On the electroporation of mash for the production of red wine

Summary form only given. In the course of the production of red wine, fermentation or heating are traditional methods for the disruption of the cells in the grape skin in order to extract the red pigments. Although fermentation is considered to guarantee the best quality of the wine, the extraction takes several days. A faster way is the thermal treatment, but extensive heat may have a bad influence on the flavor. An alternative method to foster the extraction of substances from biological cells is electroporation. It allows a fast processing without a remarkable temperature increase of the material. In recent years the electroporation of mash has been investigated. The experiments had been performed with the electroporation device KEA-WEIN manufactured by KEA-TEC based on the know-how by Forschungszentrum Karlsruhe. Although an extraction of the pigments within 24 h could be observed, the color of the electroporated must was less intense than the color of the thermally treated one. To analyze the electroporation assisted extraction process, laboratory-scale experiments have been performed. For the electroporation the numbers of applied pulses and the field strength have been varied. The electroporation effect has been verified by means of an impedance measurement. These results have been compared to a thermal denaturation with a subsequent extraction process. For the extraction the temperature has been varied. With an extraction at room temperature, both methods show nearly the same yield of tannin and color intensity. The original electroporation reactor of the electroporation device KEA-WEIN has an inhomogeneous field distribution. While high-field regions foster a flash-over inside the reactor, an incomplete opening of the membrane may occur in the low-field regions. To guarantee a good electroporation effect now a new electroporation reactor with a more homogeneous field distribution has been implemented. In autumn 2007 approximately 1 m
³
of must have been treated with the new reactor successfully. After finishing the vinification process a comparison based on chemical analysis and additional sensoric tasting will be made to evaluate the quality.