Osmotic Solution Concentration Research Articles

Enhancing physicochemical properties of papaya through osmotic dehydration with various natural sweeteners

Osmotic processes play a crucial role in developing high-quality intermediate moisture food products. This study investigates the role of osmotic dehydration focusing on using natural sweeteners to reduce health risks from refined sugar. Jaggery and honey were used for osmosis of papaya cubes, with a Box-Behnken design to determine optimal conditions: osmosis temperature (30, 40, 50 °C), osmotic solution concentration (40, 50, 60°Brix), and osmosis time (3, 4, 5 h). Simultaneous optimization of these parameters considered responses such as water loss, solid gain, weight reduction, colour change, ascorbic acid content, lycopene content, and phenolic content. The optimized conditions were identified as 49.46 °C, 40°Brix, and 5 h for jaggery osmosed samples and 39.64 °C, 60°Brix, and 4.92 h for honey osmosed samples. Drying the osmosed samples using advanced domestic solar dryer revealed superior quality (total phenolic content and lycopene content) in jaggery osmosed papaya compared to honey osmosed papaya. The study suggests that introducing a new osmotic agent, jaggery, can enhance the nutritional value of osmosed papaya cubes.

Standardization of Process Variables for the Development of Osmo-dehydrated Coconut Haustorium

Background: Coconut (Cocos nucifera L.) is considered a highly valuable and beneficial perennial crop in our country. The basal portion of the coconut embryo enlarges during germination and forms a spongy structure, haustorium, which is an excellent source of essential nutrients. Since consumer preference is shifting towards healthy food and processed coconut products have immense scope in this sector, the study was conducted to standardize the process variables for osmo-dehydration of coconut haustorium and to evaluate the nutritional qualities of the osmo-dehydrated product. Methods: The present study involved the development of osmo-dehydrated coconut haustorium by standardizing the process variables, viz., osmotic solution concentration and immersion time. Mass transfer, physical, biochemical and sensory parameters were analysed to evaluate the nutritional qualities and consumer acceptance. Result: The results on biochemical properties revealed that an increase in concentration and time of immersion increased TSS, total sugar, reducing sugar, ash and mineral content. The process variables were standardized for the development of osmo-dehydrated coconut haustorium with optimum mass transfer characters, better nutritional qualities and consumer acceptance, which has application in the food industry.

Allulose‐crystallized fruits: Effect of non‐thermal air‐drying and UV‐A light dehydration of osmotic solutions

AbstractThe purpose of this research was to confirm the suitability of allulose to produce crystallized fruits under nonthermal conditions and the suitability of UV‐A light dehydration to concentrate the osmotic solutions. Mangoes and apples were subjected to osmotic drying with either sucrose or allulose, which was followed by an air‐drying step at room temperature to further concentrate the crystallized fruits. There was no significant difference in the dehydration kinetics parameters between the two sugars in each crystallized fruit. Color evaluations showed that allulose was able to better preserve the color of the original raw fruits in the final crystallized samples. Electron microscopy images suggested a more uniform diffusion of allulose as compared to sucrose for both fruits. Similarly, liquid chromatography and infrared spectroscopy analyses confirmed the successful absorption of both sugars into both fruits, with allulose having a final higher concentration in both mango and apple (51.7 ± 5.6% and 70.8 ± 7.7% w/w, respectively) as compared to sucrose (48.6 ± 2.9% and 58.3 ± 3.4% w/w, respectively). UV‐A light dehydration showed to be able to increase the recovery of the sugars from osmotic solutions better than in conditions without UV‐A light exposure. When only air flow was used, it was possible to remove 85.3 ± 4.6% and 78.6 ± 0.6% of the original moisture in the sucrose and allulose solutions, respectively. In contrast, under UV‐A light dehydration, the percentage of the original water removed from the sucrose and allulose solutions was 95.2 ± 1.8% and 83.1 ± 1.9%, respectively.Practical applicationsThere is an increasing trend toward producing foods that are healthier for the general population. The use of rare sugars like allulose offers a promising alternative to accomplishing this. In addition, it has become imperative to develop processes that are more sustainable. The use of air‐drying at room temperature can represent an effective approach to develop more sustainable food manufacturing processes. More specifically, the use of UV‐A light dehydration (which is a non‐thermal food dehydration technique) for the recovery of solutes or the concentration of osmotic solutions can also represent an effective aid in this type of processes.

CFD simulation of osmotic membrane distillation using hollow fiber membrane contactor: Operating conditions and concentration polarization effects

Inorganic salts, when present in high concentrations, can disrupt the osmotic balance of aquatic organisms, leading to physiological and ecological harm. Osmotic membrane distillation (OMD) is an emerging technique for recovering inorganic salts from wastewater. The process involves the transfer of water vapor from a feed solution (FS) to a permeate stream due to the difference in vapor pressure across a hydrophobic membrane. It thus results in a concentrated solution at the feed outlet and purified water at the permeate side. OMD is preferred due to its straightforward scale-up and low energy requirements. In this research, a steady state 2-D axisymmetric computational fluid dynamics (CFD) model is developed to study the recovery of sodium carbonate (Na2CO3) from aqueous feed solution through OMD in a hollow fiber membrane contactor (HFMC). Aqueous sodium chloride (NaCl) solution was taken as an osmotic solution (OS). The numerical convection-diffusion mass, momentum transport, and Happel equations were scripted in COMSOL Multiphysics™ version 6.0 software. The model computed the water transport from FS to OS. Computed water flux well matched with the literature based experimental results. Simulations were carried out to investigate the parametric effects, including Reynold’s number, FS and OS concentration and the module geometrical parameters to establish an optimized operating conditions and module geometry and to achieve the desired FS concentration. Results showed that a 2-fold rise in OS concentration increased the transmembrane water flux 4-fold. However, the flow rates of both FS and OS did not significantly affect the flux. On the other hand, concentration polarization (CP) showed dependence on the FS concentration, tortuosity, and Reynolds number. A membrane tortuosity of 1.6, feed concentration of 75 g L−1, OS concentration of 300 g L−1, and a FS Reynolds number in the turbulent flow range can result in higher transmembrane flux and lower chances of CP development.

Evaluation of physicochemical, antioxidant, antibacterial activity, and sensory properties of watermelon rind candy

Watermelon (Citrullus lanatus) is consumed all over the world that contains a large number of seeds and rind, which is discarded. These by-products contain phytochemical compounds with great nutritional potential. This study aims to evaluate physicochemical properties and sensory values of watermelon rind candy. In this study in order to make the waste of watermelon a more sustainable and value-added food product, the watermelon rind was dried using an osmotic dehydration technique which comprises gradual impregnation of syrup (50 and 70% w/w – 1 to 5 h) before drying at 40 and 60 °C in 8 and 10 h. Various variables such as moisture content, chemical composition, water loss, solid gain, rehydration water, acidity, pH, antioxidant activity, antibacterial activity, residual toxins, phenolic and flavonoid contents during osmotic dehydration of watermelon were investigated. Results showed by rising temperatures, dehydration becomes more severe. Increasing the temperature in both osmotic samples in a concentrated solution (70%) and in osmotic samples with a dilute solution (50%) can enhance the mass transfer, water loss, solid absorption, as well as dehydration intensity. However, antioxidant activity, phenolic and flavonoid content significantly decreased after osmotic dehydration. TPC decreased from 35.83 mg/100 g to 27.45 mg/100 g and TFC of the watermelon rind (8.71 ± 0.01 mg/100 g) decreased to 2.63 ± 0.02 mg/100 g and also antioxidant activity after the osmotic process decreased from 61% to 40%. Also, osmotic dehydration had no significant impact on acidity and pH. The watermelon rind dehydrated sample (osmosis temperature: 40 °C, osmotic solution concentration: 70%, immersion duration: 5 h) was the best choice of panelists due to the highest score in the sensory evaluation including taste, texture, and overall acceptability. By determining the hardness of the watermelon rind candy and comparing it with the results of texture analysis of other dried products, it can be concluded that this product can be used as a healthy snack with longer shelf life properties.

The influence of ultrasound-assisted osmotic dehydration as a pre-treatment method on the quality of vacuum dried pineapple

This study investigated the effect of ultrasound-assisted osmotic dehydration (UAOD) as a pre-treatment before vacuum drying on the drying time, quality, and microstructure of pineapple. At first, the best conditions for water desorption during osmotic dehydration (OD) were optimized. Pineapple cubes were subjected to OD at different osmotic solution concentrations (30, 40, and 60°Brix), pre-treatment time (0.5 and 1 hr), and temperature (35ºC) using two types of osmotic agents (sucrose and fructose). According to the results, sucrose was the best osmotic agent because it reduced the sample's moisture content and water activity. Secondly, the influence of UAOD on sugar gain, water loss, and drying time was evaluated using sucrose as an osmotic agent. Pineapple cubes were subjected to UAOD at different osmotic solution concentrations (30 and 60°Brix), pre-treatment time (10, 20, and 30 mint), and temperature (40 ºC) in an ultrasonic bath (ultrasound frequency of 40 kHz and ultrasound power of 300 W). Results exhibited that the application of UAOD increased the sugar gain and water loss, consequently decreasing the drying time. Overall, a 15.31 % reduction in vacuum drying time on a self-designed vacuum dryer and a 9 % reduction in total processing time were observed when UAOD (30 ºBrix) was applied for 20 min. Moreover, the influence of UAOD on the quality of dried pineapple in terms of rehydration ratio, firmness, and color change was also determined. Results showed that the pre-treatment with UAOD (30 ºBrix) of 20 min provided a better rehydration ability, with minimum change in color and textural properties. However, an increase in the pre-treatment time beyond 20 min diminished the rehydration ability of the dried product. Scanning electron microscope (SEM) images of pretreated and dried pineapples were also analyzed to determine the effect of pre-treatments applied for different lengths of time on the microstructure of the pineapple. The study's results suggested that applying UAOD as a pre-treatment considerably reduced the processing time and better retention of the pineapple properties.

OSMO-Microwave Drying of Pineapple (Ananas comosus) Slices: Mass Transfer Kinetics and Product Quality Characterization

This present research aimed to investigate the effect of slice thickness and concentration of the osmotic solution on mass transfer kinetics, the color profile of osmotically dehydrated pineapple slices, and product quality characteristics of osmotically dehydrated microwave-dried (ODMWD) products. Three slice thicknesses (0.5, 1, and 1.5 cm) and three concentrations of osmotic solution (40, 50, and 60 °Brix) were used. The mass transfer kinetics (moisture reduction behaviour, weight loss, solid gain), physicochemical properties (color, TSS, pH, titratable acidity, vitamin C, and total sugar), and total phenolic content of pineapple slices were analyzed. During osmotic dehydration, the moisture reduction behaviour of 0.5 cm slices was faster in all osmotic solutions, whereas water loss and solid gain were higher for all slices treated with 60 °Brix. Both slice thickness and concentration of the solution significantly affected the color of OD pineapple slices. For ODMWD products, total soluble solids (TSS), pH, ascorbic acid content, total sugar, and total phenolic content increased for all slice thicknesses with an increase in osmotic solution concentration, whereas titratable acidity exhibited the opposite result. The rehydration ratio was higher in 0.5 cm slices for all solution concentrations. According to the finding, pineapple fruits can be dehydrated by using 60 °Brix solution concentration with 0.5 cm slices for making dehydrated pineapple fruit, and osmotic dehydration followed by microwave drying of pineapple fruit could be used for value-added processing products.

EFFECT OF ULTRASOUND ASSISTED OSMOTIC DEHYDRATION PRE-TREATMENT ON DRYING KINETICS AND SOME FUNCTIONAL PROPERTIES OF PUMPKIN (Cucurbita moschata)

Bu çalışmada balkabağının (Cucurbita moschata) kurutma kinetiği ve bazı fonksiyonel özellikleri üzerine ultrases destekli ozmotik dehidrasyon (US-OD) ön işleminin etkisi araştırılmıştır. Örnekler 3 farklı konsantrasyonda (%12.5, %25 ve %50) şeker çözeltisi içeren ultrasonik banyo içerisinde kavitasyon işlemi ile (45 kHz, 90 dakika) dehidre edilmiş ve ardından sıcak havada kurutma yöntemi kullanılarak 60oC sıcaklıkta kurutulmuştur. US-OD işlemi ile birlikte en yüksek su kaybı ve katı madde kazanımı %50’lik ozmotik çözelti kullanılarak dehidre edilen örnekte tespit edilmiştir. US-OD işlemi şeker çözeltisi konsantrasyonuna bağlı olarak kurutma süresini kontrol örneğine göre yaklaşık 180 dakika kısaltmıştır. Bununla birlikte ozmotik çözeltinin şeker konsantrasyonuna bağlı olarak rehidrasyon oranında azalma gözlenmiştir. En yüksek toplam fenolik madde miktarı (120.08 mg GAE/100 g kuru ağırlık) ve antioksidan kapasite (%38.21) %50’lik ozmotik çözeltide dehidre edilen ve kurutulan örnekte belirlenmiştir. Elde edilen çıktılar matematiksel modellere uyarlandığında US-OD ön işlemi uygulanmış balkabağının kurutulmasını en iyi tanımlayan modelin Page modeli olduğu sonucuna varılmıştır.

Studies on Impact of Processing on Physiochemical and Biochemical Properties of Osmodehydrated Pineapple (Ananas comosus (L) Merr.) Cuboid and Its Storage Stability

Osmotic dehydration of pineapple cuboids were conducted to study the effect of sugar concentration of osmotic solution on mass transfer, weight reduction, vitamin-C, total phenol content and antioxidant property of samples pretreated with steam blanching and microwave heating. As treatment time went on, there was an increase in water loss, weight loss, and solids accumulation. The sample treated with 60°B experienced the highest mass transfer during the osmotic dehydration of pineapple cuboids, whereas the sample treated with 30°B experienced the lowest mass transfer. The pineapple cuboids immersed in 60˚B sugar syrup and dried in a tray drier resulted maximum weight loss. Microwave heated samples dipped in 60˚B sugar syrup showed better retention of nutritive value(total phenol content, vitamin C and antioxidant activity) as well as better color, texture, taste and mouth feel .According to the sensory analysis, the samples treated with 60°B solution received the highest acceptability for color, flavour, texture, mouth feel, and taste. Osmodried samples were stored for 3 months at ambient condition without any adverse effect on sensory and nutritional parameters.

Mass transfer kinetics (soluble solids gain and water loss) of ultrasound-assisted osmotic dehydration of apple slices

Ultrasound (sonication) treatment can be used directly for dehydration or pre-treatment before the osmotic dehydration (OD) procedure of fruit or vegetable particles. The combination of this technique with the OD technique can further improve the dehydration process efficiencies by increasing the mass transfer rates and enhancing final product quality. In this study, apple slices were osmotically dehydrated in different hypertonic sucrose solutions and assisted with or without ultrasound. Sucrose concentrations (in three levels of 30, 40, and 50° Brix), sonication power (in three levels of 0, 75, and 150 W), and treatment time (in six time intervals: 10, 20, 30, 40, 50, and 60 min) were the factors investigated concerning weight reduction, soluble solids gain, water loss and rehydration. Also, mass transfer kinetics were modelled according to Page, Newton, Midilli, Logarithmic, Verma, and Two terms equations. Increased sucrose solution concentration resulted in higher weight reduction, soluble solids gain and water loss. Also, increased sonication power levels resulted in higher weight reduction, soluble solids gain and water loss. The average rehydration ratio of apple slices decreased from 237.7 to 177.5%, by increasing osmotic solution concentration from 30 to 50%. The Page equation showed the best fitting for water loss data. The effective moisture diffusivity (Deff) of apple slices during OD calculated using Fick’s second law applied to a slab geometry was found to be in the range of 1.48 × 10–10 and 4.62 × 10–10 m2s−1 for water loss.

Ultrasound assisted osmotic dehydration of dragon fruit slices: Modeling and optimization using integrated artificial neural networks and genetic algorithms

The effect of ultrasonication on osmotic dehydration of dragon fruit (Hylocereus undatus) slices was investigated using a feed forward backpropagation neural network in this study. The four process variables were ultrasonic power ( X UP $$ {X}_{UP} $$ : 100–300 W), ultrasound temperature ( X UT : $$ {X}_{UT}: $$ 30–50°C), osmotic solution concentration ( X SC $$ {X}_{SC} $$ : 40–60°Brix), and liquid to solid ratio ( X LS $$ {X}_{LS} $$ : 8:1–12:1 ml/g). Under different combinations of independent variables, the water loss ( Y WL $$ {Y}_{WL} $$ ), solid gain ( Y SG $$ {Y}_{SG} $$ ), and change in color ( Y ∆ E $$ {Y}_{\Delta E} $$ ) were evaluated. The ANN architecture consists of 4, 9, and 3 neurons in the input, hidden, and output layer, respectively. The three independent variables of ultrasound-assisted osmotic dehydration X UP $$ {X}_{UP} $$ , X UT $$ {X}_{UT} $$ , and X SC $$ {X}_{SC} $$ found to have a positive effect on the three responses water loss, solid gain, and change in color. The liquid to solid ratio was revealed to have a negative effect on color change and a positive impact on response water loss and solid gain. The output parameters of the ANN model (weights and bias) were integrated with genetic algorithm (GA) for the optimization purpose, and the best combination was picked based on the fitness value (FV). The optimal ultrasound-assisted osmotic dehydration condition obtained using integrated ANN-GA was 235 W, 38.74°C, 56°Brix, and 10.5 ml/g. The relative deviation between the experimental and integrated ANN-GA model predicted values for water loss, solid gain, and color change values under optimum conditions was less than 6.880%, suggesting that the predicted values for response were in good agreement with the experimental data. Practical applications The article describes the synergistic influence of sonication power and temperature on the osmotic dehydration of dragon fruit slices. Ultrasound-assisted osmotic dehydration (USOD) prevents enzymatic and oxidative browning, preserving the color. In dragon fruit slices flavor retention increases when sugar syrup is used as an osmotic agent. Furthermore, the fruit pieces absorb sugar and eliminate acid, resulting in a sweeter product than a conventionally dried product. The results showed that ultrasound assisted osmotic dehydration removed water from dragon fruit more rapidly at a lower temperature, keeping color, aroma, nutritional value, and flavor components. The combined impact of ultrasound and temperature also lowered the water activity of fruit and enhanced the product's storage life significantly.

Optimization of process parameters for ultrasound‐assisted osmotic dehydration of pineapple slices using response surface methodology

The effect of ultrasound assisted osmotic dehydration (USOD) on dehydration kinetics viz., water loss (WL), solid gain (SG) and osmotic dewatering rate (ODR) were investigated using response surface methodology, in order to optimize process parameters. Pineapple slices were subjected to USOD at three different osmotic solution concentrations (50, 60 and 70°B), sonication time (20, 30 and 40 min), temperatures (10, 20 and 30°C) using two types of osmotic agents (Glucose and Fructose) in an ultrasonic bath (ultrasound frequency of 33±3 kHz and ultrasound power of 250 W). Box-Behnken design was used as experimental design, consisting of three factors with three levels, and a categoric factor with two levels, totaling thirty four data points. Results of ANOVA and regression analysis conducted showed significant effects on responses and model’s best fit to the experimental data. Results revealed that USOD treatment led to higher water loss and osmotic dewatering rate compared to osmotic dehydration (OD). The optimized values that would give maximum WL, ODR and minimum SG were osmotic solution concentration of 50°B, sonication time of 26.6 min, temperature of 30°C and using Fructose as osmotic agent. This resulted in values of 0.266 g water/g, 0.049 g solid/g and 0.730 g/min for water loss, solid gain and osmotic dewatering rate, respectively.

Optimization of Osmotic Dehydration of Sapodilla (Achras zapota L.).

Sapodilla (Achras zapota L.) is a fruit with a great nutritional potential; however, its perishable nature is a great obstacle for commercialization/exportation. Herein, osmotic dehydration was applied to sapodilla to reduce post-harvest losses and obtain a stable product with acceptable sensorial characteristics. Initially, a 2³ full-factorial design was performed to determine the effect of temperature (30–50 °C), sucrose concentration (40–60% °Brix) and immersion time (90–240 min) on the moisture loss (ML), solid gain (SG) and dehydration efficiency index (DEI). The samples with higher DEI values were subjected to sensory analysis, followed by physicochemical, microbiological and structural analyses. The temperature and the concentration of the osmotic solution had significant influence (p < 0.05) on ML and SG, whereas DEI was significantly influenced (p < 0.05) by the concentration of osmotic solution and the immersion time. The sample produced by osmotic dehydration using the optimized conditions (40 °C, 50 °Brix; 165 min) obtained higher scores on the sensorial attributes, greater compliance with microbiological standards and generated turgor reduction and ruptures of sapodilla cell walls.

Drying of persimmon fruit (Diospyros kaki L.) pretreated by different osmotic processes

AbstractPersimmon is a short shelf life fruit with interesting potential for application in different industrial segments. The immersion of food in a hypertonic (30 and 45 °Brix) or even hypotonic medium can be used as a pretreatment for the drying process. In this study, the convective drying of persimmons was preceded by osmotic dehydration (OD) with fructose in a standard atmosphere, pulsed vacuum osmotic dehydration (PVOD), ultrasound (US)‐assisted OD, and US pretreatment in distilled water. Pretreatment times were 0, 10, and 30 min. The samples were subjected to convective drying at 40 and 60°C, 0.5 m s−1. The effects of the pretreatments on the drying kinetics, volumetric shrinkage, and rehydration capacity were investigated. Fick's model and the Dincer and Dost model were used to fit the drying evolution. In addition to the influence of the osmotic solution concentration, moisture content and solid gain were functions of the treatment type. Convective drying required 260–740 min. The use of PVOD and US pretreatments resulted in the shortest drying times. The dried fruits showed particular characteristics with each different pretreatment. Both tested models presented satisfactory adjustments, but Fick's model was the best approach. In general, the treatments caused structural modifications in the persimmon fruits that modified the drying kinetics and the properties of the dried food.Practical ApplicationsConvective drying is a food processing method used to extend the shelf life of fruits, such as persimmons. The use of pretreatments is an interesting strategy to improve the drying process. However, the combination of these technologies can influence drying kinetics. Therefore, the use of mathematical models is important to represent the behavior of these processes.

Development of mass and heat transfer coupled model of hollow fiber membrane for salt recovery from brine via osmotic membrane distillation

BackgroundIn this research work, a coupled heat and mass transfer model was developed for salt recovery from concentrated brine water through an osmotic membrane distillation (OMD) process in a hollow fiber membrane contactor (HFMC).The model was built based on the resistance-in-series concept for water transport across the hydrophobic membrane. The model was adopted to incorporate the effects of polarization layers such as temperature and concentration polarization, as well as viscosity changes during concentration.ResultsThe modeling equations were numerically simulated in MATLAB® and were successfully validated with experimental data from literature with a deviation within the range of 1–5%. The model was then applied to study the effects of key process parameters like feed concentrations, osmotic solution concentration, feed, and osmotic solution flow rates and feed temperature on the overall heat and mass transfer coefficient as well as on water transport flux to improve the process efficiency. The mass balance modeling was applied to calculate the membrane area based on the simulated mass transfer coefficient. Finally, a scale-up for the MD process for salt recovery on an industrial scale was proposed.ConclusionsThis study highlights the effect of key parameters for salt recovery from wastewater using the membrane distillation process. Further, the applicability of the OMD process for salt recovery on large scale was investigated. Sensitivity analysis was performed to identify the key parameters. From the results of this study, it is concluded that the OMD process can be promising in salt recovery from wastewater.

Glass transition and crystallization of solid model system of jujube slice as influenced by sugars and organic acids

To understand the specific contributions of amorphous sugars and organic acids to the quality of food matrix, the solid model system of jujube slice skeleton (JSS) was firstly established. Effects of fructose (F), glucose (G), malic acid (M) and citric acid (C) on the glass transition temperature (Tg) and crystallization of JSS were studied. JSS-F/G/M/C blends were prepared by osmosis in the solution at a range of 0 ~ 32 g/100 g. Sugars reduced the Tg in the system, structure of JSS-G/M blends was changed from “amorphous glassy” to “amorphous rubbery” by increasing the osmotic solute concentration. Tg was decreased from 50.8 to 14.0 °C when JSS was osmosed in a 4 g/100 g fructose solution. Organic acids induced their crystallization in JSS. The crystallinity of JSS-M immersed in 32 g/100 g osmotic solution concentration was increased from 2% to 75%. Fructose presented greater influence on the adverse quality of jujube slices.

Process optimization for dehydration of shelled peas by osmosis and three‐stage convective drying for enhanced quality

Peas are highly seasonal and perishable in nature, thereby requiring suitable preservation methods to be available throughout the year. Osmotic drying is one of the suitable methods for preserving perishable and semi-perishable produce. Osmotic drying of green peas was carried out in ternary solutions of water, sodium chloride (NaCl), and sucrose having different solution concentrations and osmotic temperatures. Three-stage drying of osmotically pretreated green peas was carried out in convective tray dryer at air temperatures of 70°C (for first 3 hr), 60°C (for next 2 hr), and 50°C (till final moisture content of below 10% wb). The samples were analyzed for moisture content, color change, sphericity, hardness, and rehydration ratio (RR). The osmotic drying process was optimized using response surface methodology (RSM). The optimized process conditions for maximum sphericity, hardness, and RR and for minimum moisture content and color change were determined as sodium chloride solution (10% w/w) and osmotic temperature of 34.41°C. Practical applications Osmotic drying of foods is advantageous when used in combination with other drying techniques as it reduces total drying time, inhibits enzymatic browning, and also reduces energy costs. This study would help to understand the effect of osmotic solution concentration and osmotic temperature on quality of osmo-convective dried peas. Optimization of process parameters would provide the best combination of osmotic solution concentration and osmotic temperature for achieving better product quality in terms of moisture content, color, hardness, rehydration ratio, and sphericity. The high-quality product hence obtained using optimized process parameters will find utilization not only in soup mixes, ready-to-eat snack foods but also as fresh-like peas upon rehydration during off-seasons.

Application of Osmotic Dehydration and Ultrasound to Enhance Hazelnut Oil Extraction

Hazelnut oil is a valuable product which can be used in various applications not limited to food processing, cosmetic product, and pharmaceutical industry. Traditionally, heating process is used to remove the moisture in various nuts and seeds prior to oil extraction stage in the industry which is relatively energy consuming. In this study, osmotic dehydration which is normally used as a pretreatment in fruit dehydration process was applied as a low-energy moisture removal method during the ultrasound-assisted extraction of oil from hazelnut. The effects of ultrasound amplitude, concentration of osmotic solution, and dehydration time on the yield and characteristics of hazelnut oil obtained were investigated in this study. Concentration of osmotic solution and dehydration time showed more significant effects on water removal as compared with ultrasound amplitude. Higher oil yield of 93% was achieved with the introduction of osmotic dehydration as pretreatment without negative impacts on quality of oil as compared with 88% oil yield in extraction without dehydration aid. The values for quality of oil obtained were in the range of 25–40 g/100 g oil, 0.5–1.1 g/100 g oil, and 2–6 mEq/kg for iodine, free fatty acid, and peroxide values, respectively. All the values were in the range of edible oil standard. Therefore, osmotic dehydration is a promising pretreatment method to enhance oil yield during extraction process in food industry.

EVALUATION OF MASS TRANSFER DURING OSMO-CONVECTIVE DRYING OF BENINCASA HISPIDA CUBES IN SALT SOLUTION USING REGRESSIONAL-DESIRABILITY METHOD

Regressional-desirability approach in Box-Behnken response surface design was employed in this study to examine and optimize the osmotic dehydration process of Benincasa hispida cubes by impregnating in salt solution as an osmotic agent. The effect of independent parameters such as, concentration of solution (1-5%), sample to solution ratio (1:5-1:15 g/ml), temperature of osmotic solution (30-50℃) and time of immersion (30-180 min) on the weight reduction (WR), solid gain (SG), water loss (WL), rehydration ratio (RR) and shrinkage (SH) were studied. Second order polynomial mathematical models were developed for the responses and all the independent process variables have considerable consequence on the responses. The optimal dehydration process condition was found by regressional-desirability method and were: osmotic solution concentration of 2.73%, sample to solution ratio of 1:14 g/ml, osmotic solution temperature of 50℃ and osmotic dehydration time of 179 minutes with the mass transfer and quality properties such as weight reduction of 24.59%, solid gain of 7.69%, water loss of 32.28%, rehydration ratio 11.43%, shrinkage 8.58% and overall acceptability 8.19. The optimized samples were subjected to convective drying in cabinet tray dryer at different drying air temperatures (40, 50 and 60℃). The results indicated that the osmotic pre-treatment of the samples using salt solution was better in terms of water removal and reduction in the processing time when combined with convective drying process. Also, the quality of the final product was found to be good for the osmo-convective dried product using salt solution.

Kinetic Mechanism of Hazelnut Oil Extraction with Ultrasound-Assisted Osmotic Dehydration Pretreatment

Nowadays, most of the researches focus on enhancing the oil yield by adjusting the various process parameters or searching for alternative techniques. There is only limited information on investigating the effects of various extraction parameters on kinetic mechanism during oil extraction. The mechanism data can provide additional information to the industry when optimization is needed. Previous work had investigated the effect of ultrasound in extraction process. The main purposes of this study are to apply osmotic dehydration as pretreatment and to investigate the effects of ultrasound amplitude, concentration of osmotic dehydration, and dehydration time on extraction mechanism of hazelnut oil. The kinetic modeling showed that So and Macdonald model was more suitable to describe the mechanism of hazelnut oil extraction with higher R2 values ranged from 0.944 to 0.987 as compared with Perez et al. model. The results showed that applying 30% ultrasound amplitude in dehydration stage could increase the mass transfer coefficient for diffusion step (kd) from 0.019 to 0.044 min−1 due to cavitation effect. Besides, 15% concentration of osmotic solution could limit the diffusion step with lowest kd value of 0.055 min−1 as compared with 5 and 10% concentrations due to blocking of surface by solute in higher concentration of osmotic solution. Lastly, increasing the dehydration time from 45 to 150 min could enhance the oil diffusion process with kd values increased from 0.058 to 0.075 min−1 due to lower moisture content in sample.