Effect of short heat treatments with a sodium bicarbonate solution on storability of the yellow germoplasm plum 'Meloni'

The behavior of a Sardinian plum cv Meloni was investigated according to short-heat treatments at 20, 50, 55 or 60 °C in water with 0 or 2% NaHCO3 (SBC) for 0, 15, 30, 45 or 60 seconds. Fruit were stored for 1 month at 5 °C and 95% RH followed by a simulated marketing period (SMP) at 20 °C and 80% RH for 6 days. Quality and decay percentage were monitored. Moreover fruit were artificially inoculated with P. expansum and stored for 10 days at 25 °C and 95% RH. Compared to control, all short-heat dip treatments lowered the degree of decay, and the efficacy was positively correlated with temperature and treatment duration. The use of SBC increased the efficacy in the decay control and the best results were attained at 55 and 60° C. Heat treatments increased levels of total flavonoids and antioxidant activity after SMP. Any of the heat treatments induced rind damage (browning or discoloration), but the overall appearance decreased significantly when fruit was treated at 55 or 60 °C for 60 s after SMP. Scanning electron microscopy (SEM) observations showed that treatments at 55 and 60 °C with SBC cause damages and loss of cuticular wax on fruit surface.