ABSTRACT
The effect of pre- and postharvest applications of 200 and 400 μgL-1 aqueous solutions of 1-methylcyclopropene (1-MCP) on yellow pitaya (maturity stage 3) was assessed. Changes in respiratory rate, color, firmness, soluble solids content, titratable acidity, maturity index, weight loss and commercial preservation were measured. Results showed that the preharvest application of 400 μgL-1 1-MCP enhanced fruit color, preserved firmness, and reduced weight loss and maturity index of fruits. It is suggested that these results were explained by the reduction of available membrane receptors able to bind ethylene, thus increasing ethylene sensitivity and response magnitude. The preharvest application of 1-MCP could potentially be used to accelerate pitaya fruit ripening. The preharvest application of 200 μgL-1 1-MCP resulted in smaller changes in color and titratable acidity vs. control. Total soluble solids and pH were not significantly affected by the treatments. The postharvest application of 1-MCP maintained the texture of fruits by three additional days when compared to the untreated control.
Subject(s)
Color , Crops, AgriculturalABSTRACT
La liofilización es una alternativa de interés como método de conservación de alimentos, la cual permite prolongar el tiempo de vida útil manteniendo significativamente las propiedades físicas y fisicoquímicas relacionadas con su calidad. El objetivo de este trabajo fue evaluar el efecto de la liofilización y la osmoliofilización sobre las cinéticas de congelación y de secado, la actividad de agua, el volumen, la porosidad y la capacidad de rehidratación en rodajas de pitahaya amarilla (Selenicereus megalanthus). Como pretratamiento osmótico a la liofilización (osmoliofilización), las rodajas se sumergieron en una solución de sacarosa con 55 ºBrix a 25ºC; se congelaron a -35°C, la sublimación se llevó a presión de vacío de 8 Pa y el secado se realizó desde -35 hasta 35°C. Los resultados de los tratamientos evidenciaron, al final del proceso, diferencias significativas en la porosidad, volumen y capacidad de rehidratación (que fueron mayores para el tratamiento liofilizado), mientras que la cinética de secado y la actividad de agua no presentaron diferencias significativas. El tratamiento de liofilización fue adecuado para la conservación de rodajas de pitahaya amarilla, ya que permitió reducir la actividad de agua por debajo de 0,4; conservó significativamente el volumen y presentó alta capacidad de rehidratación.
Freeze-drying is an interesting alternative as a food preservation method allowing to extend the shelf life and significantly preserving physical and physicochemical properties related to quality. The objective of this study was to evaluate the effect of freeze-drying and osmo-freeze-drying on the kinetics of freezing and drying, water activity, volume, porosity and rehydration capacity of sliced yellow pitahaya (Selenicereus megalanthus). As osmotic pretreatment to freeze-drying (osmo-freeze-drying), slices were immersed in a sucrose solution at 55°Brix. The slices were frozen at -35°C. The sublimation was carried at vacuum pressure of 8 Pa and drying was carried out from -35 to 35°C. The results of these treatments at the end of the process showed significant differences in porosity, volume and rehydration capacity (being higher for freeze-drying treatment), while the kinetics of drying and water activity were not significant. The freeze drying treatment was suitable for the preservation of sliced yellow pitahaya, because it helped to decrease water activity below 0.4, preserved and showed significant volumes of high rehydration capacity.