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A new equation for converting EC50 into TEAC values and TEAC into EC50 is presented in this paper. The model was fitted to 180 data points of electron paramagnetic resonance (EPR) spectroscopy measurements of various food products. The model was tested basing on 75 EPR spectroscopy measurements. Moreover, the equation was tested on literature data. The determination coefficient between EC50cal and EC50exp was found to be R2 = 0.9762, while the determination coefficient between TEACcal and TEACexp was found to be R2 = 0.9686. Based on obtained results it can be concluded that the proposed model for converting EC50 into TEAC values and TEAC into EC50 values works properly. This will enable a comparison of the antioxidant properties of products identified in literature through the use of different parameters (TEAC, EC50).

A new equation for converting EC

The antioxidant properties of various kinds of beers were investigated using electron paramagnetic resonance (EPR) spectroscopy. This was possible by measuring the changes in the intensity of the EPR spectrum that resulted from the interaction of the stable radical DPPH (1,1-diphenyl-2-picrylhydrazyl) with the antioxidants found in a beer sample. The antioxidant capacity was then presented in Trolox Equivalents, e.g. μM trolox in a beer sample of 100 ml. The influence of the type, colour, the content of the extract and alcohol on the antioxidant activities of commercial beer samples was investigated using two-way hierarchical clustering and analysis of variance. The results showed that all of the beers investigated exhibit antioxidant properties. By performing an analysis of variance, it was found that the value of the antioxidant capacity significantly (0.05 level of significance) depends on the content of the extract and the colour of the beer. It seems that additives also influence the antioxidant properties to some extent, but neither the alcohol content nor the kind of fermentation affects the antioxidant properties of beer.

The antioxidant properties of samples of different kinds of commercially available alcoholic beverages were investigated by electron paramagnetic resonance (EPR) spectroscopy. This analytical technique is chiefly designed to enable accurate detection of free radicals. The determination of antioxidant activity by the EPR method is conducted by measuring the changes of the intensity of the EPR spectrum of stable radicals, which results from their interaction with antioxidants. Antioxidant capacity of alcoholic beverages samples was assessed with the use of the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH ). The highest antioxidant activity was found in red wines, followed by a blend of wine and brandy and then by whiskies, whereas plain vodkas and gin showed negative values of antioxidant activity. From our studies it can be concluded that the value of antioxidant capacity depends on the polyphenolic content, the time and method of ageing, as well as on the flavour and colour additives.