Deff Values Research Articles

Effects of gum-based coatings combined with ultrasonic pretreatment before drying on quality of sour cherries

Application of pretreatment methods such as ultrasound and edible coatings is used to reduce processing time and/or preserve food product quality in drying technology. The aim of this research was to measure the impacts of gum-based coatings (guar, sodium alginate, and basil seed gums) in combination with sonication before drying on total phenolic content (TPC), antioxidant capacity (AC), effective water diffusivity (Deff), total color difference (ΔE), surface shrinkage (SS), and rehydration ratio (RR) of sour cherries. Ultrasonic pretreatment (40 kHz, 150 W, at 25 °C, for 12 min) increased the TPC, AC, Deff, and RR, and decreased the drying time, ΔE, and SS values of sour cherries. Edible coating increased the TPC, AC, drying time, and RR, and decreased the Deff, ΔE, and SS values of sonicated sour cherries. The TPC for untreated, uncoated-sonicated, guar gum-coated, sodium alginate-coated, and basil seed gum-coated sour cherries were 2965.9, 3398.1, 3480.8, 3511.0, and 3898.3 µg gallic acid equivalent/g dry, respectively. The highest value of AC (71.2±3.7 %) was observed on coated sour cherries by basil seed gum. The experimental data for drying curves were fitted to several widely used models, and the Midilli model using the experimental constants that best represent the drying rate of sour cherries. The edible coatings significantly reduced the color changes and shrinkage of dried sour cherries, with the lowest ΔE and SS values in the basil seed gum-coated samples (p < 0.05).

Effects of edible coatings and ultrasonic pretreatment on the phenolic content, antioxidant potential, drying rate, and rehydration ratio of sweet cherry

The target of this study was to examine the influence of ultrasound pretreatment and edible coatings (xanthan, guar, and wild sage seed gums) on the total phenols content, antioxidant potential, mass transfer rate, effective moisture diffusivity (Deff), and rehydration rate of sweet cherries (SC). For the edible coating of SC, a 0.2% gum solution (xanthan, guar, and wild sage seed) was prepared and the SC were dipped into the aqueous solution. Also, the ultrasound process (40 kHz and 150 W) was performed in an ultrasonic bath for 3 min. The gums coating increased the total phenols content, antioxidant properties, and drying time and decreased the Deff values. The highest value of DPPH (2,2-Diphenyl-1-picrylhydrazyl) radical scavenging activity (61.04 ± 2.09%) was observed on coated SC by guar gum. The mean drying times for uncoated, xanthan gum-coated, guar gum-coated, and wild sage seed gum-coated SC were 130, 160, 175, and 140 min, respectively. In this study, the SC Deff as determined by the second Fick law varied from 1.39 × 10−9 m2/s to 2.46 × 10−9 m2/s. The Midilli model gave the best results for describing single-layer drying of SC. The mean rehydration ratio for uncoated, xanthan gum-coated, guar gum-coated, and wild sage seed gum-coated SC were 141.81, 167.26, 176.21, and 156.87 %, respectively. Considering the total phenols content, antioxidant activity, and rehydration ratio, edible coating and ultrasonic pretreatment will be more promising for SC pretreatment before drying and other processes.

Evaluating Kinetics of Convection Drying and Microstructure Characteristics of Asian Seabass Fish Skin without and with Ultrasound Pretreatment.

Convection drying in combination with ultrasound pretreatment has emerged as a promising technology for seafood manufacturing. The primary objective of this research was to model the mass transfer process of Asian seabass (Lates calcarifer) fish skin without and with ultrasound pretreatment during convection drying at different temperatures (45, 55, and 65 °C). Additionally, the study aimed to examine the impact of ultrasound pretreatment and temperatures on the drying characteristics and specific energy consumption for drying of Asian seabass fish skin. Seven semi-theoretical models, namely Lewis, Page, modified Page, Vega-Lemus, Verma, Henderson and Pabis, and two-term models, were employed to characterize the moisture transfer process. The results of the study indicated a decrease in the moisture content as the drying time increased at different drying temperatures. Higher drying temperatures were associated with an increased drying rate. Among the mathematical models tested, the modified Page model provided a satisfactory description of the thin-layer drying characteristics of fish skin. Fick's law of diffusion was utilized to determine the effective moisture diffusivities. Comparing the drying of fish skin without (SS) and with ultrasound pretreatment (US-SS), the drying of the latter generally showed higher Deff values. The temperature dependence of the effective diffusivity coefficient was well described by the Arrhenius-type model. An increase in the drying temperature resulted in an increment of the effective moisture diffusivity. In general, the skin pretreated using ultrasound had a reduced drying time, by up to 28%. Additionally, this approach contributed to an approximate 22% reduction in the specific energy consumption, concurrently enhancing the energy efficiency. The microstructure analysis showed that fresh and dried US-SS samples had a more open structure and higher porosity, in comparison to the corresponding SS samples. These findings contribute to the knowledge on the application of ultrasound as the pretreatment of fish skin before drying and provide valuable insights for the development of potential drying techniques in the seafood industry.

Effect of convective and infrared drying on kinetics, activation energy, and quality of eggshells reinforced kaolin composites: Comparative study

The present work is focused on the influence of convective (CV) and Infrared (IR) drying of a novel bio-ceramic material, namely, Eggshells (ES) reinforced kaolin (K) composite, on the drying kinetics, moisture distribution, the effective moisture diffusivity and activation energy as well as the quality and the mechanical strength of the dried product. CV and IR drying experiments were carried out at four temperatures (60, 70, 80, and 90 °C), and different ES content varied from 20 to 50 wt%. The evolution of the moisture ratio and drying rate has been assessed to study the CV and IR drying kinetics of the prepared composites. Moisture diffusivity data and activation energy, determined from experimental drying kinetics, were reported. Based on the obtained results, temperature and ES content had a positive effect on drying kinetics and moisture diffusion. Compared to the CV mode, IR drying decreased the drying time, accelerated the drying process at lower energy consumption, and enhanced the moisture content distribution. The highest moisture diffusivity coefficient (Deff) values inside the bio-composites were achieved using an IR dryer. At 90 °C, K-50%ES dried in an IR dryer showed rapid drying kinetics (40 min) and moisture diffusivity coefficient of 5.88 × 10-6 m2/s, a low activation energy of 52.74 KJ/mol, and better moisture diffusion inside the composite. Nevertheless, the best quality of the dried product K-50%ES was achieved at a mild drying temperature (60 °C). IR drying showed the best results in terms of preserving time, kaolin material and energy consumption during bio-composite drying.

Drying and Rehydration Characteristics of Microwave Dried Mytilus edulis

Rehydration is a critical factor in the processing and consumption of dried food products. This study investigated the kinetics of microwave drying and rehydration of blue mussels (Mytilus edulis) in the range of 140 - 350 W power levels and 20 - 40°C temperatures, respectively. The drying data were utilized to calculate effective diffusivity coefficients (Deff) and activation energy (EA), while rehydration rates and time were also determined. Mathematical modeling was employed to describe the drying and rehydration processes, and the performance of different models was evaluated. The drying process took between 13 - 4.5 minutes, while rehydration was concluded within 360 - 480 minutes. The Deff values ranged from 1.22 - 3.91×10-7 m2/s, and the EA was calculated as 11.417 kW/kg. Rehydration rates resulted in 0.000061 - 0.000126 g/g×min at the highest 40°C and 0.000018 - 0.000032 g/g×min at the lowest 20°C. The drying and rehydration processes were best described by the Alibas model among 11 models and the Two-Term Exponential model among 2 models, respectively. Overall, this study aims to provide valuable insights into the kinetics of microwave drying and rehydration of blue mussels, which can help optimize the processing and preservation of dried food products before consumption.

Effect of electric field on mass transfer during oleuropein extraction

The use of alternative extraction methods has increased since conventional methods have disadvantages like long processing time and limited extraction yield. It is known that the extraction yield is enhanced, and the processing time is shortened by the electric field. However, the mathematical characterization of the electrically assisted processes is needed for a better understanding and the improvement of extraction. In this study, effects of the moderate electric field extraction (MEF-E) parameters (frequencies of 1, 1000, and 2000 Hz, and wave types of sine and square) on yield, cell disintegration index (Zc), microstructure, and mass transfer coefficient (Deff) were investigated to examine mass transfer characteristics of the extraction of oleuropein from olive leaves. Correlation analysis was performed to investigate the relations between yield, Zc, Deff, and the changes in the cross section areas of palisade cells. The frequency and wave significantly affected yield, Zc, microstructural changes, and Deff values (p &amp;lt; 0.05). Additionally, the Zc value showed a good correlation with yield, microstructure, and Deff in both sine and square waves (p &amp;lt; 0.05). It was concluded that the extraction level and microstructural changes could be controlled by Zc during the MEF-E process. Two different finite element models (model 1: fixed Deff and model 2: Deff depending on the Zc) were used for mass transfer, and model 2 gave better predictions (p &amp;lt; 0.05). Thus, it will be possible to characterize and monitor oleuropein transfer depending on the effects of frequency and wave type applications during the MEF process. The model consisting of the Zc–Deff relationship showed that the use of Zc would be preferred for the characterization of mass transfer rather than calculating the Deff value. It is thought that the effects of electric field parameters on microstructure with the developed models will be determined and successfully characterized, thus contributing to the understanding of the effects of electric field extraction processes on mass transfer. However, it is recommended that similar studies are conducted for other plants in order to develop a valid approach on the extraction process from plants.

The Investigation of Oven and Vacuum Oven Drying Kinetics and Mathematical Modelling of Golden Berries

Golden berry (Physalis peruviana) is a fruit that is natively cultivated in the Andean region. Due to its significant nutritional and functional properties, golden berry has been gradually attracting worldwide attention. In this study, oven and vacuum oven drying of golden berries were performed at 60, 70 and 80 °C. Throughout the experiments, the drying kinetic parameters of effective moisture diffusivity (Deff) and activation energy (Ea) were investigated. Moreover, mathematical modeling of drying data was established with the most known modeling equations presented in literature. Experiments revealed that the drying times decreased with increasing temperature and with vacuum addition. The highest and lowest drying times were encountered as 480 minutes in oven drying at 60 °C, and 195 minutes in vacuum oven drying at 80 °C, respectively. Deff values were calculated between 1.95×10-10-3.80×10-10 m2/s and 2.20×10-10-5.45×10-10 m2/s for oven and vacuum oven drying, respectively. Ea values, on the other hand, were found as 32.81 kJ/mol for oven drying and 44.30 kJ/mol for vacuum oven drying. Among the fourteen mathematical models applied to drying curve data, Midilli &amp;amp; Kucuk model provided the best fit for both oven and vacuum oven drying.

The Effect of Drying Temperature and Thickness on the Drying Kinetic, Antioxidant Activity, Phenolic Compounds, and Color Values of Apple Slices

Dried fruit slices are important, healthy, and popular snacks and gain importance day by day due to their high nutritional content. In this context, this study mainly focused on the production of healthy apple chips snacks and the determination of degradation kinetics of antioxidant activity, total phenolic compounds, and color values of apple chip snacks during convective hot air drying at three different temperatures (45, 55, and 65°C) and sample thicknesses (1.5 and 5 ± 0.5 mm). The drying kinetics, desorption isotherms, activation energy, and half-life of the apple chip snack were also calculated. The Page and GAB models are the best models for the determination of the drying (&gt;0.992) and desorption (&gt;0.9979) behavior of apple snacks with the highest R2 values. The drying of all samples took place in the falling rate period. The Deff values increased depending on the increasing air temperature and slice thickness. The antioxidant activity, total phenolic compounds, and total color change of the 5 mm thick samples were degraded following the first-order reaction kinetics. The higher antioxidant activity, phenolic compounds, L∗ values, and lower half-life values were observed in conditions where the thickness (1.5 mm) and temperature (45°C) are low. The activation energy values calculated for the total phenolic compounds are higher than those calculated for the antioxidant activity. As a result, it can be concluded that apple chip snacks with high nutritional value can be produced by choosing low temperatures and slice thickness.

Effect of Turntable Rotation Rate on Drying Kinetics and Functional Properties of Lemon Peel during Microwave Drying

The aim of this study is to investigate the effect of the rotational rate of the turntable on drying kinetics of lemon peels and some functional and flow properties of lemon peel powders. Lemon peels were dried by microwave drying using different rates of rotation (0, 6.5, 9.5, and 12.5 rpm) at different microwave power levels (180W, 300W, 450W and 600W), and dried by oven drying and freeze-drying methods. Drying time was shortened by 72- 95% by microwave drying compared to oven drying. Microwave drying with rotation provided 5.6-23.8% reduction in drying time of peels compared to drying without rotation. Effect of rotation rate on drying time of lemon peels depended on the microwave power level. Page model provided lower SSE, RMSE, and higher R2 values within 5 different thin layer models. The effective moisture diffusivity value, ranging between 1.7x10-8 m2 s -1 -7.6x10-8 m2 s -1, was higher during microwave drying with rotation. The activation energy ranged between 21.3-22.7 W/g. Microwave drying provided higher bulk density, similar or lower water holding capacity and oil retention capacity values compared to freeze drying and oven drying. Freeze dried lemon peel powder had the lowest bulk density due to its porous structure. Microwave drying without rotation and the highest power level caused lower bulk density. At higher power levels, influence of turntable rotation on water holding capacity was more notable. Microwave drying technique can be used as alternative drying techniques to obtain high quality dried lemon peel powder if appropriate processing conditions are selected.

Effective moisture diffusivity and activation energy during convective drying of bread containing clove oil/orange oil

The aim of present study was to investigate the characteristic drying behaviour of bread with the convective drying method for increasing bread shelf life. Effective moisture diffusivity and activation energy were compared in detail. According to the results, bread samples were dried between 0 and 450 min for 40 °C, 0–180 min for 50 °C and 60 °C, respectively. The experimental data with high coefficient of determination (R2) changed between 0.889 and 0.998. The values of Deff were obtained between 1.21 × 10−9-1.22 × 10−8 m2/s. Also, Ea values were found to be in range of 82.47–100.49 kJ/mol for bread samples which had additive-free and additive. When the bread samples without additives and the breads with essential oils were compared, it was found that the activation energy increased with the use of additives. Moisture content values decreased with the increase in time. Drying rate and moisture content relation showed the expected behaviour, thermally and morphologically.

Accuracy of IndoseCT for Measuring Effective Diameter from axial CT Images

We investigated the accuracy of automatic measurements of the effective diameter (Deff) using IndoseCT software with axial computed tomography (CT) images of polyester-resin (PESR) phantoms of various diameters. The phantoms used PESR as the base material mixed with Methyl Ethyl Ketone Peroxide (MEKP) as the catalyst. The phantom diameters were 8, 16, 24, and 32 cm. The phantoms were scanned with a CT scanner from edge-to-edge position with field of views (FOVs) of 30, 35, 40, 45, and 50 cm. The Deff was measured from all slices along the z-axis. It was found that the automatic Deff measurements were very accurate. The Deff values were different by less than 0.02 cm for all diameters and all FOVs used. The maximum difference was obtained a ta diameter of 16 cm and FOV of 35 cm. We found that the precision of Deff measurements along the z-axis was very good with a maximum standard deviation of 0.01 cm. The relationships between phantom diameter and measured Deff for all FOVs had p-values &lt; 0.001 and r2 = 1.000. Therefore, the IndoseCT is able to accurately and precisely measure Deff to facilitate estimating the patient dose in the SSDE metric.

Drying Characteristics, Kinetic Modeling, Energy and Exergy Analyses of Water Yam (Dioscorea alata) in a Hot Air Dryer

In this study, drying characteristics, kinetic modelling, energy and exergy analyses of a convective hot air dryer are presented for water yam. The drying experiments were carried out at temperature levels of 50, 60, and 70°C and slice thicknesses of 3, 6, and 9 mm. The effects of drying variables on the drying rate (DR), moisture diffusivity (Deff), activation energy (Ea), energy utilization (EU), energy utilization ratio (EUR), exergy loss (EXL), exergy efficiency (EXeff), improvement potential (IP), and exergetic sustainability index (ESI) were investigated. The results showed that increasing air temperature increased the DR, Deff, EU, EUR, EXL, EXeff, IP, and ESI, while increasing the slice thickness increased Deff and Ea, but decreased the DR. The highest Deff and Ea values were 4.2 × 10−8 m2/s, and 53 KJ/mol, respectively. EU and EUR varied from 10 to 150 J/s and 0.39 to 0.79, respectively. EXL and EXeff varied between 2 and 12.5 J/s and 58 to 75 %, respectively. Midilli’s model had the best performance in predicting the moisture ratio of water yam with coefficient of determination (R2 = 0.9998), root mean square error (RMSE = 0.0049), and sum of square error (SSE = 0.0023).

Drying and Quality Characteristics of Whole Jujubes Subjected to Air Assisted Radio Frequency Heating

Highlights The effect of air temperature and electrode gap (EG) on RF drying efficiency was evaluated. Drying rate (Dr), the mathematical modeling of drying curves, heating uniformity, effective moisture diffusivity coefficient (Deff), and quality parameters after drying were analyzed. Drying rate was accelerated by reducing EG or increasing air temperature under EG RF drying. The trend of heating uniformity was the same as that of Deff value. The evaluated quality parameters of treated whole jujubes showed that 40°C air assisted 17 cm EG RF drying had the best quality. Abstract. This study aims to investigate the drying and quality characteristics of whole jujubes heated by air assisted radio frequency (RF) energy. The effect of air temperature and electrode gap (EG) on RF drying efficiency was evaluated. The drying rate (Dr), the mathematical modeling of drying curves, heating uniformity, effective moisture diffusivity coefficient (Deff), and quality parameters after drying were analyzed. The results showed that under the conditions of 30°C air temperature or 17 cm EG RF drying, Dr was accelerated by reducing EG from 18 cm to 16 cm or increasing air temperature from 20°C to 40°C. The Midilli model had the best fitting to drying curves under 30°C RF treatments with 16 cm, 17 cm, and 18 cm EG, and 40°C RF heating with 17 cm EG conditions. But the Logarithmic model was better for 20°C air assisted 17 cm EG RF heating due to the largest R2 with lowest RMSE. The largest Deff value was shown at 40°C air assisted 17 cm EG RF drying, followed by 30°C air assisted 16 cm, 17 cm, and 18 cm EG RF heating, and 20°C air assisted 17 cm EG RF drying. The trend of heating uniformity was the same as that of the Deff value. The evaluated quality parameters of treated whole jujubes showed that 40°C air assisted 17 cm EG RF drying had the best quality. Therefore, 40°C air assisted 17 cm EG RF heating was chosen for drying jujubes due to its faster drying rate and better quality. Keywords: Air temperature, Drying characteristics, Jujube; Quality, Radio frequency heating.

Effect of Ultrasonic Pretreatment on Radio Frequency Vacuum Drying Characteristics and Quality of Codonopsis pilosula Slices

In this paper, the effects of ultrasonic pretreatment on the drying kinetics, bioactive components (polysaccharides, total phenols, total flavonoids and antioxidant), qualitative characteristics (color index, lobetyolin and syringin) and microstructure of Codonopsis pilosula during radio frequency vacuum drying (RFVD) were studied. The average drying rate curve showed that the whole drying process could be divided into three stages: accelerating period, constant drying rate period and falling drying rate period. Deff values ranged from 6.61425 to 9.46745 × 10−8. Analysis of the drying rate constants revealed that different conditions of pretreatment were effective in increasing the drying rate. Ultrasonic pretreatment has a positive effect on the retention of polysaccharide content; low frequency favors retention of total phenols, flavonoids and syringin; and with the increase in ultrasonic time and ultrasonic power, the antioxidant capacity was higher than that without ultrasonic treatment. Ultrasonic pretreatment significantly improved color and microstructure. In summary, the pretreatment condition of ultrasonic frequency 20 kHz and power 60 W for 30 min is suitable, which provides a certain reference for the application of ultrasonic pretreatment technology in RFVD of Codonopsis pilosula slices.

Dose optimization of adult head computed tomography examination in an academic hospital in Ghana

The study investigated radiation doses and image quality of adult head CT and optimization options using an anthropomorphic RANDO phantom on the only available AquilionONE CT scanner in Ghana. Dose length product (DLP) and volume-weighted CT dose index (CTDIvol) dose descriptors were retrospectively obtained from 402 adult head CT examinations performed (from 2020 to 2021) at a Ghanaian hospital, while the effective dose (Deff) was estimated from the product of the DLP and a convention coefficient (k = 0.0023). Using the same routine head CT protocol, the anthropomorphic RANDO phantom was scanned with the hospital's 640-slice Toshiba AquilionONE CT scanner. Subsequently, exposure factors were varied to study their effects on the dose and image quality. The adult head and phantom images were obtained in Digital Imaging and Communications in Medicine (DICOM) format, and their signal-to-noise (SNR) ratios were analyzed with ImageJ software. The facility's mean CTDIvol, DLP, and effective dose (Deff) were 86.00 ± 0.00 mGy, 1559.68 ± 197.18 mGy cm, and 3.57 ± 0.46 mSv respectively (SNR = 7.04). For a fixed tube potential, CTDIvol, DLP, and Deff of 51.30 mGy, 1013.80 mGy cm, and 2.33 mSv were respectively achieved (SNR = 5.49) after optimization. Using automatic exposure control (AEC) in the optimization process, the respective CTDIvol, DLP and Deff values were 59.50 mGy, 1176.00 mGy cm and 2.70 mSv (SNR = 5.62). We conclude that substantial Deff reductions of 40.4% and 31.0% using a fixed tube potential, and AEC while maintaining diagnostic image quality were respectively achieved. The protocols associated with these dose-reductions are, therefore, recommended as optimization measures for head CT on the AquilionONE scanner in Ghana.

Mathematical Modeling of Thin Layer Drying Kinetics and Moisture Diffusivity Study of Pretreated Moringa oleifera Leaves Using Fluidized Bed Dryer

Investigations were undertaken to study the drying kinetics of pretreated and unblanched leaves of Moringa oleifera dried in a fluidized bed dryer (FBD) using nine established thin layer drying mathematical models. The statistical software tool Statistica was utilized to carry out regression analysis, and the model constants were evaluated using nonlinear regression. In nonlinear regression, the R2 and reduced χ2 were employed to evaluate the goodness of fit of several mathematical models to the data generated experimentally. The model with the highest R2 and the lowest reduced χ2 and root mean square error (RMSE) values was adjudged as best fit to the drying curves. The drying kinetics of drumstick leaves was best explained by the Midilli–Kucuk model, followed by the Logarithmic model. The R2, reduced χ2, and RMSE values of the Midilli–Kucuk model under fluidized bed drying varied from 0.9982–0.9997, 0.00003–0.00029, and 0.0059–0.0166 in pretreated and 0.9945–0.9961, 0.00019–0.00054 and 0.0136–0.227 in unblanched Moringa leaves dried at 50–70 °C, respectively. The diffusivity (Deff) values ranged between 2.96 × 10−9–3.59 × 10−9 m2 s−1 and 2.92 × 10−9–3.04 × 10−9 m2 s−1, and activation energy varied from 13.67–14.07 (KJ/mol) and 13.85–14.11 (KJ/mol) for pretreated and unblanched dried leaves at 50–70 °C drying temperatures, respectively.

Interaction of Different Drying Methods and Storage on Appearance, Surface Structure, Energy, and Quality of Berberis vulgaris var. asperma.

Seedless barberry fruit is native small fruit in Iran. To examine the impact of various drying methods and storage on the biochemical attributes (Vitamin C, Anthocyanin, Phenol, pH, TA), color index (a*, b*, L*, ab, and Chroma), drying time, and fruit microstructure (by SEM) of seedless barberry (Berberis vulgaris var. asperma), and effective moisture diffusivity coefficient (Deff), specific energy consumption (SEC), energy efficiency (EE) of the dryers, this experiment was performed. Drying treatments include microwave (100, 170, and 270 W), oven (60 and 70 °C), cabinet (50 and 70 °C), shade, sun, and fresh samples (control) and storage 6 months after drying (in polyethylene packaging and at a temperature of 5–10 °C). Results showed minimum and maximum drying times (50 min and 696 h), were related to microwave (270 W) and shade methods, respectively. The highest color values were observed in fruits treated with control, shade and sun treatments and the lowest values were observed in cabinet (70 °C) methods. According to the SEM results, microwave significantly affected surface structure of the dried sample compared to others. The findings indicated that the use of artificial drying methods than natural methods (sun and shade) cause a more significant reduction in color indexes, while vitamin C, soluble solids, and anthocyanin were significantly maintained at a high level. Storage reduced anthocyanin content of fruits almost 12%. Moreover, it was discovered EE and SEC values varied in the range of 1.16–25.26% and 12.20–1182 MJ/kg, respectively. Deff values were higher in microwave 270 W.

Effect of yerba mate ( Ilex paraguariensis St. Hil.) extract on the drying behavior of cassava starch films enriched with rebaudioside A

In this study, the drying behavior of cassava starch-based edible films was investigated. Formulations were elaborated with rebaudioside A, glycerol, and low concentrations (0.5, 2, and 4%, w/w) of yerba mate (Ilex paraguariensis St. Hil.) extract (YM%). Physicochemical properties (pH, apparent viscosity, and density) and film-forming capacity (dip-coating method) were evaluated at 25°C. Films were casted by drying and mathematically described using the Henderson and Pabis thin-layer model. Effective moisture diffusion coefficients (Deff) were determined using theoretical film thicknesses evaluated at the critical moisture content. The Deff dependency on temperature and YM% was analyzed using an Arrhenius-type model. Based on the results, as YM% increased, values of pH, and apparent viscosity decreased. Low YM% increased the drying rates and the values of Deff of cassava starch-based edible films elaborated with rebaudioside A as a sweetener and bioactive compound, obtaining the highest values at 4% (w/w) and 70°C. Novelty impact statement The optimization and control of the drying process are important to produce coated foods with high-quality and nutritional value in the industry. Yerba mate extract powder added to cassava starch-based formulations at low concentrations (<5%, w/w) is suitable for obtaining edible films and coatings with higher drying rates and effective moisture diffusion coefficients that control film casting due to the better hydrophobicity and plasticizing effect. This information could be useful to manufacture new film-forming fluids with bioactive compounds (e.g., rebaudioside A), such as alternative bio-packages that allow to replace the disposable composite synthetic plastic containers, and products for people with special diet requirements due to its low or sugar-free nature.

Drying and rehydration kinetics of peeled and unpeeled green apple slices (Granny Smith cv)

In this work, the kinetics of drying and rehydration of green apple slices peeled and unpeeled (Granny Smith cv) were studied. The apple slices were dried at 50, 60, and 70 °C, and after that, rehydrated at ambient (Ta ) and boiling temperature (Tb ). The drying kinetics were adjusted with the Dincer and Dost model, giving a good fit. Effective diffusivity (Deff ) and the convective mass transfer coefficient (hm ) were also determined, both coefficients increase with drying temperature, being 1.25 × 10−9 m2 s−1 and 9.53 × 10−7 m2 s−1 the highest values obtained for the peeled apple slices respectively. Peleg and Weibull models were adjusted to the rehydration experimental data obtaining a good fit (R 2 > 0.99). Deff values increase significantly with rehydration temperature but take similar values between peeled and unpeeled samples. Acidity, pH, moisture content, solid soluble content, and equivalent diameter were determined to compare the fresh apple slices with those after dehydration and the post-rehydration process. The apple slices rehydrated at boiling temperature better preserved the characteristics of fresh samples due to the short immersion times in water, no significant differences were observed between peeled and unpeeled apples. According to the results, it is convenient to dry the apple slices unpeeled at 70 °C and rehydrate them at Tb .

Semi-Empirical Mathematical Modeling, Energy and Exergy Analysis, and Textural Characteristics of Convectively Dried Plantain Banana Slices.

Thin-layer convective drying of plantain banana was performed at four different temperatures from 50 to 80 °C, with slice thicknesses from 2 to 8 mm. The drying curves, fitted to seven different semi-empirical mathematical models, were successfully used to fit experimental data ( 0.72–0.99). The diffusion approach had better applicability in envisaging the moisture ratio at any time during the drying process, with the maximum correlation value ( 0.99) and minimum value of (2 and RMSE (5.0 . The , , and values were calculated on the basis of the experimental data, and overall ranged from to m2 s−1, to 2.20 m s−1 and 13.70 to 18.23 kJ mol−1, respectively. The process energy consumption varied from 23.3 to 121.4 kWh kg−1. The correlation study showed that the drying temperature had a close correlation with value and sample hardness. A significant (p < 0.05) increase in hardness of dried plantain banana was observed at 80 °C compared to the other temperatures. Additionally, the sample hardness and process energy consumption were more positively correlated with the thickness of the samples.