On the Fate of Certain Hop Substances during Dry Hopping

Dry hopping is becoming increasingly popular especially in small breweries. It is a complex and sophisticated method, but it is exactly those qualities which make it a highly efficient method for craft brewers to stand out among the mass of other beers. Empirical experience is the key factor here in the choice of hops and type of application. There is still little known about the transfer rates of hop substances during dry hopping which can provide a great variability of application.

A test was made in which four dry hopped pale lager beers were contrasted with a similar produced beer without dry hopping. Here the new German varieties Mandarina Bavaria, H¨¹ll Melon, Hallertauer Blanc and Polaris were used for dry hopping. The dosed quantity of 1.5 ml/hl was based on the hop oil content. The transfer rates were calculated from the difference between analysis values of the dry hopped beers and the control beer divided by the dosed dry hopping quantities. As the calculations were made from three analytical values they inevitably produced relatively large ranges of fluctuation.

Of the dosed ¦Á-acids, 4 to 5 % can be found in the beers, of the total polyphenols 50 to 60 % and of the low-molecular polyphenols 60 to 70 %. The transfer rates of individual polyphenols show systematic differences; there is no recognizable dependence on variety. The behaviour of the aroma components examined is also not uniform. Terpene hydrocarbons show low yields of about 3 %; linalool transfers to about 100 %. Geraniol seems to react variety-specific with two yields of approx. 50 % and two significantly over 100 %. There is also a variety-specific phenomenon with 2- and 3-methylbutyl-2-propanoate. Chemical transformations with or without yeast enzymes are probably the cause. The results show just how much more work has to be done.

The reductions in and transformations of hop aroma substances during ageing of beers are an indication that intensity and type of aroma are subject to changes.

The five beers were tasted by a consumer panel of 30. The dry hopped beers had a very intense hop aroma and also a surprisingly intense body. The quality of the hop aroma prevailed over personal preferences and the quality of bitterness was appraised the same.

BrewingScience - Monatsschrift für Brauwissenschaft, 66 (July/August 2013), pp. 93-103