Abstract: The effect of 1-methylcyclopropene (1-MCP) treatment on softening-related compound contents and enzyme activities in “Yueshuai” apples during cold storage was investigated, and the regulatory mechanism of 1-MCP treatment on the softening of “Yueshuai” apples was also explored for the purpose of providing the theoretical basis for the preservation of “Yueshuai” apples. The apples were stored at (0.0 ± 0.5) ℃ and relative humidity of 90%–95% after pretreatment with 0.0, 0.5, 1.0 and 2.0 μL/L 1-MCP. The fruit firmness, respiration intensity, ethylene production rate, cell wall components and related enzyme activities of “Yueshuai” apples were determined at regular intervals during storage. The peaks of respiration and ethylene production rate appeared after cold storage for 30 days; at the same time, polygalacturonase activity reached its peak. The peaks of pectin methyl esterase, cellulose and β-glucosidase appeared after cold storage for 45 days; the water-soluble pectin content was increased rapidly and protopectin and cellulose content were decreased constantly during the 45 days of storage. Treatment with 0.5 μL/L 1-MCP delayed the peaks of respiration intensity, ethylene production rate, and polygalacturonase (PG) and cellulose (Cx) activity. It significantly inhibited the decline in protopectin and water-soluble pectin contents rather than the decline in fruit firmness at the end of cold storage (P < 0.05). In addition, 1.0 and 2.0 μL/L 1-MCP treatment could significantly inhibit respiration intensity, ethylene production rate, the activities of cell wall-degrading enzymes, the contents of pectin and cellulose, and the decline of fruit firmness (P < 0.05). During cold storage, protopectin and cellulose were decomposed continuously, leading to continuous generation of water-soluble pectin and a rapid decline of fruit firmness. The activity peak of all cell wall-degrading enzymes expect PG appeared after the peaks of respiration and ethylene production rate. Respiration intensity and ethylene production rate could control the softening of “Yueshuai” apples. In conclusion, 1-MCP treatment can delay the degradation of cell wall components and suppress the softening of “Yueshuai” apples by inhibiting respiration intensity, ethylene production rate and fruit softening-related enzyme activities. Meanwhile, the effect of 1.0 and 2.0 μL/L treatment is more significant.

Key words: 1-methylcyclopropene treatment, “Yueshuai” apple, cold storage, softening, physiology