Constant storage temperature delays firmness decreasing and pectin solubilization of apple during post-harvest storage

The aim of this study was to evaluate the effect of storage temperature fluctuation (temperature variation cycles about 6 hr) on the firmness and pectin solubilization of "Fuji" and "Golden Delicious" during storage. Results showed that apples in 5 +/- 0 degrees C group showed the lowest firmness decreasing level (15.86% for "Fuji", 24.76% for "Golden Delicious") coupled with the minimum ethylene production, and the slowest inter-converting of chelate-soluble pectin and sodium carbonate-soluble pectin to water-soluble pectin compared with that of 5 +/- 5 degrees C and 5 +/- 1 degrees C. Moreover, the enzymatic activities (PG, PME, beta-Gal, alpha-L-Af) were at the lowest level in 5 +/- 0 degrees C temperature fluctuation groups both of "Fuji" and "Golden Delicious". Ultrastructural observations also revealed that constant temperature could restrain the solubilization of pectin and the dissolution of middle lamella. Besides, the impact of 5 +/- 1 degrees C on "Golden Delicious" was more significant relative to "Fuji". In practical applications, the temperature supervision on "Fuji" could be appropriately relaxed compared with "Golden Delicious" during short-term storage. Novelty impact statement Constant storage temperature retarded the firmness decreasing by delaying the solubilization of cell wall pectin and suppressed the activities of cell wall degrading enzymes of "Fuji" and "Golden Delicious" cultivars. Constant storage temperature Constant storage temperature retarded the dissolution of the middle lamella between the cell walls of "Fuji" and "Golden Delicious" cultivars. "Golden Delicious" cultivar was more sensitive to the variation of storage temperature compared with "Fuji" cultivar.