Osmotic Dehydration Treatment Research Articles

Effect of Pulsed Electric Fields on the Shelf Stability and Sensory Acceptability of Osmotically Dehydrated Spinach: A Mathematical Modeling Approach.

This study focused on the osmotic dehydration (OD) of ready-to-eat spinach leaves combined with the pulsed electric field (PEF) pre-treatment. Untreated and PEF-treated (0.6 kV/cm, 0-200 pulses) spinach leaves were osmotically dehydrated at room temperature for up to 120 min. The application of PEF (0.6 kV/20 pulses) prior to OD (60% glycerol, 25 °C, 60 min) lowered water activity (aw = 0.891) while achieving satisfactory product acceptability (total sensory hedonic scoring of 8). During the storage of the product (at 4, 8, 12, and 20 °C for up to 30 d), a significant reduction in total microbial count evolution was observed (9.7 logCFU/g for the untreated samples vs. 5.1 logCFU/g for the PEF-OD-treated samples after 13 d of storage at 4 °C). The selection of these PEF and OD treatment conditions enabled the extension of the product shelf life by up to 33 d under chilled storage. Osmotically treated spinach could find application in ready-to-eat salad products with an extended shelf life, which is currently not possible due to the high perishability of the specific plant tissue.

Inhibition of enzymatic browning in freeze-thawed apricot fruit by combined chlorogenic acid and osmotic dehydration treatments

In this study, the inhibitors of apricot browning were analyzed by investigating the effects of osmotic dehydration (OD) pretreatment combined with chlorogenic acid (CA) on cell disruption, loss of phenolic substrates, and changes in key enzymes during freeze-thawing. Both OD and OD-CA mitigated the deterioration caused by ice crystal damage during freeze-thawing. OD and OD-CA significantly reduces the BI of apricots by 43.27 and 59.55 compared to CK. The PPO and POD activity in OD-CA apricots are only 61.11% and 42.13% of those in OD. OD-CA could also protect SOD and CAT activity, with their activity in the OD-CA being 1.41 and 1.14 times that of OD group. This indicated that OD-CA treatment protected against the activities of ROS-scavenging enzymes. Compared with OD, OD-CA could better protect the bioactive substance of apricot. The contents of ascorbic acid, total phenols, and total flavonoids in OD-CA were 1.32 times, 1.11 times, and 1.05 times higher than those in OD. OD-CA also effectively protected chlorogenic acid, neochlorogenic acid, cryptochlorogenic acid, catechins, and rutin. In summary, OD-CA primarily reduced the browning by protecting the integrity of cell structures, minimizing the potential for exposure to air, enzymes, and phenolic substrates, and inhibiting browning enzymes activity.

Effect of osmotic dehydration with different osmosis agents on water status, texture properties, sugars, and total carotenoid of dehydrated yellow peach slices.

The water status, texture properties, sugars, and total carotenoid of dehydrated yellow peach slices pretreated with or without osmotic dehydration (OD) combined with heat pump drying were studied. In this study, different osmotic agents were used, namely, sucrose and isomaltooligosaccharide (IMO) with 30 °Brix for 1, 3, and 5h. Results showed that the dehydrated samples pretreated by sucrose-OD with the best shape and cell structure showed lower hardness compared to the dehydrated yellow peach slices with IMO-OD pretreatment and without OD pretreatment. Notably, the highest total carotenoid content was found in dehydrated yellow peach slices pretreated by IMO-OD, followed by samples without OD, and samples with sucrose-OD pretreatment. In addition, the lowest aW (0.517) was obtained in samples with IMO-OD for 5h, which was beneficial for storage. The assessment of water status and total carotenoid content of dehydrated yellow peach slices showed that IMO-OD pretreatment could better improve the quality of dehydrated fruits. Moreover, the use of IMO in OD treatment was a good alternative to sucrose.

Effects of different pretreatment methods on drying kinetics, three-dimensional deformation, quality characteristics and microstructure of dried apple slices

The purpose of this study was to evaluate the effects of different pretreatment methods including blanching (30, 60 and 90 s), ultrasound (10, 30 and 60 min), pectinase treatment (15, 30 and 60 min), and osmotic dehydration treatment (0.5, 1.0 and 4.5 h) on the drying characteristics, three-dimensional (3D) deformation, color, total polyphenol content (TPC), antioxidant activity and microstructure of apple slices during drying. The shrinkage and height standard deviation (HSD) were calculated to evaluate the 3D deformation such as surface curl and flatness of the apple slices. The results showed that blanching, pectinase and osmotic dehydration treatment could increase the shrinkage and reduce the surface curl of the samples. Blanching, ultrasound and osmotic dehydration pretreatment could inhibit the color changes of dried apple slices, while pectinase treatment could aggravate the color deterioration of the samples. The apple slices pretreated with blanching for 60 s contained the highest TPC of 4.86 mg/g, and the samples also had the highest antioxidant activity. In addition, microstructure of the pretreated samples was significantly different from those of untreated samples. Therefore, pretreatment technology before drying is of great significance to improve the appearance and quality of products.

Combined effect of pulsed electric field and osmotic dehydration pretreatments on mass transfer and quality of air-dried pumpkin.

Pulsed electric field (PEF) and osmotic dehydration (OD) pretreatment can accelerate the time-consuming drying process and minimize its high energy demands. The effect of PEF and OD pre-processing conditions and osmotic solution composition on mass transfer kinetics (water loss, solid gain, water activity) and quality properties (color, texture, total sensory quality) during OD and subsequent air-drying (AD) of pumpkin was studied. Application of PEF (2.0kV/cm-1500 pulses) significantly enhanced mass transfer during subsequent air-drying (increased effective diffusivity coefficient Des and drying rate kdrying , respectively). PEF and OD treatments led to a significant reduction of the processing time by 12 and 10%, respectively (p<0.05). The maximum reduction of processing time by 27% (p<0.05) (compared to untreated sample) resulted in combined use of PEF and OD as pretreatments prior to AD. When PEF pretreatment was combined with OD prior to AD, the corresponding energy was by 50% less than the respective energy required for nonprocessed samples. PRACTICAL APPLICATION: Pulsed electric fields (PEF) and osmotic dehydration (OD) can be applied for the production of air-dried pumpkin cuts of superior quality (in terms of quality and sensory characteristics) and reduced energy requirements (as a result of total processing time decrease).

Effect of Osmotic Dehydration Pretreatment on the Drying Characteristics and Quality Properties of Semi-Dried (Intermediate) Kumquat (Citrus japonica) Slices by Vacuum Dryer.

The effect of osmotic dehydration (OD) pretreatments at different temperatures and immersion times on drying characteristics, total phenolic content (TPC), total antioxidant activity (TAA) (DPPH and CUPRAC methods), and color of kumquat slices dried under vacuum conditions (70 °C-100 mbar) was investigated. The OD pretreatment was performed in a sucrose solution (45 °Bx) at the temperatures of 40 and 50 °C and immersed at times of 30, 60, and 90 min. OD before vacuum drying decreased the total required drying time by up to 70 min compared to the control non-pretreated samples. Page, Modified Page, Henderson Pabis, and Two Terms Exponential models were found to satisfactorily describe the drying behavior of thin layer dried kumquat slices. The minimum and maximum values of effective moisture diffusivity (Deff) for semi-dried kumquat slices were 5.04 × 10−8 to 7.19 × 10−8, respectively. OD treatments induced a decline in TPC (5.30–33.92%) and TAA (23.63–59.34% and 4.17–31.67% for DPPH and CUPRAC assays, respectively) of kumquat slices. It was observed that OD pre-treatment can decrease the gross drying time, and make the color and sensorial attributes of dried kumquats better.

The Prediction of Drying Performance of Banana Rings Dried By Osmo-solar Dehydration Method

Solar drying is known as the oldest and most common traditional food preservation method. However, if the product is indirectly contacted with the sun light, there is negative effect in the color and nutrient values of the product. Solar dryers have been developed to utilize the heat effect of the sun to solve these problems. It can be used in combination with osmotic dehydration to increase the efficiency of the solar drying process. Osmotic dehydration is applied as a pretreatment technique in the drying process. The pretreatments to be applied before drying have important effects on the quality and operating cost of the product to be dried. In addition, the osmotic dehydration pretreatment enables to shorten the drying time and increase the drying potential. In this study, bananas with high drying temperature and high moisture content were sliced into 3 mm rings, then osmotic dehydration pre-drying was applied, and then they were dried in a solar tray dryer. Sucrose and citric acid solution in 2.5%, 5%, 7.5% and 10% (w/v) concentrations were used for osmotic dehydration treatment. In addition, samples without osmotic dehydration were dried in a solar dryer to determine the effect of pretreatment. The input variables of the drying process are solution concentration (0%, 2.5%, 5%, 7.5% and 10%), type of solution (sucrose solution and citric acid solution), osmotic dehydration time (10, 30, 60 and 90 min) and sun drying time (60, 120, 180, 240 and 300 min). Output variables were chosen as moisture ratio and shrinkage rate. The results clearly showed that both the moisture ratio and the shrinkage ratio have increased due to increased solar dryer time, solution concentration and immerse time. Osmotic dehydration was found to be effective in dried banana rings in the solar tray dryer. Gradient Boosting Machine (GBM) was used to model the drying conditions and the model was successful. The correlation coefficient (R2) values of the GBM model were respectively found as 0.94 and 0.83 for the moisture ratio and the shrinkage ratio.

Review: Effect of the combined application of edible coatings and osmotic dehydration on the performance of the process and the quality of pear cubes

SummaryThe objective of the present work was to evaluate the combined effect of the application of edible coatings (sodium alginate and low methoxyl pectin) and different osmotic dehydration conditions (sucrose solution: 40 and 60 °Brix, temperatures: 20 and 40°C and times: 1, 2, 4, 8 and 16 h) on pear cubes (water loss, solid gain, performance ratio, the total colour differences, mechanical properties, phenolic content and sensory analysis). The results indicated that samples coated with low methoxyl pectin and treated under 60 °Brix for 16 h at both temperatures (20 and 40°C) presented the best process performance. Statistical analysis showed that the application of the coatings resulted in greater firmness and stiffness of the pear cubes at the end of osmotic dehydration. Besides, alginate coating best preserved the phenolic content (31.4%) than uncoated (26.04%) and pectin‐coated (20.77%) ones. However, total colour differences were not improved with the use of edible coatings (alginate or pectin). In terms of quality, the samples coated with both hydrogels had good overall acceptability by the evaluators and good mechanical properties. However, further studies are required to decrease the difference in colour and leaching of bioactive compounds in pear cubes due to the osmotic dehydration treatment.

Osmotic dehydration of mushroom

Response surface methodology with Central Composite Rotatable design was used to know the effect of three independent variables at five levels [Salt Concentration - 10, 15, 20, 25, 30%; Solution Temperature - 45, 50, 55, 60, 65 oC; Immersion Time - 60, 120, 180, 240, 300 min.] on dependent variables like Water Loss, Solute Gain and Weight Reduction of osmo-dehydrated button mushrooms. The best combination was selected on the basis of optimization by Response Surface Methodology. Second order multiple regression equations were developed for all the dependent variables to know the effect of independent variables. Osmotic dehydration treatment facilitates better results with optimum solution of Salt Concentration -10.21%, Solution Temperature - 50 and Immersion Time - 120 minutes with an optimized yield as Water loss- 52.585%, Solute gain -5.946% and Weight reduction of osmo-dehydrated sample - 47.023% with desirability 0.878.

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.

Physicochemical properties and sensory acceptability of beetroot chips pre-treated by osmotic dehydration and ultrasound

Abstract Red beet (or beetroot) is highly nutritious and can be preserved by drying, in order to avoid wastage, to take advantage of crop surpluses, and to add value during the off-season. The objective of this study was to evaluate the effects of osmotic dehydration (OD) and ultrasound (US) pre-treatments on the nutritional quality and sensory characteristics of dried beetroot chips. The kinetics of moisture loss during OD and US were predicted by fitting the experimental data with thin-layer models. The physicochemical parameters (moisture, protein, lipid, carbohydrate, energy, ash, sodium and nitrate) and sensory properties (affective preference-ordering and acceptance test) were determined. Correlations between the treatments and the sensory acceptability evaluated by consumer’s perceptions were performed by applying unsupervised chemometric techniques (Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA)). The two-term exponential model provided the best fit for the experimental drying data. The US treatment promoted a higher drying rate and lower lipid, ash and energy values, while the OD process resulted in higher ash and sodium values. Multivariate analysis revealed that the US and OD treatments improved the sensory properties of the beetroot chips. The US was more efficient pre-treatment for producing beet chips due to its leads a significant reduction on drying time and intermediate level of sensory preference.

Osmo- and cryotherapy of sugarcane (Saccharum spp. L.) shoot-tips infected with sugarcane mosaic virus (SCMV).

In this work, we investigated the effect of different osmoprotective treatments and of cryopreservation using a droplet-vitrification (D-V) protocol to eliminate sugarcane mosaic virus (SCMV) of shoot-tips excised from in vitro propagated infected plantlets. Shoot-tips of sugarcane (Saccharum spp. L.) were precultured on semisolid MS medium supplemented with 0.3M sucrose for 1day, loaded in solution with 0.4M sucrose and 2M glycerol for 30min and exposed to plant vitrification solution 2 for 15min at room temperature prior to ultra-rapid cooling in liquid nitrogen. Virus indexing was performed by the DAS-ELISA immunoenzymatic test. The presence of SCMV was confirmed in the donor-plantlets derived of infected field material. No virus was detected in the regenerated plantlets from shoot-tips subjected to cryopreservation protocol. The progressive decrease in absorbances occurred from the first preculture treatment and no significant differences (P ≤ 0.05) were found with respect to following steps of D-V protocol. These results indicate that the osmotic dehydration treatments (osmotherapy) and cryopreservation (cryotherapy) may be potentially effective strategies to remove the SCMV from infected plants.

Diffusional analysis and textural properties of coated strawberries during osmotic dehydration treatment

BACKGROUND: The use of polysaccharide based edible coatings as a barrier against the solute entry of high caloric constituents, such as sucrose, is a suitable strategy to develop pro-healthy osmo-dehydrated products. OBJECTIVE: This work aims to study the effect of a calcium alginate film over the drying kinetics of strawberries during an osmotic dehydration (OD) treatment at 60°Brix, 4 h, 40°C (sucrose). Also, textural parameters were evaluated. METHODS: It was determined the changes in some selected physical properties, such as: moisture, total solid contents, one-dimensional shrinkage and texture, at 30 min steps during OD treatment. Besides, water and solid diffusion coefficients ( D e W and D e TS , respectively) were calculated by using the analytical solution of Fick’s equation. RESULTS: Diffusion coefficients for water and solids showed significant differences due to coating presence as an evidence of the barrier effect. Coated strawberry samples presented several changes after 2 h of OD treatment at the assayed conditions for most of the parameters evaluated. CONCLUSIONS: Alginate coating at the tested conditions acts as a barrier to sucrose influx and to water outflux until 2 and 3 h of OD treatment, respectively. Besides, a good textural quality for osmotically-dehydrated strawberries was obtained.

Metabolic response of organic strawberries and kiwifruit subjected to PEF assisted-osmotic dehydration

Abstract This research aims to evaluate the effect of pulsed electric field (PEF) pre-treatment for osmotic dehydration (OD) on physiological changes in organic strawberries and kiwifruits, in terms of metabolic heat production, measured by isothermal calorimeter, and of tissue damage, evaluated by fluorescence microscopy, texture analysis, and electrolytes leakage. Fruits were pre-treated at two electric field strengths (100 and 200 V/cm) using 100 near-rectangular shaped pulses (pulse width: 10 μs, repetition time: 10 ms) and then subjected to OD in hypertonic solutions (40% w/w) of sucrose or trehalose, both added with calcium lactate 1%. Results showed that OD alone allowed to retain the functionality of the membranes causing only a decrease in the endogenous heat production. The application of low electric field strength (100 V/cm) generally preserved the cell viability, which was drastically reduced after OD treatment. On the contrary, the application of 200 V/cm caused tissue damage and loss of cell vitality, probably due to irreversible electroporation. Industrial application PEF could be an interesting pre-treatment for reducing the intensity of osmotic dehydration of fruits. However, it is important to understand the implication of the treatment on the tissue metabolism and structure to control the effect on the quality of the final product. This study provides some useful information that could be exploited for the industrial production of intermediate moisture fruit products.

Effects of ultrasound, osmotic dehydration, and osmosonication pretreatments on bioactive compounds, chemical characterization, enzyme inactivation, color, and antioxidant activity of dried ginger slices.

The effect of ultrasound (US), osmotic dehydration (OD), and osmosonication (OS) pretreatments on total phenolic content (TPC), total flavonoids content, (TFC), phytochemical constituents (gingerol derivatives and diarylheptanoids), polyphenol oxidase (PPO), peroxidase (POD), 2,2-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), cupric ion reducing capacity (CUPRAC), 1,1-diphenyl-2-picrylhydrazyl (DPPH), ferric reducing antioxidant power capacity (FRAP), and color of ginger slices dried under relative humidity convective dryer was investigated. OS pretreatment improved the preservation of TPC (13.80-34.79mg GAE/g d.w), TFC (26.46-62.16mg CE/g d.w), ABTS (30.37%-86.10%), CUPRAC (36.89-73.97 mg/g), DPPH (50.57%-92.60%), FRAP (26.44-83 mg/g), and phytochemical constituents than US and OD. The OS-treated sample was more effective in inactivating both PPO (12.09%-35.93%) and POD (16.21%-39.58%) enzymes compared to US and OD-treated samples. However, US pretreatment retained the color quality of dried ginger slices than the OS and OD treatments. OS pretreatment (5.43) also increased the total color change (ΔE) of the dried ginger samples compared to US (2.81) and OD (4.60). PRACTICAL APPLICATIONS: Ginger is commonly used in the food, beverage, and pharmaceutical industries owing to their distinctive flavor and various health potentials. However, its high moisture content makes its inappropriate for long-term storage which results in its high perishability. Drying is one of the most common techniques to prolong its shelf life. Hence, any pretreatment for ginger that reduces the moistures content and lessens the drying time by preserving the quality of the crop is of vital importance. Ultrasound, osmotic dehydration, and osmosonication are novel pretreatment techniques that are widely used prior to drying of various agricultural products due to its numerous advantages over conventional methods. Its application in drying of foods could help shorten the drying time, reduce processing costs, improve energy consumption and efficiency, and preserve the physical and nutritional properties of the dried product. The current findings will also offer more information for selecting pretreatment techniques for ginger drying.

Influence of pretreatments on oil absorption of plantain and cassava chips.

The objective was to evaluate the effect of pretreatments of CaCl2 and osmotic dehydration (OD) on oil absorption in plantain and cassava chips. Plantain and cassava slices (1mm thickness and 35mm diameter) were prepared. Pretreatment with and without 5% CaCl2 solution before applying OD with sucrose solutions at 30 and 45%, and NaCl at 3 and 6% in a product/solution ratio of 1:25, at 40°C were employed. OD kinetics and diffusivity were estimated by Page's model and Fick's law, respectively. Best OD treatments for plantain chips were 45% sucrose with CaCl2 and 6% NaCl without CaCl2. However, for cassava chips, the best OD treatments were 45% sucrose without CaCl2 and 3% NaCl with CaCl2. Page's model predicted the OD experimental results with an R2 = 0.94-0.97. Effective diffusivity of water (EDW) and effective diffusivity of solids (EDS) for osmo-dehydrated cassava samples, with and without CaCl2, decreased as the concentration of the osmotic solutions was increased. However, in general, the inverse effect was obtained for plantain samples for EDW and EDS. Use of CaCl2 when applying OD reduced EDW and EDS in plantain and cassava chips. In general, it was observed that when increasing the concentration of the osmotic solution, oil absorption capacity decreased. Treatments that showed the lowest oil absorption were 45% sucrose OD in plantain chips pretreated with CaCl2 (11.49%) and fresh cassava chips with 45% sucrose OD (10.72%). The results and effectiveness will depend on food, process conditions and type of osmotic agent.

Characterization of water status and water soluble pectin from peaches under the combined drying processing

Characterization of water status and water soluble pectin (WSP) from peach were evaluated after different stage of combined drying in which osmotic dehydration (OD) was considered as the pre-treatment prior to instant controlled pressure drop (DIC) - assisted infrared radiation drying (IRD) (IR-DIC). Results showed that the contents of free water and immobilized water decreased to 0 g after the combined drying. The content of bound water increased after IRD treatment. The residual PME activity in peach slices was 153.3–179.6% after OD treatment, while, the PG were totally inactivated after IRD. The degree of esterification (DE), WSP content and average molar mass (Mw) decreased significantly (from 75.00 to 43.74, from 156.00 to 74.91 mg/g AIR and from 2.28 to 0.49 × 105 Da, respectively) after the combined drying. The neutral sugar of WSP was mainly composed by galactose, arabinose and rhamnose, whose contents decreased after the combined drying. However, OD treatment would slow down the degradation. There was a low peak at 1740 cm−1 in FT-IR spectrum observed for WSP after IRD and DIC treatment, which might illustrate the degradation of WSP during the combined drying.

Effect of different sugars on the freezing characteristics of Kyoho grape.

The aim of this work was to analyze the effect of different osmotic dehydration (OD) processes (sucrose, trehalose, glucose, and lactose) as a pretreatment for grape before exposure to freezing. The osmotic treatment had less effect on blueberry moisture content among different sugars. Impregnation with sugars decreases the freezing time of grapes, compared to untreated grapes. Trehalose and lactose had a remarkable effect on shortening the time for grapes to pass the zone of maximum crystallization of ice. It was concluded that drip loss and electrolyte permeability of cell membranes decreased and the soluble solids content increased after OD treatment. In addition, the firmness and L* values of trehalose-treated grapes were significantly higher than those of other treatments (p < .05). In summary, osmosis with a carbohydrate solution not only increased the freezing rate but improved quality characteristics of grapes after freezing and thawing. PRACTICAL APPLICATIONS: Grapes are subject to freezing damage during storage, including significant water loss, berry softening, off flavor occurrence, which reduce the commodity and consumption of grapes. OD can improve the freezing rate by reducing the moisture content in the raw material and reducing the impact of freezing on the quality of fruits and vegetables, which may be beneficial to the process of freezing grapes.

Application of osmotic dehydration and microwave drying to strawberries coated with edible films

Osmotic dehydration (OD) is one of the conventional methods to increase the shelf-life of vegetables and fruits. However, the operating conditions can adversely affect the organoleptic and nutritional quality of fresh products due to the high sugar uptake during processing and the loss of water-soluble constituents to the osmotic medium. The application of edible films has attracted interest due to their ability to reduce the entry of solutes and simultaneously increase the removal of water during OD treatments. Microwave (MW) is one of the most effective emerging technologies to accelerate dehydration processes in vegetable matrices. This aspect is particularly relevant in strawberries, given its high content in bioactive and nutritional compounds. Thus, the aim of this paper was to assess the influence of edible film application (alginate–lactate) in strawberry slabs during combined OD-microwaves dehydration processes. Samples of 1 cm thickness were treated with sucrose solution (60°Bx, 40 °C, 4 h) and then were dehydrated in a microwave oven (1.2 W/g). The application of alginate–lactate edible films resulted in similar weight and water losses but lower solids gain compared to uncoated samples during OD treatment. OD pre-treated MW-dried strawberry slabs with moisture contents up to 0.15 kg dry basis were obtained after 100 min of MW drying. Besides, the effective diffusional coefficient (De) was estimated for MW drying process, values ranged from 4.5 to 8.8 10−10 m2/s when shrinkage effect was considered, and from 1.1 to 2.3 10−9 m2/s for constant thickness assumption.

Metabolic and sensory evaluation of ultrasound-assisted osmo-dehydrated kiwifruit

Abstract The aim of this work was to investigate the effect of ultrasound (US) pre-treatment on endogenous metabolic activity of kiwifruits slices subjected to osmotic dehydration (OD), measured by metabolic heat production in isothermal calorimeter, respiration rate, structure changes and cell viability. Moreover, the overall changes on minimally processed kiwifruit were also studied by means of electronic tongue system. Kiwifruit slices (10 mm thick) were treated with US in the bath at a frequency of 35 kHz for 10, 20 and 30 min. The OD process was conducted in a 61.5% sucrose solution at 25 °C for pre-established contact period of 0, 10, 20, 30, 60 and 120 min. The results showed that the application of US pre-treatment and OD process promoted the reduction of metabolic heat as a consequence of a partial loss of vitality. Moreover, US and US + OD treatment specifically impacted the structure and the chemical picture of kiwifruit samples. Industrial relevance Ultrasound treatment coupled with osmotic dehydration could be applied at industrial level in order to save time and energy for a further dehydration process. Moreover, fruit tissue treated with ultrasound treatment promoted structural modifications and chemical changes in the kiwifruit tissue, as resulted from the present study, which could be useful for the industries to design novel products with intermediate moisture content.