Effect of hydrodrying conditions on shrinkage of pumpkin (Cucurbita maxima) pieces

espanolEl metodo para secar apropiadamente frutas y vegetales debe incrementar la calidad del producto terminado ademas de ser economicamente viable, por tal motivo, se han aplicado y desarrollado varias tecnologias que incluyen pre-tratamientos y mejoras a la tecnica de secado misma. Mediante la metodologia para muestras gruesas llamada “hidrosecado conductivo” basada en la tecnica de Ventana de Refractancia (RWTM), se deshidrataron trozos rectangulares de zapallo (1.2 x 1.1 x 5.9 cm3) usando un bano termostatico con agua a una temperatura de 90±2°C, durante 3 h. Se realizo un diseno factorial 22 para analizar el efecto de la conveccion y la conduccion sobre el encogimiento de las muestras. Los factores evaluados fueron el tipo de conveccion con dos niveles: conveccion natural (NC) y conveccion forzada (FC); y el tipo de lamina empleada para el secado con dos niveles: MylarTM(MY) y MylarTM con papel aluminio (MY/AL). Se evaluo el factor de cambio de volumen (V/V0) a partir de las dimensiones primarias (ancho, alto, y largo) de las muestras durante el secado. El menor y el mayor encogimiento de acuerdo al factor de cambio de volumen se observo en los tratamientos de conveccion natural NC-MY/AL y NC-MY, respectivamente. Se encontro una relacion exponencial entre el cambio de volumen y la tasa de secado. El ANOVA indico que el tipo de conveccion y la interaccion conveccion-lamina fueron estadisticamente significantes en los diferentes analisis EnglishThe method for properly drying fruits and vegetables should guarantee the quality of the finished product in addition to being economically viable. For this reason, several technologies, including pre-treatments and improvements to the drying technique itself, have been applied and developed. Using the methodology called “conductive hydro-drying” based on the Refractance Window (RWTM) technique, rectangular pieces of pumpkin (1.2 x 1.1 x 5.9 cm3) were dehydrated using a thermostatic bath with water at 90±2 °C, for 3 hours. Hence, a 22 factorial design were performed to analyse the effect of convection and conduction on the shrinkage of samples. The tested factors were the type of convection with two levels: natural convection (NC) and forced convection (FC); and the type of drying foil with two levels: MylarTM (MY) and MylarTMwith aluminium foil (MY/AL). The volume change factor (V/V0) from primary dimensions (width, height and length) of the samples was evaluated during drying. The smaller and the larger shrinkage, according to the volume change factor, were observed in natural convection treatments NC-MY/AL and NC-MY, respectively. An exponential relationship between drying rate and volume change factor was found. The ANOVA indicated that convection and convection-film interaction were statistically significan