THE BEER’S VOLATOLOME, A COMPARATIVE STUDY BY COMPREHENSIVE TWO-DIMENSIONAL GAS CHROMATOGRAPHY TIME-OF-FLIGHT MASS SPECTROMETRY

Fermented beverages, such as beer, are considered as complex mixtures by flavor
and food chemists. The beer volatolome contains hundreds of compounds, which
affect the taste and the mouthfeel. In this highly competitive market, it is crucial
for brewers to master each step of the process to understand and control the taste
and to guarantee aroma quality and stability. Aroma compounds are essentially
derived from the raw ingredients and the conditions used to produce beers. This
study aims to determine the impact of the yeast used for bottle fermentation on
beer’s volatolome.
We brewed 5 different beers with the same feedstock. During the bottling, we used
5 distinct yeasts generally used by brewers. After an aging period of 8 weeks, all
samples were analyzed using solid-phase microextraction couple with
comprehensive two-dimensional gas chromatography coupled to mass spectrometry
(SPME-GC×GC-TOFMS). A dedicated data processing workflow was then optimized.
Principal component analysis (PCA) was used to visualize the clustering between
samples.
After data curation, peaks area of VOCs founds in each beer were used to carry out
unsupervised statistical analyses. Three distinct groups were observed on PCA; two
beers are considered very different regarding the VOCs while the remaining three
constitute another cluster. Based on these results, the aroma profile of the different
beers could be dressed. While the two first beers were dominated by specific ethyl
esters giving fruity aromas, less associated fruity fragrance esters were expressed
in the other group.