- Controlled atmosphere (CA) allows long-term storage of European pears (Pyrus communis L.) without chemical treatment to deliver a natural melting (buttery and juicy) texture for consumers. However, the relationship between textural properties and cell wall metabolism as influenced by O-2 regimes has not been comprehensively determined. In this study, 'Golden Bosc' and 'd'Anjou' pears were stored in 21 (air), 2, 1, or 0.5% O-2 with < 0.5% CO2 for up to 8 and 10 months at -1.1 degrees C plus 7 d of ripening at 20 degrees C, respectively. Melting texture development in both cultivars showed high correlations with the level of water-soluble polyuronides (WSP) and activity of beta-galactosidase (beta-GAL). Also, activities of pectin methylesterase (PME) and alpha-arabinofuranosidase (alpha-ARF) were associated with softening in 'Golden Bosc' pears. Concentrations of CDTA-soluble polyuronides (CSP) and WSP + CSP + sodium carbonate-soluble polyuronides (SSP), as well as ethylene production showed positive correlations to melting texture in 'd'Anjou' pears. Reducing O-2 concentrations from 21% to 2--1% and 1-0.5% in 'Golden Bosc' and 'd'Anjou' pears allowed pears to develop a desirable eating texture during ripening for up to 8 and 10 months, respectively, with a commercially acceptable levels of postharvest disorders. Use of 1-0.5% O-2 resulted in a melting texture in 'Golden Bosc' pears, but fruit developed more core browning when ripe. These results indicate that O-2 regimes regulate textural qualifies by influencing WSP level and beta-GAL activity.