Utilisation of SmartFreshSM and /or pre-ripening to enable successful shipping of dual-temperature regime plums at a single temperature of -0.55 °C for 24 days for cold-sterilization purposes

This project was conducted to establish if SmartFresh^SM application and warming treatments utilized during cold storage can counter quality losses which may develop during cold-sterilization treatment of plums traditionally stored at dual-temperature.

Five cultivars were sourced from Franschhoek, Montagu and Stellenbosch over three seasons, and subjected to the different treatments and temperature regimes as indicated in the report. The fruit were evaluated after applicable cold storage periods and after a subsequent shelf life period of 5 days at 10 °C.

Cultivar differences were evident. Quality maintenance of African Rose, Sapphire, Fortune and Ruby Red plums were best maintained over the 3 seasons of testing, by applying SmartFresh^SM during the accumulation period, followed by no warming before shipping [T6] and applying SmartFresh^SM during the accumulation period, followed by 3 days warming at 20 °C before shipping [T4]. However, quality maintenance of African Rose, Sunkiss and Sapphire (based on end of cold storage results of Sapphire) plums were also maintained by applying SmartFresh^SM during the accumulation period, followed by 10 days warming at 7.5 °C before shipping [T1] in some of the seasons. Quality maintenance was worst by not applying SmartFresh^SM during the accumulation period, followed by no warming or 3 days warming at 20 °C before shipping [T7 and T5, respectively].

The results obtained over the three seasons needs to be confirmed, since growing conditions across seasons and different populations of fruit may affect the reaction of the fruit to the treatments along with the cold-sterilization conditions.