Hops contain many biochemical compounds, which partially defend the plant against all kinds of possible adverse environmental factors. These protective substances are concentrated in external organs, the lupulin glands, behind the bracts of the hop cone. Only the lupulin glands are of interest for beer production and for their health-giving properties. Each gland - a sort of little ball - is covered with a fine yellow resinous powder called lupulin. Lupulin powder contains, among other things, hop acids, essential hop oil and hop polyphenols. These constituents are present in varying concentrations in the different varieties of hop. Each hop variety therefore has its own intrinsic properties, which differ from all other hop varieties. The wholesale division of hops into bitter types and more scented types does not do sufficient justice to these finer characteristics.