Osmotic Solution Concentration Research Articles

Optimization of Osmotic Dehydration of Tomatoes in Solutions of Non-Conventional Sweeteners by Response Surface Methodology and Desirability Approach.

The osmotic dehydration (OD) of tomatoes in solutions of alternative sweeteners was investigated using Response Surface Methodology (RSM), while selected desirability functions were implemented in order to define the optimum process parameters (temperature/duration of osmotic treatment, osmotic solution composition and concentration). Mass exchange, color and texture were measured during the process. Changes in color occurred rapidly at the beginning of the process, while firmness was significantly increased, indicating that OD processing led to tomato texture improvement. Color and firmness changes were adequately modeled using a polynomial model. RSM coupled with desirability functions was applied to optimize OD procedure in terms of color retention and maximum solid gain, a requirement for candied products. A maximum desirability was obtained by incorporating oligofructose into the osmotic solution, at relatively short treatment times. Results were validated and sensory analysis was conducted at the optimized conditions to assess samples’ organoleptic acceptance.

Osmotic Dehydration of Garden Egg (Solanum aethiopicum): The Shrinkage and Mass Transfer Phenomena

Osmotic dehydration is usually employed to lower the water activity of fruits and vegetables and thus has a wide range of applications in food preservation. This study investigates the osmotic dehydration of garden egg (Solanum aethiopicum) using sodium chloride solution (NaCl) of varying concentrations (20, 40 and 60)% w/w as osmotic solutions. Different parameters such as percentage water loss (%WL), weight reduction (%WR) and solid gain (%SG) were investigated at different solution temperature (25, 35, 45, 55, and 65)°C, agitation time (20, 40, 60, 80, 100, 120, 140, 160 and 180) min and osmotic solution concentration (20, 40 and 60)% w/w to ascertain the optimum dehydration performance of the process. The performance efficiency of the process was evaluated at different osmotic solution concentrations (20, 40 and 60)% w/w with respect to time (20-180) min at a constant temperature of 40°C. The performance efficiency of the process was also evaluated at different osmotic solution concentrations (20, 40 and 60)% w/w with respect to temperature (25, 35, 45, 55, and 65)°C at the constant time (180 min). The results of this study showed that %SG and %WL increased with increase in concentration with respect to time whereby the optimum values for these parameters being 157% and 45.80% respectively were achieved at 60% w/w osmotic solution concentration, while optimum %WR (34.70%) with respect to time was achieved at 40% w/w osmotic solution concentration. Therefore, the order of %SG and %WL by the garden egg with respect to time was (60>40>20)% w/w. The optimum %SG, %WL, and %WR were achieved at 65°C in 60% w/w osmotic solution with the values of (133, 53.11 and 40.10)% respectively. The results from this study, therefore, showed that osmotic dehydration could potentially reduce the water activity of the garden egg.

Effect of temperature and concentration of osmotic solution on moisture loss and solid gain during osmotic dehydration of carrot

The effect of temperature and osmotic solution concentration on solid gain and moisture loss drying characteristics of carrot were studied. The moisture loss and solid gain increased with increase in salt and sugar concentration and temperature. The moisture loss by carrot slices increased non-linearly with increase in duration of osmosis, solution concentrations and temperature. Mass transfer was faster in initial period of osmosis than the later period. Maximum moisture loss was obtained at 60 oC for osmotically dehydrated carrot (60% sugar, 3% salt) and it ranged from 13.32% to 56.93%. Solid gain increased with duration of osmosis and did not approach the equilibrium after 3hrs of osmotic dehydration. Solid gain at 60 oC solution temperature for osmotically dehydrated carrot (60% sugar, 3% salt) ranged from 2.34% to 5.86%. 60% sugar and 3% salt concentration with 60 0C solution temperature was found as an optimum process condition for osmosis with 3 h duration.

RICE SEEDLING ESTABLISHMENT AS INFLUENCED BY CULTIVARS AND SEED PRIMING WITH POTASSIUM NITRATE

Poor crop establishment is one of the major constraints to obtain the higher potential of rice, particularly in areas prone to environmental stresses. Therefore, present study was conducted to evaluate the effects of potassium nitrate on germination dynamics, seedling growth and associated physiological and biochemical events of two rice cultivars. For this purpose, various seed priming treatments were tested in lab and greenhouse. The percent concentrations of potassium nitrate were 0.25, 0.50, 0.75, 1.0 and 1.25 in both lab evaluation and greenhouse experiment. Non-primed seeds were maintained as a control for comparison. The results depicted that soaking rice seeds at higher concentrations of KNO3 could delay emergence time and final emergence (%) in both cultivars under lab and greenhouse conditions. Seed priming with 0.75% KNO3 significantly increased the stand establishment and seedling vigor attributes of both cultivars compared with other concentrations and naked rice seeds both in lab evaluation and greenhouse screening. Similarly, highest values for photosynthesis rate, evaporation rate and CO2 index were observed in experimental units receiving primed seeds with 0.75% KNO3 under greenhouse screening. Interestingly, no variance was observed among both rice cultivars. Overall, higher seed emergence, seedling vigor and associated biochemical attributes due to seed priming with 0.75% KNO3 was associated with decrease in alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDH) activities in lab and greenhouse screening.

Electrospun hydrophobe nanofibrous membrane based on polysulfone/Triton x‐100: A novel vehicle to concentrate pomegranate juice

AbstractAimsThe present work aimed to fabricate an electrospun hydrophobe nanofibrous membrane based on polysulfone (PSF) to concentrate pomegranate juice, and evaluate the effect of Triton x‐100 (TR‐100) on the physicochemical properties of the fabricated membrane.MethodsMorphological properties, surface hydrophobicity, and mechanical performance of the nanofibrous membrane were evaluated, and then, its ability to concentrate pomegranate juice was tested.ResultsThe viscosity of PSF and PSF/TR‐100 solutions was 1.006 and 0.715 Pa·s, respectively, indicating a positive effect of the surfactant on the quality of the fabricated fibers. Scanning electron microscopy exhibited the formation of smoother and finer fibers in the presence of TR‐100 surfactant. Contact angle for the PSF and PSF/TR‐100 nanofibrous membrane was 90° and 103°, respectively, showing their hydrophobic surface. The addition of TR‐100 led to an increase in the membrane's tensile strength. The optimal conditions to produce concentrated juice were osmotic solution concentration of 4 M and a temperature of 31.2°C. The anthocyanins and phenolic content, as well as the antioxidant activity of the concentrated juice, were not significantly different from the fresh sample.ConclusionThe use of the developed membrane can be introduced as a suitable method to produce pomegranate juice with preserved qualitative attributes.Practical ApplicationsConsidering the various benefits of the fabricated membrane, it can be used to produce pomegranate juice with preserved qualitative properties.

Effect of concentration of osmotic solution on: Aloe vera

Aloe vera, a tropical and subtropical plant belonging to the Liliaceae family, contains a transparent mucilaginous jelly known as Aloe vera gel. The drying of osmo air consists of preheating the sample by osmotic dehydration and subjecting it. Osmotic dehydration is incomplete removal by osmotic agent of water from a food product. Initial moisture content of Aloe vera gel was found to be 98.8% and minimum moisture content of dried Aloe vera was found to be 3.01% (wb) after 12hr of osmo-air dehydration treatment. Osmotic dehydration of Aloe vera reduces the initial moisture content of 98.8% to 48.9% at 300 brix sugar concentration whereas reduction from 98.8% to 25.14% was observed in case of 70˚ brix. An intermediate value of reduction to 36.61% wb was observed in case of osmotic treatment at 500 brix. In osmotic treatment at 30o brix the drying rate decreased from 0.2838, 0.1741,0.1233, 0.1138 and 0.0911g/min from 1st to 5th hour, whereas in 70o brix drying rate obtained was found to be highest in the first hour 0.6268 g/min and starts gradually decreasing from 0.6268, 0.2176, 0.1238, 0.0970 and 0.0505 g/min within five hours.

Combined Osmotic and Air Dehydration for the Production of Shelf-Stable White Cheese

The research targeted on the production of an innovative shelf-stable cheese of high quality, through the combinatory effect of osmotic dehydration (OD) as pretreatment and conventional air-drying. The optimum OD processing conditions (process time/temperature, concentration of osmotic solution, food to OD agent ratio) were determined through a kinetic study of the effect of OD parameters on the water activity (aw) and water/solid transport phenomena, organoleptic and quality characteristics of the white cheese in cubes. Through Fick’s second law for mass transfer, water and solid diffusion coefficients were determined. Taking into consideration the aw, the quality, and organoleptic characteristics of the final product, the optimum OD conditions were selected as 15 °C process temperature, food to osmotic agent ratio 1:4 (w/w), concentration of osmotic agent 65% to glycerol, and treatment time 30 min. The final moisture and aw of the OD-treated product were calculated as 40% and 0.88, respectively. The time of OD-pretreated product for air-drying at 40, 55, and 67 °C to 5% residual moisture was reduced by 35, 51, and 65% respectively. The selected air-drying conditions were 67 °C for 4 h. Quality parameters of the final white cheese product were studied during its storage at 15–40 °C, and the shelf life was estimated as 6 months at ambient temperature.

Effects of convective drying assisted by ultrasound and osmotic solution on polyphenol, antioxidant and microstructure of murtilla (Ugni molinae Turcz) fruit.

The effects of pretreatment with ultrasound and an osmotic solution combined with hot air convection drying on the total polyphenol content (TPC), antioxidant activity and microstructural of murtilla skin fruit were evaluated. The effects of ultrasound frequency (0 and 130kHz), osmotic solution concentration (0 and 70°Brix) and time (60 or 120min) on the TPC and the antioxidant activities as measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC) assays were evaluated. The TPC and DPPH antioxidant activity decreased significantly (p < 0.05) when ultrasound was applied at 0°Brix for 60min. Higher FRAP activity was obtained upon treatment with ultrasound and an osmotic solution for 60min. The ORAC values did not significantly differ based on the pretreatment methods but decreased when an osmotic solution was applied for 120min without ultrasound. When ultrasound and the osmotic solution were applied, the skin cells of the dried murtilla fruit became more distorted, resulting in larger spaces between them and causing loss of shape. Although the application of pretreatment procedures before murtilla fruit drying did not positively affect the TPC, DPPH or ORAC individually, the application of a Global Standardized Response based on the followed by a mathematical model adjustment indicated that a 70°Brix osmotic solution applied for 60min was the best treatment for preparing murtilla fruit aiming a high antioxidant activity in dried product.

Influences of Osmotic Dehydration on Drying Behavior and Product Quality of Coconut (Cocos nucifera)

This research was conducted to assess the drying kinetics and product quality during osmotic dehydration and air drying of coconut cuts. The coconuts were osmotically pretreated by different concentration of sugar solution (40 °Brix, 50 °Brix, and 60 °Brix) and temperature of osmotic solution (35°C, 45°C and 55°C) were maintained. The proportion of fruit to solution was maintained 1:4 (w/v) and pretreatment process length was 3 hours. Higher osmotic solution temperature at 55°C with low concentration 40 °Brix resulted in a huge reduction of antioxidant activity, vitamin C, polyphenol, and color contents while higher osmotic solution concentration at 50 °Brix with lower temperature 35°C held more. The present investigation likewise exhibited that moisture loss and solute gain rate extended with the increasing of osmotic solution temperature and concentration. The outcomes demonstrated that drying regime was typically in the falling rate period. We used regression analysis to the experimental drying data to fit three thin layer drying models. The most appropriate model(s) was selected using correlation coefficient (R2) and root mean square error (RMSE). The page model showed a better fit of the experimental drying data (as compared to other models) on the basis that R2&gt; 0.9997 and RMSE &lt; 0.0011. These data represent a good contribution to further investigation on the mass transfer kinetics and also demonstrated that fruits could be preserved with higher nutrient applying osmotic dehydration technique.

Analysis of the Vacuum-Steam Defrosting Process of Plums Pre-Treated with Dehydrofreezing

Abstract The research material was prune plums (Prunus domestica L.), subjected to osmotic pre-treatment, with variable process time parameters and osmotic solution concentration. Plums thus fixed were frozen and stored for 6 months. At even (monthly) intervals, the product was defrosted by the vacuum-steam method, using the s-p-p chamber, until the thermocouple indicated a temperature of 4ºC in the sample’s thermal center. In order to study the kinetics of phenomena occurring during the defrosting process, the chamber was equipped with a measuring system to enable measurement and recording of temperature changes in time in the geometric center of the sample, as well as the temperature on the sample surface. The conducted tests proved that the time of vacuum-steam defrosting of fruit depended on the amount of water contained in it. In plums dehydrated in 45-65% sucrose solutions, duration of the defrosting process was shortened already after three months of frozen storage. After 6 months of storage, defrosting of these fruits was twice as fast as that of control samples.

Convective drying kinetics of osmotically pretreated papaya cubes

ABSTRACT This study assessed the fitting of mathematical models to the convective drying kinetics of osmotically pre-dehydrated papaya cubes. Papaya cubes were subjected to osmotic dehydration in sucrose solutions at 40 and 50 ºBrix, at temperatures of 50 and 60 ºC, followed by complementary convective drying in forced air circulation oven under three temperatures (50, 60 and 70 °C) and constant air velocity of 1.0 m s-1. Ten thin-layer drying mathematical models were fitted to the experimental data. The increase in air temperature and the decrease in osmotic solution concentration resulted in increased water removal rate. Based on the statistical indices, the Two Terms model was the one that best described the drying kinetics of the samples for all evaluated conditions. The effective diffusion coefficients increased with the elevation of air temperature, ranging from 1.766 x 10-10 to 3.910 x 10-6 m2 s-1, whereas the convective mass transfer coefficients ranged from 3.910 x 10-7 to 1.201 x 10-6 m s-1 with Biot number from 0.001 to 12.500.

Mathematical modelling of the effect of solution concentration and the combined application of pulsed electric fields on mass transfer during osmotic dehydration of sea bass fillets

The objective of the study was to evaluate the effect of osmotic solution concentration and a pretreatment with pulsed electric fields (PEF) (1.6 kV/cm, up to 1500 pulses/19.7 kJ kg−1) on mass transfer during osmotic dehydration (OD) of sea bass fillets. Osmotic solutions of 40–60% glycerol and 5% NaCl were applied at 15 °C for processing times up to 240 min. The increase in glycerol concentration enhanced significantly mass transfer expressed by the effective diffusivities of water (Dew values ranged from 1.9 to 3.6 × 10-9 m2 s−1) and solubles (Des values ranged from 1.8 to 4.1 × 10-9 m2 s−1). PEF pretreatment further increased Dew and Des values up to 50% and 66% respectively (for 1500 pulses/19.7 kJ kg−1). The energy input correlated with the calculated Dew and Des values, following a logistic mathematical model. The logistic model had a center point at 7.28 kJ kg−1 and 7.15 kJ kg−1 for water and solubles, respectively and showed a sharp increase of the diffusivity values between 3.3 and 9.8 kJ kg−1 ranging from 3.0 × 10-9 m2 s−1 to 4.0 × 10-9 m2 s−1 for Dew and from 2.7 × 10-9 m2 s−1 to 4.1 × 10-9 m2 s−1 for Des.

Optimization of process parameters for hybrid drying of apple

The processing parameters viz. thickness of fruit slices, osmotic solution concentration and temperature during dehydration are considered most important for determining the drying kinetics and quality of final product. Hence, the present study was designed with the objective to optimize the processing conditions of hybrid drying involved ultrasound, osmotic followed by convective dehydration of apple. Data for the optimization were analyzed by using Response Surface Methodology. The experimental design involved sucrose concentration (30-70°B), thickness of apple rings (3.00–5.00 mm) and ultrasonicated time (0-60 min) and the response variables were solids gain and water loss. Results showed that maximum water loss and solid gain obtained at optimal conditions of 30 min ultrasonicated osmotic treatment at 50°B and thickness of 4.5 mm apple rings. The study concluded that application of ultrasound improved the product quality through 30-40 per cent reduction in dehydration time.

Osmotic Dehydration of Garden Egg (Solanum aethiopicum): the Shrinkage and Mass Transfer Phenomena

Osmotic dehydration is usually employed to lower the water activity of fruits and vegetables and thus has a wide range of application in the food preservation. This study investigates the osmotic dehydration of garden egg (Solanum aethiopicum) using sodium chloride solution (NaCl) of varying concentration (20, 40 and 60 %w/w) as osmotic solutions. Different parameters such as percentage water loss (%WL), weight reduction (%WR) and solid gain (%SG) were investigated at different solution temperature (25, 35, 45, 55, and 65°C), agitation time (20, 40, 60, 80, 100, 120, 140, 160 and 180 min) and osmotic solution concentration (20, 40 and 60 %w/w) to ascertain the optimum dehydration performance of the process. The performance efficiency of the process was evaluated at different osmotic solution concentration (20, 40 and 60 %w/w) with respect to time (20-180 min) at constant temperature (40 OC). The performance efficiency of the process was also evaluated at different osmotic solution concentration (20, 40 and 60 %w/w) with respect to temperature (25, 35, 45, 55, and 65°C) at constant time (180 min). The results of this study showed that %SG and %WL increased with increase in concentration with respect to time whereby the optimum values for these parameters being 157% and 45.80% respectively were achieved at 60 %w/w osmotic solution concentration, while optimum %WR (34.70%) with respect to time was achieved at J Anal Tech Res 2020; 3 (1): 1-17 DOI: 10.26502/jatri.009 Journal of Analytical Techniques and Research 2 40 %ww osmotic solution concentration. Therefore, the order of %SG and %WL by the garden egg with respect to time was 60 > 40 > 20 %w/w. The optimum %SG, %WL and %WR were achieved at 65 oC in 60 %w/w osmotic solution with the values of 133, 53.11 and 40.10% respectively. The results from this study therefore showed that osmotic dehydration could potentially reduce water activity of garden egg.

PENGARUH KONSENTRASI DAN SUHU LARUTAN OSMOTIK TERHADAP PENYUSUTAN VOLUME, KEKERASAN DAN WARNA PADA BUAH NAGA

Osmotic dehydration is one of the methods in making of intermediate moisture food. Osmotic dehydration is done by immersing the material in a osmotic solution in the form of a sugar solution. The purpose of this research is to investigate the effect of concentration and temperature of osmotic solution on volume shrinkage, hardness and color change during the process of osmotic dehydration of dragon fruit.Dragon fruit has been immersed in osmotic solution with varying concentrations of 30 oBrix, 50 oBrix, and 70 oBrix and a solution temperature of 30 oC, 40 oC, and 50 oC. The average value of the largest to the smallest volume shrinkage in succession is in the treatment of 70 oBrix, 50 oBrix, and 30 oBrix. The lowest level of material hardness during osmotic dehydration is found in the treatment of 70 oBrix and 50 oC (B3T3). The CIELAB diagram values ​​show that the average color of the material for all treatments is in the purple-red color column. Based on anova test, the difference in concentration and temperature of the solution did not have a significant effect on the discoloration of dragon fruit after osmotic dehydration.

Hot air drying kinetics of novel functional carrot snack: Impregnated using polyphenolic rich osmotic solution with ultrasound pretreatment

AbstractIn this study, osmotic impregnation technique combined with ultrasonic pretreatment was applied to carrot slices followed by hot air drying in order to production of functional and healthy snack enriched with polyphenolic compounds derived from roselle extract (at least 400 ppm). The purposes of osmotic impregnation‐dehydration process were the maximum amount of dehydration and phenolic compounds diffusion along with the minimum sugar gain. Results revealed that increasing osmotic solution concentration and process time over optimal points, resulted in reduction of phenolic compounds saturation inside the samples. Also, it was found that prolonged ultrasound pretreatment had a damaging effect on fruit tissue microchannels and led to a decrease in the mass transfer rate. The optimal conditions of this stage were osmotic solution concentration of 60% and the process time of 60 min without ultrasonic pretreatment. In the second stage, the results of hot air drying showed that the highest amount in the total phenolic content was achieved at 70°C. Furthermore, among the several models evaluated, Jena &amp; Das model with a determination coefficient of 0.99 and minimum error indexes, was the best fitted to drying experimental data and activation energy for effective diffusivity coefficient was calculated as 35.987 kJ/mol.Practical applicationsDue to elevation in consumer's awareness in recent decades about the importance of food composition for healthier life and diseases prevention, demand for functional foods has been increasing. Food enrichment with bioactive compounds like polyphenol compounds from different plant sources is an applicable method for this purpose. In this study, carrot, which is a valuable vegetable itself, was further extended to a more functional food by enrichment with rosella plant extract and then hot air dried to produce a snack which has more nutritional quality than conventional ones. Also, osmotic dehydration results in lower moisture content of carrot slices which helps reduced hot air drying time and lower energy consumption. Overall, results from this research is usable to develop a functional snack based on carrot and rosella extract.

Effective diffusion coefficients and mass flux ratio during osmotic dehydration considering real shape and shrinkage

The aim of this work was to solve a model regarding water loss and soluble solids gain during osmotic dehydration (OD), considering real shape and solid shrinkage along the process. As an experimental case of study, OD of tomatoes halves of semi-ellipsoidal shape in hypertonic solutions of sucrose and NaCl, was selected. OD assays were carried out in two hypertonic solutions (soluble solids 35% and 50% (w/w)) with 1:8 (w/w) tomato/solution at 25 °C. Comsol Multiphysics coupled with Matlab computational tools were used for solving model's equations applying finite elements method and optimization algorithms for parameter estimation. Effective diffusion coefficients and water to soluble solids total mass flux ratios were determined. Diffusion coefficients resulted smaller than those for a rigid solid and are independent of the solids geometry and contraction. Water to soluble solids flux ratio was bigger than 1 and increased with the osmotic solution concentration and solid shrinkage.

Energy efficiency of hollow fibre membrane module in the forward osmosis seawater desalination process

This study provided new insights regarding the energy efficiency of hollow fibre forward osmosis modules for seawater desalination; and as a consequence an approach was developed to improve the process performance. Previous analysis overlooked the relationship between the energy efficiency and operating modes of the hollow fibre forward osmosis membrane when the process was scaled-up. In this study, the module length and operating parameters were incorporated in the design of an energy-efficient forward osmosis system. The minimum specific power consumption for seawater desalination was calculated at the thermodynamic limits. Two FO operating modes: (1) draw solution in the lumen and (2) feed solution in the lumen, were evaluated in terms of the desalination energy requirements at a minimum draw solution flow rate. The results revealed that the operating mode of the forward osmosis membrane was important in terms of reducing the desalination energy. In addition, the length of the forward osmosis module was also a significant factor and surprisingly increasing the length of the forward osmosis module was not always advantageous in improving the performance. The study outcomes also showed that seawater desalination by the forward osmosis process was less energy efficient at low and high osmotic draw solution concentration and performed better at 1.2–1.4 M sodium chloride draw solution concentrations. The findings of this study provided a platform to the manufacturers and operators of hollow fibre forward osmosis membrane to improve the energy efficiency of the desalination process.

Influence of Osmotic Dehydration on Mass Transfer Kinetics and Quality Retention of Ripe Papaya (Carica papaya L) during Drying

The study aimed to investigate the mass transfer kinetics and nutritional quality during osmotic dehydration (OD) and air-drying of papaya. The papaya was osmotically pretreated by different concentrations of sugar solutions (40, 50 and 60 °Brix) and osmotic solution temperatures (35, 45 and 55 °C). The ratio of fruit to the solution was kept at 1:4 (w/v) and pretreated process duration varied from 0 to 240 min. The present study demonstrated that water loss and the solute gain rate increased with the increasing of osmotic solution temperature, concentration and time. Mass transfer kinetics of osmotically pretreated papaya cubes were investigated based on the Peleg’s and Penetration models. The Peleg model showed the best fitted for water loss and solute gain whereas the Penetration model best described the water loss during osmotic dehydration of papaya. Effective diffusivity of water and solute gain was estimated using the analytical solution of Fick’s law of diffusion. Average effective diffusivity of water loss and solute gain was obtained in the range from 2.25 × 10−9 to 4.31 × 10−9 m2/s and 3.01 × 10−9 to 5.61 × 10−9 m2/s, respectively. Osmotically pretreated samples were dried with a convective method at a temperature of 70 °C. The moisture content, water activity and shrinkage of the dried papaya were decreased when the samples pretreated with a higher concentration of the osmotic solution and greater process temperature. The results also indicated that the highest osmotic solution temperature of 55 °C with the lowest concentration of 40 °Brix resulted in a significant decrease in phenolic content, antioxidant activity, and vitamin C content while higher osmotic solution concentration of 60 °Brix and the lowest temperature of the process (35 °C) retained maximum bioactive compounds.

Use of ultrasound for dehydration of mangoes (Mangifera indica L.): kinetic modeling of ultrasound-assisted osmotic dehydration and convective air-drying.

This work evaluated the production of dehydrated mangoes (Mangifera indica L.) and the effectiveness of ultrasonic-assisted osmotic dehydration on the drying kinetics of mangoes. Cube shaped mango samples were pretreated using ultrasound-assisted osmotic dehydration (UAOD) and dried in a circulating drying oven. An experimental design was created to evaluate the effect of pretreatment time and osmotic solution concentration on the water loss and sugar gain in the osmotic dehydration and on the drying time. The ultrasonic pretreatment was carried out in a bath ultrasound operating at 25kHz and outputting 55W/m3 of power. Osmotic solution ranging from 0 to 500kg sucrose/m3 was applied in the treatments, and air drying was carried out at 60°C. A mathematical model was developed for the osmotic pretreatment, and Fick's law was used to model the air-drying process. The mass transfer coefficients were estimated for the ultrasonic-assisted osmotic dehydration, and the apparent water diffusivity was estimated for the air-drying process. The mass transfer coefficient ranged from 0.017 to 0.109m2/s and the resistance to mass transfer at the surface ranged from 0.26 × 10-6 to 1.22 × 10-6m2/s on the UAOD, while the apparent water diffusivity during air drying ranged from 5.94 × 10-9 to 8.41 × 10-9m2/s. Mangoes presented a different behavior when compared to other fruits. The ultrasonic pretreatment was effective only when associated with an osmotic solution at 500kg sucrose/m3.