Auxiliary bitter compounds in hops and the quality of bitterness in beer

摘要

The term auxiliary bitter compounds in hops refers to all bitter compounds in the hop resin which are transferred to the beer and are not iso-a-acids. This includes all such components found in fresh hops and excludes those formed through oxidative aging reactions. There are numerous auxiliary bitter compounds found in hops that are either present in a directly soluble form in hops or are formed from a-acids and P-acids during the wort boiling process. The majority of these substances are considered desirable from a sensory perspective. They reduce a lingering character of bitterness and make a positive contribution to the quality and harmony of the bitterness in beer. The ratio of the non-specific EBC bitterlng units (spectrophotometric method) to the specific iso-a-acids (HPLC method) serves as an indicator for the amount of auxiliary bitter compounds in beer. This ratio is equal to 1 in beers brewed with only one hop addition of high-ct hops at the beginning of the boil. By contrast, beers brewed with a complex hopping regimen, e.g. with several additions of aroma hops, exhibit significantly higher levels of bittering units than iso-a-acids. Here, the values for IBU to iso-a-acids have been measured as even higher than 2. In this situation, the iso-a-acids are present in comparable quantities to the non-iso-a bittering units. Thus, auxiliary bitter compounds make up a sizable portion of the bittering units. The results from the brewing trials described previously show that the bitterness of beers with higher ratios of IBU to iso-a-acids is less harsh and lingering, while the overall impression is more balanced and pleasant. Adding larger amounts of aroma hops over several additions not only influences the aroma but also serves to improve the harmony of the beer bitterness.