Repeated application of dynamic controlled atmospheres reduced superficial scald incidence in ‘Granny Smith’ apples

This study investigated the influence of repeated dynamic controlled atmosphere (DCA) application to control superficial scald of ‘Granny Smith’ apples. Fruit were stored for up to 16 w in DCA with a 14 d of interruption with regular air (RA) at −0.5 °C, 95% RH. Fruit was again stored in DCA. The scald potential for each storage time in each season was assessed by storing fruit in RA and used as the control, in order to ascertain the efficacy of repeated DCA treatments. Superficial scald incidence, total soluble solids (TSS), titratable acidity (TA), ground colour, fruit firmness and ethylene production were measured. Alpha-farnesene and 6-methyl-5-hepten-2-one (MHO) production were also measured using gas chromatography (GC–MS). Principal component analysis (PCA) was used to visualize metabolic changes and the relationship among them. Results showed maximum superficial scald incidence of 2% and 99% in repeated DCA and RA, respectively. Fruit stored in DCA repeatedly was characterized by a higher fruit firmness, ground colour and titratable acidity. Ethylene, α-farnesene and MHO production were significantly lower in repeated DCA compared to only RA stored fruit. Seasonal changes had no significant effect on metabolic parameters studied. The data distribution in the PCA displayed two clusters that could easily be identified. These clusters allowed distinction between fruit stored in RA only and repeated DCA. Ethylene, α-farnesene and MHO production had a strong and positive correlation with scald incidence. This study demonstrated that repeated DCA treatments can effectively control superficial scald.