Drying kinetics of fresh and osmotically pre-treated papaya (Carica papaya L.)

Abstract

The aim of this work was to study and to model the drying kinetics of fresh and osmotically pre-treated papaya cubes (Carica papaya L.) using the diffusional model (FickÕs second law) adapted to a cubic geometry, and an empirical two parameters model. The osmotic pre-treatment was carried out in an incubator at constant temperature and agitation. The drying process was carried out in a fixed bed dryer at two different temperatures and air velocities. At the beginning of the drying process of fresh papaya, drying rate was influenced by both air velocity and air temperature. But lose to the equilibrium condition, the drying rate was affected only by the air temperature. The physico-chemical changes in the papaya cubes during osmotic pre-treatment caused differences in the drying rate in the subsequent air drying process when compared to fresh papaya cubes. The effective diffusivities of water, calculated by diffusional model, were of the order of 10 À9 m 2 /s.

Effect of osmotic pretreatment on air drying characteristics and colour of pepper (Capsicum spp) cultivars

“…Moreover, the effective diffusivities of water calculated from the diffusional model were higher for fresh fruits than those for osmosed papaya and varied from 1.72×10 −9 to 4.98×10 −9 m 2 /sec for fresh papaya and 1.03× 10 −9 to 1.78×10 −9 m 2 /sec for osmosed fruits (El-Aouar et al 2003). Comparison of diffusivities reported in the literature is difficult because of different estimation methods and models employed together with the variation in food composition and physical structure (El-Aouar et al 2003). The natural logarithm of the calculated effective moisture diffusivities (ln D eff ) was plotted against the reciprocal of the temperature (1/T abs ).…”

“…Calculated apparent moisture diffusivites at 60°C ranged from 34.8×10 −10 to 8.8 × 10 −10 m 2 /sec for fresh and dried banana, respectively (Sankat et al 1996). Moreover, the effective diffusivities of water calculated from the diffusional model were higher for fresh fruits than those for osmosed papaya and varied from 1.72×10 −9 to 4.98×10 −9 m 2 /sec for fresh papaya and 1.03× 10 −9 to 1.78×10 −9 m 2 /sec for osmosed fruits (El-Aouar et al 2003). Comparison of diffusivities reported in the literature is difficult because of different estimation methods and models employed together with the variation in food composition and physical structure (El-Aouar et al 2003).…”

Osmoconvective dehydration in fruits and vegetables: A review of recent developments

“…Los investigadores concluyeron que la deshidratación osmótica aplicada a la mora de castilla para los tres jarabes utilizados, mostró buena retención de las características sensoriales de la fruta (color, olor y sabor). El-Aouar et al (2003) observaron un incremento en la resistencia interna al movimiento del agua, causado principalmente por el encogimiento y la absorción de sólidos durante el pre-tratamiento osmótico en muestras de papaya previamente deshidratadas con tratamiento osmótico con concentraciones de sacarosa 70 % w/w y secadas con aire caliente a temperaturas de 40 y 60 °C. Góngora-Chávez (2012) estudió la técnica combinada del secado osmoconvectivo con aire caliente en rodajas de carambolo (Averrhoa carambola L.) sobre sus propiedades físico-químicas, empleando sacarosa como medio osmodeshidratante con un nivel de 55 °Brix, 28 °C, con agitación a 1000 r.p.m.…”

Changes in liquid phase and mechanical properties during osmodehydrofreezing of papaya (carica papaya L.)

“…Sucrose was used as solute due to its wide use in the dehydration fruit processing [17]. Concentration levels were selected according to previous research on osmotic dehydration in papaya fruits [18,19]. The weight ratio of osmotic solution for papaya was 20:1 to maintain a constant concentration of the osmotic solution during OD [15,20].…”

“…Afterwards, they were frozen at -40°C in a freezer (Revco, USA) and stored in a commercial freezer at -18°C during 10, 20, 30 and 60 days. For each storage time, the samples were removed from the freezer and taken a commercial refrigerator at 8°C for 18 h to ensure complete thawing process [17,18]. Once papaya samples were thawed, physical properties were evaluated (freezing rate, DL and mechanical properties in terms of ME and σ L).…”