Effect of preharvest solar radiation on apple skin oxidative disorders during cold storage
Sunscald and superficial scald are physiological disorders of apple that develop during low temperature storage. Sunscald is exclusively observed on sun-exposed section, while superficial scald manifests itself on non-exposed skin. Malus × domestica, 'Granny Smith' sun-exposed (ET) and non-exposed tissues (NET) were compared during 0, 90, 120, 150, and 180 days of cold-storage (DCS) in terms of sunscald and superficial scald incidence, α-farnesene (AF) and conjugated trienes (CT), antioxidant activity (DPPH radical-scavenging), lipid peroxidation (thiobarbituric acid-reactive substances, TBARs) and maturity indices. After 90 DCS and 1 week at 20°C, sunscald was observed in ET and affected 41.4% of the fruit. Superficial scald was detected in NET and affected 66.5% of the fruit. At 180 DCS these disorders reached 100%. After long storage, AF concentration increased. The highest level (125.5 and 95.8 nmol cm-2 for ET and NET, respectively) was measured at 120 days of storage, but decreased at 180 days. CT in ET were lower during all storage period, but increased significantly in NET after 90 days in parallel with superficial scald symptoms. During all cold-storage period DPPH was significantly higher (P<0.05) in ET than NET. At harvest, ET showed significantly more TBARs (59.8 nmol g-1 FW) than NET (43.8 nmol g-1 FW). During storage, lipid peroxidation increased and reached at 180 days 101.8 nmol g-1 FW in NET and 75.5 nmol g-1 FW in ET. There were significant differences in fruit maturity between ET and NET. Flesh firmness and soluble solid concentration were higher in ET than NET throughout the sampling period. These results showed that different physiological oxidative process may occur in exposed and non-exposed tissues during cold storage and the higher antioxidant activities found in sun-exposed tissue were ineffective in preventing sunscald.
Vita, L.I., Gonzalez, N.F. and Colavita, G.M. (2016). Effect of preharvest solar radiation on apple skin oxidative disorders during cold storage. Acta Hortic. 1144, 325-332
Malus × domestica, sunscald, superficial scald, antioxidants, fruit quality