ANALYSIS OF FIVE BOTTLE-REFERMENTED HANDMADE BEERS BY COMPREHENSIVE TWO-DIMENSIONAL GAS CHROMATOGRAPHY TIME-OF-FLIGHT MASS SPECTROMETRY, A COMPARATIVE STUDY

Beers 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, including the fermenting yeast strain. This study aims to determine the impact of the yeast, used for bottle fermentation, on beer’s volatolome.
Five different beers were brewed with the same feedstock and fermenting yeast. During the bottling, we used 5 different yeasts generally used by brewers. After an aging period of 8 weeks, samples were analyzed using solid-phase microextraction coupled with comprehensive two-dimensional gas chromatography coupled to mass spectrometry (SPME-GC×GC-TOFMS).
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 Principal Component Analysis (PCA); two beers are considered different regarding the VOCs while the remaining three constitute one big cluster. Based on these results, the aroma profile of the different beers could be dressed. While the two first beers were dominated by ethyl esters (fruity aromas), less associated fruity fragrance esters were expressed in the other group.
The beer aroma profile was impacted by the yeast strain used for the bottle fermentation. Specific esters
were produced, resulting in beer-type classification on PCA.