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AbstractThe convective drying of spherical biosolids particles from two wastewater treatment plants (Type 1: anaerobic/anoxic treatment with belt filter press dewatering; Type 2: aerobic/anoxic treatment with centrifuge dewatering) was studied under 10 conditions across 44 trials. A wide spectrum of conditions including three drying temperatures (88, 109, and 138°C), two gas velocities (1.6 and 2 m s−1), and particle sizes of 2 cm and 4 cm were investigated. Measured variables included particle mass, center/internal temperature, surface temperature, shrinkage, and qualitative observations of morphological changes. Most samples showed two drying periods, a constant rate period followed by a falling rate period. Additionally, it was found that drying rates and morphological changes depended significantly on particle size and drying intensity (i.e., drying gas temperature and gas velocity) with higher intensities resulting in larger, more porous particles. Internal temperature profiles displayed a consistent pattern, an initial heating phase where internal temperatures quickly rose to approximately the wet bulb temperature of the drying gas, a quasi-constant temperature phase at that temperature, and a final sharp increase/spike to reach equilibrium with the drying gas temperature. Moreover, IR images showed that sub-surface temperatures (between the core and surface) were significantly lower than surface temperatures. Surface temperatures showed a more linear increase throughout drying until equilibrium with the drying gas temperature. The consistent temperature difference between the center and surface, as well as the internal temperature profile, suggests the existence of a drying front, moving radially inward as the particle dries. This research contributes to a better understanding of biosolids drying dynamics, offering insights to improve thermal treatment strategies thereby contributing to the broader field of waste management. [ABSTRACT FROM AUTHOR]

Combined drying, an energy-efficient method that includes osmotic pretreatment in molasses and shortened successive lyophilization, was used to obtain celery root powder and incorporate it in the formulation of cookies, with the aim of obtaining a new product. Wheat flour was substituted with combinedly dehydrated celery root powder at levels from 0 to 30%, and optimization of the amount of wheat flour substitution regarding technological, sensory and nutritive characteristics was performed. The optimal level of 20% substitution was determined using Z-score analysis, from the aspect of the best nutritive improvement and the mildest adverse impact on the technological and sensory quality. In the second research phase, comparison of the cookies with the 20% celery root powder substitution, dehydrated by different methods, indicated that combined dehydration showed upgraded results in terms of the overall quality of the final product, for 28.85 percentile points higher than cookies with lyophilized and for 65.24 percentile points higher than cookies with the addition of convectively dried celery root powder. The cookie containing celery powder previously osmodehydrated in molasses had higher contents of analyzed minerals (1.2–3.3 times), total phenols (10.8%) and antioxidant activities (14% for DPPH and 4% for ABTS) compared to the cookie with lyophilized powder. [ABSTRACT FROM AUTHOR]

The EU's circular economy concept necessitates increasing the recycling ratio of municipal solid wastes. There are many existing mechanical–biological processing plants in Hungary for the preparation of residual municipal solid wastes (RMSWs). The two most important products of these plants are the bio-fraction and the refuse derived fuel (RDF). Currently, there are problems with both of these material streams in Hungary, since most of the bio-fraction is still landfilled, and the local thermal utilisation of the RDF has not been implemented yet. The high moisture content of the produced bio-fraction and RDF causes difficulties for the downstream operations; therefore, there is recent engineering interest in drying and agglomeration of these materials. The authors have carried out systematic and parallel drying and briquetting experimental series to study the effect of the material, material composition, mass (volume or surface) of the material, particle size distribution and pre-treatment with a cutting mill on drying intensity in a 1 m3 oven and their effect on briquettability by a laboratory briquette press. The initial slope of the relative moisture loss as function of time was determined. Process engineering design methods of convective hot air-drying can be further developed taking into account the research results. Results can be used for the design of the feed of a pyrolysis reactor once reactor experiments have provided the optimal feed requirements. [ABSTRACT FROM AUTHOR]

By increasing the permeability of the cell membrane of the treated material, pulsed electric fields (PEF) enhance the internal transport of various chemical substances. Changing the distribution of these components can modify the chemical and thermal properties of the given material. This study aimed to analyze the impact of PEF (1 kV/cm; 1 and 4 kJ/kg) applied to strawberries prior to drying by various methods (convective, infrared-convective, microwave-convective, and vacuum) on the chemical and thermal properties of the obtained dried materials (sugars content, total phenolic content, and antioxidant capacity (ABTS and DPPH assays); thermal properties (TGA and DSC); and molecular composition (FTIR)). PEF could have induced and/or enhanced sucrose inversion because, compared to untreated samples, PEF-pretreated samples were characterized by a lower share of sucrose in the total sugar content but a higher share of glucose and fructose. Reduced exposure to oxygen and decreased drying temperature during vacuum drying led to obtaining dried strawberries with the highest content of antioxidant compounds, which are sensitive to these factors. All PEF-pretreated dried strawberries exhibited a lower glass transition temperature (Tg) than the untreated samples, which confirms the increased mobility of the system after the application of an electric field. [ABSTRACT FROM AUTHOR]

Convective drying is a method of preserving fruit. Due to the low energy efficiency of the dryers, it is also one of the most energy intensive. For this reason, modern drying techniques are being sought. They are required to be energy efficient, sustainable and produce high quality products. The aim of this work was to determine the effect of ultrasound on the kinetics and energy consumption of convective drying of apples and the quality of the products. The convective drying process and two US-convective processes with different ultrasonic power were tested. Three apple varieties were dried. Drying kinetics, energy consumption, and product quality (water activity and color change) were compared for the tested processes. Drying kinetics was mathematically modeled. The use of ultrasound accelerated the process in each case. The drying time was reduced and the speed of the process increased. This increase was mainly due to the vibration effect, which caused an increase in the mass transfer coefficient. The use of ultrasound resulted in a decrease in the water activity of the product and a decrease in the color change of the dried material compared to that obtained by the convection method. [ABSTRACT FROM AUTHOR]

Hydrogels are polymeric materials with specific mechanical handling and encapsulation properties. Despite their widespread application, the modelling of the drying behaviour of hydrogels, particularly the evolution of texture stiffness with moisture loss, requires further development. This work aimed to develop numerical models to predict the moisture and deformation of cornstarch–alginate hydrogels under convective drying at 60 °C and 0.5 m/s. Cylindrical solids were used, and a transient three-dimensional FEM model predicted drying profiles via diffusion–convection mass transport. Texture analysis evaluating the hyperelastic coefficients of the hydrogels was performed for moisture contents ranging from 0.91 to 0.55 kg∙kg−1 w.b., yielding Young's modulus values from 24 to 147 kPa. A dimensionless relationship between the moisture ratio and elastic modulus produced a stiffness coefficient, used to adjust the moving boundary velocity and predict volumetric deformation. The model fitting returned an R2 higher than 0.95 and an RMSE lower than 0.04. The FEM model simulated hydrogel shrinkage by assessing the molar flux of water and mesh deformation at the boundaries, with mass diffusivity ranging from 2.38 to 5.46 × 10−10 m2∙s−1. Shrinkage reduced the surface area of solids during drying, revealing a pseudo-constant rate period in the drying profiles. The developed models effectively describe the drying of food materials with high shrinkage ratios. [ABSTRACT FROM AUTHOR]

Cashew apple is a source of by-products in the cashew industry. Powder products provide convenience to the process of use, transport, and preservation of nutrients. In this study, the production of soluble powder from cashew apples was developed through the investigation of hydrolysis process (time, temperature, and enzyme tannase) and convective drying conditions (temperature and maltodextrin content). The following indicators are evaluated, such as the total polyphenol content (TPC), total tannin content, total ascorbic acid, solubility, turbidity, and color. The results have shown that TPC increased by 1.67 times, and more than 50% of tannins was removed after the hydrolysis process. At the same time, the efficiency of the process over 30% under all processing conditions was evaluated. These results are the foundation for the development of cashew apple powder and related products, thereby improving the economy of the cashew industry in Vietnam and the world.

Drying food products and materials is one of the most common methods in processing raw materials, yet it remains an energy-intensive process. The main drawback of traditional electric convective household dryers is the loss of heat and the wet waste drying agent into the environment. Furthermore, such units are characterized by uneven heating of the dried product, attributed to a temperature decrease and increasing humidity from bottom to top. (Research purpose) The purpose of this study is to conduct laboratory experiments on the drying process of apples focusing on evaluating the energy consumption required to evaporate 1 kilogram of moisture using a newly developed convective thermoelectric drying unit and compare its energy efficiency with mass-produced convective dryers. (Materials and methods) The findings from theoretical and experimental studies facilitated the development of a functional diagram and a laboratory prototype of a convective thermoelectric dryer using a thermoelectric heat pump. The drying process involves the utilization of a drying agent (heated air) with partial air recirculation, and heat recovery from the exhaust air. (Results and discussion) Temperature variations at designated control points and the relative humidity of the drying agent at both inlet and outlet of the developed unit were graphed and analyzed. The parameters of apples before and after drying in the thermoelectric drying unit are compared with those dried in a conventional household convective dryer. The study has resulted in developing an electrical control circuit for a thermoelectric drying unit and providing expressions to calculate the hot junction radiator of an air-to-air thermoelectric heat pump integrated into the developed drying unit. (Conclusions) The study estimated the average heat recovery by the cold junction radiator of a thermoelectric heat pump from the exhaust drying agent during the drying process, amounting to approximately 20 percent of the total energy consumption by the thermoelectric drying unit from the electrical grid. The research findings demonstrate that the laboratory prototype offers a more consistent drying process for the product. This is attributed to the incorporation of side air channels and a more efficient arrangement of the drying agent’s movement within the working chamber, as opposed to traditional convective dryers. These conclusions are substantiated by the test results. It is illustrated that the use of a developed thermoelectric heat pump with heat recovery from the waste drying agent can lead to a reduction in the installed power capacity of the drying agent heater and a decrease in the energy consumption for the drying process in the developed convective thermoelectric drying unit compared to mass-produced household convective dryers.

Drying process was used in this study as a preserving method of octopus quality during storage. Octopus vulgaris quality attributes in terms of pH, water activity, color properties, total volatile basic nitrogen (TVB-N), trimethylamine (TMA), total viable count, and yeast and molds (YM) were evaluated. Samples were dried under sun drying and convective air drying and stored at ambient temperature. During storage, TVBN and TMA obtained were within the recommended level for good quality of dried samples. Accelerating shelf-life test was evaluated based on TVB-N, TMA, and YM, with shelf lives of 388 and 603 days for convective air drying and sun drying, respectively. [ABSTRACT FROM AUTHOR]

This study investigated the impacts of a drying process under low temperature and reduced pressure (non-thermal drying) on the final dehydrated products characteristics. This process is based on the retention of water on molecular sieves with a good selectivity against these molecules. In this study, drying experiments of 7mm thick apple slices (AS) were performed and compared to apple slices pretreated by freezing. It was concluded that the dehydrated apple slices were depleted of the maximum amount of water after 12 hours of drying, with a final water content equal to 12 ± 1.75%, whereas after freezing pretreatment, a decrease in drying time to 7 hours was observed, as well as a decrease in water content to 10 ± 0.5%. This explains the effect of freezing pretreatment on accelerating water transfer. In addition, a convective drying was performed on the apple slices at 60°C, which allows comparison with the slices dried by our non-thermal drying process. In order to characterize the obtained fruits, characteristic analyses such as water activity (Aw), color, texture (hardness), and dimensions (diameter and thickness) were performed before and after each drying experiment. Thus, continuous measurements of temperature, humidity, and pressure, within the enclosure, were determined during the experiments using a wireless sensor system controlled by a programming Arduino. Finally, mathematical modeling by various models (Newton, Page, Midilli, etc.) was performed to determine the most suitable model describing the non-thermal and convective drying of apple slices. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Non-isothermal convective drying schemes were examined for Lavandula × allardii leaves and inflorescences. Drying process parameters were optimized using response surface methodology (RSM) to ensure the peak operational performance. The effects of temperature increase rate (2–4 °C/h) and the airflow velocity (1–3 m/s) on the essential oil yield, drying duration and consumption, were investigated. A face-centered central composite design was deployed and the experimental data was adapted to the most suitable polynomial models, as determined by the regression analysis. Analysis of variance was applied to assess the effects of the process variables, their interactions and the statistical significance of the examined models. Both factors of temperature increase rate and airflow velocity had a significant impact on the drying duration. Airflow velocity had a greater effect on leaves’ essential oil yield and inflorescences’ process energy consumption, whereas the rates of temperature increase had a greater influence on the inflorescences’ essential oil yield and leaves’ energy consumption. The minimum drying duration and energy consumption were obtained for the maximum temperature increasing rate at 3 and 1 m/s airflow velocities respectively; and the highest essential oil yield was obtained for the least rate of temperature increase and airflow velocity for both leaves and inflorescences. Numerical optimization was performed for minimizing drying duration and energy consumption by maximizing the essential oil yield. The rate of temperature increases of 4 °C/h and the airflow velocity of 1 m/s, were proposed as the optimum non-isothermal drying conditions for both leaves and inflorescences of Lavandula × allardii. Predicted values of essential oil content have been 1.387/3.05 mL/g, 4.21/4.18 h drying time and 0.809/0.732 kWh energy consumption at the optimum operation point for leaves and inflorescences, respectively. The resulted optimized non-stationary temperature scheme considerably improved the drying kinetics and the process consumption by achieving a similar essential oil recovery with the standard low-temperature convective drying. The present study aimed to eliminate the preexisting gap of the optimum selection of the process parameters for the particular type of the examined non-isothermal drying schemes. Previous findings could be utilized for designing dryers and drying schedules aiming to retain the qualitative attributes, by reducing the cost and duration of the drying operations.

Salam leaves, a traditional food flavoring spice, is a widely recognized herb in Indonesia and is used in many regions. This study aimed to investigate salam leaves' drying kinetics, comprising mathematical modeling, moisture diffusivity, and other nutritional values as qualitative parameters. The drying process was examined using a forced convective system (CSD) and open sun drying (OSD). The drying behavior was examined by observing the drying kinetics characteristics using 12 thin-layer semi-theoretical mathematical for drying of agricultural products., determining the moisture diffusivity, and measuring the content of chlorophyll a, b, and total dissolved solids as nutritional quality indicators of the drying products. According to the obtained results from the non-linear regression analysis, the Midilli model demonstrates the highest degree of appropriateness for drying salam leaves. The moisture diffusivity of CSD is greater than that of open-air solar drying. Regarding nutritional composition, the study revealed that chlorophyll a, b, and carotenoid levels in the dried leaves obtained through CSD were more significant than those obtained by OSD. As an environmentally friendly dryer, the CSD can potentially be applied in herb-drying industries, especially salam leaves.

This study aims to comprehensively investigate the effects of hot-air dehydration on the quality of blue honeysuckle berries (Lonicera caerulea L.). The results demonstrated that drying with hot air at 40–65 °C for 7–72 h resulted in blue honeysuckle berries with a moisture content of 0.21–1.10 g H2O/g dry weight. Generally, low to medium temperatures (40–55 °C) showed a better effect on the quality than high temperatures (60–65 °C). Specifically, drying at 40 °C exclusively resulted in better retention of cuticular wax, the best sensory appearance, and the highest total phenolic content. Drying at 45 °C and 50 °C resulted in the highest antioxidant capacity and the optimal sensory flavor. Drying at 55 °C led to the highest soluble solid/acid ratio, ascorbic acid concentration, total flavonoid, and total anthocyanin. The work introduces an innovative raw berry product and provides a comprehensive practical and theoretical framework for convective dehydration of blue honeysuckle berries. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Almaty Technological University is the property of Almaty Technological University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present study investigated the Interval Starting Accessibility Drying (ISAD) process with the main objective to optimize the main processing parameters, i.e. the active time (toN) and the tempering time (toFF)> which ranged between 5 to 30 s and 1 to 3 min, respectively. ISAD performances were compared with continuous airflow drying for several quality parameters and energy consumption. The modulation of the time related operating conditions allowed rewetting the surface after each tempering time in a total way with toN= 5s-and toFF=2 or 3min. ISAD significantly affected (p<0.05) the effective drying time and the energy saving which reached as much as 87.26% compared to continuous drying when toN= 5s and toFF =3 min. The processes did not significantly impact the shrinkage, rehydration capacity or total color change. However, drying processes notably influenced the content of polyphenols and carotenoids. The optimal conditions of combined optimized responses were toN = 5 s of toFF = 2.52 min with a desirability D= 0.924. [ABSTRACT FROM AUTHOR]

Salam leaves, a traditional food flavoring spice, are a widely recognized herb in Indonesia and are used in many regions. This study aimed to investigate the drying kinetics of salam leaves, comprising mathematical modeling, moisture diffusivity, and other nutritional values as qualitative parameters. The drying process was examined using a forced convective system (CSD) and open sun drying (OSD). The drying behavior was examined by observing the drying kinetics characteristics using 12 thin-layer semi-theoretical mathematical for drying of agricultural products, determining the moisture diffusivity, as well as measuring the content of chlorophyll a, b, and total dissolved solids as nutritional quality indicators of the drying products. According to the obtained results from the non-linear regression analysis, the Midilli model demonstrates the highest degree of appropriateness for drying salam leaves. The moisture diffusivity of CSD is greater than that of open-air solar drying. Regarding nutritional composition, the study revealed that chlorophyll a, b, and carotenoid levels in the dried leaves obtained through CSD were more significant than those obtained by OSD. As an environmentally friendly dryer, CSD can potentially be applied in herb-drying industries, especially salam leaves. [ABSTRACT FROM AUTHOR]

The present study focused on evaluating the biochemical profiles of four apricot cultivars (cv.) (Prunus armeniaca L.) grown in Latvia and demonstrating their processing to obtain the food product, dried candied fruit (DCF). The fingerprinting of apricot fruit approached by LC-MS and ultraviolet–visible spectroscopy revealed the abundance of bioactives responsible for the antioxidant activity. The outstanding composition of group compounds, i.e., phenolics, flavonoids, and vitamin C, was observed in the cv. 'Dimaija', followed by cv. 'Gundega' and cv. 'Velta'. The lowest values were found in the cv. 'Boriss' and fruit from a market of Greek origin. However, the latter two contained the highest carotenoid levels due to a more pronounced maturity. Amongst the 13 individual phenolics detected, rutin, chlorogenic and neochlorogenic acids, catechin, and epicatechin prevailed. The concentrations observed were the highest in cv. 'Dimaija', followed by cv. 'Velta' and cv. 'Gundega'. Osmotic dehydration and convective drying of apricot fruit variedly influenced the content of bioactives in DCF products. The most substantial decrease due to thermal lability was observed in the vitamin C content in DCF, accounting for a 95.3% loss for all cultivars. The content of total phenolics, flavonoids, and carotenoids in DCF, on average, was 62.7%, 49.6%, and 87.6% lower than that observed in the raw fruit, respectively. On average, the content of individual phenolics in DCF, such as rutin and chlorogenic acid, decreased by 63.8% and 20.8%, respectively. The decline in the content of bioactives was conditioned by the physical migration of the cell components to the hypertonic solution. However, the increase in the content of cell wall-bound phytochemicals, such as catechin and epicatechin, after osmotic dehydration and convective drying, was observed in DCF, corresponding to a 59.5% and 255.64% increase compared with the raw fruit, respectively. Panelists generally responded positively to the developed DCF; however, greater preference was given to products with a lower phenolic content, such as cv. 'Boriss' and those produced from the market fruit. It is believed that the high flavan-3-ols content, along with chlorogenic acid, contributed to the bitter taste of DCF. Overall, apricot fruits represent the abundance of bioactives retained in DCF after osmotic dehydration and convective drying. The findings observed in the current study allow to consider DCF as a functional food; however, given the high sugar content, their consumption should be in moderation. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effect of convective and microwave drying on the bioactive-compounds content of blackberry (Rubus fruticosus) fruits, as well as drying parameters and energy consumption. The fruit was dehydrated in a convective dehydrator at a temperature of 50 °C and 70 °C and in a microwave oven at power levels of 90 W, 180 W and 240 W. The highest amount of anthocyanins, polyphenols and antioxidant capacity were obtained in blackberry fruits that were microwave dried at 90 W and 180 W (46.3–52.5 and 51.8–83.5 mg 100 g−1 dm of total anthocyanins, 296.3–255.8 and 418.4–502.2 mg 100 g−1 dm of total phenolics, and 1.20–1.51 and 1.45–2.35 mmol TE 100 g−1 dm of antioxidant capacity for 90 W and 180 W models, respectively). It turned out that microwave dehydration shortened the processing time and lowered the energy consumption compared to convective drying (a significantly reduced drying time of 92–99% with microwave dehydration). Blackberry fruits dehydrated at 240 W showed the shortest dehydration time (59–67 min), minimal energy consumption (0.23 kWh) and the most efficient diffusion (1.48–1.66 × 10−8 m2 s−1). [ABSTRACT FROM AUTHOR]

Tisane is a fruit or herbal infusion, commonly referred to as herbal tea. These products are consumed as part of a balanced diet, which is closely related to the trend of a healthier lifestyle. In this work, tisanes prepared from rosehip (R), and herbal mixtures containing rosehip/hibiscus flowers (R/H) and rosehip/hibiscus flowers/saffron (R/H/S) were studied. Rosehip was dried by the convective drying method at 40, 50 and 60 °C. Total phenolic content (TPC), total flavonoid content (TFC), total flavonol content (TFlC), total anthocyanin content (TAC), antioxidant properties (DPPH∙ and ABTS∙+ assays) and in vitro inhibitory potential toward α-amylase of tisanes were examined. The highest TPC (based on dry weight (dw)) was measured in tisane obtained from rosehip dried at 60 °C (37.84 mg GAE/g dw). Tisanes prepared from a R/H/S mixture had the highest values of TFC (4.66–6.13 mg QUE/g dw), TFlC (2.67–3.98 mg QUE/g dw) and TAC (1.35–2.27 mg Cy 3-glc/g dw). The highest DPPH∙ scavenging activity (53.42 mg TE/g dw) was measured in rosehip (dried at 60 °C) tisane, whereas tisane prepared from a rosehip (dried at 60 °C)/hibiscus mixture expressed the best ABTS∙+ scavenging activity (107.44 mg TE/g dw). All tisane samples expressed high inhibitory potential toward α-amylase, with the highest activity of 85.03% and 89.90%, measured for tisanes prepared from rosehip/hibiscus flowers mixture (rosehip dried at 50 and 60 °C, respectively). [ABSTRACT FROM AUTHOR]

Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study examined the convective drying of red cabbage at temperatures ranging from 50 to 90 °C. Mathematical modeling was used to describe isotherms, drying kinetics and rehydration process. The effects of drying conditions on energy consumption and microstructure were also evaluated. The Halsey model had the best fit to the isotherm data and the equilibrium moisture was determined to be 0.0672, 0.0490, 0 0.0379, 0.0324 and 0.0279 g water/g d.m. at 50, 60, 70, 80 and 90 °C, respectively. Drying kinetics were described most accurately by the Midilli and Kuçuk model. Also, the diffusion coefficient values increased with drying temperature. Lower energy consumption was found for drying at 90 °C and the rehydration process was best described by the Weibull model. Samples dehydrated at 90 °C showed high water holding capacity and better maintenance of microstructure. These results could be used to foster a sustainable drying process for red cabbage. [ABSTRACT FROM AUTHOR]

The spatial reaction engineering approach (S‐REA) was used to simulate hot air drying of sawdust. The studies extended the previous work reported in literature where the sawdusts were dried using hot air at 70 °C, 80 °C, and 90 °C. The simulated results were found to agree well with the experimental moisture content (R2 > 0.98) and temperature (R2 > 0.82) profiles. In a further analysis using S‐REA, the spatial profiles of moisture content and vapor concentration were generated to understand better the physics behind. Simulation also revealed that the external mass transfer resistance was more dominant as compared to the internal diffusion resistance. The vapor concentrations were observed peaked at time range of about 10 800– 18 000 s and dropped thereafter upon further heating. This observation could be supported by the variation in the vapor effective diffusivities where peak diffusivity values typically occur after most of the moisture evaporates towards the end of drying. [ABSTRACT FROM AUTHOR]

The drying kinetics of porous media are crucial for controlling the drying process, which is a vital component in many processes. A mathematical model of the drying process in a granular bed was developed using Whitaker's model, and its accuracy was verified through experimental results. The results indicated that the three stages of porous media drying are closely linked to the heat flow to the media and the latent heat of evaporation required by the liquid water inside it. Moreover, as the influence of gravity weakens and the capillary force strengthens, specifically due to the gradual decrease in the pore size of the bed, significant differences in the drying kinetics of the bed are observed, particularly in the third stage of drying, which is most affected. The onset of saturation in the third stage of bed drying varies with the pore size of the particles, with smaller pore sizes exhibiting an earlier onset. Additionally, the temperature change in this stage demonstrates the occurrence of secondary warming as the pore size decreases. [ABSTRACT FROM AUTHOR]

Researchers worldwide are studying thermal energy storage with phase change materials because of their substantial benefits in the enhancement of energy efficiency of thermal drying systems. A two-stage convective-vacuum impulsive drying plant is a technology for the manufacturing of chemical and food products with high quality and low energy costs. Energy consumption during the drying process is the main indicator in terms of economy. In this paper, a brief and focused review of the peculiarities of TEAs with PPCMs and opportunities of their application in such drying systems is done and discussed. The paper described the mentioned manufacturing system. The advantages of paraffin wax and thermal conductivity improvement techniques were demonstrated for their use as heat storage materials in CVID drying units. The results of similar previous studies were presented. The results of the experimental studies conducted by the researchers proved that the use of heat accumulators with PCMs increased the overall energy efficiency of drying systems. Finally, integration of TEAs based on modified PPCMs in the CVID system was recommended to intensify thermal energy, reduce thermal influence on the main indicators of the vacuum pump during the evacuation process, and decrease production costs.

ABSTRACTIn this investigation, the drying of Stevia rebaudiana leaves was carried out in a lab scale convective hot-air dryer at a varying temperature of 30–80°C to analyze the drying behavior, fit mathematical, Artificial Neural Networks (ANNs), and Adaptive Neuro-Fuzzy System (ANFIS) models to predict the drying kinetics of leaves. Further, dried leaf powders were analyzed for color properties, ascorbic acid and total phenol contents, antioxidant activity, water activity (aw), water solubility index (WSI), hygroscopicity (HG), density (bulk, tapped, and particle), bulk porosity, and flowability indices (Hausner ratio (HR), Carr index (CI), and angle of repose (α)). The results showed that ANFIS model with R2 of 0.9998, offers a more accurate forecast of the drying kinetics of leaves dried in a convective hot-air dryer in comparison to mathematical and ANN modeling. The convective drying significantly (p

Combined drying, an energy-efficient method that includes osmotic pretreatment in molasses and shortened successive lyophilization, was used to obtain celery root powder and incorporate it in the formulation of cookies, with the aim of obtaining a new product. Wheat flour was substituted with combinedly dehydrated celery root powder at levels from 0 to 30%, and optimization of the amount of wheat flour substitution regarding technological, sensory and nutritive characteristics was performed. The optimal level of 20% substitution was determined using Z-score analysis, from the aspect of the best nutritive improvement and the mildest adverse impact on the technological and sensory quality. In the second research phase, comparison of the cookies with the 20% celery root powder substitution, dehydrated by different methods, indicated that combined dehydration showed upgraded results in terms of the overall quality of the final product, for 28.85 percentile points higher than cookies with lyophilized and for 65.24 percentile points higher than cookies with the addition of convectively dried celery root powder. The cookie containing celery powder previously osmodehydrated in molasses had higher contents of analyzed minerals (1.2–3.3 times), total phenols (10.8%) and antioxidant activities (14% for DPPH and 4% for ABTS) compared to the cookie with lyophilized powder.

By increasing the permeability of the cell membrane of the treated material, pulsed electric fields (PEF) enhance the internal transport of various chemical substances. Changing the distribution of these components can modify the chemical and thermal properties of the given material. This study aimed to analyze the impact of PEF (1 kV/cm; 1 and 4 kJ/kg) applied to strawberries prior to drying by various methods (convective, infrared-convective, microwave-convective, and vacuum) on the chemical and thermal properties of the obtained dried materials (sugars content, total phenolic content, and antioxidant capacity (ABTS and DPPH assays); thermal properties (TGA and DSC); and molecular composition (FTIR)). PEF could have induced and/or enhanced sucrose inversion because, compared to untreated samples, PEF-pretreated samples were characterized by a lower share of sucrose in the total sugar content but a higher share of glucose and fructose. Reduced exposure to oxygen and decreased drying temperature during vacuum drying led to obtaining dried strawberries with the highest content of antioxidant compounds, which are sensitive to these factors. All PEF-pretreated dried strawberries exhibited a lower glass transition temperature (Tg) than the untreated samples, which confirms the increased mobility of the system after the application of an electric field.

In this work, a model sensitive to changes of process parameters such as temperature, air velocity, air initial relative humidity, and wet material layer thickness has been developed and verified by two different experimental methods. A laboratory convective batch dryer was used to measure drying behavior of 11 types of products at various process conditions to determine the model parameters. An independent solar drying system was used to experimentally verify the model. The model can predict drying kinetics at any point within a defined range of process conditions: model parameters were determined for temperature range of 40-50 °C, air velocity of 0.6-1.2 m/s, initial air relative humidity of 27-45%, and layer thickness of 4-12 mm. However, the model was verified also for extrapolated air velocity and humidity with good agreement between experimental and model data despite the use of a different independent experimental system. [ABSTRACT FROM AUTHOR]

The study presents the effect of blanching, ultrasound, and ethanol pretreatments on the drying characteristics and rehydration properties of carrot slices, comparison of modelling, and total energy consumption. After the pretreatments, water and solid loss and weight reduction were determined at the samples. The highest water loss (%), solid loss (%), and weight reduction (%) were detected at the samples immersed in 100% ethanol solution for 30 min with the values of 16.45, 4.67, and 21.12, respectively. All pretreatments accelerated drying rate and improved the rehydration rate of the samples. Pretreatment time had also positive contribution to drying rate and rehydration rate. The highest rehydration rate was observed at the samples immersed in 100% ethanol solution for 30 min as 5.81 ± 0.06. Additionally, moisture diffusion and mass transfer rate increased with the increment in drying rate. The highest moisture diffusivity (D) from Dincer and Dost model, effective moisture diffusivity (Deff) from Crank equation, and mass transfer coefficient (hm) values were calculated in the samples immersed in 100% ethanol solution for 30 min as 7.52 × 10−9 m2 s−1, 8.64 × 10−10 m2 s−1, and 8.15 × 10−7 m s−1, respectively. Pretreatments reduced the total energy consumption. The highest reduction rate was found in samples immersed in 100% ethanol solution for 30 min as 37.50%. Artificial neural network (ANN) modelling gave the best fitting with the highest determination coefficient (R2) values (0.9997–0.9999), lower the root mean square error (RMSE), and lower sum of square error (SSE) values (0.006740690–0.000900453 and 0.000818–0.00000162). [ABSTRACT FROM AUTHOR]

This study explores the unexploited potential of Artificial Neural Network (ANN) optimization techniques in enhancing different drying methods and their influence on the characteristics of various sweet potato varieties. Focusing on the intricate interplay between drying methods and the unique characteristics of white, pink, orange, and purple sweet potatoes, the presented experimental study indicates the impact of ANN-driven optimization on food-related characteristics such as color, phenols content, biological activities (antioxidant, antimicrobial, anti-hyperglycemic, and anti-inflammatory), chemical, and mineral contents. The results unveil significant variations in drying method efficacy across different sweet potato types, underscoring the need for tailored optimization strategies. Specifically, purple sweet potatoes emerge as robust carriers of phenolic compounds, showcasing superior antioxidant activities. Furthermore, this study reveals the optimized parameters of dried sweet potato, such as total phenols content of 1677.76 mg/100 g and anti-inflammatory activity of 8.93%, anti-hyperglycemic activity of 24.42%. The upgraded antioxidant capability is presented through DPPH●, ABTS●+, RP, and SoA assays with values of 1500.56, 10,083.37, 3130.81, and 22,753.97 μg TE/100 g, respectively. Additionally, the moisture content in the lyophilized sample reached a minimum of 2.97%, holding favorable chemical and mineral contents. The utilization of ANN optimization proves instrumental in interpreting complex interactions and unlocking efficiencies in sweet potato drying processes, thereby contributing valuable insights to food science and technology. [ABSTRACT FROM AUTHOR]

The goal of this research is to explore if a natural disinfectant can be made to replace the chemical disinfectant (Phenol) using an aqueous extract of Pistacia atlantica leaves. The leaves of the Atlas pistachio tree (Pistacia atlantica), a plant known for its medicinal powers and other uses, have piqued our curiosity. The study compares two techniques for drying Pistacia atlantica leaves: in a convection dryer and in the open air. We examine the effects of convective drying processes on the disinfecting effect of Pistacia atlantica leaves to those of drying in the shade in order to establish the most efficient technique of conservation. The goal of this study is to compare phenolic disinfectants to numerous natural disinfectants extracted from Pistacia atlantica leaves. The disinfectant has a surprising effect on the two bacterial strains investigated; development of Salmonella typhi and Staphylococcus aureus is significantly reduced. The influence of convective drying on the disinfecting effect of Pistacia atlantica leaves allowed us to remark that the disinfection effect reported on Salmonella typhimurium is increased after drying; by the first three aerothermal conditions: 40 °C/1, 1.5, and 2.5m3/s. This effect, on the other hand, is durable against Staphylococcus aureus after drying at 40 °C/2.5m3/s (disinfectant 4). [ABSTRACT FROM AUTHOR]

Moisture transport during food drying can be phenomenologically described by Fick's second law and by the so-called anomalous diffusion model. However, in the literature, many studies have shown the extensive use of empirical/semiempirical models (EMs/SEMs) to adjust experimental data for the drying of thin-layer foods. This research aims to perform a critical analysis of the most commonly used EMs/SEMs and compare them with Fick's second law and an anomalous diffusion model using two different sets of hot-air drying data. Two waste byproducts from the food industry, spent coffee grounds and passion fruit peels, were selected for analysis. The selected EMs/SEMs were found to be mathematically interrelated (i.e., some are a subset of others), and their appropriateness was incorrectly justified mainly by their statistical goodness-of-fit. As shown, it is highly recommended that researchers start analyzing drying data with phenomenological models. The extensive use of EMs and SEMs can be replaced by the anomalous diffusion model, which has a high capacity to adjust empirical data and a sound phenomenological description of the process. [ABSTRACT FROM AUTHOR]

This work aimed to develop numerical models to predict the moisture content and deformation of potato slices during convective drying (40–80 °C, 0.5 m·s−1). Three-dimensional slices were considered in cylindrical, cubic, parallelepiped, and prism geometries. The first classic model coupled the linear constant drying rate period with the analytical solution of Fick's law in spherical coordinates, evaluating the mass diffusion coefficients (4.2–15.5·10−10 m2·s−1), critical drying time (1640–5085 s), and critical moisture content (1.8–2.4 kg·kg−1). The Finite Element Method (FEM) was a more robust model, that combined momentum and mass transfer to three-dimensional solid deformation of polyhedrons by ALE method, evaluating the mass diffusivity (1.4–6.5·10−10 m2·s−1). The FEM model could predict the shrinkage due to water molar flux removal on moving solid boundaries and explain the pseudo-constant drying rate detected in experimental data. The developed models accurately described the drying of food materials with a high shrinkage ratio. [ABSTRACT FROM AUTHOR]

The study aimed to evaluate the influence of different drying techniques (Convective and microwave drying) on beef meat's drying kinetics and color parameters. While drying rates with convective drying vary between.005 and.009 g water/g dry matter, it varies between.014 and.166 g water/g dry matter for microwave drying. Among the model proposed, for the conditions applied in the microwave and convective drying methods, the Midilli model gave a better fit. The Arrhenius‐type equation calculated the activation energies of beef samples. Activation energies were 64.15 and 449.86 kJ/mol for convective and microwave drying, respectively. According to measured L*, a*, and b* values and calculated ΔE, C*, and h° values, convective drying at 80°C provided the closest color characteristics to fresh meat. Practical applications: Beef is a perishable food and storage conditions are very important. It is important to have information about the drying methods to be applied in the preservation of these foods in terms of process control. In this study, microwave drying and convective drying methods were examined and it was shown that microwave drying, which is one of the drying methods, shortens the processing time. However, in the convective drying method, color properties similar to the fresh product are provided. This research can provide theoretical guidance for further processing and preservation. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the effect of temperature and time of convective drying on the content of fructooligosaccharides (FOS) in apples, plums and strawberries to which FOS had been introduced by osmoconcentration. The share of oligosaccharides in total sugars was analyzed. In apple tissue, fructooligosaccharides were stable in the temperature range 40–80 °C during drying for up to 8 h. Convective drying of osmotically dehydrated strawberries caused FOS losses; the FOS retention after 8 h at 80 °C was 40%. In the case of plums, 40% retention was recorded after just two hours at 80 °C. Therefore, in the case of some fruits, obtaining a satisfactory level of fructooligosaccharides in the dried material with the assumed level of dry substance requires the determination of appropriate process parameters. [ABSTRACT FROM AUTHOR]

An environmentally ecological approach to the reuse of agro-industrial products in the food industry involves extracting biologically active substances or using them as supplementary products rich in dietary fibers. Apple pomace obtained after juice extraction presents a product rich in biologically active substances, soluble and insoluble fibers, organic acids, and minerals. Convective drying of apple pomace is an alternative method for long-term preservation by maintaining the biologically active substances. The research aimed to study the influence of temperature in the range of 60-80 °C on the drying of apple pomace to a final moisture content of 12.0±0.13% using the convective method, and the effect of temperature on the yield of bioactive compounds and antioxidant activity in Gold Delicious apple pomace. Changing the air temperature during convective drying from 60 to 80 °C reduced the drying time by 1.6 times and demonstrated a 1.4-fold increase in drying rate. The increase in the thermal agent's temperature led to an increase in the kinetic characteristic values; KIvalues increased by 4%, and KIIvalues increased by 44%. Spectrophotometric analysis demonstrated that apple pomace dried at a temperature of 70 °C had the highest total content of polyphenols, tannins, and carotenoids. Thus, the convective drying method of apple pomace in the temperature range of 60-80 °C exerts a significant influence on the composition of biologically active compounds in the apple pomace composition.

Drying is the simultaneous transfer of heat and mass, which is defined as the reduction of moisture in food. The aim of the study the drying performances of refractance window drying (95°C), fluidized bed drying (95°C, 2m3/m air velocity), and convective drying (95°C) were examined in the drying of Maraş green pepper (C.annuum). Drying performance was evaluated for effective diffusion coefficient (Deff), activation energy (Ea), Chroma (C) and total color change (ΔE). Drying curves were obtained by recording sample weights in 10-min periods. For the refractance window drying, fluidized bed drying and convective drying the time for the samples to reach 6-7% humidity level according to the wet base was found to be 70, 80 and 110min, and the effective diffusion coefficient was 6.49x10-10, 5.68x10-10 and 4.87x10-10 m2/s the activation energy was 53.54, 54.65 and 55.93kJ/mol, respectively. When the color properties are examined the Chroma value was determined as 18.23, 8.85 and 4.80 and the total color as 15.42, 26.29 and 30.33, respectively. It was seen that the closest value to the fresh product was in the samples dried with a refractance window drying. In the study, it was concluded that the use of a refractance window drying shortened the drying time by 14-36%, increased the effective diffusion coefficient, provided drying with lower activation energy, and better preserved the color quality in the production of dried Maraş green pepper.

One of the food preservation technologies is the drying process, which requires heat and is significantly energy-intensive, resulting in high costs. This caused the search for new design solutions for dryers, which requires continuous experimental research and the creation of new decision-supporting models for the optimization of drying processes. In this work, four models of the kinetics of convective onion drying were developed using Artificial Neural Networks (ANNs), taking into account pre-treatment before drying and the different temperatures of the drying agent. The moisture content in the dried material at a specific moment in time was taken as the dependent variable (ANN output). The following were accepted as independent variables (ANN inputs): drying temperature, initial sample thickness, initial moisture content, initial mass of the sample, time of drying, and material pre-treatment (no pre-treatment—blanching–osmotic dehydration). Four semantic models were formulated, the general Ann1 model taking into account all input variables and three detailed Ann2 models for individual types of pre-treatment. For the best Ann1, the MAPE values were 5.88–7.02% (for different data: Training, Test, Validation). For the detailed Ann2 models, the error values were more than twice lower. The MAPE values ranged from 1.14% to 3.12%.

Selected cultivars form part of the neglected and underutilized species (NUS), which can contribute to building sustainable and resilient food systems, particularly for food-insecure households. Advances in the drying of pumpkin cultivars are briefly reviewed. Background on drying, including pretreatment techniques, is discussed. It emerged that convective air drying remains the most used dehydration technique, while most pretreatment and drying approaches, although innovative and promising, have not yet been investigated for pumpkin species. Areas for future scientific investigations are also suggested. A closer look at the literature data revealed notable inconsistencies for pumpkin diffusivity data even for the same species. For this reason, independently of the review, new data are reported in this study for the Cucurbita Pepo cultivar in a quest for more accuracy and a wider temperature validity range. A convective dryer using hot air was used to determine the drying characteristics of pumpkin (Cucurbita pepo L.) slices at four different temperatures (40, 45, 50, 55 and 65) °C at a constant velocity of 1.5 m/s. The extended temperature range and the large number of experimental temperatures were meant to increase the newly reported properties’ accuracy and validity range. The Page model stood out as the most accurate approach to describe the investigated dehydration process. Pumpkin effective diffusivity was calculated as 3.74–7.30 × 10−9 m2/s while the activation energy was 21.07 kJ/mol based on experiments undertaken in the present study. The newly obtained data did not solve the problem associated with inconsistencies between the two data sets found in the literature for drying the same pumpkin cultivar. The reported data would be helpful in the accurate determination of diffusivity data instrumental for convective drying process modelling and optimization.

Strawberries are among the most consumed fruits due to their sensory attributes and nutritional richness. However, they are highly perishable due to their high moisture content, soft texture and high physiological activity after harvest. To overcome such challenges, this work evaluated the influence of osmotic dehydration (OD) using coconut sugar or sucrose solution and ethanol pre-treatment (ET) on the drying kinetics and qualitative parameters of strawberries. The strawberries were cut into 13 mm cubes. Osmotic dehydration was performed using osmotic solutions of sucrose or coconut sugar at 60% for 300 min. Non- and osmo-dehydrated samples were submitted to ET, totaling 6 treatments. Convective drying was carried out at 60 °C. ET reduced drying time and increased the preservation of acidity and anthocyanins in non-osmo-dehydrated strawberries. OD decreased the drying rate, shrinkage, acidity and anthocyanin content, and increased the hardness of the samples. The use of coconut sugar instead of sucrose during OD showed little influence on the drying kinetics of the samples, however, it resulted in browner and healthier dried strawberries. [ABSTRACT FROM AUTHOR]

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