Correlation of softening and polyamines levels during controlled atmosphere storage of avocado

Correlation of Softening and Polyamines levels during the Controlled Atmospheres Storage of Avocado were examined. The fruit was harvested then stored for 9 weeks at 0oC in Controlled Atmospheres (CA) containing 2.5, 7.5 % O2 with 5 and 10 % CO2 in all combinations (4 mixtures) and air (20 % O2). The incidence of CI, textural change and polyamines concentration, rates of respiration, ethylene production was determined. Fruit stored for 9 weeks in 2.5 % O2 and 10 % CO2 softened after transfer to air while fruit from other mixtures containing 10 % CO2 did not soften. The polyamines concentrations were high on the day fruit were transferred from 0oC to 28oC after storage 3, 6 and 9 weeks and subsequently decreased during the ripening stage at 28oC. Polyamine concentrations in CA stored avocado were higher than those in air stored fruit. After 9 weeks of storage in CA at 0oC then transferred to air resulted in a slight increase in putrescine (PUT), a slight increase in spermidine (SPD) and a major decrease in spermine (SPN). Low oxygen concentration (2.5 %) at 0oC storage induced higher levels of polyamines and significantly inhibited the softening of fruit compared to fruit stored in air (20 % O2). Following 3 weeks storage at 0oC no indication of CI in all treatments after ripening for 6 days, but was light discoloration after 6 and 9 weeks storage and very severe in air storage. The rate of respiration and ethylene production of fruit stored in air were higher than those of fruit stored in CA treatments.