Impact of fermentation technology on the phenolic and volatile compositionof German red wines

Homogenous grape material of the red Varieties c.v. Pinot noir, c.v. Dornfe lder and c.v. Portugieser were fermented on an industrial scale using a spe cial fermenter for pump over and punch down treatment. On pilot scale, ther movinfication was carried out at 60 degrees C and a manual punch down treat ment was used in open containers. Both the mechanical punch down and pump o ver treatment significantly enhanced the extraction of all phenolic compoun ds and their polymerization in comparison to the traditional manual punch d own treatment. Applying an excess of mechanical maceration increased the ex traction of seed and stem phenols, but slowed down their polymerization. As sessing volatile composition, the biggest differences occurred between wine s made by thermovinification versus those fermented on their skins. Slow fe rmentation kinetics and low solid content in the juice enhanced ester forma tion in thermovinied wines. Thermal inactivation of lipoxygenase enzyme sys tems reduced C-6-alcohols and their subsequent esters in thermovinified win es. Only small differences occurred between punch down and pump over tanks except that the pump over regime gave all varieties of wines significantly higher quercetin levels. In conclusion, the application of modem fermentati on equipment seemed to be more relevant to improve extraction and polymeriz ation of phenolic compounds, while thermovinification yielded wines with hi gh ester content giving a more fruity style.