Ultrasound-assisted Osmotic Dehydration Research Articles

Modifications on the Processing Parameters of Traditional Pineapple Slices by Stabilized Sound Pressure of Multiple Frequency Ultrasonic-Assisted Osmotic Dehydration

This study investigated the practical feasibility of synergistically and optimally applying ultrasound-assisted osmotic dehydration (UAOD) practices for the pineapple slice picking process (in sugar osmotic solution), with potential implications for improving current practices. This study was carried out to evaluate the effects of different treatment conditions of single (40 and 80 kHz)/multiple (40/80 kHz) frequencies, output powers (300, 450, and 600 W), and treatment time (5–40 min) at 30, 45, and 60 °Brix applied, respectively, on the pineapple slices picking process. The sound pressure of the UA was also measured to confirm that it provided the corresponding effect stably under different conditions. The ideal UAOD operating condition for pineapple slices is a 45 °Brix sugar osmotic solution, with frequency multiplexing at 40/80 kHz and an output power of 450 W for 25 min, which yields the optimal solids gain (SG) rate of 7.58%. The above results of this study indicated that UAOD could improve the accelerated quality transfer of pineapple slices and enhance the final product quality, thereby increasing the efficiency of the dehydration process and saving processing costs and time.

Vacuum frying of parsnip slices: Optimization by taguchi and response surface methodology and modeling the kinetics of water loss

We examined the optimization feasibility of frying conditions at 3 phases to produce crisp fried parsnip slices. In the first phase, the time of ultrasound-assisted osmotic dehydration, time of pre-drying by microwave, and frying pressure were considered as response-affecting factors and Taguchi technique effectively used in analyzing multiple parameters. The impact of process parameters (frying time, thermal driving force, & slice thickness) over the quality fried features parsnip slices (crispness, oil uptake, & optical features) was examined in the second phase. Cooling was performed in different conditions in the third phase. The vacuum frying’s optimal condition to produce fried parsnip slices was determined (parsnip slice thickness of 4.553 mm, ultrasound-assisted osmotic dehydration (immersed for 60 min in fructose solution), frying at 56.273 °C thermal driving force (146.2 °C) for 2.746 min at 70.1 frying pressure (kPa), & removing surface oil by centrifuging at 1200 rpm for 4 min). In this setting, the breaking force, oil uptake, and total color difference were predicted to be 12.217 %, 21.524 N, and 13.394, respectively. The impact of optimum frying conditions on the frying kinetics of parsnip slices was investigated. According to the findings, the model of Midilli et al. was considered the best.

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.

Mass transfer analysis and kinetic modeling of ultrasound-assisted osmotic dehydration of kiwifruit slices

Ultrasound treatments (sonication) in combination with osmotic dehydration process accelerate the rate of moisture removal from the fruits or vegetables pieces and decrease the dehydration duration. The purpose of this study was to examine the influence of ultrasound-assisted osmotic dehydration (UAOD) on mass transfer kinetic (soluble solids gain and moisture loss) of kiwifruit slices. The UAOD process was performed using 20, 30, and 40% sucrose solutions in ultrasonic bath (40 kHz, 75 and 150 W) for 10, 20, 30, 40, 50, 60, 70, and 80 min. After treatments, processed kiwifruit slices were dried at 70 °C using hot air oven. UAOD process reveals that mass reduction, soluble solid gain, moisture loss and rehydration capacity affected by treatments time, sucrose solution concentration and sonication power. The results showed that the UAOD treatment increased moisture loss and soluble solids gain. Furthermore, kiwifruit slices treated with higher ultrasound intensity (150 W) showed reduced dehydration duration (higher water loss), improved dehydration rate, and increased effective moisture diffusivity (Deff). The Deff determined by Fick's second law was varied from 9.05 × 10–11 to 29.28 × 10–11 m2s-1. The experimental data of dehydration curve of kiwifruit slices were fitted to different thin-layer equations and the Page equation with empirical constants was the best describing the of kiwifruit slices dehydration.

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.

Modelling of ultrasonic assisted osmotic dehydration of cape gooseberry using adaptive neuro-fuzzy inference system (ANFIS)

In the present investigation, the cape gooseberry (Physalis peruviana L.) was preserved by the application of osmotic dehydration (sugar solution) with ultrasonication. The experiments were planned based on central composite circumscribed design with four independent variables and four dependent variables, which yielded 30 experimental runs. The four independent variables used were ultrasonication power (XP) with a range of 100–500 W, immersion time (XT) in the range of 30–55 min, solvent concentration (XC) of 45–65 % and solid to solvent ratio (XS) with range 1:6–1:14 w/w. The effect of these process parameters on the responses weight loss (YW), solid gain (YS), change in color (YC) and water activity (YA) of ultrasound assisted osmotic dehydration (UOD) cape gooseberry was studied by using response surface methodology (RSM) and adaptive neuro-fuzzy inference system (ANFIS). The second order polynomial equation successfully modeled the data with an average coefficient of determination (R2) was found to be 0.964 for RSM. While for the ANFIS modeling, Gaussian type membership function (MF) and linear type MF was used for the input and output, respectively. The ANFIS model formed after 500 epochs and trained by hybrid model was found to have average R2 value of 0.998. On comparing the R2 value the ANFIS model found to be superior over RSM in predicting the responses of the UOD cape gooseberry process. So, the ANFIS was integrated with a genetic algorithm (GA) for optimization with the aim of maximum YW and minimum YS, YC and YA. Depending on the higher fitness value of 3.4, the integrated ANFIS-GA picked the ideal combination of independent variables and was found to be XP of 282.434 W, XT of 50.280 min, XC of 55.836 % and XS of 9.250 w/w. The predicted and experimental values of response at optimum condition predicted by integrated ANN-GA were in close agreement, which was evident by the relative deviation less than 7%.

Effect of ultrasound assisted vacuum osmotic dehydration on the mass transfer kinetics and qualities of orange slices

This research aimed to explore the effects of combined ultrasound and vacuum assisted osmotic dehydration on the mass transfer kinetics and qualities of fresh-cut orange slices. The experiments were carried out under four different conditions, i.e., osmotic dehydration (OD), vacuum osmotic dehydration (VOD), ultrasound assisted osmotic dehydration (UOD) and ultrasound assisted vacuum osmotic dehydration (UVOD). Aqueous solutions of the four osmotic agents – sucrose, xylitol, sorbitol, and maltitol at a concentration of 50°Brix were used in each condition. The results showed that UVOD had the highest (p < 0.05) water loss (WL) and solid gain (SG). The high regression coefficient (R2 > 0.99) and low χ2 and RMSE values revealed the applicability of Peleg model for fitting mass transfer of orange slice during osmotic dehydration. Low-field nuclear magnetic resonance (LF-NMR) spectra revealed the water distribution in orange cells. Electronic nose data indicated that osmotic dehydration did not significantly (p > 0.05) change the flavor of orange slices. Fourier transform infrared (FTIR) spectra indicated osmotic dehydration could preserve internal chemical composition of orange slice. Scanning electron microscope (SEM) images illustrated the mechanisms of VOD, UOD and UVOD. The results of mass transfer kinetics and qualities showed that sugar alcohols were good alternative osmotic agents to sucrose. Although UVOD led to the largest loss of vitamin C due to its highest WL, UVOD exhibited better hardness and could combine the advantages of VOD and UOD in water activity and color, respectively.

Ultrasound-assisted osmotic dehydration, followed by convective drying of papaya: effect on physicochemical and functional quality parameters

Papaya is a rich source of nutrients, antioxidants, and vitamins; however, it is highly perishable and hence needs to be preserved using suitable unit operations. Drying is an economical method of papaya treatment, but results in the loss of essential nutrients and also degrades its pigments, color, and texture. Therefore, this work aims to utilize ultrasound and osmotic dehydration as pretreatment strategies to preserve the rich composition of papaya during conventional hot air drying. The dried papaya slices were evaluated for moisture content, water activity, total phenolic content, β-carotene, color, antioxidant activity, microstructure, and texture. Results showed that sample pretreatment with 33 kHz ultrasound frequency and dehydrated with 35°Brix osmotic solution resulted in lower moisture content (< 12% w.b.) and water activity (< 0.41), high phenolic content (88.5 mg GAE/mL), high β-carotene content (184.54 mg/g) and antioxidant capacity (48.3%), and preserved color after drying. The texture (hardness) of the pretreated samples was also more desirable from an industrial standpoint, which was further validated using SEM micrographs that showed a more porous structure. The study concludes that pretreatment of papaya slices with ultrasound and osmotic dehydration is recommended before drying.

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.

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.

Color enhancement mechanisms analysis of freeze-dried carrots treated by ultrasound-assisted osmosis (ascorbic acid-CaCl2) dehydration

Color enhancement mechanisms of freeze-dried carrot sample (FDS) treated by ultrasound-assisted osmotic (ascorbic acid-CaCl2) dehydration (UAA) were comprehensively investigated from physical microstructures and color-related carotenoid compounds. Results of scanning electron microscope and confocal laser scanning microscopy showed that cells in samples treated by UAA were intact, had less porosity and showed stronger carotenoid autofluorescence. As for color-related compounds, UAA not only increased the retention ratios of total carotenoid content (36.38%) and β-carotene (51.73%) of FDS, but also preserved the high raman intensity of CC in-plane expansion (9986 A.U) and induced the formation of coloring-carotenoid-derivatives. Additionally, correlation and PCA-X model analysis showed that fresh carrot had higher extractable color value (78.46), which was positively linearly related to 2-n-pentylfuran (p < 0.01), whereas FDS mainly affected the surface color that was dominated by β-carotene. This work provided the practical analysis and theoretical basis of color enhancement of freeze-dried carrot foods.

Hybrid drying of ultrasound assisted osmotic dehydration (UOAD) and hot air drying of Eucalyptus deglupta

Eucalyptus deglupta is one of the promising medicinal plants from Mytracea family consisting of bioactive compounds that are to be used in medications. The bioactive compounds present in Eucalyptus deglupta were extracted at the best yield using a hybrid drying method consisting of ultrasound assisted osmotic dehydration (UOAD) and hot air drying in this study. The drying conditions of UAOD were optimised with response surface methodology (RSM) to attain the highest antioxidant activity via of DPPH radical scavenging assay. Four parameters were optimised with response surface methodology, namely concentration of sucrose (v/w), temperature (°C), duration of drying and intensity of ultrasound (%) ranged from 30% to 50%, 20°C to 60°C, 40 min to 100 min and 60% to 100%, respectively. A series of 27 combinations of the UAOD drying conditions were performed and followed by hot air drying performed at 60°C until a constant weight was achieved. A moderate scavenging activity of DPPH assay (56.12%) was achieved at a concentration of sucrose, temperature, duration of drying and intensity of ultrasound of 50%, 40°C, 100 min and 264 W, respectively.

Ultrasound-Assisted Osmotic Dehydration as a Method for Supplementing Potato with Unused Chokeberries Phenolics

Ultrasound-Assisted Osmotic Dehydration as a Method for Supplementing Potato with Unused Chokeberries Phenolics

Effect of ultrasound on mass transfer kinetics and phenolic compounds of apple cubes during osmotic dehydration

This study investigated the impacts of ultrasound-assisted osmotic dehydration (UOD) with different frequency (40 kHz, 80 kHz, 40 + 80 kHz) and intensity (25 W/L, 50 W/L, 75 W/L) on the kinetics of mass transfer, phenolic losses and the antioxidant properties of apple cubes (8 mm). The mass transfer efficiency of solid gain (SG) was greater under dual-frequency (β = 0.413) than 40 kHz (β = 0.707) and 80 kHz (β = 0.793) under the same intensity. Moreover, the mass transfer efficiency of SG under 75 W/L 40 kHz UOD was higher than that of 25 W/L and 50 W/L UOD based on β values. Notably, the loss of phenolic content under 75 W/L UOD (18.9 %) was substantially higher than that of the 25 W/L UOD treatment (1.2–1.8 %). A UOD treatment of 50 W/L and 40 + 80 kHz is recommended to optimize mass transfer efficiency and phenolic retention of dehydrated apple cubes.

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.

Effect of ultrasound-assisted osmotic dehydration pretreatments on drying and quality characteristics of pulsed fluidized bed microwave freeze-dried strawberries

In order to improve the shortcomings of low heat and mass transfer efficiency and uneven heating of freeze-drying technology, microwave heating and pulsed fluidized bed technology have been introduced, and ultrasonic-assisted osmotic dehydration (USOD) has been used for pretreatment of strawberries in this study. Using different ultrasonic power (180W, 240W, 300W) and different osmotic sugar solutes (sucrose, trehalose, sucrose and maltodextrin combination) to pretreat strawberries, and determine the dielectric properties, mass transfer, and water status and distribution of strawberries. The drying performance is evaluated by the drying rate, and the drying quality is determined by the color, texture, and total polyphenols and total flavones content. It was found that compared with freeze-drying, pulsed fluidized bed microwave freeze-drying (PFBMFD) can reduce the drying time by 45%, while USOD treatment helps to further increase the drying rate and reduce drying time by 10% because it increases water loss. In addition, dried strawberries pretreated with USOD may have better texture and nutritional quality, and sugar with low hygroscopicity and low sweetness value is more suitable for the USOD process of strawberries.

Antimicrobial and antioxidant properties of Saturn peach subjected to ultrasound-assisted osmotic dehydration

This study was performed to investigate the effectiveness of ultrasound-assisted osmotic dehydration on reducing foodborne pathogens (Escherichia coli, Enterococcus faecalis, Salmonella Typhi and Shigella sonnei), as well as its impact on moisture content and antioxidant properties of Saturn peach. Peach samples were inoculated and underwent ultrasonic waves (50 and 75% amplitudes). Afterwards, the osmotic dehydration was performed by immersing the samples in 70% sucrose solution (for 4, 8 and 12 h). Results indicated that ultrasound pre-treatment markedly diminished the microbial count and the reduction levels of pathogens enhanced with the increase of ultrasound amplitude. The greatest reduction in pathogens was observed at 75% amplitude after 12 h storage in osmotic solution, in which the mean number of E. coli, E. faecalis, S. Typhi and S. sonnei was reduced to 0.1, 4.2, 3.7 and 0.1 log CFU/g, respectively. Additionally, osmotic dehydration treatment significantly reduced the amount of moisture content, total phenolics and DPPH antiradical activity of samples. It should be added that increasing the ultrasound amplitude led to a further decrease in the mentioned parameters.

Current Applications of Ultrasound in Fruit and Vegetables Osmotic Dehydration Processes

Ultrasound (US) is a promising technology, which can be used to improve the efficacy of the processes in food technology and the quality of final product. US technique is used, e.g., to support mass and heat transfer processes, such as osmotic dehydration, drying and freezing, as well as extraction, crystallization, emulsification, filtration, etc. Osmotic dehydration (OD) is a well-known process applied in food processing; however, improvements are required due to the long duration of the process. Therefore, many recent studies focus on the development of OD combined with sonication as a pretreatment method and support during the OD process. The article describes the mechanism of the OD process as well as those of US and changes in microstructure caused by sonication. Furthermore, it focuses on current applications of US in fruits and vegetables OD processes, comparison of ultrasound-assisted osmotic dehydration to sonication treatment and synergic effect of US and other innovative technics/treatments in OD (such as innovative osmotic solutions, blanching, pulsed electric field, reduced pressure and edible coatings). Additionally, the physical and functional properties of tissue subjected to ultrasound pretreatment before OD as well as ultrasound-assisted osmotic dehydration are described.