Effect of ripening on texture, microstructure and cell wall polysaccharidecomposition of olive fruit (Olea europaea)

Olive fruits at the green, cherry and black stages were used to investigate the structural and microstructural changes in tissues during ripening. Sca nning electron microscopy (SEM) tissue fracture of green olives resulted in cell wall breakage of epicarp and mesocarp cells. Tissue fracture resulted in fewer broken cells in cherry than in green olives and even less in blac k olive tissues. Cell separation occurred in the middle lamella region in s ome of the cells of the cherry fruit and in most of the black olive cells. Solubilization and loss of pectic polysaccharides, mainly the arabinan moie ty, and glucuronoxylans occurred in the green to cherry stages. The pulp ce ll wall constituent polysaccharides, pectic polysaccharides, cellulose, glu curonoxylans and xyloglucans, were degraded and/or solubilized at the cherr y to black ripening stages. The resultant depolymerization of the pectic po lymers, especially those of the middle lamella region, was consistent with the progressive cell separation at the different ripening stages by SEM. Th is showed that partial solubilization of pectic, hemicellulosic and cellulo sic polysaccharides within the cell wall matrix weakened the cell wall stru ctures, preventing the breaking of cells when the tissues were fractured.