Antioxidant activity, browning and volatile Maillard compounds in Pedro Ximénez sweet wines under accelerated oxidative aging

Pedro Ximénez wine, aged by thermal treatment during 10, 20 and 30 days in the presence or absence of oak chips, was studied in terms of antioxidant activity, browning and volatile Maillard compounds. The phenolic fractions obtained by the SepPack tC-18 column revealed that the antioxidant activity after 10 days of thermal treatment was due to the presence of phenols and polar compounds possibly formed by the Maillard reaction. After 30 days, however, the antioxidant activity was also due to high-molecular weight procyanidins. Volatile Maillard compounds increased throughout the thermal treatment. It should be noted that there was an increase in the 5-ethoxymethylfurfural content and the presence of 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-2-one, which was recently shown to inhibit growth of colon tumor cells. The presence of oak chips had a substantial effect on the contents in volatile Maillard compounds after the thermal treatment with the exception of corylon. The wine obtained after 10 days of thermal treatment was judged to be the best in terms of sensory properties. In fact, it exhibited the optimum balance between varietal and aging aromas due to Maillard compounds.