Effect of different pre-treatment maceration techniques on the content of phenolic compounds and color of Dornfelder wines elaborated in cold climate.

This study present the effects of different pre-treatment maceration techniques (microwave, thermo-maceration, and enzymatic treatment) on the content of phenolic compounds (by UPLC-PDA) and their redox potential by cyclic voltammetry (CV), antioxidant capacity (ABTS radical cation decolorization assay and FRAP as Ferric Reducing Ability of Plasma), and other basic chemical properties of red wine made from cv. Dornfelder. The pre-treatment maceration technique significantly (p < 0.05) affected the content of total phenolics in Dornfelder must (freshly crushed grapes), with particularly high amounts in the must pre-treated by microwaves (4344.0 mg/100 mL), and the lowest in the must pre-treatment by thermo-maceration (2979.8 mg/100 mL). A positive correlation was found between the content of total phenolics and antioxidant activity (R = 0.69 and 0.52 by ABTS and FRAP assay, respectively) and individual groups of polyphenols (for ABTS assay with anthocyanins, flavonols, flavan-3-ols, respectively R = 0.60, 0.64 and 0.66, while for FRAP method only for anthocyanins R = 0.79). The highest antioxidant activity was also determined for the variant with microwave pre-treatment (must 3.31 mM and 3.05 mM Trolox/100 mL for ABTS and FRAP assay, respectively). Following the fermentation and maturation, the amount of polyphenols decreased. No thermal pre-treatment maceration methods gave lighter or redder must. After winemaking process all the samples were characterized by less red and more yellow shade.