Evaluation of induced pitting damage of late season cherries ’Regina’ and ’Sweetheart’ using an impact energy method
Late season cherry (Prunus avium [L.] L.) cultivars have turned of important relevance in production systems of the south of Chile with a continuous increase in exports. Cherries reach final markets after long distance ocean shipping and pitting damage continues to be the main postharvest detrimental quality loss during this period. Different factors affect pitting expression responses during harvest and postharvest fruit management. The aim of this study was to determine the influence of postharvest factors in pitting development of two late cherry ’Regina’ and ’Sweetheart’ using an impact energy method. Maturity stage (red and dark red), impact energy (0.00342 and 0.0107 J) and storage time (0, 7, 14, 21, 28 d) were evaluated. Fruit composition (soluble solids, pH, and titratable acidity), weight loss (%) and firmness were measured. Induced pitting was determined after allocating a known impact energy level and obtaining an imprint of the damaged area. Pit diameter, depth and volume were determined by light microscopy techniques and image analysis. Pitting damage that occurred naturally on fruit picked at commercial maturity stage was determined at harvest and during cold storage. The induced pitting device allowed for the application of a mechanical injury of known impact energy, useful to determine pitting susceptibility differences among cultivars. The coefficient of variation of the method was 0.18 for pit diameter, 0.37 for pit depth and 0.6 for pit volume, indicating repeatability of results independent of the impact energy applied or the variety studied. ’Sweetheart’ showed higher incidence of induced pitting during storage, with an average 2.8 pit volume increase compared to a 2.2 increase in ’Regina’ during the same period. Naturally occurring damage of commercial fruit verified results obtained with the induced pitting device, with ’Sweetheart’ more susceptible than ’Regina’ (P < 0.05).