Application of optimized methods to determine the endogenous anti-oxidative potential of beer and other beverages

摘要

EPR determination of the endogenous anti-oxidative potential (EAP) is an efficient tool to predict the flavour stability of beer. A new method has been developed using POBN as a spin trap instead of PBN. The advantage of the "new EAP-determination" is based on the avoidance of the pH effect caused by the spin trap PBN. Thus the distortions of the measurement used up to now can almost be completely avoided. The results especially in case of high lag time values are much more precise by using lower spin trap concentrations. Opposite to PBN, POBN shows a beer specific linear dependence on SO_2. Therefore the beverage anti-oxidative index (BAX) has been introduced to compare the different consumption of the anti-oxidative potential. In practical application it could be shown that crossflow filtered beer leads to better EAP and to lower formation of stale flavour in beer than kieselguhr filtered. The method can also be used to compare the efficiency of different crown corks for bottles. Furthermore the method is applicable to determine the EAP in fruit and vegetable juices.