Research was carried out to study the mode of action of diphenylamine (DPA) and 1-methylcyclopropene (1-MCP), on control of superficial scald of Granny Smith apples (Malus domestica Borkh.), and its relation with chemical compounds. Fruit was harvested from a commercial orchard in Chile, 182 and 189 days after full bloom and received the following treatments: DPA (2,000 ppm); 1-MCP (1.2 ppm) and control (no treatment). All fruit was stored for 4 or 6 months at 0°C. A completely randomized factorial design was used (2 harvest dates by 3 postharvest treatments). Monthly measurements were made on maturity indices, ethylene production rate (EPR), scald related compounds [α-farnesene (AF), conjugated trienes (CT), total anti-oxidants (AO)], and cell membrane stability. Following 4 and 6 months of storage, plus 7 days at 20°C, scald was evaluated. After 6 months, DPA-treated fruit, from both harvests, showed similar firmness, EPR and AO, compared to the control. However, AF and CT were lower, and cell membrane stability higher. Conversely, 1-MCP-treated fruit showed a noticeable EPR suppression and AF inhibition, along with higher firmness, lower CT and AO, compared to the control and DPA. Furthermore, cell membrane stability was superior to that of the control and similar to that of the DPA. Treated fruit (DPA and 1-MCP) showed an important reduction in scald compared to the control. The effect of 1-MCP on the investigated compounds and the reduction in scald, confirms that ethylene plays a major role on its development.Additional key words: alpha-farnesene, anti-oxidants, cell membrane stability, conjugated trienes, ethylene. ResumenEfecto de la aplicación de DPA y 1-MCP sobre compuestos químicos relacionados con el desarrollo de escaldado superficial de manzanas Granny Smith Se realizó una investigación para estudiar el modo de acción de difenilamina (DPA) y 1-metilciclopropeno (1-MCP) en el control de escaldado superficial de manzanas (Malus domestica Borkh.) Granny Smith y su relación con compuestos químicos. La fruta fue cosechada de un huerto comercial en Chile, 182 y 189 días después de plena flor y recibió los siguientes tratamientos: DPA (200 ppm), 1-MCP (1,2 ppm) y control (sin tratamiento). Toda la fruta fue almacenada de 4 a 6 meses a 0°C. Se utilizó un diseño factorial completamente al azar (2 fechas de cosecha × 3 tratamientos postcosecha). Mensualmente se realizaron mediciones de índices de madurez, tasa de producción de etileno (EPR), compuestos relacionados con el escaldado [α-farneseno (AF), trienos conjugados (CT), antioxidantes totales (AO)] y estabilidad de la membrana celular. El escaldado fue evaluado después de 4 y 6 meses de almacenaje, más 7 días a 20°C. Después de 6 meses, la fruta tratada con DPA, de ambas cosechas, mostró similar firmeza, EPR y AO en comparación al control. Sin embargo, AF y CT fueron menores y la estabilidad de la membrana celular mayor. Por otra parte, la fruta tratada con 1-MCP mostró una notable supresión de EPR e inhibición de AF, junto a una mayor firmeza, m...

A study was carried out to determine the effects of two cooling systems and the application of 1-methylcyclopropene (1-MCP, SmartFresh TM ) 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.

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