Spectrophotometric methods to differentiate beers and evaluate beer ageing

The methodology most widely used to detect the antioxidant capacity (indirectly by ABTS+ discoloration) has been modified to be applied to beer samples due to signal instabilities. A new and direct method to follow beer ageing has been developed based on a simple organic solvent extraction follow by molecular absorption spectrophotometry UV–VIS (MAS) measurement. Polyphenols and Maillard reaction products (MRPs) implied in beer ageing have been identified in the organic extract. A wide sampling of beers has been performed considering different countries, raw materials and brewing process. The two methods mentioned have been applied to the samples as well as the determination of total polyphenols, iron, copper and manganese by its role in ageing and in fermentation. In all cases, the data were obtained by triplicates. High correlation coefficients have been obtained between the ABTS+ and the extraction method, therefore, this second method is proposed to differentiate antioxidant capacity and to follow beer ageing. The analysis of variance (ANOVA) has shown the possibility to differentiate types of beers and ecological from non-ecological beers.