For the prognosis of the flavour stability of beer the electron spin resonance (ESR) spectroscopy has been used for the determination of the lag time. The spin-trap reagent (PBN) used to assess the lag time has a significant impact on the results due to an increasing pH-value during the analysis, resulting in a falsification of the rations in a beer sample.

We offer a novel method for the assessment of the endogenous antioxidative potential (EAP) of beer and other beverages using a different spin-trap reagent (POBN) in lower concentrations, which results in a beer matrix dependent, linear correlation between the SO2-content and the EAPvalue. This correlation offers a new beneficial index number for the evaluation of the beer specific flavor stability (BAX: Beverage Antioxidative IndeX). The BAX provides additional information about the anti- and pro-oxidative properties of the beer matrix independent on the SO2-content. The BAX is affected by the content of metallic ions, hop-acids, sugar, proteins, intermediate Maillard reaction products, etc. and gives information about the consumption rate of the existing antioxidative potential during storage. Besides the higher significance of the EAP-values, the breweries that in future are going to employ EAP-determination and Beverage Antioxidative IndeX (BAX) as a matter of routine, will be able to detect deviations in the brewing process in time and to intervene selectively. They will also be able to considerably lower the costs in the area of quality assurance.