Electronic microscopy observations have shown that the pectolytic enzymes act differently on grape skin cell walls degradation and tannins release. PG and PL degrade the pectins from the middle lamella and the primary cell wall. They also favor mainly the release of the intravacuolar tannins. Cellulase degrades the cellulose fibres and allows the release of cell wall bound tannins; this result supports the idea that tannins from the cell wall may be linked to cellulose fibers. Skin hydrolysis occurs from the pulp cells up to the epidermic cell ones, mainly because the outer part of the skin is protected by the cuticule. Besides, the diffusion of the tannins remains uncertain since these observations have shown that despite the degradation of the cell wall, the cell keeps its integrity. This is due to cell and vacuole membranes that prevent the intra cellular compounds from spreading from the vacuole to the outer medium. (We advise you to read the entire article. Original title:"EXAMEN EN MICROSCOPIE ELECTRONIQUE DE L’INFLUENCE D’ACTIVITES ENZYMATIQUES PURIFIÉES SUR LES PAROIS CELLULAIRES DES PELLICULES DE RAISINS »)
