HVG Germany: Hopfen

Mirror, mirror on the wall, which is the bitterest iso-humulone fraction of them all?

If you look at this subject from an historical aspect then the varieties which have prevailed in the struggle to win the brewers' favour are those which impart a soft, pleasant bitterness. Because as many hops as possible had to be dosed in the copper to ensure that the beer would keep longer. Nowadays we know that these varieties - the traditional aroma varieties - possess special characteristics with regard to their resin-polyphenol and aroma composition. 

In the 1960s the traditional varieties were crossed with wild hops in order to increase the resin proportion. Through this the composition of the components shifted in the new varieties, the flavour differed from that of the traditional varieties. During the course of time efforts were made to maintain certain characteristics of the traditional aroma varieties despite a higher resin proportion. Therefore in Germany today there are e.g. bitter varieties which are very similar to the aroma hops in their oil spectrum and their alpha-acid composition.

The difference in taste between the various resin fractions is debated controversially in the pertinent literature. Traditional aroma hops have a low co-humulone content and their bitterness is described as being very pleasant. Therefore nowadays the trend is to breed varieties which have the lowest possible co-humulone content.

Aging and oxidation products of the alpha- and beta-acids as well as certain fractions of the hop polyphenols also contribute to the bitter taste in the beer. It is a fact that each and every hop variety has different compositions in this respect. In the brewery Ð according to the required goal Ð the corresponding variety /the corresponding product has to be found by trial and error.

As for the bitterness of the beer, the brewery also has to pay attention to its stability in the product. As seen from analysis the iso-humulone values in the beers on sale deteriorate between 11 % and 26 % by the time their shelf-life expires. A beer which has 29 mg/l iso-humulone fresh from the brewery, might only have 22 mg/l iso-humulone months later when poured into the consumer's glass. As far as stability goes, the hop product and variety seem to play a subordinate role: The overall state of the beer is of greater importance here - refer to the publication "Zum Abbau von Hopfenbitterstoffen während der Lagerung von Bier" (Forster, Massinger, Schmidt). "Zum Abbau von Hopfenbitterstoffen während der Lagerung von Bier" (Forster, Massinger, Schmidt).

Every brewery has its preferences as far as hops are concerned. How far the positions differ can be seen in two extreme points of view:

There are breweries which use a quite specific variety from a specific hop-producing region. The identical variety from another production region is not accepted for reasons of taste. On the other hand other breweries procure for their hopping chemically completely different varieties from quite different production regions.