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A superheated steam fluidized bed dryer (SSFBD) in a self-heat recuperative configuration has a great potential of improving thermal efficiency of a lignite-fired power plant by recovering both of latent heat of vaporization of water kept in the fuel and part of sensible heat during the fuel processing. However, the optimal design of the dryer requires the fundamental knowledge of drying characteristics in respect to the individual properties of the utilized fuel. Experimental investigation to determine the correlation between a specific coal properties originated from geological background and its drying characteristics is thus the major concern in this paper. The investigated lignite is a representative of Turoszow deposit in Poland. Experimental attempts unveiling drying kinetics were carried out for 5 mm and 10 mm diameter spherical samples in the superheated steam atmosphere in the temperature range of 110 °C–170 °C. Simultaneous and continuous measurements of changes in weight, surface and interior temperatures and appearance on each tested sample were carried out for describing drying behavior. Analytical investigation was applied to explain the drying characteristics, which are strongly affected by the individual properties of coal and the inherent ash composition.

Ultrasonic (US) maltreatment was performed before the vacuum far-infrared drying (VFID) of Codonopsis pilosula (CP) slices to investigate the effects of different US parameters on the drying characteristics and nutrients of CP slices. The grey correlation method with relative correlation degree (ri) as the evaluation measure was used to construct a model for the evaluation of the pretreatment quality of CP and to determine the optimal pretreatment conditions. The results showed that with the increase in US frequency and power, the drying rate increased. Under the conditions of US power of 180 W, frequency of 60 kHz and a pre-treatment time of 30 min, the drying time reduced by 28.6%. The contents of polysaccharide and syringin in dried CP slices pretreated by US increased by 14.7% and 62.0%, respectively, compared to the non-pre-treated samples, while the total flavonoid content decreased by 10.0%. In terms of colour, pretreatment had a certain protective effect on the red colour of dried products. The highest relative correlation (0.574) and the best overall quality of performance were observed at 180 W, 60 kHz and 30 min. Overall, US technology is suitable for the pretreatment processing of CP, which is of great significance to the drying of CP.

Demand for value-added spices all year round has warranted suitable post-harvest processing, since most are non-perennial by nature and perishable owing to enzymatic or maillard reactions and pathogenic microbial contamination. Drying involves the minimization of biologically active water up to the safe water activity level and increases the shelf life. An optimized drying technique is needed to be chosen critically because one particular drying condition suitable for a group of spices may be detrimental for others. Therefore, the current review emphasizes the permissible ranges of influencing operating parameters, comparative effects of several drying technologies on drying characteristics, and quality attributes of spices. The paper also provided an up-to-date technological advancement in novel hybrid and staged drying to alleviate the shortcomings of a solo drying technique. As drying is an energy-intensive process, pre-drying treatments and intermittent phenomena have also been explored for energy saving with better quality retention. The paper also highlights the significance of thin layer modeling for predicting the moisture transport phenomena during drying.

Large amounts of waste result from licorice mold rot; moreover, prompt drying directly influences product quality and value. This study compared various glycyrrhiza drying methods (Hot air drying (HAD), infrared combined hot air drying (IR-HAD), vacuum freeze drying (VFD), microwave vacuum drying (MVD), and vacuum pulsation drying (VPD)) that are used in the processing of traditional Chinese medicine. To investigate the effects of various drying methods on the drying characteristics and internal quality of licorice slices, their color, browning, total phenol, total flavonoid, and active components (liquiritin and glycyrrhizic acid) were chosen as qualitative and quantitative evaluation indices. Our results revealed that VFD had the longest drying time, but it could effectively maintain the contents of total phenol, total flavonoid, and liquiritin and glycyrrhizic acid. The results also showed that VFD samples had the best color and the lowest degree of browning, followed by HAD, IR-HAD, and VPD. We think that VFD is the best approach to ensure that licorice is dry.

In this study, fresh wolfberry in the current season was used as the experimental material, and a radio frequency (RF)-hot air combined segmented drying process was adopted for berry preservation. Ultrasonic treatment, hot water blanching, sucrose infiltration, ultrasonic and blanching, ultrasonic and infiltration, and NaOH and NaCl solution impregnation were used for pre-treatment of combined drying. Taking natural drying and conventional Na2CO3 dewaxing treatment as the control group, the effects of different pretreatment methods on drying characteristics, quality, and microstructure of wolfberry during combined drying were investigated. The drying time after ultrasonic and blanching pretreatment was the shortest (13.5 h), which effectively retained total flavonoids (1.79 mg/g) and enhanced their antioxidant activity (I = 60.78%). NaCl impregnation treatment significantly increased the total phenol content (8.77 mg/g), whereas the retention rate of soluble sugar (0.73 g/g), ascorbic acid (3.96 mg/100 g), betaine (2.72%), and other nutrients increased significantly after ultrasonic and infiltration treatment, with improved color, rehydration rate and microstructure over other treatment methods. The Weibull distribution function can accurately describe the RF-hot air combined drying process of wolfberry after different pretreatment, and simulated results were consistent with the results of the combined drying characteristic curve of wolfberry. The aim of this study was to explore suitable pretreatment methods to improve the drying rate and ensure the quality of dried products of wolfberry.

The present study investigated the drying characteristics and quality attributes of tomato pulp leather prepared using tray drying and hot air oven methods at temperatures of 60°C, 65°C, and 70°C. Sensory evaluation identified the best samples as T3 (hot air oven at 70°C for 6-5 hours) and T5 (tray dryer at 65°C for 8-9 hours), which exhibited superior drying and sensory characteristics according to a 9-point hedonic scale. Physicochemical analysis revealed that the moisture content, ash content, pH, total soluble solids (TSS), total sugars, and vitamin C content decreased gradually during the 45-day storage period for both T3 and T5 samples. The initial moisture content of the prepared tomato pulp leather was 18.5% and 18.6% for T3 and T5, respectively, which decreased to 17.9% for both samples by the 45th day of storage. The ash content, pH, TSS, total sugars, and vitamin C content also showed a decreasing trend during storage. The drying kinetics of the T3 sample showed a maximum drying rate of 0.33 g/min in the first hour, which decreased to g/min in the last hour, reaching an equilibrium moisture content of 18.5% after 7 hours of drying. The decrease in drying rate was consistent with the lower rate of moisture diffusion inside the tomato pulp leather compared to the rate of moisture evaporation from the surface. In conclusion, tray drying at 70°C for 7 hours proved to be the most effective method for producing high-quality tomato pulp leather, ensuring optimal drying rate, superior retention of nutrients, and good sensory attributes, making it suitable for commercial production of tomato-based snack products. Microbiological analysis revealed that yeast and mold counts increased gradually during the 45-day storage period. However, the microbial load remained within acceptable limits, ensuring the microbiological safety of the tomato pulp leather throughout storage.

This study investigates the kinetics and optimization of fluidized bed drying of onion slices using CCRD design by Response Surface Methodology, aiming to enhance drying efficiency and preserve product quality. The effects of drying process parameters viz., drying temperature (43.18, 50,60,70, & 76.82 °C), NaCl concentration (6.59, 10, 15, 20, & 23.41%) and bed thickness (1.636, 3,5, 7, & 8.362 mm) on dehydration ratio, rehydration ratio, color change, ascorbic acid content and overall acceptability were evaluated using multiple response optimization techniques. Optimization analysis revealed that a drying temperature of 70 °C, NaCl concentration of 20%, and bed thickness of 3 mm yielded the highest desirability value of 0.637. Under these optimized conditions, the dehydration ratio, rehydration ratio, color change, ascorbic acid content, and overall acceptability of onion slices were measured at 6.76, 5.87, 4.85, 8.06 and 4.02, respectively. Higher drying temperatures, NaCl concentrations and lower bed thickness were associated with faster drying rates. Various mathematical models, including Page, Logarithmic, Henderson and Pabis, Midilli and Newton models, were employed to characterize the drying kinetics, with the Page Model demonstrating superior fit to experimental data. Furthermore, quality parameters such as moisture content, water activity, ascorbic acid content, color change and crispiness of onion slices stored for three months under optimized conditions and packaged in different materials (LDPE and HDPE) were evaluated. Results indicate that the optimized fluidized bed drying process parameters effectively maintained the quality of onion slices during storage.

Solar dryers offer a sustainable and efficient method for drying many agricultural products, preserving their quality, color, and medicinal properties while minimizing energy consumption and environmental impact. Current research on henna processing reveals a significant gap in drying engineering studies, creating a critical barrier to process optimization and quality enhancement. While numerous studies have investigated henna’s physical and chemical characteristics, the engineering aspects of drying—including heat and mass transfer mechanisms, equipment design, and process parameter optimization—remain substantially understudied. This knowledge gap hinders the development of efficient, standardized drying methods that could improve product quality, reduce energy consumption, and increase production yields in commercial henna processing. So, during the present study, a direct solar dryer integrated with a photovoltaic system was used for drying Henna leaves at Aswan University, Egypt, during January 2025. Where a comparison study was conducted between the drying of Henna leaves by the developed direct solar dryer (DDSD) and open-air drying (OAD) at three-layer thicknesses of 2 cm, 4 cm, and 6 cm. The comparison study between both drying systems was established in terms of mathematical modeling, drying parameters, EMD, and economic analysis. The obtained results showed that the equilibrium moisture contents of Henna leaves samples dried in OAD and (DDSD) reach ranged between 2.52 and 3.23% (2.17 and 2.69%) on a dry base. Applying the DDSD to dry Henna leaves resulted in a reduction in drying time by approximately 7.14%, 13.33%, and 18.75% for layer thicknesses of approximately 2, 4, and 6 cm, respectively. Additionally, the EMD of the Henna leaves dried using the DDSD ranged from 2.84 × 10 –9 to 22.96 × 10 –9 m 2 /s. Furthermore, Lewis (Newton), Weibullian, and Page were the most appropriate mathematical drying models for Henna leaves at layer thicknesses of approximately 2, 4, and 6 cm, respectively, for dried samples by DDSD. On the other hand, the economic analysis revealed that the DDSD has the potential to generate substantial cost savings, amounting to 3,348 USD per year. Additionally, the payback period was calculated to be 0.077 years (less than one month), demonstrating the system’s rapid return on investment and economic viability.

To improve the drying rate and energy efficiency of Angelica sinensis, and maximally maintain quality after harvest, this study investigated the effects of temperature, ultrasonic power and ultrasonic frequency on the water migration, physicochemical quality and microstructure of Angelica sinensis by ultrasonic-assisted vacuum far-infrared drying. The results showed that compared with the samples without ultrasound, the material drying time after the ultrasonic-assisted far-infrared drying treatment was reduced by 18.2%~50.0%. Six different mathematical models were investigated and the Midilli model was the best-fitted model for all samples (R2 was 0.9956~0.9992, RMSE was 0.86 × 10–4~1.20 × 10–4). After ultrasonic treatment, the color, rehydration ratio, natural active ingredients, total phenolic, total flavonoid, polysaccharides, antioxidant capacity in samples were significantly increased (P < 0.05), and the shrinkage ratio of dried products was reduced significantly (P < 0.05). In addition, it greatly improved the internal structures of the dried products, and a uniform and regular honeycomb-like pore structure appeared inside the material after ultrasound. Therefore, ultrasonic-assisted vacuum far-infrared drying could improve drying rate and final product quality of Angelica sinensis.

Investigating the effect of drying temperature on the quality of the leaf and petiole parts of Figl is essential to use the leaf and petiole for food formulation or as food ingredients in developing countries to overcome the problem of food security. In this study, the effect of drying temperature (27.20 ° C ± 2.1 ° Cor in the sun, 40°C, 50°C, and 60°C) on drying rate, moisture diffusivity, color, and functional and chemical properties of the leaf and petiole was investigated. A two‐way analysis of variance was performed using a Statistical Analysis System to evaluate the effect of drying temperature on the drying characteristics, color, and chemical and functional properties of the leaves and petioles of Figl. The effective diffusivity values changed from 4 × 10 −12 to 8.2 × 10 −12 m 2 /s and 2.1 × 10 −08 to 4.9 × 10 −8 m 2 /s for the leaf and petiole of Figl, respectively, within the given temperature range. The bulk densities of the leaf and petiole of Figl were in the range of 0.20–0.35 g/mL and 0.27–0.41 g/mL, respectively. The results indicated that drying rate, moisture diffusivity, water activity, ascorbic acids, and delta decreased with drying temperature, whereas the functional properties of both the leaf and petiole increased with drying temperature. Comparatively, the petiole part showed better results in terms of functional and chemical properties than the leaf at all drying temperatures. From the results of the study, in terms of functional and chemical properties, drying of the petiole at 50°C for 120 min was found to be the optimum temperature for better quality.