Responses of apple fruit to high shelf life temperatures

Abstract

Postharvest experiments include a shelf-life assessment following storage to ensure that retailers and consumers are presented with produce that is fresh and will not spoil too quickly once purchased. Typically, shelf-life assessments involve exposing produce to temperatures of 18-22°C for a period of up to 1 week, simulating conditions in retail outlets where environmental conditions are tightly controlled. However, these shelf-life assessments are not relevant for many markets including Asia where there can be limited or discontinuous cool-chain close to the point of sale (e.g., wet markets), exposing the fruit to temperatures exceeding 30°C. Changes in market demand have meant that increasing volumes of fresh fruits are being exported to these parts of the world and being exposed to these conditions. This research highlights the response of two apple cultivars exposed to high shelf-life temperatures (30°C). Results were found to be strongly cultivar dependent, with one cultivar expressing severe flesh browning within three days of exposure to 30°C, while the other cultivar was free from flesh browning under the same conditions. The susceptible cultivar had a respiration rate that was nearly two-fold higher than the other cultivar at these high temperatures, and had lower rates of ethylene production. The application of the ethylene inhibitor SmartFreshSM was found to exacerbate flesh browning, while treatments that advance ripening were found to reduce the condition. Overall, these results highlight the need to re-think the approach of postharvest scientists to shelf-life testing for fresh produce in new export markets. These results also indicate there may be a point at which ethylene production can be too low in apples, and that future strategies for managing ethylene may not be one of total elimination.