Postharvest physiology of kiwifruit in tropical environments

New Zealand's kiwifruit export supply chain includes distribution to tropical climates. Notably, the Middle East and southeast Asian countries represent large developing markets with substantially higher ambient temperature and relative humidity conditions. Fruit sales in these regions can be dominated by wet markets causing fruit exposure to extreme environmental conditions before consumer purchase. There is a general paucity of data on how temperate fresh produce respond to tropical environmental conditions postharvest at the end of the supply chain. The objective of this study was to compare shelf-life performance for kiwifruit (Actinidia sp.) exposed to regional extremes i.e., hot/humid: 33 degrees C and 87% RH and hot/dry: 40 degrees C and 30% RH conditions, with typically studied shelf-life conditions (20 degrees C and 75% RH). The influence of packing with a layer of polyethylene in these conditions was also studied. Respiration rate and fruit quality parameters (weight loss, firmness, total soluble solids and titratable acidity) were monitored for 5 days. As expected, fruit stored at 40 degrees C conditions had the highest rate of respiration, softening and weight loss followed by 33 and 20 degrees C. An approximate 6-fold rise in respiration rate (when compared to 20 degrees C peak range) was observed in the initial 12 h of exposure to 40 degrees C which later plummeted to less than 20% of the peak 2 days later. In contrast at 33 degrees C, the respiration rate was found to remain within 80% of the peak range during the entire storage period. It appears that 40 degrees C and 30% RH led to significant changes in fruit physiology within less than 1 d that may result in fruit damage as evidenced by rapid respiratory decline. This result raises the question of what combination of conditions (temperature and time of exposure) will cause damage to kiwifruit in these potential end of market scenarios.