The effect of temperature on the color of red wines.

UNLABELLED: The effect of increased temperature on the color of red wines was studied due to its importance during storage and transport. The chemical reactions induced by elevated temperature were investigated by measuring the UV-VIS spectra. The temperature of the wines was increased from its common storage temperature (about 14 °C) to higher temperatures (t= 20 °C, 25 °C, 30 °C, 35 °C, and 40 °C) and the UV/VIS spectra were recorded during several hours. The spectral changes obtained indicate the presence of quasi-first-order chemical processes justifying determination of the activation energies using their temperature dependence. The determined decay values (Villányi Portugieser: E(VP) (a,420 nm) = 90.02 kJ/mol, E(VP) (a,520 nm) = 34.18 kJ/mol, E(VP) (a,620 nm) = 54.55 kJ/mol; half-life values of 46.5 d [25 °C] and 9.5 d [35 °C] at 420 nm; 4.67 d [25 °C] and 2.0 d [35 °C] at 520 nm; 9.5 d [25 °C] and 2.4 d [35 °C] at 620 nm; Bikatory wine: E(Bk) (a,420 nm) = 82.07 kJ/mol and half-life values of 41.35 d [25 °C] and 4.001 d [35 °C] at 420 nm) of these reactions highlight a considerable change in the quality of wines stored for a few hours at elevated temperatures. Depending on polyphenol composition the wines show different half-life with regard to their color stability and browning reactions. Higher polyphenolic content helps to stabilize the wine against detrimental temperature effects. PRACTICAL APPLICATION: This research can be applicable to estimate the optimal temperature of red wines during storage and transport.