Osmotic Concentration – Drying of Mango Slices

ABSTRACT

The effect of initial water activity (a_w) of mango slices obtained by osmotic concentration pre-treatments with sucrose syrups on their air-drying behavior at 50, 60 and 70°C were evaluated calculating the apparent diffusion coefficients with second Fick's law. The increase in sucrose concentration or reduction in e_w of mango slices affects the moisture transport during the air drying step. The diffusion coefficients decrease with the increasing in solid content during the osmosis and increase with the drying temperature. The time needed to reach a final moisture content of 0.7 g water/g ds was 50 to 75% lower in osmosed mangoes than those obtained for fresh mango.     

Influence of osmotic dehydration process parameters on the quality of candied pumpkins

The influence of osmotic dehydration process parameters on the efficiency of water loss and sucrose gain of pumpkins and the influence on the quality of the final product are essential for production of superior quality candied pumpkins. Mass transfer kinetics during osmotic dehydration of pumpkins were modelled by assuming Fickian diffusion of sucrose and water in unsteady state conditions, which described very well the experimental results for water loss and sugar gain. Water and sucrose effective diffusion coefficients increase significantly with temperature. Temperature and sucrose concentration had a significant influence on both water and sugar diffusion, increasing as the solution temperature increased. Significant increase in the effective water diffusivity and decrease in the sucrose effective diffusivity was observed when the sucrose solution concentration increased from 40 °Brix to 50 and 60 °Brix. From 50 to 60 °Brix, no difference in the effective diffusivities was observed. Candied pumpkins with higher sucrose content have a higher breaking stress, less breaking strain and lower work to fracture. Moreover, the product becomes harder and less elastic with increasing sucrose content, resulting in more brittle products, which seems to be related with reinforcement of the pumpkin cell wall matrix.     

Effect of sucrose concentration of osmotic dehydration pretreatment on drying characteristics and texture of peach chips dried by infrared drying coupled with explosion puffing drying

Effects of osmotic dehydration (OD) pretreatment on the texture characteristics of peach chips after combination drying were investigated. Peach slices were immersed into 100, 300, and 500?g/L sucrose solution for 4?h, respectively, at room temperature and then predried to a critical moisture content of 0.5?kg water/kg dry matter that was determined by the effective moisture diffusivity (D_eff) curves under infrared drying at 80°C. The peach chips were then dried using explosion puffing drying (EPD). The sucrose solution with lower concentration (100?g/L) would improve the drying rate (DR) of peach slices during infrared drying. However, sucrose solution with higher concentration (500?g/L) might affect water diffusion, resulting in lower drying rate. The changes of texture characteristics of dehydrated peach were ascribed to sucrose uptake during the impregnation step. The content and constitutes of soluble sugars in peach tissue, which was significantly affected by OD treatment, were also detected in the research. The results indicated that the combined infrared and EPD drying, in which OD with appropriate concentration (300?g/L) was applied as pretreatment, could improve the drying characteristics and texture of peach chips.     

Osmotic Dehydration Kinetics of Pumpkin Fruits Using Ternary Solutions of Sodium Chloride and Sucrose

The objective of this work was to obtain experimental data and modeling of osmotic dehydration kinetics of pumpkin fruits (Cucurbita pepo L.) with aqueous NaCl/sucrose solutions. For this purpose, effective diffusion coefficients for water, sucrose, and NaCl were calculated by means of a simple model based on Fick's second law. Water loss achieved 80%, sucrose 13%, and NaCl 6% of the initial sample weight. Effective diffusion coefficients ranged from 0.58–1.40 × 10^?9 m²/s, 0.75–1.23 × 10^?9 m²/s, and 2.60–4.11 × 10^?9 m²/s for water, sucrose, and NaCl, respectively. The proposed model gave a good correlation of the experimental data. The quality of the operation was evaluated by analysis of the values of WL/SG ratio.     

DETERMINATION OF MOISTURE DIFFUSIVITY AND BEHAVIOR OF TOMATO CONCENTRATE DROPLETS DURING DRYING IN AIR

ABSTRACT

The drying mechanism and diffusion coefficient of water in spherical droplets (1.73 – 2.08 mm diameter) of tomato concentrates were successfully interpreted and modelled by using Fick's law. Solids content of the initial concentrate (5–15% w/w), and drying temperature (60^° – 100^° C) were varied but the drying air was kept at constant velocity and humidity.

The effective moisture diffusivity was estimated from the drying rate curves and expressed by an Arrhenius relation. Further, it was observed that case hardening has a large effect on the diffusion process causing the effective diffusional distance and the rate of moisture accumulation in the hardened crust to vary with the moisture content, according to a sorption controlled mechanism.     

EFFECTS OF GLYCEROL ON THE DRYING OF GELATIN AND SUGAR SOLUTIONS

ABSTRACT

The water diffusion coefficients D of gelatin, sucrose arid maltodextrin solutions were determined from the isothermal drying (desorption) rates as a function of water content u ( 0.1 < u < 1.0 ) and temperature (303, 323K) for various glycerol contents ( W_G = 0 – 0.43 kg-glycerol/kg-total solid). When W_G was above 0.2, D increased especially at low water contents (u < 0.25). The desorption isotherms were measured for the same systems. The equilibrium water content at a given water activity A_w decreased with an increase in W_G when A_w < 0.5. This indicates that adding glycerol weakens the water-solute interaction especially at low water contents. Glycerol also softened gelatin films and resulted in loss possibilities of surface cracks during drying.     

CONVECTIVE-AIR DRYING KINETICS OF OSMOTICALLY PRE-TREATED BLUEBERRIES

Abstract

The second stage convective drying behavior of osmo-dehydrated blueberries was evaluated in a forced-air cabinet dryer (temperature: 50°C, relative humidity: 14%, air velocity: 0.6 m/s) with a cross-flow tray arrangement. Fick's second law of unsteady state diffusion was used to model the air drying kinetics. The results showed that the convective-air drying of the blueberries occurred in two falling rate periods. The effective diffusion coefficients, D_eff, during the first falling rate period ranged from 1.19 × 10^?10 m²/s to 2.14 × 10^?10 m²s and ranged from 4.04 × 10^?11 m²/s to 1.32 × 10^?10 m²/s during the second falling rate period. Among the pre-treatment conditions, the temperature and sucrose concentration during osmotic dehydration significantly (p < 0.05) influenced the air drying time, while the effect of contact time was not significant (p > 0.05).     

OSMOTIC DEHYDRATION KINETICS OF BLUEBERRIES

Abstract

The kinetics of moisture loss and solids gain during osmotic dehydration of blueberries under different conditions of temperature (37°C - 60°C), concentration of the sucrose solution (47°Brix - 70°Brix) and contact time between fruit and sucrose solution (0.5 h - 5.5 h) were studied, and modeled based on Fick's law of unsteady state diffusion. The study showed that all factors influenced moisture loss and solids gain (p<0.001), both generally increasing with temperature (T) and sucrose concentration (C). Based on the diffusion model, the calculated effective moisture diffusivity (D_m) ranged from 1.98 × 10^?10 to 5.10 × 10^?10 m²/s and the effective solids diffusivity (D_s) ranged from 2.54 × 10^?11 to 2.22 × 10^?10 m²/s. Both D_m and D_s showed increasing trends with temperature and sucrose concentration, and could be modeled as quadratic functions of T and C.     

Analysis of the Drying Processes of Osmotically Dehydrated Apple Using the Characteristic Curve Model

ABSTRACT

Round slices (2 mm thick) of fresh apple and of apple subjected to osmo-dehydration processes in sucrose syrups until reaching a_w values of 0.979, 0.968. and 0.958. were air-dried at 50. 60. and 70°C. Analysis of the drying curves showed that the products do not present a constant rate period (except for fresh apple) but showed two falling rate periods. Initial a_w greatly affects the fraction of water lost during the drying processes. The use of the Fick's Second Law was not adequate to describe the experimental drying curves. However, apple drying processes can be modeled by the Characteristic Drying Curve model, using several equations (polynomial and logarithmic) with a high confidence level. The parameters of each equation showed a great dependence on product's a_w These models can be used to predict drying curves within the studied limits in each case, presenting great advantages when compared to classical models based on effective diffusion coefficients.     

MASS TRANSFER IN BANANA CHIPS DURING OSMOTIC DEHYDRATION

ABSTRACT

The effects of temperature ( 50, 60 and 70 °C ), sucrose concentration ( 50, 60 and 70° Brix ) and pH ( 6,7 and 8 ) on the mass transfer during osmotic dehydration of banana chips were studied. Fitting a diffusion model gave apparent diffusivity values varied from 2.77 to 2.66 × 10^?9 m² s^?1 and depending on temperature and sucrose concentration but not on pH changes. The effct of syrup/product volume ratio on the mass transfer kinetics was also investigated.     

Convective drying of osmotically dehydrated apples described by three-dimensional numerical solution of the diffusion equation with analysis of water effective diffusivity spatial distribution

Abstract

This study presents two liquid diffusion models to represent the convective drying of apple, osmotically dehydrated in sucrose solution, cut into parallelepiped-shaped pieces. Model 1 considered water diffusivity and the volume of the slices with constant values. Model 2 considered water effective diffusivity and the dimensions of the slices as variable. The numerical solution of the three-dimensional diffusion equation in Cartesian coordinates was obtained through the finite volume method, with a fully implicit formulation and boundary condition of the third kind. Process parameters were estimated by an optimizer using experimental data. A spatial distribution analysis was carried out for water effective diffusivity and moisture content in the apple slices. The results showed that the concentration of the osmotic solution used in the pretreatment influenced the drying process and that the mathematical model that considered a variable diffusivity and shrinkage was more suitable to describe the experimental data.     

STRUCTURAL CHANGES AND MASS TRANSFER DURING GLUCOSE INFUSION OF APPLES AS AFFECTED BY BLANCHING AND PROCESS VARIABLES

ABSTRACT

The effect of process variables and blanching on the rate of dewatering of apple slices through immersion in glucose solutions was analyzed. The adequacy of the Hawkes and Flink's and Peleg's models for fitting the rate data was evaluated as well as the structural changes produced in the tissue subjected to osmotic process. High concentration values (33-42 % (w/w)) of the soaking solution favored significantly water loss (WL) but only slightly affected solid gain (SG). Increasing system temperature over the range 20-50 °C generally provided an increase in WL and in SG. The increase in thickness decreased significantly both mass transfer rates. The use of sucrose instead of glucose lead to a greater SG while blanched samples showed higher rates of WL and SG. Microscopic studies revealed that, when applying short treatments, cells appeared slightly shrinked and cells walls folded. After long treatments, although an extensive     

Air-Drying Kinetics of Osmotically Dehydrated Fruits

ABSTRACT

The air drying kinetics of fresh and osmotically dehydrated fruits (apples) was determined. Two sugars, glucose and sucrose, were used as osmotic dehydration agents. Three levels of sugar concentration (15%, 30% and 45%) and several times of immersion into the sugar solution were used. Following the osmotic preconcentration, the fruit samples were dried at 55°C and the weight of material was recorded. The effective water diffusivity of samples treated under various osmotic conditions was estimated and the results were related to the sugar content and the bulk porosity of the samples. The effective water diffusivity, resulting from the application of the diffusion equation to the drying kinetics of the apples was found to decrease significantly for the samples pretreated by a concentrated sugar solution (e.g. 45%), evidently due to the lower porosity and other physicochemical factors. The low diffusivity may be beneficial in the storage stability and utilization of dehydrated fruits.     

DRYING OF CARBOHYDRATE AND PROTEIN SOLUTIONS

ABSTRACT

Drying behavior of a single suspended droplet of various protein and carbohydrate solutions was investigated experimentally For small molecular weight carbohydrates such as sucrose and glucose, the constant-rate period was observed, which was followed by the falling rate period characterized as the “regular regime”. During the falling rate period, the drying rate was very low due to a sharp decrease of the water diffusion coefficient with decreasing water concentration. No remarkable constant-rate periods were observed for large-molecular carbohydrates and proteins. This is because the water diffusion coefficient is low even at high water concentrations. The drying curves of bovine serum albumin, skimmilk and model-food liquid solutions were found to be predicted by a computer simulation with the concentration dependent water diffusion coefficient of maltodextrin of dextrose equivalent = 11.The experimental investigations on the ethanol and enzyme retention during drying indicated that the ethanol is lost during the constant-rate period and the enzyme inactivation occurs during the constant-rate period (regular regime).     

Drying of Carbohydrate and Protein Solutions

ABSTRACT

Drying behavior of a single suspended droplet of various protein and carbohydrate solutions was investigated experimentally. For small molecular weight carbohydrates such as sucrose and glucose, the constant-rate period was observed, which was followed by the falling rate period characterized as the “regular regime”. During the falling rate period. the drying rate was very low due to a sharp decrease of the water diffusion coefficient with decreasing water concentration No remarkable constant rate periods were observed for large-molecular carbohydrates and proteins. This is because the water diffusion coefficient is low even at high water concentrations. The drying curves or bovine serum albumin, skimmilk and model-food liquid solutions were found to be predicted by a computer simulation with the concentration dependent water diffusion coefficient of maltodextrin of dextrose equivalent =11. The experimental investigations on the ethanol and enzyme retention during drying indicated that the ethanol is lost during the costant-rate period and the enzyme inactivation occurs during the constant-rate period (regular regime).     

THE USE OF PELEG'S EQUATION TO MODEL OSMOTIC CONCENTRATION OF PAPAYA

ABSTRACT

A two parameter non exponential model was recently proposed by Peleg to describe moisture sorption curves. This study was designed to examine the predictive capacity of the model for osmotic concentration data and to further investigate the characteristics of the parameters in the equation. The equation was used to model the kinetics of water removal and solute uptake, in terms of moisture content (MC) and soluble solids (SS) respectively, during the osmotic concentration of papaya. The model - fitted the experimental observations accurately, with regression coefficients that varied from 0.982 to 0.997 and from 0.976 to 0.996 for MC and SS respectively, and with maximum root-mean-square deviations of 0.6 g water/100g and 0.5°Brix, for moisture content and soluble solids respectively. An inverse relationship was found between k₂ parameter and syrup concentration as well with MC and SS.     

Optimization of Enzymatic Hydrolysis of Sacha Inchi Oil using Conventional and Supercritical Carbon Dioxide Processes

Sacha inchi (Plukenetia volubilis) oil has high polyunsaturated fatty acids content. The hydrolysis of this oil is an efficient way to obtain desirable free fatty acids (FFA). The optimization of parameters was carried out according to the maximum production of FFA using two enzymatic hydrolysis processes. The effect of enzyme concentration (5–40 % based on weight of oil), temperature (40–60 °C), and oil:water molar ratio (1:5–1:70) were studied for the conventional enzymatic hydrolysis process, while pressure (10–30 MPa) and oil:water molar ratio (1:5–1:30) were studied for the enzymatic hydrolysis in supercritical carbon dioxide (SC-CO₂) media. The hydrolysis in SC-CO₂ media resulted in higher production of FFA (77.98 % w/w) at 30 MPa and an oil:water molar ratio equal to 1:5 compared to the conventional process (68.40 ± 0.98 % w/w) at 60 °C, oil:water molar ratio equal to 1:70, and 26.17 % w/w, enzyme/oil. The only significant parameter on the production of FFA for conventional enzymatic hydrolysis was enzyme concentration, while for the hydrolysis in SC-CO₂ media both pressure and the molar ratio of oil:water were significant. Lipid class analyses showed that with both methods, FFA, monoglycerides, and diglycerides content in the final product increased compared to pure oil, while triglycerides content decreased. Fatty acid composition analysis showed that the content of fatty acids in the FFA form were similar to their triglyceride form.     

Continuous Separation of Sugarcane Molasses with a Simulated Moving-Bed Adsorber. Adsorption Equilibria,Kinetics, and Application

Abstract

Fundamental chromatographic properties are reported that are related to the industrial separation of sugarcane molasses in a simulated moving-bed adsorber. The distribution coefficients of KCl, sucrose, glucose, and fructose on XUS-40166.00 (K⁺) cation exchanger were determined by pulse testing to be 0.00, 0.22, 0.45, and 0.50 at infinite dilution at 70°C. The adsorption isotherm of KCl is quadratic; those of the sugars only slightly nonlinear and dependent on KCl concentration. HETP was found to be independent of fluid velocity for KCl in the range of the interstitial velocity of 5 to 35 cm/min, and increasing with v for sucrose. At high fluid velocities the broadening of the sucrose band in a packed bed comes primarily from intraparticle mass transfer, with axial dispersion and film diffusion playing minor roles. The process for separation of sugarcane molasses was demonstrated on a 47-L, eight-column simulated moving-bed adsorber. A theoretical, staged model of the simulated moving-bed adsorber with one inert totally excluded and three linearly adsorbing components was found to give an excellent representation of the transient and steady-state behavior of the continuous separation of sugarcane molasses.     

Variability in Transport Properties Regarding Drying Behavior for Blackbutt Timber in New South Wales

ABSTRACT

Variability is a key issue in the processing of many biological materials, in this case the drying of hardwood timber. This article reports the measurements of variability of the diffusion coefficient (a transport property), the initial moisture content, and the basic density that are relevant to the drying of blackbutt, Eucalyptus pilularis Sm, from northern New South Wales in Australia. The diffusion coefficient was quantified using a mathematical model solving Fick's second law of diffusion for mass transfer, and Fourier's law for heat transfer. The initial moisture content and the basic density were measured using experimental procedures. Specifically, within-tree and between-tree variations are reported. The coefficients of variation of the initial moisture contents and final moisture contents are 0.24 and 0.19, respectively, for within-tree variability. A similar result was found for the amount of between-tree variability. Compensating differences in the diffusion coefficients of the timber boards were a significant reason for the small dispersion of final moisture contents, despite the large variation in initial moisture contents.

An analysis of variance showed that some timber properties were affected by the board positions within trees and between trees. Circumferential and radial effects were significant for the within-tree variability of most transport properties. Moreover, principal components analysis suggested that timber boards with low densities have high initial moisture contents and high diffusion coefficients. A potential reason is that if there is less wood material per unit volume (lower density), then there is more space to be occupied by water (higher initial moisture content), and there is also less resistance to the diffusive transport of moisture (higher diffusion coefficients).     

Study on Demulsification of Crude Oil Emulsions by Microwave Chemical Method

Abstract

The demulsifying and separating experiments of crude oil emulsion were performed by using the heating method, the thermal chemical method, the microwave radiating method, and the microwave chemical method separately. The water content of this emulsion was 78 v/v%, and the type was water‐in‐oil (w/o). The influence tendencies of the key factors on demulsification effect were explored by changing the heating temperature, the demulsifier amount used and the microwave radiating time in this paper. With the microwave chemical experiments on the self‐made emulsions of different water content, the demulsification rate and separation efficiency were explored. The type of these emulsions were oil‐in‐water (o/w), water‐in‐oil (w/o) and the multiple type, related to the water content scopes which were less than 30 v/v%, more than 70 v/v% and between them, respectively. The separation effect by the microwave chemical method for the high water content crude oil emulsion was better than that of emulsion with lower water content. For the crude oil used in this experiment, the result could be obtained that the separation efficiency was about 95 v/v% under the conditions of 50 ppm of demulsifier, 10 seconds radiation time, and 1 minute settling time for the microwave chemical method.