DYNAMIC CONTROLLED ATMOSPHERE STORAGE OF NEW ZEALAND-GROWN 'HASS' AVOCADO FRUIT

Abstract

To obtain the maximum benefits from dynamic controlled atmosphere (DCA) storage, several parameters of operation need to be optimised. These parameters include the time after harvest at which the lowest safe O 2 level is first established (delay), the degree of back-off in O 2 above the low O 2 stress point (back-off), and the frequency of resetting the lowest safe O 2 level during storage (frequency). The DCA operating parameters delay, back-off and frequency were investigated by storing 'Hass' avocado fruit for 6 weeks at 5°C in DCA. Fruit were held in air for 48 or 96h after harvest before the initial lowest safe O 2 level was established by backing-off by 0.2 or 0.8% O 2 . The lowest safe O 2 level was reset every 10 d (repeat) throughout storage, or left as that achieved at the start of DCA (once). In addition, to determine whether the fruit response to the DCA operating parameters changes through the harvest season, fruit were harvested during the early (late October), mid (mid December) and late (mid February) periods of the harvest season. Fruit quality following DCA was optimised by setting the DCA O 2 level soon after harvest, backing-off to just above the low O 2 stress point, and repeatedly re-setting the O 2 level during storage. The main effect of frequency was on skin colour and rots (fuzzy patches; FP) at the end of storage, and on the time to ripen after storage. In contrast, the effects of back-off were on FP and diffuse flesh discoloration and delay on stem-end rot expression. There were no major differences in the responses of fruit harvested at different times of the season to the DCA operating parameters. It is concluded that for New Zealand-grown 'Hass' avocados, DCA should be established within 2-4 days of harvest, backing-off to just above the low O 2 stress point and resetting the lowest safe O 2 level every 10 days.