Optimization of Osmotic Dehydration of Kiwifruit

Mass transfer rates were quantitatively investigated during osmotic dehydration of kiwifruit slices using response surface methodology with the sucrose concentration (20-80%, w/w), temperature of sucrose solution (15-75°C), osmotic time (60-420 min), and slice thickness (2-10 mm) as the independent process variables. Quadratic regression equations are obtained to describe the effects of independent process variables on the water loss (WL), sucrose gain (SG), and ascorbic acid loss (AAL). It was found that all factors had significant effect on the WL during osmotic dehydration of kiwifruit. Effects of temperature, time, and slice thickness were more pronounced on SG than the effect of concentration of sucrose solution. The osmotic solution temperature was the most significant factor affecting the AAL, followed by slice thickness and duration of treatment. The optimal conditions for osmotic dehydration were: 60% sucrose concentration, 30-40°C osmotic temperature, 150 min osmotic time, and 8 mm slice thickness.     

Osmotic dehydration of lemon (Citrus limon L.) slices: Modeling mass transfer kinetics correlated with dry matter holding capacity and juice sac losses

Osmotic dehydration of lemon slices was performed using hypertonic NaCl solution. Due to low dry matter holding capacity (DHC) of lemon, the moisture loss, salt gain, and solid loss kinetics during osmotic dehydration were studied by considering the loss of juice sacs from lemon. The slices were immersed in the osmotic solutions maintained with four concentrations of NaCl (5–20%, w/v) and three temperatures (30, 40, and 50°C) for predetermined time intervals (10–180?min). The sample to solution ratio was maintained at 1:10. Azuara model based on Peleg model was used to determine the equilibrium moisture loss and salt gain. Apart from the moisture loss and salt gain, it was found that the loss of solid constituents and juice sacs from the fruit into the osmotic solution was significant. Therefore, the DHC was determined to correlate the rate of solid loss. The DHC was found to be greatly affected by temperature as lemon was less capable to withhold its cell integrity at higher temperature. A combined correlation model was used to determine the effect of osmosis time, solution concentration, and temperature on moisture loss, salt gain, and solid loss. High temperature is not preferable for osmotic dehydration of lemon as it increases losses. The optimal condition was found to be 20% salt concentration and 30°C osmotic solution for 180?min to attain high moisture loss, less solid loss, and required salt uptake within allowable limits.     

On the Development of Osmotically Dehydrated Seabuckthorn Fruits: Pretreatments,Osmotic Dehydration,Postdrying Techniques,and Nutritional Quality

Osmotic dehydration of whole seabuckthorn berries, followed by convective or vacuum drying, was investigated. First, different pretreatments were applied to the fruits in order to accelerate the rate of osmotic dehydration: immersion in liquid nitrogen, steam blanching, or freeze cycles. Immersion in liquid nitrogen was found to be the best pretreatment to maximize dehydration rate and to increase sugar gain during osmotic dehydration. An evaluation of moisture loss and sugar gain kinetics during osmotic dehydration of seabuckthorn fruits pretreated with liquid nitrogen, followed by vacuum or hot-air drying, was then performed. Loss of nutritional compounds due to processing was also measured. Sugar intake and partial dehydration of seabuckthorn samples increased with osmosis time and reached an equilibrium value after 4 h treatment. The finish drying methods (vacuum or convective) applied after OD showed a marked impact on the remaining moisture content of seabuckthorn samples. Concentration of some nutritional compounds was, however, dramatically reduced after the combined osmotic dehydration/drying processes.     

Effect of Immersion Time in Osmosis and Ultrasound on Papaya Cell Structure during Dehydration

The effect of ultrasound-assisted osmotic dehydration applied at atmospheric pressure for different lengths of time on papaya tissue structure was evaluated. Ultrasound induced the loss of cellular adhesion, formation of large cell interspaces, and light rupture of the cell walls. The changes in the tissue structure caused by ultrasound application increased sugar loss, water loss, and effective water diffusivity. Ultrasound-assisted osmotic dehydration induced a gradual distortion in the shape of the cells, loss of cellular adhesion, and the formation of large channels caused by rupture of the cell walls. The changes caused by the application of osmotic dehydration resulted in high water loss and sugar gain.     

Kinetic Aspects, Texture, and Color Evaluation of Some Tropical Fruits during Osmotic Dehydration

Osmotic dehydration of some tropical fruits like guava, melon, and papaya using sucrose and maltose solutions is presented in this article. The influence of sugar type and concentration, process temperature, and calcium salt addition on osmotic solution was investigated. Water loss and sugar gain up to 6 h of processing were evaluated and the effect of osmotic dehydration on fruit quality parameters like color and texture was analyzed. All studied variables affected the osmotic process kinetics, while for quality parameters the influence of sugar type or solution concentration and temperature was dependent on fruit and process conditions.     

Pulsed Electric Field Pretreatment for Osmotic Dehydration of Apple Tissue: Experimental and Mathematical Modeling Studies

The aim of this study was to analyze the influence of pulsed electric field pretreatment (PEF) on the osmotic dehydration of apple tissue. Osmotic dehydration was carried out in sucrose solution at 40°C and 100 rpm in a water-bath shaker. PEF pretreatment was performed using varying field strength of 5 and 10 kV/cm and 10 and 50 pulses. On the basis of electric conductivity measurement, the cell disintegration index was calculated. The course of osmotic dehydration was described by means of water loss, solid gain, weight reduction, and water content changes. Moreover, the course of the process was described by different mathematical models that are commonly used in the literature. PEF application before osmotic dehydration significantly increased water loss after 60 minutes of the process. In turn, no significant differences were found in the case of solid gain. The highest osmotic dehydration efficiency ratio (WL/SG) was noticed for samples treated by PEF at the electric field strength of 5 kV/cm and 10 pulses. The statistical analysis of mathematical modeling of the process showed the equations utilized generally exhibit a good fit to the experimental data.     

Effects of pretreatments on properties of microwave-vacuum drying of sweet potato slices

Abstract

Pretreatments of blanching (BL); osmotic dehydration at 35°Brix of sucrose (OD); ultrasound in distilled water (UD), and ultrasound-assisted osmotic dehydration (UO) were carried out for microwave-vacuum drying (MVD) orange- and purple-flesh sweet potato slices, and effects on their properties were investigated in this study. UO had improvements effects on water loss, solid gain, and relaxation time of the samples compared to other pretreatments. Low-field nuclear magnetic resonance results offered a view of water state concerning the effects of different pretreatments on sweet potato. UD treatment following by BL showed a long relaxation time corresponding to the weaker degree of bound hydrogen proton or the greater freedom degree of hydrogen comparing to other pretreated samples. Differential scanning calorimetry parameters appeared to be sensitive to pretreatments by increased Tg value compared to blanched sample. The value of Tg shows that it does not depend only of the water content but also on the experimental conditions (pretreatments). The dried sweet potato exhibited amorphous structures as evidenced by the X-ray diffractograms due to the BL treatment and MVD. Concentration of total phenolics and anthocyanins were high in purple sweet potatoes, whereas content of vitamin C and total carotenoid were high in orange ones. Application of UO is suitable for retention of bioactive compound and stability of MVD sweet potato slices.     

脱水莴苣片的护色工艺研究

针对脱水莴苣片在贮藏过程中的变色问题进行研究,寻找出有效的护色方法。首先。通过研究最佳的热烫条件,保证酶活对颜色没有影响,并尽量减少热烫对颜色的损失,选择出最佳的热烫条件为95℃、4min。然后,采用各种护色方法进行试验,最终得出了糖和盐的渗透处理是最好的护色方法。并研究了渗透处理对莴苣片的其他影响,得出渗透处理不但提高了色素的稳定性,而且降低了水分活度。增加了产品的得率,提高了复水速率。     

Optimization of Osmotic Dehydration of Potato Cubes Under Pulsed Microwave Vacuum Environment in Ternary Solution

Optimization of the process parameters for osmotic dehydration of 12.2-mm potato cubes was carried out using response surface methodology. The experiments were conducted using a central composite rotatable design (CCRD) with four factors, viz. sucrose concentration (27.5–42.5% w/w), salt concentration (7.5–12.5% w/w), total osmosis time (26.25–68.75 min), and microwave power density for the initial 4 min (0.375–1.125 W/g of total weight of solution and potato cubes) at two levels each to take into account the individual and interaction effects of the factors. A sample-to-solution ratio of 1:10 and pressure of 0.16 kPa for the initial 4 min were kept constant throughout all of the experiments. It was found that the linear effects of all factors on the water loss (WL) and solids gain (SG) were highly significant. The optimum condition was found at a sucrose concentration of 36.35%, salt concentration of 12.50%, osmosis time of 68.72 min, and microwave power density of 0.38 W/g for the initial 4 min, with a WL of 37.26% initial weight and SG of 8.74% initial weight. The drying of potato cubes was carried out using hot air, microwave–vacuum, and osmotic microwave–vacuum drying methods. It was found that potato cubes dried by combined osmotic microwave–vacuum had better sensory qualities.     

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.     

Assessment of Osmotic Process in Combination with Coating on Effective Diffusivities during Drying of Apple Slices

The effect of carboxymethyl cellulose (CMC) coating on the mass exchanges during the osmotic dehydration of apples and its effect on the quality of final product were studied. Coating semi-rings of apple with CMC solution (1%) was found to prevent solute uptake and to reduce salt diffusion coefficient from 4.35 × 10^-10 m²/s to 2.86 × 10^-10 m²/s. However, coating did not significantly affect the diffusivity of water. The effective diffusivity of salt and consequently solids gain were found to be depended on the concentration of CMC solution in the range of 0-1%. Increasing the concentration of CMC further from 1% had no effect on the mass exchanges during the osmotic process. Maximum performance ratio, defined as water loss/solids gain, and the lowest solids diffusion was observed for coated samples (with 1% CMC solution) treated with an osmotic solution containing glucose syrup (50%) and NaCl (2%).     

Ultrasound-assisted osmotic process on quality of microwave vacuum drying sweet potato

The effects of pretreatment before microwave vacuum drying (MVD) on texture, color, expansion, rehydration, drying rate, microstructure, sensory evaluation, and other properties of sweet potato were investigated in this study. The pretreatment consisted in five processing conditions, using blanching; osmotic dehydration at 35°Brix of sucrose (OD); ultrasound in distilled water (US); ultrasound in distilled water before osmotic dehydration (US?+?OD), and ultrasound-assisted osmotic dehydration (USOD). Pretreatments of sweet potato before MVD have shown success in reducing drying time with US treatment relatively more effective regarding drying time than other treatments. Compared with other treatments, US showed the highest rehydration ratio values. The osmotic group pretreatment exhibited a pronounced effect on water loss and solid gain, improved the color, aroma, and taste of dried sweet potato, whereas sucrose impregnation resulted in a hard texture observed with OD sample. USOD samples had a higher expansion ratio, lower hardness and color difference values, appeared less cell damaged, and recorded better overall quality than the other samples. There was a slight difference between USOD and US?+?OD samples. Combining osmotic dehydration with ultrasound as a pretreatment can significantly accelerate the heat transfer rate, reducing the dried time accordingly and increasing energy efficiency.     

Osmotic Dehydration Pretreatment in Drying of Fruits and Vegetables

Several vegetables and fruits, apple, ginger, carrot, and pumpkin were dehydrated under various osmotic conditions using sucrose and salt as the permeating agents. The dehydrated materials were then dried. The influence of solute concentration, process temperature and the type of solute on osmotic dehydration and further thermal drying were investigated. The nutrition loss during the osmotic process was measured using carotene as the nutrition index. The effect of calcium chloride present in osmotic solution on the product quality was also studied. A first order kinetic model was chosen to describe the mass transfer phenomena of the osmotic process. The equilibrium value of water loss, solute gained, kinetic constants K_WL and K_SG under various conditions are successfully predicted by the model. The relationship between the equilibrium value and four major factors that influence osmotic process of carrot was obtained based on the experimental data. The relations between the loss constant of carotene and the solute concentration in carrot and pumpkin were obtained based on the experimental data. The qualities of dried products are better for the osmotic dehydration pretreated samples than those dried directly.     

Application of Ultrasound and Ultrasound-Assisted Osmotic Dehydration in Drying of Fruits

This work examines the influence of ultrasonic and ultrasonic assisted osmotic dehydration pretreatments on the dehydration of eight fruits (banana, genipap, jambo, melon, papaya, pineapple, pinha, and sapota). An overview of the effects of ultrasound application on water loss, sugar gain, and effective diffusivity of water during the dehydration process is presented. The results showed significant differences for water loss and sugar gain among the fruits that were studied, which were analyzed based on the changes observed on the tissue structure of the fruit. The results also showed that the effective diffusivity of water in the fruit increased after application of ultrasound reducing air-drying time.     

Assessment of Osmotic Process in Combination with Coating on Effective Diffusivities during Drying of Apple Slices

The effect of carboxymethyl cellulose (CMC) coating on the mass exchanges during the osmotic dehydration of apples and its effect on the quality of final product were studied. Coating semi-rings of apple with CMC solution (1%) was found to prevent solute uptake and to reduce salt diffusion coefficient from 4.35 × 10^?10 m²/s to 2.86 × 10^?10 m²/s. However, coating did not significantly affect the diffusivity of water. The effective diffusivity of salt and consequently solids gain were found to be depended on the concentration of CMC solution in the range of 0–1%. Increasing the concentration of CMC further from 1% had no effect on the mass exchanges during the osmotic process. Maximum performance ratio, defined as water loss/solids gain, and the lowest solids diffusion was observed for coated samples (with 1% CMC solution) treated with an osmotic solution containing glucose syrup (50%) and NaCl (2%).     

Osmotic Dehydration of Apple Slices with Carboxy-Methyl Cellulose Coating

The effect of carboxy-methyl cellulose (CMC) coating on mass transfer process during osmotic dehydration of apple slices and its effect on salt absorption were investigated. The study was conducted using four concentrations of CMC (0.5, 1, 1.5, and 3%) and nine osmotic solutions comprising of glucose syrup (30, 40, and 50%) and salt (2, 4, and 6%). Sample contact time with the hypertonic solution was 15, 30, 60, 120, 180, 240, and 360 min. Both coated and uncoated samples were evaluated in terms of water loss (WL), solids gain (SG), WL/SG ratio, and salt absorption. Optimal condition was obtained when the CMC concentration of 1% was used with hypertonic solution comprising of 50% glucose syrup and 2% salt.     

Ultrasound-Assisted Osmotic Dehydration of Strawberries: Effect of Pretreatment Time and Ultrasonic Frequency

Pretreatment of fruits prior to drying has shown success in reducing drying time and costs. In this work, ultrasound-assisted osmotic dehydration has been implemented as a method to increase water diffusivity and reduce drying time in strawberries. Strawberry halves were immersed in distilled water and in two different concentrations of sucrose solutions while pretreatment time and ultrasonic frequency levels were varied to determine their effect on drying time, water loss, and soluble solids gain. A microscopic analysis was carried out to evaluate the formation of microchannels and other changes to the fruit tissue structure. Greater sucrose concentration used in ultrasound-assisted osmotic dehydration resulted in greater water loss with greatest loss observed for the strawberry halves pretreated for 45 min in a 50% w/w sucrose solution. The pretreatment carried out for 30 min employing an osmotic solution of 50% w/w of sucrose resulted in the highest drying rate among the pretreatments. Osmotic dehydration used alone during pretreatment increased total processing time, whereas osmotic dehydration combined with ultrasonic energy during pretreatment reduced total processing time and increased effective water diffusivity. Cell distortion and breakdown were observed not only in pretreatments employing ultrasound-assisted osmotic dehydration but in conventional osmotic dehydration. Formation of microchannels through ultrasonic application and effects of osmotic pressure differential were considered to be largely responsible for reducing drying time for strawberry halves.     

Osmotic dehydration of blueberries pretreated with pulsed electric fields: Effects on dehydration kinetics,and microbiological and nutritional qualities

Fresh blueberries were treated by pulsed electric fields (PEF) at 2?kV/cm before osmotic dehydration in 70% cane sugar syrup. The changes in water loss, solids gain, populations of native microorganisms, antioxidant activity, contents of anthocyanins, predominant phenolic acids and flavonols, and total phenolics in blueberries were investigated after PEF pretreatment and during osmotic dehydration at 40°C. Compared with non-PEF-pretreated blueberry samples, PEF pretreatment reduced the osmotic dehydration time of blueberry samples from 120 to 48?h at target moisture content (3.0?g/g initial dry matter). No significant differences (p?>?0.05) in total phenolics, antioxidant activity, anthocyanins, and predominant phenolic acids and flavonols were observed between the PEF-pretreated and non-PEF-pretreated blueberry samples. The PEF-pretreated blueberry samples had lower microbial populations than those which were not subjected to PEF pretreatment. Regardless of pretreatment, decreases in anthocyanins, predominant phenolic acids and flavonols, total phenolics, and antioxidant activity in blueberries were observed during the osmotic dehydration process. The results demonstrate that PEF pretreatment significantly reduced the dehydration time and enhanced the microbiological quality of blueberries without affecting their nutritional quality.     

声空化强化渗透脱水

引　言渗透脱水是指果蔬在一定温度下 ,放入高渗透压介质中 ,利用膜两边的浓度不同产生的渗透压除去其中部分水分的一种方法 .它是基于天然果蔬细胞壁作为半透膜 ,在渗透脱水中 ,主要存在两个相反过程 ,一方面果蔬中的水分向溶液中传递 ,另一　　方面溶液中的溶质逐渐渗入果蔬 ,最终达到渗透平衡 .渗透脱水可以在较短时间内除去果蔬的水分而不损坏果蔬的组织结构 .从生产的角度来说 ,经渗透脱水的果蔬再进行干燥 ,产品的干燥时间可缩短10 %～ 15 % [1] .通常 ,渗透脱水是一非常缓慢的过程 ,因此在不影响果蔬品质的前提下有必要采用一定方法…     

OSMOTIC DEHYDRATION OF PINEAPPLE

The effects of sugar type, sugar concentration, immersion time and temperature on the mass transfer of osmotic dehydration were studied using pie shape slices (7 mm thick with its center cork thrown away) of fresh pineapple (Queen variety, 90% maturity). The dehydration process was performed using two type of sugar as an osmotic agent (glucose and sucrose), three levels of sugar concentration (50, 60, and 70%), three levels of temperature (30, 50, and 70 °C), and three levels of immersion time (3, 6, and 9 hours). Following the osmotic dehydration process, the pineapple was dried at 70 °C for 48 hours. The mass transfer was then calculated and analyzed statistically. Sugar type, concentration, temperature, and length of immersion, have a significant effect on the mass transfer of osmotically dehydrated pineapple. The highest mass transfer of pineapple was found by using sucrose at the concentration of 70%, temperature 50 °C and 9 hours of immersion time.