Stable free radicals and peroxyl radical trapping capacity in red wines.

Thirty-two experimental red wines, obtained from eight cultivars and aged in bottles for 2 and 7 years, were examined for the presence of stable free radicals (SFR), for the peroxyl radical trapping capacity (PRTC), and for the concentrations of some important polyphenol families. Aging significantly increases SFR, polyphenol polymers with n > or = 5 (HMWP), and PRTC and is accompanied by a strong decrease of free anthocyanins. Multivariate regression analyses show that HMWP and SFR are independently associated with PRTC while HMWP and anthocyanins are independently associated with the formation of SFR. These results indicate that polymeric polyphenols generated from anthocyanins and proanthocyanidins during wine aging are able to convert highly reactive free radicals into nonreactive radicals through electron delocalization. The strict correlation between SFR and antioxidant activity that we found suggests that these characteristics are related to the functional properties of food.