Influence of postharvest temperatures and the rate of fruit ripening on internal postharvest rots and disorders of New Zealand ‘Hass’ avocado fruit

Abstract

Postharvest rots and internal disorders of 'Hass' avocado (Persea americana) fruit develop during the latter stages of fruit ripening, with symptoms first appearing when fruit are minimally ripe but often becoming quite severe before the fruit are oversoft. Fruit ripened at 20°C and assessed at the same stage of ripeness, just before the flesh becomes oversoft, had fewer postharvest rots if they had been previously stored at 4 or 6°C, than if they had been stored at either lower or higher temperatures. Postharvest disorders increased with increased length of storage. Fruit failed to ripen properly at 30°C. Even at 25°C (a temperature typically experienced by fruit exported from New Zealand), the level of postharvest disorders was greater than in fruit ripened at 20°C. Best final quality was obtained with fruit coolstored at 6°C and then ripened at 15 °C. However, if fruit are to be ripened at c. 25°C, then final quality was better if the fruit were not coolstored but held at a temperature closer to the final ripening temperature. Fruit from a single orchard block, harvested, coolstored, and ripened together, individually reached minimum eating ripeness over an 8-day period. Fruit which ripened earliest had the fewest disorders, with later ripening fruit typically having high levels of postharvest rots and internal browning.

Influence of cold storage prior to and after ripening on quality factors and sensory attributes of ‘Hass’ avocados

“…The fruit that were not partially ripened prior to storage showed a declining amount of decay with storage. This observation is in line with the observations of Hopkirk et al (1994) and Smilanick et al (2002). In avocados receiving cold storage, however, stem end rots occurred more frequently in the partially ripened fruit, particularly in fruit stored for 14 d. In this fruit decay rates exceeded 30% and 50% for fruit stored at 5 C and 12 C, respectively.…”

Low temperature conditioning treatments reduce external chilling injury of ‘Hass’ avocados

“…For the November experiment, fruit were ripened at 15 8C and fruit quality assessed. A temperature of 15 8C was employed to reduce disease incidence (Hopkirk et al, 1994). Fruit temperatures were monitored throughout treatment using Squirrel Data Loggers (Model 1206; Grant, Cambridge, UK) equipped with thermistor temperature probes (CM-UU-V5-1; Grant, Cambridge, UK).…”

“…Once ripe, fruit quality was determined by cutting fruit into quarters longitudinally, and the following factors evaluated: hard skin (hardness or brittleness of the skin determined when cutting and peeling back the skin), uneven ripening (uneven flesh softening such that flesh tissue adhered to the seed when fruit was cut in half), tissue breakdown (breakdown of emerald green flesh adjacent to the skin such that tissue adhered to the skin when peeled), body rots (rots entering through the skin), stem end rots (rots entering only through the fruit peduncle), vascular browning (browning of the vascular strands running longitudinally through the fruit tissue), flesh browning (browning of the fruit tissue not due to disease or vascular browning), and seed cavity browning (browning of the fruit tissue in the seed cavity which is not due to disease or flesh browning). Each factor was rated on a scale from 0 to 3 in 0.5 intervals, where 0 0/no occurrence; 10/slight; 20/a level at which the consumer would possibly reject the fruit; 30/ severe (Hopkirk et al, 1994). The proportion of sound fruit was defined as the percentage of fruit with no unacceptable damage levels (rating B/2) with each fruit rated individually as sound or not at the time of assessment.…”

Hot water treatments improve ‘Hass’ avocado fruit quality after cold disinfestation

“…The lower ripening temperatures used in the second experiment can reduce fruit rots (Hopkirk et al, 1994), but probably contributed to the poor purple-black skin colour on ripe fruit (Hofman, unpublished results). The skin colour of eating soft 'Hass' fruit is important, since poor skin colour in ripe fruit can result in consumption being delayed until full purple/black colour is obtained.…”