Effect of the Cooling System and 1-MCP on the Incidence of Superficial Scald in ’Granny Smith’ Apples
A study was carried out to determine the effects of two cooling systems and the application of 1-methylcyclopropene (1-MCP, SmartFreshTM) on the incidence of superficial scald in apples (Malus domestica Borkh.) cv. Granny Smith. Fruit were collected from a commercial orchard (Colbún, Maule Region, Chile) during 2004-2005 season. A completely randomized design was used in a 2 x 2 factorial arrangement, using cooling systems (normal and step-wise cooling) and application of 1-MCP (0 and 625 nL L-1 i.a.) as the main factors. Fruit from normal cooling were kept at 0 °C throughout the storage period (180 days). Step-wise cooling consisted of storing the fruit at 10 °C for 10 days; 4 °C for the next 20 days and 0 °C for the remaining 150 days. Every month, maturity indices and the chemicals, global antioxidant content (AO), α-farnesene (AF) and conjugated trienes (TC), were measured. Incidence of superficial scald was determined after 180 days of storage, plus 10 days at 20 °C . The application of 1-MCP with both cooling systems was capable of maintaining firmness values around 8,2 kg up to the end of the storage period, as well as decreasing the concentration of AF, TC and AO during storage. Incidence of superficial scald on fruit with 1-MCP was 0%, regardless of the type of cooling. Among treatments without 1-MCP, step-wise-cooling was more effective in preventing superficial scald, resulting in 1.3% incidence compared to 75.6% with the normal cooling system. Nevertheless, from the fourth month onwards firmness was lower than that required for export.