Effect of ripening on texture, microstructure and cell wall polysaccharide composition 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. Scanning 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 black olive tissues. Cell separation occurred in the middle lamella region in some of the cells of the cherry fruit and in most of the black olive cells. Solubilization and loss of pectic polysaccharides, mainly the arabinan moiety, and glucuronoxylans occurred in the green to cherry stages. The pulp cell wall constituent polysaccharides, pectic polysaccharides, cellulose, glucuronoxylans and xyloglucans, were degraded and/or solubilized at the cherry to black ripening stages. The resultant depolymerization of the pectic polymers, especially those of the middle lamella region, was consistent with the progressive cell separation at the different ripening stages by SEM. This showed that partial solubilization of pectic, hemicellulosic and cellulosic polysaccharides within the cell wall matrix weakened the cell wall structures, preventing the breaking of cells when the tissues were fractured.
Mafra
Isabel
I
Departamento de Química, Universidade de Aveiro, P-3810-193 Aveiro, Portugal; Istituto Sperimentale per la Elaiotecnica, Contrada Fonte Umano n.37, Città S. Angelo (PE), I-65013 Italy.
Lanza
Barbara
B
Reis
Ana
A
Marsilio
Vincenzo
V
Campestre
Cristina
C
De Angelis
Mario
M
Coimbra
Manuel A.
MA