Hop Science Newsletter (March 2017)
In this issue: CO2 extract for better flavour stability, bitter components during storage, and the true bitterness of humulinones.
CO2 EXTRACT FOR BETTER FLAVOUR STABILITY!
This German research group is looking into beneficial components in hops to improve flavour stability. In their latest publication, they summarize their trails using CO2 extract in context with reducing the iron content in beer. In comparison to dosing the extract at the beginning of boil they tried different versions of dividing the hop dosing throughout the boil. With this they were able to reduce the iron content by about 30%, resulting in improved flavour stability not only based on analytical values but also on sensory evaluation.¹
ABOUT THE STABILITY OF BITTER COMPONENTS IN HOPS DURING STORAGE…
These German researchers are specialists in identifying and quantifying bitter components in hops. In this project, heat maps were developed for all bitter components during the storage of several years. The data presented gives profound insight into the molecular bitter compound variability of certain hops. Quantitative analyses of hops stored with and without the influence of oxygen revealed that the decline of distinct hop constituents cannot be explained by an increase in transformation products formed during beer aging, thus implying unknown degradation mechanisms in hops. In a controlled, cool and oxygen free environment, the relevant bitter components proved to be stable for a period of 2 years.²
THE TRUE BITTERNESS OF HUMULINONES
A couple of recent studies revealed that the increased bitterness in dry hopped beers is greatly influenced by the formation of humulinones (oxidized hop α-acids).Using previously established synthesis methods and preparative liquid chromatography, high-purity extracts of humulinones and hulupones were prepared for sensory testing. A trained flavour descriptive panel found humulinones to be 66% as bitter as iso-α-acids, and hulupones to be 84% as bitter as iso-α-acids. This study also found that the bitterness intensity of humulinones and hulupones are substantially higher than previous estimates of 35% and 50%, respectively. Whereas iso-α-acids were confirmed to be more bitter than oxidized α-acids and ß-acids, both hulupones and humulinones were bitter enough to potentially have a significant impact in beer, especially in dry hopped beers. The threshold value of humulinones was found to be around 8 mg/L in unhopped beer.3
EVENTS
Upcoming Barth-Haas Hops Academy
April 21-22, CERB, University of Perugia, Italy. All About Hop Flavour (lectures in English/Italian). Registration at giuseppe.perretti@unipg.it
Make sure to attend the this year’s Hop Summit:
The 2nd International Brewers Symposium on Hops, July 26th to 28th, Corvallis OR USA. http://hopsflavor2017.com/
Other hoppy events:
• April 10-13, Craft Brewers Conference, Washington DC, USA
• May, 14-18, EBC Congress, Lubiljana, Slovenia
• June 4-7, ASBC Annual Meeting, Ft. Myers, FL, USA
