Aroma Active Monocarboxylic Acids – Origin and Analytical Characterization in Fresh and Aged Hops

During hop storage secondary metabolites, primarily bitter acids, terpene hydrocarbons and terpenoids, undergo qualitative and quantitative changes. One reaction that influences both – bitter properties and aroma – is the release of extremely flavour active short chain monocarboxylic acids by cleavage of the acyl-side chain of bitter substances. Short chain acids exhibit very intense unpleasant cheesy, sweaty, and rancid smells, however they are key precursors of highly positive flavourings of late hopped beer.

In the current paper a stable isotope dilution assay for precise quantification of short chain carboxylic acids was integrated into conventional hop oil analysis. Short chain acids, terpene hydrocarbons, terpenoids, and hop bitter substances where analyzed in fresh as well as in moderately and excessively aged hop samples.

BrewingScience - Monatsschrift für Brauwissenschaft, 67 (March/April 2014), pp. 33-47