Rezumat articol ediţie STUDIA UNIVERSITATIS BABEŞ-BOLYAI

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The kinetics of formation of malvidin-caffeic acid and malvidin-catechin complexes was studied by time-dependent recording of the photo­luminescence (PL) signal of malvidin. The molecular environment was changed according to the fermentation process in red wines: water – ethanol mixtures with up to 14 %vol of ethanol was applied as binary solvent. Two reaction channels were examined according to the order of complex formation. In the first case, the aqueous solutions of malvidin and polyphenols were mixed, then the ethanol content was elevated according to the actual grade of fermentation. In the second case, the stock solutions are prepared as binary solvent mixtures. Our results show a faster formation of the complexes in the former case. Kinetic parameters show that the activation energy of the first reaction channel is lower and the frequency factor is higher, supporting a higher reaction rate. These observations are applicable to a wide range of chemistry where the molecular environment is composed of binary solutions. In particular, it has significant consequences for winemaking procedures, where one method of color improvement is based on the association of the species examined in this work.