Effect of the rate and duration of forced air cooling on the quality of Imperial apricots and Pioneer and Songold plums
The original publication is available at http://www.actahort.org/books/682/682_218.htm
Gel breakdown (GB) and overripeness (OR) remain the biggest internal Problems with Prunus armeniaca L. ‘Imperial’, which makes the biggest contribution to the total volume of apricots exported from South Africa per annum. Prunus salicina L. ‘Pioneer’, an early season South African plum cultivar, ripens quickly on and off the tree which results in rejections for soft fruit at packing and on arrival overseas. ‘Songold’, a yellow, midseason plum cultivar tends to develop GB and OR during cold-storage in some seasons, which renders the fruit inedible and results in high rejection rates. Prompt cooling and good temperature management are essential to lower the rate of physiological deterioration of stone fruit. In some commercial depots in South Africa, forced air cooling (FAC) of stone fruit can take as long as 48 to 72 h, depending on the type of packaging. Consequently, the objective of this study was to determine the effect of the rate and duration of FAC on the fruit quality of different stone fruit cultivars. Fruit was subjected to the following FAC rates at a delivery air temperature of -1.0°C to a pulp temperature of 0°C for 6 h, 12 h, 24 h stepwise cooling and 48 h stepwise cooling for the apricot, and 12 h, 24 h, 48 h stepwise cooling, and 72 h stepwise cooling for the two plum cultivars. The fruit was evaluated after cold-storage and a simulated shelf-life period. The trial was conducted in two consecutive seasons. ‘Imperial’ apricots had the best internal quality after 6 h of FAC, ‘Pioneer’ plums were not affected by FAC rate or duration, and ‘Songold’ plums had the best internal quality when FAC was applied for 12 h and longer. These results on plums demonstrate that cultivar differences must be considered when drawing up handling protocols for stone fruit, as a blanket recommendation may lead to the induction of quality defects.