Effects of Low Oxygen/High Carbon Dioxide Controlled Atmosphere Combined with 1-Methylcyclopropene on Quality of Yuluxiang Pear During Cold Storage

The objective of this study was to clarify the effects of a controlled atmosphere (CA) with low oxygen (O₂)/high carbon dioxide (CO₂) on chlorophyll maintenance and quality of Yuluxiang pears during cold storage, so as to provide a theoretical basis and technical support for prolonging the storage life of Yuluxiang pear.

The storage experiments were performed with commercial mature Yuluxiang pears treated with 1.0 µL·L^-1 1-Methylcyclopropene (1-MCP), 1% O₂, 3% CO₂, and 1.0 µL·L^-1 1-MCP combined with 1% O₂ and 3% CO₂, with air treatment as the control. The peel color, chlorophyll content, firmness, total soluble solids, titratable acid, ascorbic acid, and other quality indices were measured at 210 and 240 days of storage and 7 days of shelf life, respectively. Ethanol and acetaldehyde content, ethylene production, and respiratory rate of the fruits were detected by gas chromatography, and the browning indices of the fruit stalk and core were investigated and calculated.

Compared with ordinary cold storage, 1-MCP, CA, and CA+1-MCP could better maintain the green color of Yuluxiang pear fruits and effectively reduce the degree of greasiness on the fruit surface. CA+1-MCP had a more pronounced effect on the green color maintenance and greasiness control of the peel when they were refrigerated for 240 days and 240+7 days. 1-MCP and CA could inhibit the decline in fruit firmness, total soluble solids, and titratable acid. CA could inhibit browning of the core and stalk, but CA used alone reduced the content of ascorbic acid in the fruits, and CA+1-MCP slowed the decline of ascorbic acid in CA fruits. The inhibitory effect of CA+1-MCP on ethanol and acetaldehyde was more apparent when stored for 240 days, and the ethanol content of 20 mg·L^-1 was below the tolerance threshold of Yuluxiang pears. CA+1-MCP and 1-MCP had strong inhibitory effects on ethylene production across the entire storage period. At 240 days, CA+1-MCP and CA had a stronger inhibitory effect on the respiratory rate than 1-MCP.

Yuluxiang pears were respiratory climacteric pears, resistant to low O₂ and high CO₂. The freshness maintenance effect of CA+1-MCP on Yuluxiang pear was maintained after 210 days. Therefore, when the cold storage period was less than 210 days, a single 1-MCP treatment of 1.0 µL·L^-1 could be used. When the cold storage period was greater than 210 days, the fruit should be first treated with 1.0 µL·L^-1 1-MCP, and then stored under CA with low O₂/high CO₂ of 1% O₂ and 3% CO₂, which could maintain the appearance and internal quality of fruits, as well as significantly prolong the cold storage life.