Comprehensive characterization of Chinese beers based on chemical composition, antioxidant activity and volatile metabolomics.

Four different commercial beers in the Chinese market were compared and analyzed systematically, in order to provide more guidance for consumers. In this experimental study, various physicochemical parameters such as alcohol content, color, bitterness, total acidity, and carbohydrates were evaluated. The total phenolics content was determined using the Folin-ciocalteu method, while the total flavone and melanoidins were measured using colorimetric and spectrophotometric methods, respectively. The antioxidant capacity was determined by ORAC, DPPH and ABTS assays. Non-targeted metabolomics was used to analyze the composition and differences of volatile compounds in different beers. The results indicated significant physicochemical variations among the four different commercial beers. The higher the chroma of beer, the greater the content of active substances, and the corresponding antioxidant capacity in vitro was also stronger. The alcohol content of the four beers ranged from 4.23 to 7.54% (ABV), the color values of the four beers ranged from 4.8 to 141.5 EBC, and the bitterness ranged from 11.2 to 36.6 IBU. The total phenolics content varied between 159.10 mg/ L and 269.13 mg/ L, the total flavone content was in the range of 39.94 -144.59 mg/L, and the melanoidins content was in the range of 271.07-296.68 mg/L. The antioxidant activity ranged from 0.570 mmol TE/L to 0.873 mmol TE/L (ABTS), from 3.700 mmol TE/L to 26.73 mmol TE/L (ORAC), and from 26.12 to 86.72% (DPPH clearance rate). A total of 453 volatile compounds were detected in the four beers, primarily comprising terpenoids (21.24%), esters (19.47%), heterocyclic compound (14.16%), alcohol (9.96%) and hydrocarbons (9.96%), etc. Compared to Premium lager beer, the other three kinds of beers had unique and common metabolites, with only 9 common metabolites. The flavors of the differential metabolites were mainly green, floral, sweet, fruity, etc.