Effect of Combined Processes of Osmotic Dehydration and Freezing on Papaya Preservation

Abstract

The effect of combined processes of osmotic dehydration and freezing on papaya pieces preservation was evaluated. Sucrose solutions were used as osmotic medium. Two multifactorial experimental designs, in two levels, were conducted consecutively to quantify the effect of the following factors: temperature, osmotic dehydration time, concentration of the osmotic medium and freezing rate. The response variables considered were: sensory evaluation, instrumental colour, instrumental texture, water activity (a w ), drip loss, and reducing and total sugars. The first experimental design selected fast freezing as the best process to preserve the texture of the fruit. From the second experimental design, under fast freezing, were obtained the following optimal levels: 65 Bx for the concentration of the osmotic medium, 20 C for the syrup temperature and 60 min for the osmotic dehydration time. An acceptability test was performed under these conditions with 100 potential consumers on a 7-point hedonic scale, which gave 98% acceptance. Glass transition temperature (T g 0) of the maximally cryoconcentrated liquid was À 33.74 C for the product processed under optimum conditions, which was the closest value to the common storage temperature (À 18 C) among all the measured samples.

Influence of ultrasound pretreatments on diffusion coefficients, texture and colour of osmodehydrated sweet potato (Ipomea batatas)

“…In this case, ultrasound was found to enhance the yellowness appearance of sweet potato, which might indicate the presence of beta carotene. The yellowness appearance of sweet potato can also be attributed to the sucrose uptake during the OD and UOD (Moyano et al, 2004;Zou et al, 2013;Kowalski & Szadzi nska, 2014). Deng & Zhao (2008a) observed no significant differences in the b* values of apples treated in ultrasound-assisted freeze dryer and that of the fresh (untreated) samples.…”

Modelos Matemáticos De Transferencia De Masa en Deshidratación Osmótica Mathematical Models of Mass Transfer in Osmotic Dehydration Modelos Matemáticos De Transferencia De Masa en Deshidratación Osmótica

“…También se sabe que la ganancia de sólidos es proporcional a la concentración de la disolución, la temperatura y el tiempo de inmersión (Saputra, 2001;Madamba y López, 2002;Parjoko et al, 1996;Van Nieuwenhuijzen et al, 2001;Panagiotou et al, 1998) e inversamente proporcional al área (van Nieuwenhuijzen et al, 2001;Panagiotou et al, 1998) y al espesor de la muestra (Madamba y López, 2002). Se ha concluido además que después de tres horas de deshidratación ya se ha reducido el agua en más del 50% y ha ocurrido la mayor ganancia de sólidos (Saputra, 2001); que la fuerza máxima, la dureza, la calidad del color y la dulzura aumentan con el tiempo de inmersión y con la concentración de la disolución y que el olor se reduce con el incremento de la temperatura (Moyano et al, 2002). En general, se sabe que el incremento en la concentración y la temperatura de la disolución osmótica y la disminución en el tamaño de muestra incrementa la velocidad de transferencia de masa hasta un punto por encima del cual se obtienen cambios indeseables de sabor, color y textura (Rastogi y Raghavarao, 1996;van Nieuwenhuijzen et al, 2001), el uso de solutos de alto peso molecular favorece la pérdida de agua a expensas de la ganancia de sólidos (Spiazzi y Mascheroni;1997;Rastogi et al, 2002) y la disminución de la presión del sistema aumenta la velocidad de transferencia de masa (Rastogi y Raghvarao, 1996;Moreno et al, 2004).…”

Modeling of pre-treatment protocols for frozen pineapple slices

“…Bartolome et al (1996a) studied the freezing rate and frozen storage of pineapple slices and found no differences in sensory characteristics of the slices after 1 year of frozen storage at À18 C. The effect of freezing and frozen storage on volatile aroma and flavour compounds is mainly governed by enzymatic activities and lipid oxidation (Lim, McFetridge, & Liesebach, 2004) and, in this study, blanching of pineapple slices, prior to freezing, was used as a pretreatment to inactivate the enzymes that cause changes in flavour resulting in higher sensory scores for frozen pineapple slices. Moyano, Vega, Bunger, Garreton, and Osorio (2002) also reported sugar dip of papaya slices before freezing resulted in better sensory scores. The effect of different variables on sensory responses could be predicted by following equations:…”