Gail B. Nickerson

Sensory and analytical evaluation of beers brewed with three varieties of hops and unhopped beer

SUMMARY Pilot brews made with Hallertauer Mittelfruh, U.S.D.A. 21459, U.S.D.A. 21455 (Mt. Hood), and a beer brewed without hops were evaluated for aroma by a descriptive sensory panel (DSP). The extracts from the beers were evaluated using Osme, a GC olfactometry method: The beer extract samples were injected into the gas chromatograph-olfactometer (GCO) and the effluents evaluated qualitatively and quantitatively by four trained subjects. A time-intensity device connected to an IBM computer was used to record the odor intensities. The samples were analyzed by mass spectrometry to identify the odor active compounds. Sensory profiles of the hopped beers were similar indicating that beers brewed with U.S.D.A. 21455 and U.S.D.A. 21459 contribute “noble” hop aroma.

Comparative chemical attributes of native North American hop, Humulus lupulus var. lupuloides E. Small.

The genetic diversity of 159 representative genotypes of native hop (Humulus lupulus var. lupuloides E. Small, Cannabaceae) from 34 selected populations was assessed by relative magnitudes and ranges of alpha acids (AA), beta acids (BA), and the cohumulone (CoH) component of alpha acids, with reference to temporal changes between 1989-1990 and 2001, and to the same attributes in American and European hop cultivars, principally H. lupulus var. lupulus L. Chemical profiles of these genotypes were generated by high pressure liquid chromatography (HPLC) of methanol extracts from their processed samples (cones). The alpha ratio (AR, alpha acids / alpha+beta acids) measured the degree to which alpha acids predominated in cone extracts. Synchronous ranges of AR and CoH were also selected for graphic portrayals of native hop genotypic diversity. Cones sampled and analyzed from eight populations that were accessible in both 1989 and 2001 were distinct in chemical attributes, indicating a succession of genotypes, and suggesting temporal cycling of H. lupulus var.lupuloides germplasm. The principal distinctions between the two sub-species were a markedly higher proportion of CoH (38-88% vs. 19-41%) in alpha acids of H. l. var. lupuloides, and generally higher concentrations of AA in cultivars of both American and European commercial hop cultivars, predominantly H. lupulus var. lupulus. All of the 159 native hop genotypes also contained detectable levels of xanthohumol and xanthogalenol, prenylflavonoids recently reported to have mammalian anti-cancer activity. Some native genotypes had previously exhibited natural repellence of insect and mite pests; thus H. lupulus var. lupuloides germplasm offers a diverse resource of underutilized and yet undefined biochemicals.

Sensory and Analytical Evaluation of Hop Oil Oxygenated Fractions

SUMMARY Oxygenated fractions of Hallertauer Mittelfruh, U.S.D.A. 21455 (Mt. Hood), and U.S.D.A. 21459 were evaluated for aroma by a descriptive sensory panel (DSP). The same fractions were injected into a gas chromatograph-olfactometer (GCO) and the effluents evaluated qualitatively and quantitatively by four trained subjects. The GCO data was collected using a method called Osme based on a time intensity (TI) device connected to an IBM computer. The samples were analyzed by mass spectrometry (MS) to identify the odor active compounds. Correlation analysis was performed between the descriptive sensory analysis data and the intensity rates of the compounds sniffed through the GC. Chemical and sensory profiles of the samples were similar indicating that the new varieties are good representatives of “noble aroma” hops. Linalool and oxidation products of caryophyllene and humulene were important contributors to the overall aroma of the samples. Differences found seemed to be associated with the amount of oxidation products present due to different oxidative stages of the samples.