The effect of chilling and 1-MCP on quality attributes and physicochemical aspects of cell wall components of Passe-Crassane pears

Most winter pear cultivars, including Passe-Crassane, do not ripen at warm temperatures. Post-harvest exposure to chilling temperatures is re-quired for synchronize the onset of the climacteric increase in ethylene production and the ripening of individual fruit. During ripening pears softened, developing a melting texture after a period of shelf life. Softening and textural changes result principally from primary cell wall modifications. This study was initiated to evaluate the changes in cell wall fractions throughout the postharvest life of Passe-Crassane, comparing them with loss of firmness and with the production of ethylene dur-ing cold storage, ripening and failure to ripen. Pears (Pyrus communis L. ‘Passa Crassana’) were picked at commercial ripening stage; one group was kept at 20°C, another was stored at 0° C and a third group was treated with 400 ppb of 1-MCP for 12 h before cold stor-age. Fruits were sampled after 30 days and cold-stored fruits after 135 days too. Flesh firmness was evaluated using a hand penetrometer. Internal ethylene concentration was determined with a gas chromatograph equipped with an alumina column. Isolation of cell wall material (alcohol insoluble solids, AIS) was obtained by extraction of fruit tissue in boiling ethanol. Samples of water-soluble and water-insoluble fractions of AIS were assayed spectrophotometrically for total uronic acid (UA) and by GLC for noncellulosic neutral sugar compositio