Osmotic Dehydration Pretreatment Research Articles

Freeze-thawing and osmotic dehydration pretreatments on physicochemical properties and quality of orange-fleshed sweet potato slice during hot air drying.

Freeze-thawing and osmotic dehydration pretreatments on physicochemical properties and quality of orange-fleshed sweet potato slice during hot air drying.

Osmotic dehydration with different agents induced pectin diversity: Physicochemical and structural properties of pectin from instant controlled pressure drop dried peach chips

Pectin as an important cell wall matrix that can be affected by osmotic dehydration (OD) pretreatment, determines the texture characteristics of dried fruit and vegetable products. This study investigated the effect of OD on the structural, thermal and rheological properties of pectin extracted from peach chips prepared by instant controlled pressure drop (DIC) drying. In detail, erythritol, glucose, and trehalose were selected as the osmotic agents (300 g/L). Pectin extracted from Ery-OD samples with a loose structure presented the highest molecular weight (432.9 kDa). The lowest content of arabinose (155.16 mg/g) and galactose (32.80 mg/g) were obtained in Glc-OD samples. With the infiltration of trehalose, the thermal stability of pectin was improved, which contributed to the uniform and complete network structure of pectin. 1H and 13C spectra analysis showed the significant alteration in pectin molecular structure induced by OD pretreatments, which affected the shear thinning behavior of pectin solution. Overall, the type of osmotic agents played a crucial role in the structural, thermal and rheological properties of pectin, which could reflect on the macro-texture characteristics of peach chips. This study would provide a theoretical basis for revealing the effect mechanism of OD on the texture of DIC fruit and vegetable chips at molecular level.

Effect of ultrasound‐assisted osmotic dehydration on the drying characteristics and quality properties of goji

AbstractThe waxy layer on the surface of the goji fruit increases the dehydration time. In this study, the novel use of ultrasound pretreatment (10, 20, and 30 min) assisted with osmotic dehydration was utilized to improve drying efficiency and product quality of goji. The results showed that goji treated with ultrasound‐assisted osmotic dehydration lost more water and gained more solids during osmotic dehydration than goji treated with osmotic dehydration only. Furthermore, the ultrasound‐assisted osmotic dehydration pretreatment method shortened the drying time for freezing drying goji and lowered the water activity of the dried goji. This may be due to the destruction of the wax layer on the surface of the goji by ultrasound. The rehydration rate of the goji treated with ultrasound for 20 min was significantly higher than that of the samples dried by osmosis dehydration only. The application of ultrasound‐assisted osmotic dehydration resulted in the best color and the highest glutathione and total free amino acid content of goji, especially the taurine. Besides the above, the antioxidant capacity of ultrasound‐assisted osmotic dehydration‐treated goji was enhanced, with the highest 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging capacity and ferric reducing antioxidant power (FRAP) values for the samples in the 20‐min ultrasound‐assisted group. The results demonstrate that ultrasound‐assisted osmotic dehydration not only reduces the drying time of goji but also enhances its product quality.Practical applicationsThis study explored the effects of different ultrasound‐assisted osmotic dehydration methods on the drying efficiency and quality of freeze‐dried goji. The findings provide a scientific basis for improving goji drying engineering and offer a potential strategy for enhancing goji quality.

Sustainable Utilization of Mushroom By-Products Processed with a Combined Osmotic Dehydration Pretreatment and a Hot-Air-Drying Step.

Mushroom production and consumption are gaining increased interest due to their unique flavor and nutritional value. However, in the mushroom industry, large amounts of by-products are generated, which have a high negative environmental and economic impact. In this study, an osmotic dehydration process followed by hot-air-drying was applied to mushroom stems to produce dried mushrooms as the end product. The osmotic dehydration conditions (concentration of hypertonic solution, specifically, 10-30% maltodextrin and 20-40% oligofructose; a treatment time of 40-80 min; and a temperature range of 30-50 °C) were optimized using response surface methodology (RSM). The results showed that a four-factor three-level Box-Behnken experimental design was effectively implemented to evaluate the effect of the process parameters and identify the optimal osmotic dehydration conditions for producing osmotically dehydrated mushrooms. The main factor affecting mass transfer was the osmosis temperature, and the optimal conditions were found to be 38 °C, 40% oligofructose and 19.3% maltodextrin as the osmotic agents, and 80 min of immersion time. Moreover, the results showed that osmotic pretreatment, in the optimal conditions, significantly reduced the required drying time of the by-products compared to traditional hot-air-drying, especially at milder drying temperatures. Consequently, the required energy was also reduced by at least 40% at 50 °C.

Textural formation of instant controlled pressure drop–dried peach chips: Investigation of the electrical, thermal, and textural properties of predried peach slices with osmotic dehydration pretreatment

In this study, the effect of osmotic dehydration (OD) pretreatment with various sugar (erythritol, glucose, and trehalose) on the quality of hot-air-predried peach slices was investigated, particularly focusing on electrical properties, texture, thermal stability, and cell wall strength. Furthermore, the correlation between the properties of predried peach slices and the texture of the instant controlled pressure drop (DIC) dried peach chips was explored. OD pretreatments improved the stability and integrity of the cell wall and cell membrane of pre-dried peach slices, which inhibited the excessive expansion of samples during DIC drying. Especially, peach chips with trehalose-OD exhibited the highest crispiness (1.05 mm), the highest hardness (101.34 N) was obtained in erythritol-OD samples. Overall, the type of osmotic agents affected the texture of DIC peach chips with OD pretreatments. It should be noted that trehalose is a promising osmotic agent for controlling and regulating the quality of DIC peach chips.

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.

Influence of ultrasonic-assisted osmotic dehydration pretreatment on hot air-assisted radio frequency drying of bitter gourd

Bitter gourd is a versatile vegetable that brings health-promoting benefits to consumers. To maintain its high nutrition values and ensure year-round availability, proper post-harvest processes are essential for preserving its original properties. However, there is limited knowledge regarding how pretreatment methods impact the physicochemical properties of pretreated bitter gourd and the performance of subsequent hot air-assisted radio frequency drying (HARFD) process. In the present study, bitter gourd underwent osmotic dehydration (OD) and ultrasonic-assisted osmotic dehydration (UAOD) pretreatment with different ultrasound power levels (400, 800, and 1200 W). The physicochemical properties of the pretreated samples, such as mass transfer behavior, water migration status, dielectric loss factor, and others, were compared. The drying duration, energy consumption, and various quality attributes (e.g., color index, rehydration, nutritional compositions, antioxidant activity, etc.) of the HARFD dried products were also examined. The microstructure observations demonstrated that acoustic waves induced the structural changes and created microchannels. Additionally, physicochemical properties of the pretreated samples showed that OD and UAOD methods significantly facilitated water migration status and increased the dielectric loss factor. Compared to control and OD methods, three UAOD methods successfully reduced the drying duration by 7.9%–30.3% and total energy consumption by 5.8%–28.3% for the entire processing steps. Furthermore, UAOD methods improved the total phenolic content, total chlorophyll retention, DPPH and ABTS values of dried bitter gourds by 32.3%–36.7%, 12.6%–20.3%, 23.4%–31.6%, and 20.7%–26.3%, respectively, compared to the control methods. Overall, UAOD-400 W samples after drying exhibited improved quality characteristics, including reduced color difference, increased retention of bioactive compounds, higher rehydration ratio, and enhanced antioxidant capacity. This study underscores the effectiveness of UAOD application in improving both processing efficiency and quality of bitter gourds produced by HARFD.

Insight into the effect of osmosis agents on macro- and micro- texture, water distribution, and thermal stability of instant controlled pressure drop drying peach chips

To investigate the influence of sugar structure on the quality of peach chips produced using osmotic dehydration (OD) in combination with instant controlled pressure drop (DIC) drying, erythritol, glucose, maltose, and trehalose were selected as osmotic agents. The properties of the osmotic solutions, as well as the macro- and micro-texture, water distribution, and thermal stability of peach chips were investigated. Results showed that OD pretreatments inhibited the formation of large cavity structures. The highest hardness (101.34 N) and the lowest hydrophobicity (0°) were obtained in erythritol-OD samples. Trehalose-OD samples with the most homogeneous pore structure exhibited the highest crispness (1.05 mm) and the highest glass transition temperature (52.06 °C). Various absorption peaks of peach chips pretreated with different OD methods, characterized by Raman spectroscopy, suggested changes in composition and functional groups due to the diffusion of sugars into the cells of peach tissues, which also contributed to the higher Tg.

Effects of osmotic dehydration pretreatment on the drying and characteristics of pineapple slices after microwave hot air rolling bed drying

Abstract This study aimed to investigate the effects of osmotic dehydration (OD) pretreatment on the drying and quality of pineapple slices dehydrated using microwave hot air rolling bed drying method. The result suggested the OD pretreatment significantly reduced the moisture content of the food material before drying. It also slightly increased the moisture ratio decreasing rate in the early stage of drying based on the formation of microchannels during the pretreatment. The pretreatment also increased overall temperature and facilitated the transition of free water to bounded water during drying. Based on the pretreatment, the undesired browning of pineapple slices during drying was significantly inhibited. However, the OD pretreatment with 60 % (w/v) sucrose solution caused significant dehydration of the sample before drying, finally resulting in more dramatic browning. Compared with the sample without OD pretreatment, the dried pretreated pineapple slices exhibited an increased amount of collapsed cell structures and pores, due to the cell deformation and water diffusion during the pretreatment. These microstructure changes finally contributed to their increased hardness, springiness and chewiness. Although the pretreatment caused a slightly higher ascorbic acid loss in the final dried food materials, the product with an improved sugar-to-acid ratio was prepared, indicating its improved acceptability. Considering the overall characteristics profile of the dried pineapple slices, the OD pretreatment using 50 % sucrose solution for 24 h was the optimum condition to develop promising dried pineapple slices products.

Effects of osmotic dehydration pre-treatment on process and quality of freeze-dried strawberries (Fragaria x ananassa var. Mencir)

The freeze-drying of fruits is one alternative to increase the added value of fresh fruit, extend the shelf life which the product, and still have properties like fresh fruit. Osmotic dehydration pre-treatment can be applied before drying techniques to produce a new product, maintain nutritional and sensory quality, and improve the drying process. In this research, the effects of osmotic dehydration on freeze-drying performance and the quality characteristics of freeze-dried strawberries were evaluated. Freeze-dried strawberries were made using fresh strawberries without pre-treatments and pre-treatments by osmotic dehydration (OD) with the freeze-drying method. The treatment of materials and processes used were the duration of storage in the freezer of 36 to 48 h; vertically cutting strawberry before OD; osmotic dehydration agents with a concentration of 50°Brix; immersion time for 30 min at temperature a 30°C; and freeze-drying time of 24 h. Results of each treatment in terms of physical quality parameters (color of skin fruit (L*a*b*), change of color (ΔE), and hardness) and phytochemical quality parameters (water content, vitamin C, total phenolic content, and antioxidant activity by DPPH) were compared and discussed. The osmotic dehydration process causes a water loss of 13%, has a significant difference on the parameters of colors (redness and color of change), hardness, vitamin C, total phenolic content, and antioxidant activity by DPPH.

Influence of different osmotic dehydration pretreatment on the physiochemical and sensory characteristics of fried cassava chips (Manihotesculenta)

This study was conducted to evaluate the influence of different concentrations of sodium chloride (NAC) and sucrose (SC) as osmotic agents for the osmotic dehydration and water pretreatment (WO) on the physical properties and sensory characteristics of fried cassava (Manihot esculenta) chips. Cassava was sliced into chips and pretreated using sodium chloride (30% w/v), sucrose (30% w/v) and water. Pretreated cassava chips were fried after which the weight loss: NAC (85%), SC (70%), and WO (65%) pretreated samples, as well as the control (40%), had a significant effect on % weight loss (p < 0.05), but the cassava chips treated with NAC attained the highest % WL compared to the SC and WO. Sensory Analysis showed high acceptance for NAC pretreated fried cassava chips than the SC and WO pretreated fried cassava chips. The SC, WO, and untreated fried cassava chip samples came in second third and fourth respectively, while the NAC pretreated fried cassava chip samples received the highest ratings for appearance, color, texture (mouth feel), flavor, and overall acceptability: Mass transfer and shrinkage properties were assessed. The sensory attributes of the samples were assessed using 15 untrained panels. The study revealed that sample (NAC) pretreated fried chips from the sensory analysis were most preferred by the respondents in terms of texture, taste, colour, and overall acceptance. The weibul model matched the experimental findings more closely than the Newton model and enhanced the frying kinetics.

Optimization of ultrasonic-assisted osmotic dehydration as a pretreatment for microwave drying of beetroot (Beta vulgaris).

The aim of this study was to optimize drying conditions during ultrasonic-assisted osmotic dehydration and subsequent microwave drying of red beetroot using the Box-Behnken design. For this purpose, ultrasonic-assisted osmotic dehydration was performed at different ultrasonic powers (50, 75, and 100 W), sonication times (20, 40, and 60 min), and salt concentrations (0%, 15%, and 30%). The subsequent drying procedures were conducted with 231, 518, and 805 W microwave power. The best condition was selected as 5.15% salt concentration, 20 min sonication time, 50 W ultrasonic power, and 716.45 W microwave power. The responses obtained under optimum conditions were determined as 68.06%, 9.54 mg GAE/g dm, 28.23, 42.66, and 3.08 for DPPH• % inhibition, total phenolic content, L*, a*, and b* values, respectively. While favorable impacts on color were detected for the applied pretreatments, the DPPH• scavenging activities of the dried beetroot were determined to be more significant after ultrasonic-assisted osmotic dehydration. Furthermore, the drying kinetics of beetroot were evaluated according to the Midilli et al. model. When the fit to the model was investigated, it was compatible at R2 > 0.90 level. As a result, the ultrasonic-assisted osmotic dehydration pretreatment performed before the microwave drying method preserved the quality characteristics of beetroot samples and was successfully applied.

Texture formation of dehydrated yellow peach slices pretreated by osmotic dehydration with different sugars via cell wall pectin polymers modification

In this study, texture of heat pump drying (HPD) yellow peaches pretreated by osmotic dehydration (OD) with different sugars (sucrose/Suc, isomaltooligosaccharide/IMO, glucose/Glc) were evaluated. Properties of pectin fractions, namely water soluble pectin (WSP), chelator soluble pectin (CSP) and sodium carbonate soluble pectin (NSP) from yellow peach slices were also determined. Results showed that IMO-HPD samples exhibited the highest hardness (22.218 ± 1.661 N) and chewiness (6.741 ± 0.729 N). WSP fractions from IMO-HPD samples showed the lowest degree of methylation (28.5 ± 0.5%), illustrating IMO could catalyze the demethylation of homogalacturonan in WSP. Glc-HPD samples exhibited the highest resilience (35.732 ± 2.748%), springiness (82.255 ± 3.868%), and pectin content, in which the content of WSP, CSP, and NSP fractions were 88.55, 29.60, and 55.96 mg/g AIR, respectively. Both CSP and NSP extracted from Glc-HPD samples showed the smallest molar mass, namely 4.630 ×10 5 Da and 6.639 ×10 5 Da, respectively, contributing to the breakage of the linkage between CSP and NSP and the cell wall induced by the infiltration of Glc. Correlation analysis suggested that the degradation or conversation was the pivotal cause of texture formation of OD-HPD yellow peach slices. In conclusion, the interaction between osmosis solutes and pectin could significantly affect the texture formation of OD-HPD yellow peach slices, which would provide theoretical guidance for improving the texture properties of dehydrated fruits with OD pretreatments. • Osmotic dehydration markedly hardened the texture of yellow peach slices. • Isomaltooligosaccharide catalyzed the demethoxylation of water soluble pectin. • Heat pump drying caused water-insoluble pectin shift to water-soluble pectin. • The infiltration of glucose could break the linkages between cell walls. • Strong correlation between texture formation and pectin features was explored.

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.

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.

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).

Modeling the Effects of Osmotic Dehydration Pretreatment Parameters and Lyophilization Kinetics on Mass Transfer and Selected Nutritive Parameters of Peaches

The effects of the osmodehydration pretreatment parameters on successive lyophilization mass transfer kinetics of the peaches, dehydrated in the combined dehydration process, were investigated and mathematically modelled. The obtained results showed the statistically significant effect of osmotic dehydration pretreatment and its parameters on the final dry matter content and water activity values of the dehydrated peaches. The maximum dry matter content and minimal water activity values of dehydrated peach samples were 84.60 % and 0.423, respectively, produced in osmodehydration pretreatment in molasses of 80 % concentration, at 50 °C, during a 5-hour process and subsequent 6-hour lyophilization. With the increase of all osmodehydration pretreatment parameters it is possible to reduce the duration of the lyophilization process, reducing the high energy demand of the dehydration method (lyophilization) and substituting it with low energy demanding dehydration method (osmodehydration) without compromising the quality of the final product, regarding the dry matter content and water activity values. Mathematical models describing the effect of the duration of the lyophilization on the dry matter content and water activity values of the fresh and dehydrated peaches were developed. They showed a good correlation between calculated and experimental values, allowing a good prediction of the investigated responses. In the combined method, protein, sugar, K and Fe content of the dehydrated peach samples were enriched and further enhanced in prolonged lyophilization stages.

Effect of Osmotic Dehydration as a Pre -Treatment on Air Fried Sweet Potato (Ipomoea batatas) Chips

Air frying is a modern frying technique that promises low oil content of fried products. However, the main limitation of air frying is that it requires a longer operating time than deep fat frying. Previous studies found that osmotic dehydration is beneficial as frying pre-treatment to improve the quality of fried products and reduce frying time, but to date, there is no study investigating its application in air frying. Therefore, this study aims to examine the effect of osmotic dehydration as pre-treatment on the quality of air-fried sweet potato chips. Sweet potatoes were cut into slices with the same thickness, and then soaked in distilled water, 5% sodium chloride solution, and 10% sodium chloride solution for one hour. The potato slices were then air fried at two temperatures: 160˚ and 180˚C for 3, 6, 9, 12, and 15 minutes. Then, moisture content, colour, texture, diameter shrinkage and thickness expansion were analysed. The moisture content of air fried chips decreased with the increasing of frying time. The osmo-dehydrated sample showed lower moisture content which could the reduce frying time from 12 mins to 9 mins at 160ºC. Osmo-dehydrated sweet potato slices produce paler chips, but the treatment preserved the red and yellow colour of the sample. Air fried sweet potatoes that were osmotically dehydrated samples shrank more in diameter than the control samples. The increased thickness of chips was caused by crust formation and the bubbles formed at the surface due to the barrier formed by the tight surface, resulting in vapour expansion inside the pores of the chips. The hardness of pre-treated chips increased significantly with decreasing moisture content. Using osmotic dehydration pre-treatment in the air frying process can yield promising results in less frying time and better retention in terms of red and yellow colour.

Effect of osmotic dehydration pre‐treatments on physicochemical and energy parameters of Kosia (Nashi) pear slices dried in a convective oven

In this study, the effects of osmotic dehydration pre-treatments in sucrose solutions on dried Kosia pear slices were determined. The effective diffusion, modeling, color, rehydration, specific energy consumption, specific moisture extraction rate (SMER), evaporation latent heat, energy efficiency (EE), convective heat (hc), and mass transfer coefficient (hm) parameters of fruit slices were investigated. The shortest drying time (17 h) was observed in the drying process of the samples subjected to osmotic dehydration in 25% sucrose solution for 1 h. The best thin-layer drying models were identified as Lewis (R2: .9977) and Jane-Das (R2: .9977) models. Effective diffusion values ranged between 2.13–4.94 × 10−5 m2 s−1. Rehydration ratios ranged between 2.09 and 2.71 g g−1 while rehydration capacities ranged between 57.24% and 63.05%. The least color change was observed in control samples. SMER values of the dried samples ranged between 0.0062–0.00011 kg kWh−1. EE values ranged between 4.19% and 0.03%. Mass transfer coefficient values varied between 1.57 × 10−8 and 1.06 × 10−12 m/s. Heat transfer coefficient value was calculated as 5.773 × 10−7 W m−2 K. Uncertainty that stems from measurements and cannot be controlled was calculated as ±2.324%. Novelty impact statement High sucrose solution ratios of drying pre-treatments reduced the drying time of Kosia pear slices. Control samples retained their color values better. Samples subjected to osmotic dehydration in 25% sugar solution for 1 h had is the optimum values drying performance and energy parameters.