Conference pears (Pyrus communis L.) were treated with 25 and 50 nL L(-1) 1-methylcyclopropene (1-MCP) at -0.5 degrees C for 24 h, then stored for up to 22 weeks in air (NA) and controlled atmosphere (CA). After 7 and 14 weeks of storage, fruits were retreated with 1-MCP. After 7, 14, and 22 weeks of storage, fruits were kept for up to 7 days at 20 degrees C in air for poststorage ripening. The effects of 1-MCP treatment declined with duration of storage in both storage atmospheres, indicating that retreatments had little additional effects on subsequent ripening. Ethylene production was lower and firmness was higher in 50 nL L(-1) fruits, while the 25 nL L(-1) dose was not very different from the control. Development of superficial scald was not prevented by 1-MCP treatments, but the severity of the symptoms was influenced. The 1-MCP effects were perceivable on texture (juiciness) and flavor. Control fruit and 25 nL L(-1) fruit reached their best sensory quality after 14 weeks of storage, while 50 nL L(-1) fruit reached the same sensory quality later, keeping a fresh flavor when the quality of control fruit declined and became watery or grainy. The fresh flavor in 50 nL L(-1) fruit was probably due to the presence below the odor detection threshold concentrations of the volatile compounds responsible for the "ripe pear" aroma, mainly of butanol and ethyl butanoate. CA prolonged or enhanced the effects of 1-MCP; 1-MCP cannot substitute for CA but can reinforce the CA effects.

To investigate the causes of brown heart (BH) in Conference pears, the contents of ascorbic acid (AA) and dehydroascorbic acid (DHAA) in fruits were studied during the ®rst period of storage. AA was studied in 1999 and 2000, DHAA in 1999 only. Pears from normal and very late harvest stored immediately or after a delay in a controlled atmosphere with 2% O 2 and low (0.7%) or high (5%) CO 2 were compared. DHAA content did not change during storage in any treatment. AA decreased in storage according to an exponential model. The rate of AA loss was different in the two years and was higher in late-harvest fruits and in those stored in 5% CO 2 . BH appeared in different treatments when AA decreased below a threshold, which was about 2 mg kg À1 fresh weight, corresponding to 5% of the AA content at harvest. The frequency and severity of symptoms depended linearly on the time spent by fruits in low-ascorbate conditions. Advanced maturity at harvest and storage in high CO 2 determine the appearance of BH and increase the rate of AA loss, probably through a reduction in the turnover of antioxidants.

“Big Top” nectarines picked at two dates (Pick 1 and Pick 2) and treated at harvest with 0 (control), 0.25, 0.5 and 1.0 µL/L 1‐methylcyclopropene (1‐MCP) when fruit ripening had already started were kept at 20 C until control fruit softened. Ethylene production was lowered by 0.25 and 1.0 µL/L doses in Pick 1 fruits and by all the doses in Pick 2 fruits. Fruit softening was delayed, but at the end of shelf life, treated fruits were as soft as the controls. Total volatile production was lowered by 0.25 and 1.0 µL/L doses in Pick 2 fruits. 1‐MCP influenced the aroma composition at the end of shelf life, yet it was not always dose dependent. Consequently, 1‐MCP changed fruit odor pattern by influencing the distribution of lactone odor units, the major odor contributors, reducing the “overmature” note and enhancing the “fresh” note.

No abstract

No abstract