Electron Spin Resonance Spectroscopy Suitability for Investigating the Oxidative Stability of Non-Alcoholic Beers

Seven lager beers and seven non-alcoholic counterparts, marketed by the same producers, were analyzed for their total phenolic content (TPC), radical scavenging activity (RSA) towards the DPPH radical and ThioBarbituric Index (TBI). All beers were also subjected to spin trapping experiments at 60 °C in the presence of PBN. To our knowledge, this is the first time that non-alcoholic beers (NABs) have been subjected to spin trapping experiments coupled with Electron Spin Resonance (ESR) spectroscopy. The evolution of the intensity of the PBN radical adducts during the first 150 min was represented graphically and the intensity at 150 min (I150) and the area under the curve (AUC), were measured. The I150 and the AUC of lagers and NABs are significantly different, whereas the TPC, the EC50 of the DPPH assay, and the TBI of the two groups are superimposed. A relationship, previously proposed by us, to correlate ESR spectroscopy parameters with others obtained from UV-Vis spectrophotometry, was also applied, demonstrating its practicability. Multivariate analysis shows that clustering in two separate groups occurs only if I150 and AUC are included in the model. Based on these results, ESR spectroscopy can be applied to study the oxidative stability of NABs.