The constituents of the hop which provide its particular character are:
Bittering substances = hop resin
Aromatic components = hop oils/essential oils
Tannins = polyphenols
The bittering substances and essential oils are found in the lupulin which forms in the resin glands of the cone’s bracteoles. Tannins come primarily from the coarser parts of the cone, such as the strig or stem.
As well as lending a particular note to the flavor, the use of hops in beer production also has an influence on the bacterial flora. It has an antiseptic and bacteriostatic effect, influencing the keeping qualities of the beer.