The objective of this study was to evaluate the impact of various drying methods: freeze drying, vacuum drying, convection drying, and convection-microwave drying at microwave powers of 50 W and 100 W, along with process temperatures (40 °C, 60 °C, and 80 °C), on the drying kinetics, selected physicochemical properties of dried celery stems, and their grindability. The Page model was employed to mathematically describe the drying kinetics across the entire measurement range. Convection-microwave drying significantly reduced the drying time compared to the other methods. The longest drying duration was observed with freeze drying at 40 °C. The product obtained through freeze drying at 40 °C exhibited the least alteration in color coordinates, the highest antioxidant capacity, and the greatest retention of chlorophylls and total carotenoids. At a specific temperature, the quality of the product obtained from vacuum drying was slightly lower compared to that from freeze drying. The most substantial changes in the physicochemical properties of the dried product were observed with convection-microwave drying at a microwave power of 100 W. The drying method selected had a significant impact on the energy consumption of grinding, average particle size, and the grinding energy index of the dried celery stems; these parameters worsened as the drying temperature increased. The product with the best quality characteristics and disintegration parameters was achieved using freeze drying at 40 °C.

This research aimed to assess the hot air-assisted radio frequency drying (HA-RFD) of orange slices to evaluate the possibility of producing high-quality dried orange slices and overcome the problem of the long drying time and the high energy consumption. The effect of electrode distance (60, 70, and 80 mm) and number of slices (1-3 slices; 4 mm thickness per slice) on the HA-RFD of orange slices was evaluated. Orange slices in three layers with a total thickness of 12 mm and an electrode gap of 70 mm were picked to dry the orange slices in the shortest time. The quality of orange slices dried with HA-RFD was compared with those of HA-dried (HAD) and freeze-dried (FD) samples. HA-RFD allowed a 67% decrease in the time of drying of the orange slices (from 1170 to 390 min) when compared to HAD. Total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity, and color values were affected by the drying technique. HA-RFD showed higher TPC, TFC, and antioxidant activity than HAD. The FD samples showed the highest TPC (928 mg GAE/100 g dw), TFC (200 mg rutin/100 g dw), and antioxidant activity (67.58%). Moreover, the samples dried with HA-RFD resulted in the least color change in comparison to HAD and FD samples. Regarding vitamin C, FD samples were the best, followed by HA-RFD and HAD, respectively. Considering the final product quality, and the characteristics of drying techniques, especially drying time and drying rate, HA-RFD proved to be an alternative technique to the HAD for producing dried orange slices. PRACTICAL APPLICATION: HA-RFD was applied for the first time as an alternative technology to dry orange slices. The quality of orange samples dried by HA-RFD was compared with samples that dried by HAD and FD. The results indicated that the HA-RFD technique is a good method to dry orange slices by considering the drying characteristics and the final product quality.

Freeze-drying is a commonly employed method in the food industry to extend shelf life of products. However, this process remains time and energy consuming. While higher shelf temperatures accelerate the process, they also pose the risk of product damage. The microstructure of the product, influencing heat and mass transport, is a critical factor. This study aims to understand the impact of 3-dimensional (3D) structural parameters (pore size, shape and orientation) on local primary freeze-drying kinetics. Freeze-drying experiments were conducted with maltodextrin solutions (c1 = 0.05, c2 = 0.15 and c3 = 0.3 w/w) at different shelf temperatures (T1 = -11, T2 = -15 and T3 = -33 °C) with the use of a freeze-drying stage that allows in-situ visualization of the process inside a 4D-X-Ray computed tomography (XCT). The findings show the importance of understanding the microstructure in detail to optimize the sublimation time during the freeze-drying process. It is shown that for longitudinal pores, the orientation is a crucial parameter.

The influence of pre-treatments and different dehydrating temperatures on the drying dynamics, energy consumption, and quality attribute of yam chips was studied. Dehydration was executed employing a convectional oven dryer under four temperatures (50, 60, 70, and 80 °C) and 2.0 m/s air velocity. Yam chips were subjected to pre-treatment conditions of blanching (for 1, 2, 3, 4, and 5 min), citric acid (1 and 5 %), and ascorbic acid (1 and 5 %) solutions whereas, untreated yam chips samples served as the control. Dehydrated yam chips were further assessed for textural and colour properties. The drying rate was found to be faster at a higher temperature of 80 °C compared to lower temperatures of 50, 60, and 70 °C. The asymptotic model was established to be the suitable descriptive model for predicting moisture profile in the pre-treated yam chips based on highest R2 values (0.995-0.999), lowest χ2 values (4.422-18.498), and the root mean square error (RMSE) values (2.103-4.30). Pre-treatment and drying temperature had a significant (p < 0.05) impact on the hardness and colour of dehydrated yam chips. Blanching at 4 min yielded yam chips with most preferred texture (hardness: 81.3 N) and lightness (L*) in colour values (71.07 %) after drying compared to other pre-treated samples. The effective moisture diffusivity values of the pre-treated samples were in the range of 5.17294 × 10-9m2/s to 1.10143 × 10-8m2/s for 5 % citric acid samples at 50 °C and all pre-treated samples at 80 °C respectively. The general findings of the study indicated a least energy usage of 43.68 kWh as a cost-effective method of drying. Also, 4 min blanching, 5 % citric acid, and 1 % ascorbic acid at 80 °C were found to be the optimum conditions for pre-treating yam chips based on lower energy level consumption rates and improved sensory properties thus attributing to the quality of the dried yam chips.

This study aims to maximize the post-harvest quality of Moutan Cortex and reduce energy consumption. Radio frequency vacuum (RFV) technology was used to dehydrate Moutan Cortex in this study to investigate the effects of different drying temperatures, plate spacing, and vacuum degree on the drying kinetics, physicochemical quality, and microstructure of Moutan Cortex. The results showed that RFV drying shortened the dehydration time of the Moutan Cortex by 10.71-28.57% and increased the drying rate by 15.79-54.39% compared to hot-air drying. The best color (∆E = 6.08 ± 0.28, BI = 26.97 ± 0.98) and relatively high retention of polysaccharides, total phenolics, total flavonoids, antioxidant properties, paeonol, gallic acid, paeoniflorin, and benzoylpaeoniflorin contents were observed in the dried products of Moutan Cortex at a drying temperature of 50 °C, spacing of 90 mm, and vacuum of 0.025 MPa. Analyzing the microstructure, it was found that RFV drying could effectively inhibit the shrinkage and collapse of the cellular structure, and a regular and loose honeycomb pore structure appeared inside the samples, which contributed to the rapid migration of the internal moisture. This study can provide a theoretical reference basis for the selection and application of industrialized processing methods of high-quality Moutan Cortex.

Drying, as a critical step in the production of air-dried beef, has a direct impact on the quality of the final product. Innovatively, a composite system incorporating contact ultrasound (CU) and infrared radiation (IR) as auxiliary measures within a hot air drying (HAD) framework was built in this research, and the effects of these techniques on the drying kinetics, protein denaturation, and moisture transformation of air-dried beef were investigated. In comparison to HAD treatment, the integrated CU and IR (CU-IRD) system displayed marked enhancements in heat and moisture transport efficiency, thereby saving 36.84% of time expenditure and contributing favorably to the improved moisture distribution of the end-product. This was mainly ascribed to the denaturation of myosin induced by IR thermal effect and the micro-channel produced by CU sponge effect, thus increasing T2 relaxation time and the proportion of free water. In conclusion, the composite system solved the problem of surface hardening and reduces hardness and chewiness of air-dried beef by 40.42% and 45.25% respectively, but inevitably increased the energy burden by 41.60%.

Basil (Ocimum sanctum) leaves, commonly known as holy basil, have various health benefits due to their rich phytochemical content. However, fresh basil leaves face challenges related to their perishability and short shelf life. This study explores the use of edible coating, specifically chitosan, to extend the shelf life of basil leaves. Then basil leaves with chitosan coating were dried using microwave-assisted drying (MAD) method with variations of microwave power (136, 264, 440, and 616 W), mass of basil leaves (5, 10, and 15 g), and chitosan concentration (0, 2.5, and 5 %). The purpose of this study is to analyze the color, effective moisture diffusivity, and drying kinetics. Five mathematical models and seven error functions were used. The Avhad and Marchetti Model was identified as the most suitable model to describe the drying kinetics of basil leaves with chitosan coating. The Deff value increased with decreasing mass of basil leaves, decreasing chitosan concentration, and increasing microwave power. Deff values ranged from 0.001 to 0.002 m2/s. The thickness of the basil leaves also played a role in the fluctuation of Deff values. The highest ΔE value was obtained by 5 % concentration of chitosan. The chitosan coating, especially at a concentration of 2.5 %, showed discoloration indicating better preservation of the original color of basil leaves. In conclusion, this study shows that chitosan coating and MAD are effective strategies to extend the shelf life of basil leaves and can provide valuable insights for future applications in leaf drying or thin layer drying processes.

This study investigates the effectiveness of microwave-assisted hot air drying (MAHD) on corn drying process, water migration, dielectric properties, microstructure, and quality attributes. The research compares MAHD with conventional hot air drying (HAD), employing various microwave powers (1.2-3.6 kW) and hot air temperatures (35-55 °C). The results demonstrate that MAHD significantly reduces the drying time (by 30.95-64.29%) compared to HAD. Two-term model accurately describes the drying kinetics of corn. Microwave facilitated the transformation and more uniform distribution of water within the corn, observed through LF-NMR/MRI. Additionally, MAHD was effective in preserving the color and carotenoids, while reducing fat acidity, indicating better quality retention. Microstructure analysis revealed that MAHD increases microporosity and cracks in corn, which correlates with the observed enhancement in drying efficiency. These findings underscore the potential of MAHD as a superior method for drying corn, offering benefits in terms of reduced drying time and improved quality preservation.

This study provides a comprehensive analysis of the vacuum drying process for sludge drying, with a focus on optimizing energy efficiency and emission control. The study used both lab-scale static and pilot-scale vacuum drying systems to test various parameters like vacuum levels, heat source temperatures, and sludge thicknesses. The results indicated that optimal drying conditions were achieved at a vacuum level of -0.06 MPa, a heat temperature of 140 °C, and a sludge thickness of 3.4 mm, where the drying rate reaches 0.13278 g·g-1·min-1. The study underscores the significant influence of vacuum level, temperature, and sludge thickness on drying rates. The Page model was used to analyze drying kinetics, elucidating how changes in these parameters affect drying characteristics. Furthermore, the study also examined the pollutant emissions and energy efficiency at the pilot scale. It found that high vacuum environments could efficiently dry sludge using low-temperature heat source, leading to average energy consumption per unit evaporation of 3020.29 kJ/kg, which is lower compared to traditional methods. By harnessing low-grade industrial waste heat, this can be further reduced to 875.76 kJ/kg. This study offers valuable insights for sustainable sludge management systems, highlighting the environmental and economic benefits of vacuum drying technology. The detailed experimental approach and thorough analysis make a significant contribution to the field of the sludge drying.

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