Aging impacts aroma of final beer product.

The desired bitter taste of beer is created by components that are derived from specific bittering hops. While bitterness is important to the product's flavor, most consumers recognize a beer by its aroma.

Brewers have developed techniques for determining the bitterness in beers. Yet for the most part, they have ignored using aroma components as an indicator of overall flavor. It has been determined that 22 compounds are responsible for the majority of hop aroma in beer. Changes in the concentrations of these compounds, the hop aroma component profile (HACP), occur as hops age. The aging process changes the aroma of finished beers. By monitoring the HACP, brewers could adjust hopping rates to account for changes in HACP.

The objectives of researchers at California State University were to determine the HACP of Cascade hops throughout their storage and to evaluate how HACP changed with respect to the brewing process. They determined that the aroma components of hops change with time during the brewing process. Comparing the aroma components found in hops may give an indication of how the hops will help create the aroma of the finished product.

Investigators analyzed one lot of selected Cascade hops at 7, 9 and 11 months of storage. The hops were steam-distilled. The scientists collected wort and beer samples at various points during a commercial production run. Four individual beers were analyzed. Wort and beer were simultaneously steam-distilled and extracted using the Likens-Nickerson system. All essential oils were analyzed by gas chromatography-mass spectrometry.

The HACP of the stored hops changed with time. The oxygenated components of HACP increased without a concomitant decrease in hydrocarbon or ester components. Throughout the beer-making process, concentrations of all HACP components declined significantly, with the major reduction occurring during the fermentation process. This suggests that yeast may be sequestering the aroma components.

Further information. Larry Kirk, Department of Chemistry, California State University, Chico, 216 Physical Science Building, Chico, CA 95929; phone: [phone]; fax: [phone]; email: [e-mail].