X. ZHAO (1), B. Sacher (1), S. Procopio (1), T. Becker (1); (1) Lehrstuhl für Brau- und Getränketechnologie, Freising, Germany
Friday, October 9
Glycerol and major fermentative flavors, which originate from yeast metabolism, exert the greatest impacts on the beer sensory profile. In the current investigation, we aimed to visualize the differences in fermentative flavors in various beers by principal component analysis (PCA). Furthermore, to identify the major variance of fermentative flavors within the beers 20 alcohol-free beers (AFB) produced from thermal dealcoholization, stop fermentation, and dialysis membrane and 17 of their alcoholic counterparts were kindly provided by 15 breweries in Germany. Glycerol, higher alcohols (HA), esters (ES), dimethyl sulfide (DMS), acetaldehyde, and vicinal diketones (VDK, including diacetyl and 2,3-pentanedione) were analyzed by photospectroscopy and gas chromatography. PCA was performed on the abovementioned flavors together with alcohol content, extract, pH, and viscosity. The first two principal components (PC1 and PC2), which accounted for 93% of overall flavor variances, were scattered for the 37 beers. The AFBs and the alcoholic beers clustered separately, while wheat beer and bottom-fermented beer showed no specific pattern. Nevertheless, glycerol appeared as an important attribute for AFBs produced from different production methods, whereas the thermal dealcoholization AFBs had the highest level in general. Surprisingly, HA, but not alcohol content, was identified as the major variance source, followed by ES, DMS, viscosity, glycerol, acetaldehyde, diacetyl, VDK, pH, and extract between AFBs and their counterparts. Our results further confirm that one major problem encountered by AFBs is lack of fruity flavors. Furthermore, PCA was proved as a useful method for visualizing the flavor profile of beers.
Xiangdong Zhao is currently working at TU München on her doctoral degree, with a scholarship provided by the China Scholarship Council (CSC). The research interests of Xiangdong include the sensory contribution of glycerol to beers and the flavor characters of alcohol-free beers; the increase in fermentative glycerol yield by screening of strains; and the optimization of fermentation parameters aided by a high throughput screening (HTS) system. Xiangdong worked in the application of infrared spectroscopy on food for her master’s degree at Zhejiang University.