Effect Of Ultrasound-assisted Osmotic Dehydration Research Articles

Effect of ultrasound-assisted osmotic dehydration on the drying kinetics, water state, and physicochemical properties of microwave vacuum-dried potato slices

The effects of pre-treatments on the drying characteristics, water state, thermal properties, and bulk shrinkage of potato slices during microwave vacuum drying (MVD) were investigated. The pre-treatment included ultrasound in distilled water (USOD-0%), and ultrasound-assisted osmotic dehydration in a 60% sucrose solution (USOD-60%). Results showed that the drying time of potato slices was reduced and the drying rate was increased when USOD-0% was used as a pretreatment, whereas USOD-60% had a negative effect on the drying rate of the samples. The Weibull model was effective in predicting the water changes in potato slices during the drying process. NMR analysis revealed that the relative content of immovable water (M22) increased initially, then decreased for drying, while the transverse relaxation time (T2) and the relative content of free water (M23) decreased consistently. The DSC results indicated that the glass transition temperature (Tg) had an inverse relationship with the water content of the samples, yet had virtually no influence on the volume shrinkage. The sample volumes decreased linearly with the decrease in water content during the initial drying stages. USOD pre-treatment lessened the volume shrinkage of MVD potato slices. Static gravimetry was used to determine the moisture sorption isotherms of MVD potato slices at 30 °C within the aw range of 0.113–0.923. The GAB model accurately fitted the experimental sorption data, which showed sigmoid shape curves for the MVD samples. When aw values exceeded 0.7, the USOD-60% treatment significantly reduce the water sorption capacity of MVD potato slices, while USOD-0% treatment was observed to increase the hygroscopic properties of MVD samples. Compared with the control, USOD-0% pretreatment significantly increased the monolayer water content (X0), sorption surface area (S0), the thickness of sorbed water multilayer (tm), and density of sorbed water (Ds) values of MVD potato slices, while USOD-60% decreased these values.

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.

Ultrasound-assisted osmotic dehydration of litchi: effect of pretreatment on mass transfer and quality attributes during frozen storage

Litchi (Litchi chinensis Sonn.), fruits being the perishable and high amount of moisture content, are very susceptible to fruit deterioration and reduced shelf life. A novel method of ultrasound-assisted osmotic dehydration can improve fruit quality by increasing mass transfer rate and maintaining texture characteristics. Therefore, this study aimed to investigate the effect of ultrasound-assisted osmotic dehydration on the mass transfer parameters, physicochemical and microbiological qualities of litchi fruits during frozen periods. For this purpose, litchi fruits were subjected to ultrasound-assisted osmotic dehydration as a pretreatment prior to the freezing step. The pretreatment consisted of three processing conditions: the use of osmotic dehydration at 50% (w/w) of sucrose (OD); ultrasound in an osmotic solution for 10 min before osmotic dehydration (US10 + OD); and ultrasound in an osmotic solution for 15 min before osmotic dehydration (US15 + OD). All samples were frozen and stored at − 18 °C. The obtained results indicated that ultrasound pretreatment effectively increases water loss (28.73 ± 3.25%) and solid gain (45.44 ± 6.85%) levels of litchi fruit. During the frozen storage for 90 days, the use of ultrasound, remarkably, US10 + OD treatment reduced the moisture content (76.46 ± 1.38%), drip loss (15.93 ± 1.01%), and microbial load (2.58 ± 0.06 log CFU/g) of the frozen litchi while increasing the firmness (1.46 ± 0.24 N), and a total soluble solid (17.50 ± 0.87 oBrix) amount of the samples in comparison to their controls (p < 0.05). Therefore, these results demonstrated that ultrasound-assisted osmotic dehydration could significantly improve the quality of litchi fruit in freezing and thawing processes.

Ultrasound-Assisted Osmotic Dehydration of Apples in Polyols and Dihydroxyacetone (DHA) Solutions

The aim of this work was to analyse the effect of ultrasound-assisted osmotic dehydration of apples v. Elise on mass transfer parameters, water activity, and colour changes. Ultrasound treatment was performed at a frequency of 21 kHz with a temperature of 40 °C for 30–180 min using four osmotic solutions: 30% concentrated syrups of erythritol, xylitol, maltitol, and dihydroxyacetone (DHA). The efficiency of the used solutes from the polyol groups was compared to reference dehydration in 50% concentrated sucrose solution. Peleg’s model was used to fit experimental data. Erythritol, xylitol, and DHA solutions showed similar efficiency to sucrose and good water removal properties in compared values of true water loss. The application of ultrasound by two methods was in most cases unnoticeable and weaker than was expected. On the other hand, sonication by the continuous method allowed for a significant reduction in water activity in apple tissue in all tested solutions.

Influence of ultrasound-assisted osmotic dehydration on texture, bioactive compounds and metabolites analysis of plum.

The aim of this study was to investigate the effect of ultrasound-assisted osmotic dehydration on texture, retention of bioactive compounds, nutritional quality and metabolites of plum. The osmotic dehydration was performed using 50% glucose and sucrose in ultrasound (25 kHz) for 30 and 60 min. After osmotic treatment samples were dried at 55 °C using hot air oven. In this study, the texture of the sample was determined by 20% compression of texture profile analysis and solute diffusion coefficient was calculated by Fick's law of diffusion. Further, the volatile compound and nutritional quality were determined. Furthermore, treatment difference of osmo-dehydrated plum on metabolites was measured by 1H NMR. The results showed that the ultrasound-assisted osmotic dehydration increased water loss and solid gain. It also increases the reduction of moisture content from the plum. Textural result of osmo-dehydrated plum in glucose increases the softness of plum and decreases hardness. Moreover, the increased antioxidant and phenolics were obtained in plum treated in 50% sucrose for 30 and 60 min and also at 30 min of glucose. Color of ultrasound-assisted osmotic dehydrated plum was also affected by treatment time and the osmotic solution used. Ultrasound-assisted osmotic dehydration reveals that water loss, solid gain, texture and bioactive compounds affected by treatment time and osmotic solution.

Effect of ultrasound-assisted osmotic dehydration pretreatment on the infrared drying of Pakchoi Stems

The effect of ultrasound-assisted osmotic dehydration (UOD) prior to infrared drying (IR) on the drying time and quality properties of dried Pakchoi stems was studied. Results suggested that the ultrasound application could significantly increase the mass transfer during the osmotic process. The UOD pretreated samples showed higher relaxation times of T23 and lower relative signal intensities of A23 using low-field nuclear magnetic resonance (LF-NMR) analysis. Moreover, the cell structural damage and mircrochannel formation caused by the UOD pretreatment resulted in a 25 ∼ 42% reduction in drying time. Although, the chlorophyl and ascorbic acid contents of IR dried Pakchoi stems with UOD pretreatment were relatively lower in comparison with those of untreated samples, the color was better retained and the rehydration ratio was significantly improved by UOD pretreatments.

Effect of Ultrasound-Assisted Osmotic Dehydration as a Pretreatment on Deep Fat Frying of Potatoes

The objective of this study was to investigate the possibility of using ultrasound-assisted osmotic dehydration (UAOD) as a pretreatment prior to frying and to study its effects on the quality of fried potatoes. The quality parameters, moisture content, oil uptake, color, texture, and microstructure of fried potatoes, were chosen. Quality of fried potatoes treated with UAOD was also compared with the ones treated with osmotic dehydration (OD). Potato slabs (40 × 40 × 7 mm) were pretreated with different osmotic solutions (15 % sodium chloride and 15 % sodium chloride/50 % sucrose solutions) at different temperatures (25, 45, and 65 °C) with and without ultrasonic waves for different treatment times. The pretreatment conditions which are OD for 90 min and UAOD for 30 min using 15 % sodium chloride/50 % sucrose solution were applied prior to frying at 170 °C for 2, 4, and 6 min. UAOD reduced the oil content of fried potatoes by 12.5 % (db) as compared to untreated fried potatoes at the end of frying. There was no significant difference between OD and UAOD in reduction of oil uptake in fried potatoes. However, UAOD was found to have the advantage of improving the color of French fries. In addition, it shortened the pretreatment time of OD by about 67 %. Cell structure of fried potato was damaged in the presence of pretreatments of OD and UAOD.

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.

Effect of osmosis and ultrasound on pineapple cell tissue structure during dehydration

The effect of ultrasound-assisted osmotic dehydration applied for different lengths of time on pineapple tissue structure was evaluated. Using distilled water as the liquid medium, ultrasound induced disruption of cells and formation of microscopic channels in the fruit structure but did not induce breakdown of the cells. Consequently, ultrasound application increased sugar loss and water diffusivity because of the formation of microscopic channels, which offered lower resistance to water and sugar diffusion. Osmotic dehydration induced gradual distortion of shape of the cells, disconnection between the cells and the formation of channels by breakdown of the tissue. The changes caused by the application of osmotic dehydration in the fruit tissue structure resulted in a higher water loss and higher sugar gain. During the air-drying process, the effective water diffusivity increased when an osmotic solution with low sugar content was used (35°Brix). It decreased when an osmotic solution with high sugar content was used (70°Brix) because the high sugar gain observed under this condition has saturated of the microscopic channels with sugar creating an extra mass transfer resistance for water and sugar diffusion through the channels.