Modeling Water Loss During Frying of Potato Slices

Abstract

The effect of blanching and drying on water loss and oil uptake during potato slice frying was studied. Two pretreatments were carried out for the slices: (i) blanching in hot water at 85°C for 3.5 min; (ii) blanching in hot water at 85°C for 3. 5 min and then, air-dried until a moisture content of 60 % (wet basis) was obtained. A control treatment, consisting of unblanched potato slices not air-dried was also conducted. After the pretreatments, potato slices were deep-fried in sunflower oil at 120, 150, and 180°C. With respect to the control treatment, blanching provided an increase while blanching-drying a decrease of the oil uptake. Two models, based on Fick's law, were used to describe water loss during frying. The first one is the classic model with an effective moisture diffusion coefficient, which assumed a constant value. The second model considers that the diffusion coefficient varies during the frying process. The variable diffusivity model adjusted the experimental data much better than the constant diffusivity model did. The effective moisture diffusion coefficient, in the variable diffusivity model, increased with frying time and temperature and behaved very similar for both control and blanched slices, while the increase of this coefficient was considerable higher for the blanched-dried slices.The development of a more porous structure with less oil content in the case of blanched-dried slices could explain this fact.

Vacuum Frying: An Alternative to Obtain High-Quality Dried Products

“…As a result, this phenomenon increases water content and thus final oil content [5,73]. In vacuum frying, Shyu and Hwang [85] observed that apple chips prepared by direct vacuum frying of blanched sample appeared to have shrinkage on the surface, and if the apple slices are blanched and then frozen prior to vacuum frying, the fried apple chips had a porous sponge-like structure.…”

“…In one model, they assumed that the mass transfer takes place only in the axial direction and used the one directional model proposed by Crank [19]. In the second model, they considered that effective moisture diffusion coefficient is no longer a constant value but rather a function of time due to changes in physical properties of the product during frying, and in this case, they used the analytical model proposed by Pedreschi et al [73].…”

Mass Transfer During Vacuum Frying of Eggplant Slices (Solanum melongena L.)

“…only when the steam output is reduced, the oil is transferred to the food, this depends on the permeability properties of the crust formed on the surface of the food [13], [14].…”

Aplicación de nuevas tecnologías para el diseño y desarrollo de productos de dorada (Sparus aurata) procedente de acuicultura

“…Algunos autores hablan también de una oxidación terciaria que comprendería las reacciones de polimerización de las fracciones anteriores (Nawar, 2000). Mellema, 2003;Pedreschi et al, 2005b;Pedreschi y Moyano, 2005;Rimac et al, 2004). La fritura al vacío destaca entre los procesos estudiados para conseguir dichos objetivos de mejora de la calidad.…”

“…muestra los valores de pérdida de humedad durante el proceso de fritura para los diferentes tratamientos. La evolución que presentan los datos experimentales que muestra la figura es semejante a los reportados en la literatura tanto para procesos convencionales de deshidratación de alimentos (Prothon, 2003;Sacilik y Elicin, 2006), como para fritura (Farkas et al, 1996b;Krokida et al, 2000a;Moreira et al, 1995;Pedreschi y Moyano, 2005b;Sahin et al, 1999;Vitrac et al, 2002). Se puede apreciar que los datos presentan la forma de las curvas típicas de secado en su etapa de velocidad constante, aunque en el caso de la fritura a 165 ºC parece apreciarse el inicio del periodo de velocidad decreciente (a partir de los 8 minutos de tratamiento).…”