A Study of the Fate of Volatile Hop Constituents in Beer

Abstract

SUMMARY— The volatile material from a pilot plant brewed beer (hopped) has been analyzed by the direct combination of capillary gas chromatography and mass spectrometry. None of the major volatile terpenoid hydrocarbons of hops (myrcene, caryophyllene, humulene) could be detected in the beer volatiles. The only volatile constituents in the beer which could be assigned to hops with some certainty were ethyl dec‐4‐enoate and ethyl deca‐4,9‐dienoate, which exist in the hop oil as the methyl esters. A capillary gas chromatography analysis of a beer which was brewed without hops but with methyl dec‐4‐enoate (0.02 g/L) showed that this ester was converted to the ethyl ester by the fermentation. A study was also carried out using model systems to parallel the “kettle boiling” step of brewing. This involved boiling hops with water for a set period and filtering the water extract from the hops. It was found that the pattern of volatile hop constituents in the filtrate (hopped water) was quite different from hop oil and consisted principally of free organic acids, humulene epoxide, humulenol, and other hop oil oxygenated components. With fine filteration through Celite, very little myrcene, humulene, or caryophyllene were transferred into the water, even though they form the major part of hop volatiles. If, however, only coarse filtration was used, a greater amount of these hydrocarbons were found in the filtrate. It is concluded that the amount of volatile hop oil constituents reaching the final beer probably depends upon the exact conditions of the brewing process used. No evidence could be found in the present work to support the view that the tiny amounts that do survive in beer prepared by the typical American process could contribute more than a very minor amount to the characteristic beer aroma.

Acid and Volatiles of Commercially-Available Lambic Beers

“…Octanol has been previously reported in beer [22,28,29], but never specifically lambic beers. The concentration of octanol ranged from 0.025 mg/L to 0.084 mg/L.…”

Hop Aroma Component Profile and the Aroma Unit

“…A number of these compounds, i.e., humulene oxidation products, have been isolated or synthesized and used in flavor evaluations (13,14,21,24). In addition, a great deal of work has been done on the detection of hop oil constituents in beer (4,10,16,18,20,23). Unfortunately, no consensus has been reached on which constituents contribute the most to a "hoppy" aroma in beer.…”

Coffee, cocoa, and tea

“…lying around 42 ppb, a very low value for a hydrocarbon (216,217). Combined with Z-and is-ocimenes (A-37 and A-38), it has been reported to contribute to the flavor of black tea (178).…”