Brown beer vinegar: A potentially functional product based on its phenolic profile and antioxidant activity

The aim of the present study was to create a functional, enriched in polyphenols and free of alcohol product obtained by acetic fermentation of beer. Beer and vinegar were tested first for their phenolic content and antioxidant activity, by the Folin Ciocalteu and the free radical scavenging activity by the 1,1-diphenyl-2-picrylhydrazyl free-radical scavenging assay, respectively. Then, the separation and identification of the 30 phenolic compounds was realized by high-performance liquid chromatography coupled with positive electrospray ionisation and diode array detection (HPLC-DAD-ESI(+)-MS) analysis. Identification of the phenolic compounds data was realized based on the UV spectra of each compound. Based on a calibration curve (R2= 0.9985), the amounts of the phenolic compounds, expressed as mg cathechin equivalents (CE)/L, were calculated. The total phenolic content of the beer and vinegar samples determined using Folin-Ciocalteu reagent were of 428.9±1.58 and 661.5±7.69 mg GAE L-1, respectively, which contributed to the high antioxidant activity in the vinegar sample of 82.18 %. Statistically significant differences were observed after acetic fermentation between each parameter (p < 0.05). Brown beer vinegar represents a rich source of polyphenols and phenolic derivatives, compared to beer. By its increased phenolic content and antioxidant activity, brown beer vinegar could be considered another source of valuable compounds to beer, which could also be of interest in special diets.