A nanostructural view of the cell wall disassembly process during fruit ripening and postharvest storage by atomic force microscopy

[Background] The mechanical properties of parenchyma cell walls and the strength and extension of adhesion areas between adjacent cells, jointly with cell turgor, are main determinants of firmness of fleshy fruits. These traits are modified during ripening leading to fruit softening. Cell wall modifications involve the depolymerisation of matrix glycans and pectins, the solubilisation of pectins and the loss of neutral sugars from pectin side chains. These changes weaken the cell walls and increase cell separation, which in combination with a reduction in cell turgor, bring about textural changes. Atomic force microscopy (AFM) has been used to characterise the nanostructure of cell wall polysaccharides during the ripening and postharvest storage of several fruits. This technique allows the imaging of individual polymers at high magnification with minimal sample preparation.