops were first used in beer to sterilise it and extend its shelf life.
Strig
The central stalk of the cone. With hops, farmers are not interested in the plant, or the leaf or even the fruit. They want what is in the fruit – resins and oils.
Bracts and Bracteoles
Flower parts protecting the glands within. There are tannins and other unidentified chemicals in this leaf material. These affect haze formation in brewing – but it is not known how exactly. Some claim brewing from extract rather than whole hops sacrifices this.
Lupulin Glands
Found on the surface of bracts and bracteoles as raised dots, these glands carry the resins and essential oils that make all the difference to the flavour and aroma of beer.
Essential Oils
Hops contain at least 400 different volatile oils, many of them unidentified, and many whose effects cannot be quantified. Each hop strain will be unique in the levels of oils it has, and the oils impart their own aroma and flavour.
The Drinker
Hop Effects
Hops provide the main source of aroma in finished beer along with much of the flavour and, of course, the bitterness. The essential oils provide a whole range of aromas including fruity, resinous, woody, citrus and soft fruits. But they are very hard to analyse.
Aroma
The taste interacts with the aroma. It is not well defined which part of the nose is the best receptor for hoppy aromas but young women tend to be much better at detecting hop flavours thanks to an evolutionary trait developed by the need to select potential partners.
Bitterness
Bitterness can be quantified by measuring the levels of alpha acids (IBU) but relating this to perception of bitterness is difficult because people have different sensitivities to it. The sensation will also depend on the interaction in the beer with the malt, yeast and alcohol levels.
Taste
Generally, bitterness is tasted at the back of the tongue and sweetness at the tip. The taste buds more tuned to sensing the acids in hops are clustered in greater density at the back of the tongue. If you sip a beer just tasting at the tip you will get a very different impression of a beer than if you glug it.
