Physiological disorders, textural property, and cell wall metabolism of ‘Gem’ pears (Pyrus communis L.) affected by oxygen regimes and harvest maturity under controlled atmosphere storage

Abstract

The primary purpose of this study was to develop optimal controlled atmosphere (CA) strategies for the pear industry to utilize ‘Gem’ pears. The influences of two O2 regimes (1.0% O2 and 2.2% O2 [commercial practice concentration] with ∼0.05% CO2) on decay, physiological disorders (i.e. internal breakdown, superficial scald, and black speck), storage and eating quality attributes, cell wall components, and cell wall-modifying enzymes were evaluated at two harvest maturities (H1; 48.01 N; H2; 42.19 N) of ‘Gem’ pears. Earlier harvested pears (H1) stored under regular-air (RA) conditions had lower rates of superficial scald and internal breakdown relative to later harvested pears (H2), especially in extended storage (8–10 months). However, storage and eating quality for air-stored H1 and H2 fruit deteriorated after 6 months. CA regimes extended ‘Gem’ storage longevity from 8 to 10 months, with 1.0% O2 resulting in lower incidences of superficial scald and internal breakdown disorders and higher peel chlorophyll content and titratable acidity by delaying the peak of ethylene production rate (EPR) compared to 2.2% O2. Notably, the rates of black speck in H1 and H2 fruit were controlled at below 5% in both O2 regimes. Furthermore, 1.0 and 2.2% O2 stored H1 and H2 pears ripened and developed a melting texture with full flavor and juiciness during 6–8 months of storage. Additionally, the water-soluble (WSP), cyclohexanetrans-1,2-diaminetetra-soluble (CSP), and Na2CO3-soluble polyuronides (SSP) combined with pectin methylesterase (PME), α-arabinofuranosidase (α-ARF), and β-galactosidase (β-GAL) contributed to fruit softening and desirable eating quality in ‘Gem’ pears. In conclusion, 2.2% O2 with ∼0.05% CO2 improved the fruit quality of ‘Gem’ pears harvested at 48.01 N, while the quality of fruit harvested at 42.19 N or below could be improved by the application of 1.0% O2.