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Osmotically dehydrated cherry tomatoes and spinach leaves were incorporated into Greek salad-type (including OD-treated and air-dried feta cheese trimmings and air-dried olive rings) and green salad-type (including OD-treated and air-dried feta cheese trimmings and roasted ground peanuts) ready-to-eat (RTE) product prototypes, respectively. The osmotic dehydration of cherry tomatoes and spinach leaves was conducted in a pilot scale setting (100 L) in a 60% glycerol-based solution at 35 °C and 25 °C for 180 min and 60 min, respectively. To quantify the moisture transfer between the three ingredients of different moisture content (and water activity), the moisture equilibrium curves for each ingredient of the RTE product were determined. The equilibrium water activity of RTE products was 0.86 and 0.76, respectively. The quality of the RTE products (more specifically, tomato and spinach color and texture, instrumentally measured and sensorially perceived, sensory characteristics) was evaluated. The shelf life of the prototypes (from 4 °C to 20 °C) was kinetically modeled based on sensory deterioration and microbial growth, using the zero-order kinetic model and the Gompertz model, respectively. In the case of the tomato-based product, a shelf life of 54 days (based on sensory deterioration) was achieved at 4 °C, a shelf-life extension of 40 days compared to untreated, fresh-cut tomato. The shelf life of the spinach-based product (based on sensory deterioration) was 36 days at 4 °C, 30 days longer when compared to untreated spinach. Our results indicate that osmotic dehydration was successful in significantly extending the shelf life of such products, contributing to the increased temperature resilience of their keeping quality and allowing for their distribution and storage in a variable cold chain. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

From a quality standpoint, it is desirable to preserve the characteristics of fresh-cut potatoes at their peak. However, due to the mechanical tissue damage during the cutting process, potatoes are susceptible to enzymatic browning. This study pertains to the selection of the appropriate osmotic dehydration (OD), high pressure (HP), and pulsed electric fields (PEF) processing conditions leading to effective quality retention of potato cuts. PEF (0.5 kV/cm, 200 pulses) or HP (400 MPa, 1 min) treatments prior to OD (35 °C, 120 min) were found to promote the retention of the overall quality (texture and color) of the samples. The incorporation of anti-browning agents (ascorbic acid and papain) into the osmotic solution improved the color retention, especially when combined with PEF or HP due to increased solid uptake (during OD) as indicated by DEI index (2.30, 1.93, and 2.10 for OD treated 120 min, non-pre-treated, HP pre-treated, and PEF pre-treated samples, respectively). PEF and HP combined with OD and anti-browning agent enrichment are sought to improve the quality and microbial stability of fresh-cut potatoes during refrigerator storage. Untreated fresh-cut potatoes were characterized by color degradation from the 2nd day of storage at 4 °C, and presented microbial growth (total viable counts: 6 log (CFU)/g) at day 6, whereas pre-treated potato samples retained their color and microbiologically stability after 6 days of cold storage (total viable counts, <4 log(CFU)/g). [ABSTRACT FROM AUTHOR]

This study explores the osmotic dehydration (OD) of fresh-cut cherry tomatoes through the application of Pulsed Electric Fields (PEF) and High-Pressure (HP) pre-treatments. Untreated, PEF-treated (1.8 kV/cm, 0–300 pulses), and HP-treated (0–600 MPa, 5 min) tomatoes were subjected to osmotic dehydration at 35 °C for up to 3 h. The results reveal that a 100-pulse PEF treatment and HP treatment at 600 MPa yielded optimal outcomes in terms of both OD enhancement (with effective moisture diffusion coefficients of 7.91 · 10−10 m2/s for PEF and 7.40 · 10−10 m2/s for HP-treated tomatoes compared to 5.17 · 10−10 m2/s for untreated samples) and product acceptability (achieving overall acceptance scores between 7 and 8). Applying PEF (100 pulses) and HP (600 MPa) pre-treatments reduced the water activity (aw) to 0.887 and 0.760, respectively, after 3 h of OD, compared to aw = 0.923 for untreated OD samples. The selection of these pre-treatment conditions enabled effective dehydration and quality retention, extending the shelf life by up to 40 days under chilled storage. [ABSTRACT FROM AUTHOR]

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 (2.0 kV/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). [ABSTRACT FROM AUTHOR]

The objective of this work was to investigate the potential use of pulsed electric field (PEF) in combination with osmotic dehydration (OD) as a pre-freezing step and to evaluate the effect on quality characteristics and shelf life of frozen kiwifruit. Peeled kiwifruit was subjected to PEF (1.8 kV/cm), sliced and treated in OD-solution (containing glycerol, maltodextrin, trehalose, ascorbic acid, calcium chloride, citric acid, sodium chloride; 1/5 (wfruit/wsolution)) for 30 and 60 min at 35 °C. Combined, PEF only and OD only treated samples as well as nontreated and blanched (80 °C, 60 s) samples were frozen and stored at constant (-5, -10, -15, -25 °C) and dynamic temperature conditions (-18 °C-3 d, -8 °C-2.5 d, -15 °C-3 d). Quality of frozen samples was evaluated by means of drip loss, colour, tex- ture, vitamin C and sensory evaluation (1-9 scale); and shelf life (SL) was calculated. Nontreated and blanched samples presented high drip loss and tissue softening (instrumentally measured as Fmax de- crease). The tissue integrity was well retained in all osmotically pretreated samples. PEF pretreatment caused increase of fruit whiteness (increase of L value) and yellowness (a and/or b value increase); SL calculation was based on colour change. All OD samples had high vitamin content (24.6 mg/100 g fresh material compared to 138-154 mg/100 g osmodehydrated material); PEF led to 93% (of the initial) vitamin retention; blanched samples showed the lowest retention (86.9% of the initial) (criteria for SL calculation). OD and combined PEF-OD treatment increased the shelf life of frozen kiwifruit (up to 3 times; based on sensorial criteria). The developed kinetic models for colour change, vitamin loss, and sensory quality deterioration were validated at dynamic temperature conditions. PEF pretreated OD (at significantly shorter time, 30 min compared to 60 min) kiwifruits retained optimum quality and sensory characteristics. PEF and OD could be used as a preprocessing step of good quality, longer shelf life kiwi sliced frozen products. [ABSTRACT FROM AUTHOR]

Tomatoes are perishable products due to the activity of microorganisms and endogenous enzymes. The objective was to produce cut tomatoes with extended shelf life, using the combined hurdle effect of osmotic pretreatment (OD) and high pressure (HP), instead of a conventional one-step thermal process. Samples were processed in a multicomponent osmotic solution at 35 °C, subsequently cold-pasteurised in pack at 600 MPa and stored at 5-15 °C. Quality deterioration during isothermal and nonisothermal storage was kinetically modelled. Both OD process and OD-HP combined process caused an increase in lycopene content that was well retained. Texture, colour and flavour of treated samples were evaluated as similar to fresh, with OD-HP samples showing better retention during storage. Being microbiologically stable, shelf life of OD-HP samples was limited by sensory deterioration, whereas OD samples were rejected due to eventual microbial growth. Shelf life of OD and OD-HP samples was estimated at 77 and 181 days, respectively, at 5 °C. [ABSTRACT FROM AUTHOR]

Highlights: [•] Gilthead seabream fillets were osmotically treated and stored under refrigeration. [•] Osmotic treatment extended significantly the shelf life of chilled fish fillets. [•] Pseudomonas dominated spoilage of untreated and osmotically treated fish fillets. [•] An Arrhenius-type model described the effect of processing on Pseudomonas growth. [•] Model can be used as a tool for predicting shelf life of osmotically treated fish fillets. [ABSTRACT FROM AUTHOR]

The objective of the study was the kinetic modeling of the effect of storage temperature on the quality and shelf life of chilled fish, modified atmosphere-packed (MAP), and osmotically pretreated with the addition of nisin as antimicrobial agent. Fresh gilthead seabream ( Sparus aurata) fillets were osmotically treated with 50% high dextrose equivalent maltodextrin (DE 47) plus 5% NaCl. Water loss, solid gain, salt content, and water activity were monitored throughout treatment and treatment conditions were selected for the shelf life study. Untreated and osmotically pretreated slices with and without nisin (2 × 104 IU/100 g osmotic solution), packed in air or modified atmosphere (50% CO2–50% air), and stored at controlled isothermal conditions (0, 5, 10, and 15 °C) were studied. Quality assessment and modeling were based on growth of several microbial indices, total volatile nitrogen, trimethylamine nitrogen, lipid oxidation (TBARS), and sensory scoring. Temperature dependence of quality loss rates was modeled by the Arrhenius equation, validated under dynamic conditions. Pretreated samples showed improved quality stability during subsequent refrigerated storage, in terms of microbial growth, chemical changes, and organoleptic degradation. Osmotic pretreatment with the addition of nisin in combination with MAP was the most effective treatment resulting in significant shelf life extension of gilthead seabream fillets (48 days compared to 10 days for the control at 0 °C). [ABSTRACT FROM AUTHOR]

Watermelon pieces were submitted to osmotic pre-treatment in alternative osmotic solutions of glucose, oligofructose and a high dextrose equivalent (DE) maltodextrin, in order to evaluate the quality and assess the stabilisation accomplished during the subsequent frozen storage in a wide temperature range from −5 to −20 °C. Colour change and total lycopene content loss were kinetically studied, and their temperature dependence was modelled by the Arrhenius equation. Dehydrofrozen samples exhibited significantly improved stability, with the rates of colour change and total lycopene loss being reduced up to 70% and 38%, respectively, for osmotically pre-treated watermelon, compared with the untreated samples. [ABSTRACT FROM AUTHOR]

Osmodehydrofreezing (ODF), a combined preservation process where osmotic dehydration is applied prior to freezing, achieves several advantages, especially in plant tissues, sensitive to freezing. OD pre-treatment can lead to the selective impregnation of solutes with special characteristics that reduce the freezing time and improve the quality and stability of frozen foods. ODF research has extensively focused on the effect of the osmotic process conditions (e.g., temperature, duration/composition/concentration of the hypertonic solution) on the properties of the osmodehydrofrozen tissue. A number of complimentary treatments (e.g., vacuum/pulsed vacuum, pulsed electric fields, high pressure, ultrasound) that accelerate mass transfer phenomena have been also investigated. Less research has been reported with regards the benefits of ODF during the subsequent storage of products, in comparison with their conventionally frozen counterparts. It is important to critically review, via a holistic approach, all parameters involved during the first (osmotic dehydration), second (freezing process), and third stage (storage at subfreezing temperatures) when assessing the advantages of the ODF integrated process. Mathematical modeling of the improved food quality and stability of ODF products during storage in the cold chain, as a function of the main process variables, is presented as a quantitative tool for optimal ODF process design. [ABSTRACT FROM AUTHOR]

The objective of this study was the kinetic modeling of the effect of storage temperature on the quality and shelf life of chilled tuna, vacuum packed and osmotically pre-treated with the addition of nisin as antimicrobial agent. Tuna fillets were treated at 15 °C in osmotic solution with 50% high dextrose equivalent maltodextrin (DE 47) plus 5% NaCl, for 0–360 min. Untreated and 30 min osmotically pre-treated fish slices with and without nisin (2·10 4 IU/100 g osmotic solution), vacuum packed and stored at controlled isothermal conditions (0–15 °C) were studied. Quality assessment and modeling was based on microbial growth, total volatile basic nitrogen (TVB-N), trimethylamine nitrogen (TMA-N), lipid oxidation (TBARS) and sensory scoring. The water activity decreased to 0.96 at 30 min of pre-treatment. Osmotic pre-treatment led to significant shelf life extension of fish, in terms of microbial growth and sensory quality. The addition of nisin in the osmotic solution further increased the shelf life of tuna. Based on LAB growth, the shelf life was 10 days for untreated and 27 days for osmotically treated vacuum packed fish at 5 °C. The addition of nisin increased shelf life to 51 days at 5 °C. [ABSTRACT FROM AUTHOR]

Abstract: The shelf life extension of osmotically treated chilled gilthead seabream (Sparus aurata) fillets was studied. Water-loss, solid-gain, salt content and water activity were measured. Osmotic pretreatment with 40, 50 and 60% maltodextrin (DE 47) plus 5% NaCl solutions caused substantial water loss (12.3–77.0%) and solid enrichment (2.5–34.1%) with higher solution concentrations showing the highest values of mass flow. Quality indices (colour, microbial growth, TVB-N, sensory scoring) were estimated during refrigerated storage and kinetically modelled. Temperature dependence of quality loss rates was modelled by the Arrhenius equation. Shelf-life at 5°C was 4d for untreated fillets and 9, 11 and 13d for fillets treated with 40, 50 and 60% maltodextrin, respectively. Industrial relevance: The objective of the present study was to evaluate the effect of osmotic pretreatment on the quality characteristics of gilthead seabream and to investigate the potential of using osmosis as a minimal treatment to extend the shelf life of fish products. Osmotic solution concentration had a significant effect on the osmotic dehydration of gilthead seabream fillets. Pretreated samples were found to have improved quality stability during subsequent refrigerated storage, in terms of microbial growth and organoleptic degradation, resulting in a significant shelf-life extension at all storage temperatures. [Copyright &y& Elsevier]

Abstract: Quality of frozen cucumber can significantly be improved by means of osmotic dehydration as a pre-freezing treatment. The objective of this work was to study the effect of osmotic pre-treatment with alternative osmotic solutes – oligofructose and a high DE maltodextrin – on the quality and functional properties of frozen cucumber tissue. Colour, texture and sensory characteristics of pre-treated and conventionally frozen samples were comparatively measured at 3 months time, during storage at four different temperatures, −5, −8, −12, −15 °C. Colour change was kinetically studied, and its temperature dependence was modelled by the Arrhenius equation. Dehydrofrozen samples exhibited significantly improved stability, with the rates of colour change being reduced up to 36.7% for osmotically pre-treated cucumbers, compared to the untreated samples. The results indicate that osmodehydrofrozen compared to conventionally frozen sliced cucumbers show improved firmness for prolonged storage period. Sensory evaluation also showed good organoleptic quality in osmodehydrofrozen cucumber slices. Industrial relevance: The poor quality of frozen cucumber can significantly be improved by means of the cryoprotection accomplished by a pre-freezing osmotic dehydration step. Osmotic dehydration at mild temperatures can preserve product texture, and enhance flavour and other sensory properties (colour). In this paper, the effect of osmotic pre-treatment on the quality and shelf life of frozen cucumber tissue was investigated. The aim was to develop a method of processing cucumber that maintains palatable product while optimizing quality at the beginning and during frozen storage. [Copyright &y& Elsevier]

The objective of the study was to evaluate the effect of osmotic solution concentration and a pretreatment with pulsed electric fields (PEF) (1.6 kV/cm, up to 1500 pulses/19.7 kJ kg-1) on mass transfer during osmotic dehydration (OD) of sea bass fillets. Osmotic solutions of 40-60% glycerol and 5% NaCl were applied at 15 °C for processing times up to 240 min. The increase in glycerol concentration enhanced significantly mass transfer expressed by the effective diffusivities of water (Dew values ranged from 1.9 to 3.6 × 10-9 m² s-1) and solubles (Des values ranged from 1.8 to 4.1 × 10-9 m² s-1). PEF pretreatment further increased Dew and Des values up to 50% and 66% respectively (for 1500 pulses/19.7 kJ kg-1). The energy input correlated with the calculated Dew and Des values, following a logistic mathematical model. The logistic model had a center point at 7.28 kJ kg-1) and 7.15 kJ kg-1) for water and solubles, respectively and showed a sharp increase of the diffusivity values between 3.3 and 9.8 kJ kg-1) ranging from 3.0 × 10-9 m² s-1 to 4.0 × 10-9 m² s-1 for Dew and from 2.7 × 1CF9 m² s-1 to 4.1 x 10-9 m² s-1 for Des. [ABSTRACT FROM AUTHOR]

This study examined the effect of osmotic dehydration of Kalamata natural black olives as pre-fermentation treatment in combination with partial substitution of NaCl by monosodium glutamate (MSG) on the fermentation profile of olives. Osmotic dehydration was undertaken by immersing the olives in 70% (w/w) glucose syrup overnight at room temperature. Further on, three different mixtures of NaCl and MSG with/without prior osmotic dehydration of olives were investigated, namely (i) 6.65% NaCl – 0.35% MSG (5% substitution), (ii) 6.30% NaCl – 0.70% MSG (10% substitution), (iii) 5.95% NaCl – 1.05% MSG (15% substitution), and (iv) 7% NaCl without osmotic dehydration (control treatment). Changes in the microbial association (lactic acid bacteria [LAB], yeasts, Enterobacteriaceae ), pH, titratable acidity, organic acids, sugars, and volatile compounds in the brine were analyzed for a period of 4 months. The final product was subjected to sensory analysis and the content of MSG in olives was determined. Results demonstrated that osmotic dehydration of olives prior to brining led to vigorous lactic acid processes as indicated by the obtained values of pH (3.7–4.1) and acidity (0.7–0.8%) regardless of the amount of MSG used. However, in non-osmotically dehydrated olives, the highest substitution level of MSG resulted in a final pH (4.5) that was beyond specification for this type of olives. MSG was degraded in the brines being almost completely converted to γ-aminobutyric acid (GABA) at the end of fermentation. Finally, the sensory assessment of fermented olives with/without osmotic dehydration and at all levels of MSG did not show any deviation compared to the control treatment. [ABSTRACT FROM AUTHOR]