Assessment of the development of browning, antioxidant activity and volatile organic compounds in thermally processed sugar model wines

Abstract The study evaluates the contribution of the fructose and glucose's degradation for the Madeira wine's features. The browning index, antioxidant activity and volatile organic compounds developed by the glucose and fructose model systems simulating thermally processed sweet Madeira wines were assessed. Sixteen different fructose/glucose model systems were prepared in synthetic wine and stored at 50 °C for 4 months. Then, three model wines were also submitted to 70 °C for 1 month. The browning index and the antioxidant activity ranged between 0.00 and 0.27 AU and 3.0–65.3 mg(GAE)/L, respectively. The development of several volatile organic compounds was demonstrated (up to 47). The identified compounds were mostly furans, with 5-hydroxymethylfurfural as the most abundant. For the first time, it was shown that the origin of sotolon in sweet wine can be associated with the acid-catalyzed fructose degradation mechanism. Other 2(5H)-furanones were also identified. It could be concluded that part of the browning, antioxidant activity and aroma compounds developed in sweet fortified wines is associated with the thermal degradation of fructose in acid medium.