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This study investigates groove-based controlled shape morphing in potatoes and carrots during drying. Stamps were manufactured and used to create groove depths (2 mm and 4 mm) onto the surface of the samples, which were then dried at various temperatures (45 °C, 55 °C, and 65 °C). Bending transformation, drying profiles, shrinkage, porosity, and surface morphology were measured as indicators of shape morphing. Potatoes exhibited a positive correlation between morphing transformation with increasing temperatures, reaching maximum angles of 244° (2 mm) and 263° (4 mm). Similarly, carrots showed similar observations with maximum bending angles of 145.1° (2 mm) and 153° (4 mm). The morphing in these samples was observed within the moisture content range of 1–0.5 kg water per kg solids and was concomitant with a substantial shrinkage of 80–84% in both samples. Grooving significantly affects the morphing, creating high-stress points and increasing the moisture transfer rate during drying. This study lays foundational knowledge for the controlled shape morphing of foods using drying technology. [ABSTRACT FROM AUTHOR]

Accurate prediction of moisture content is significantly crucial for ensuring process stability and product quality in the cylinder drying process. However, the drying process exhibits complex spatio-temporal characteristics and strong interference, which make accurate prediction challenging for the deep learning approach. To address this issue, this article proposes a new spatio-temporal attention-based bidirectional long-short temporal memory network (STA-BiLSTM) model for accurate moisture content prediction. First, Maximum Relevance Minimum Redundancy (mRMR) is adopted to identify optimal features highly related to moisture content. Secondly, bidirectional long-short temporal memory (Bi-LSTM) network is utilized to extract temporal dependencies from the sequential data. Subsequently, spatio-temporal attention mechanisms are designed to adaptively focus on the most relevant features and timesteps, enhancing the model's generalization ability. Finally, due to the harsh industrial environment, eXtreme Gradient Boosting (XGBoost) is adapted to improve generalizability and robustness. Extensive experiments on a real industrial dataset of the drying process demonstrate that the proposed STA-BiLSTM approach significantly outperforms alternative approaches for predicting moisture content, validating its effectiveness and superiority. [ABSTRACT FROM AUTHOR]

The demand for structural logs in wooden construction is substantial. However, logs, due to their inherent structural characteristics, are prone to developing checks during drying process. Kerf treatment is a practical and effective pretreatment technology for drying that can significantly reduce checking. Nonetheless, the optimal location for the kerf treatment remains unexplored. This study was designed to position the kerf based on the location of the pith and assessed the effects of single kerf, double kerf, and kerf-center boring treatments on log drying quality. The check ratio of kerf logs decreased significantly (p < 0.05). As kerf depth increased, the check ratio slightly decreased, while the moisture content (MC) difference between the core layer and surface layer increased. Additionally, the inclusion of kerfs in counterpoint positions exhibited a profound effect on reducing the check ratio. Eccentricity influenced the later drying stages of the logs. The check ratio of non-eccentricity logs tended to stabilize during the later drying period, while that of eccentric logs continued to increase. For eccentric logs, this study employed the counterpoint double-kerf process, resulting in a surface check ratio of 0.42%. For non-eccentric logs, utilizing a single shallow kerf significantly improved the surface drying quality, with a surface check ratio of 1.00%. [ABSTRACT FROM AUTHOR]

Monitoring and controlling the drying process is crucial, particularly for rotary dryers, to ensure optimal quality and efficiency. However, due to the process's nonlinear behavior, delays, and input disturbances, achieving this can be quite challenging. Previous research has not adequately explored online forecasting for rotary dryer control in real production settings. To bridge this gap, our study focuses on tobacco drying in an actual plant and presents a novel online prediction model for moisture content. We conducted comparative experiments to validate the model's practical application in production settings and demonstrate its effectiveness in enhancing drying control. Our approach, called MCTFormer, has proven to be scalable to high-dimensional problems. The results of our study indicate a 45% improvement in product quality through accurate prediction of outlet moisture content, better control over moisture levels, and reduced energy consumption. [ABSTRACT FROM AUTHOR]

Deformation and surface-checking defects in wood are closely related to the drying stress caused by shrinkage and moisture content (MC) gradients throughout the drying process. In this study, 50-mm-thick Masson pine (Pinus massoniana Lamb.) lumber was used as the research object. The drying stress caused by shrinkage behavior and MC changes was monitored, and the development of surface checks was observed during the drying process. Results showed that when the average MC was 60%, the free water in the surface layer of lumber evaporated completely, causing the MC to decrease below the fiber saturation point (FSP). The surface layer was subjected to tension stresses, resulting in surface checks which primarily distributed in the latewood area and propagated longitudinally. When the average MC was between 30% and 40%, the combined effects of the high MC gradient and anisotropic shrinkage of the wood resulted in further expansion of the checks. As the average MC decreased to less than 20%, the MC of the core layer lumber decreased below the FSP, resulting in the closure or even disappearance of most surface checks. The critical point (average MC of 60%) of drying stress was obtained, which can benefit the fine-tuning of kiln-drying schedules and improve the drying quality of Masson pine wood. [ABSTRACT FROM AUTHOR]

Wet beneficiation is a primary process employed by mining companies for iron ore concentration. The moisture content in the ore is a result of this beneficiation process, in addition to inherent moisture within the mineral composition. The moisture content of iron ore is a crucial parameter that requires effective control to ensure safe handling and transportation operations. Surface plasma treatment of iron ore has been investigated as a method to enhance the hydrophobicity of ore particles, thereby reducing residual moisture and water reabsorption by the particles. The samples underwent treatment using argon plasma and cold hexamethyldisiloxane (HMDSO) plasma, leading to the formation of a thin, silicon-rich surface layer. The treatments were applied to both polished ore samples and fine powder samples. The plasma treatment resulted in a reduction in moisture content and water absorption. The reabsorption of water decreased to approximately 35% of the pretreatment values. Contact angle measurements demonstrated that all HMDSO-treated samples exhibited hydrophobic behavior, with contact angles ranging from 110° to 120°, while the untreated samples exhibited angles close to 0°. Furthermore, atomic force microscopy (AFM) topographic imaging revealed a granular structure in the thin films. [ABSTRACT FROM AUTHOR]

A 2 mm thin layer of wet Spirulina platensis biomass was dried using two methods: refractance window drying (RW) and combined RW and FIR drying (RWF). The effect of drying temperature (40–60 °C) and proximity to FIR heaters (5 and 10 cm) was evaluated on falling rate drying characteristics. The moisture (Deff) and thermal (α) diffusivity coefficients were obtained in the range 1.728 × 10−8 to 5.289 × 10−9 and 1.322 × 10−8 to 4.169 × 10−9 m2 s−1, respectively (R2, 0.921–0.984). RW drying at ≥50 °C caused loss of color, phytopigments, and lipid peroxidation. At 40 °C, RW drying led to a long drying period (300.50 ± 3.53 min), poor drying rate (0.039 ± 0.002 g-H2O/min), lowest Deff and α (5.289 × 10−9 and 4.169 × 10−9 m2 s−1), and chlorophyll loss (32.2%). Combined RW and FIR drying at 40 °C and 5 cm proximity (RWF40-5cm) reduced drying time (15.1%), increased drying rate (27.8%), improved α (15%), and Deff (14.9%). RWF40-5cm dried biomass showed excellent retention of color (ΔE = 4.64 ± 1.32), protein (93.8%), γ-linolenic acid (90.1%), chlorophyll (87.9%), and phycocyanin (86.7%) from freeze-dried biomass (FD). Low-temperature RWF40-5cm drying could be a potential alternative to freeze-drying for effective and safe drying of heat-sensitive Spirulina platensis biomass. [ABSTRACT FROM AUTHOR]

Automated sorption balances are increasingly used to determine sorption isotherms of hygroscopic materials like wood. The sorption isotherms are constructed based on a number of equilibrium states between a specimen and the surrounding conditioning environment. In recent years, the uncertainty of these equilibrium states has been thoroughly discussed related to the time at constant environmental conditions needed to reach an adequate mass stability. However, uncertainties related to the conditioning environment are rarely discussed. This study describes a framework for analyzing and quantifying the effect of these uncertainties on the error in determined equilibrium moisture content. Various effects of the conditioning environment are analyzed, and the most important effects relate to the relative humidity (RH) in the instruments, both in terms of fluctuations in RH and an offset from the target value. The moisture error for these effects was found within the range 0.001–0.01 g g−1. [ABSTRACT FROM AUTHOR]

An X-ray density analyzer was used to determine the evolution of the moisture content (MC) profiles of a wood board during drying. Tests were performed on quartersawn boards of five wood species (oak, beech, Scotch pine, birch, alder) of two thicknesses (20 and 40 mm) dried at low temperature. The water vapor diffusion coefficient and liquid permeability of each wood species were determined by inverse analysis of the profiles using a computational model of coupled heat and mass transfer. These parameters were also measured by classical methods for validation purposes. The inverse method gives values close to the measured ones when using the evolution of the moisture profile, but also quite remarkably when using only the evolution of moisture at the core of the board. On the contrary, the method is less accurate when using only the average kinetics as experimental information. [ABSTRACT FROM AUTHOR]

The tobacco drying process in the cigarette production has an important effect on the final product quality. Therefore, the intelligent control methods have been widely investigated to ensure the stability of tobacco's outlet moisture content. The existing work mostly uses a relatively fixed set point of the outlet moisture content for different tobacco batches, which can lead to unforeseen product quality after several processes following the drying process and inaccessible amount of dehydration for the rotary dryer. Some tobacco moisture prediction methods have been studied recently while the relationship with the intelligent control methods remain largely unexplored. To deal with these issues, a novel method is proposed in this paper to identify the optimal set point of the drying outlet moisture content for each tobacco batch. An encoder-decoder model is first developed to forecast the post-drying moisture trajectory. Then, an adaptive filter with specially designed mechanisms and a confidence interval of the dehydration level are constructed to obtain the design constraints. Based on all above, a constrained optimization problem is formulated and solved by the genetic algorithm. Extensive experiments on 895 tobacco batches from a large cigarette factory are carried out, which involves both algorithmic evaluation and field test. It turns out that the proposed method achieves the superior performance and leads to an improvement of the product quality in real production. [ABSTRACT FROM AUTHOR]

Internal fluid flow during rice drying generates a stress gradient inside the material. If the stress gradient becomes too large or certain rice layers undergo glass transition under a significant stress gradient, stress cracks can form. In this study, modeling equations based on the Hybrid Mixture Theory were solved to simulate moisture transport and the viscoelastic stress that occurs during rice drying. The model's accuracy was evaluated using experimental moisture content data for two rice varieties: Pusa Basmati 1121 (MAEs: 0.0079–0.0162 g/g solids) and California M206 (MAEs: 0.0022–0.0061 g/g solids). Simulations were then conducted under continuous and time-varying drying conditions to determine the best drying strategy for minimizing stress crack formation. The results showed that gradually increasing the inlet air temperature by 5 °C every 5 min after an initial 28.5 min at 40 °C could reduce stress crack formation effectively while drying rice in only 38.5 min. [ABSTRACT FROM AUTHOR]

This work presents the prototype of a solar still that can be used as a complement to the traditional fossil fuel-based drying process of olive pomace, a thick sludge with a high moisture content that is massively by-produced in the olive oil industry. In addition, the system allows to recover distilled water, which can be used to irrigate the adjacent fields. The feasibility of the system for the target application was experimentally validated by designing a wireless data acquisition circuit for data collection, remote storage, visualization and analysis in real-time, with access possible from multiple devices. The results from a test campaign revealed that the moisture content of the olive pomace was effectively reduced from 67.17% to 39.90% in a 10-day period. A maximum drying efficiency of 16.64% was achieved, with potential for higher values under favorable weather conditions. The simplicity of the design and the low-cost solution can facilitate the future large-scale implementation of a similar system. [ABSTRACT FROM AUTHOR]

Dust emissions resulting from handling and transporting particulate materials are a problem in the mining industry. These emissions are more accentuated when the materials are not very humid because the reduced humidity makes the particles lighter and more susceptible to dispersion. Faced with these issues, this study proposes a methodology for the theoretical and experimental study of the drying process that occurs when iron ore fines are transported in wagons. The objective is to clarify the effect of surface moisture in the process of dragging wind iron ores on moist surfaces, such as those found when transporting iron ore in open wagons. In this study, wind tunnel tests were carried out using a wagon model with fine iron ore. A numerical CFD model was developed, and the results agreed well with the experimental results. The numerical model allowed the evaluation of the drying behavior for different values of air flow velocity and the prediction of the thermal conditions that influence the drying process. [ABSTRACT FROM AUTHOR]

Drying agricultural products allows farmers to extend the life of their products for a longer time. In recent years, nondestructive testing provided an alternative to moisture estimation in the dehydrated products industry. This work improves a methodology to estimate moisture based on pulsed thermography. Furthermore, to demonstrate the principle of operation, an infrared camera monitored evolution across time from dry leaves stimulated with a heat pulse; a heat-response curve was generated from the images sequence, and several regressions (linear, polynomial, exponential, among others) related the moisture content to the reaction to the heat stimulation. Cross-validated best results, 0.91, 0.085164, 0.0072529 and 0.068838 of R-squared, RMSE, MSE, and MAE, respectively, indicated that pulsed thermography is an efficient method to estimate the moisture content in neem (Azadirachta indica) leaves. [ABSTRACT FROM AUTHOR]

A structured approach to derive the water activity function of cellulose-based materials which describe the sorption behavior from dry fiber up to the fiber saturation point is proposed. The coupling between the sorption isotherm and the net isosteric heat of sorption is incorporated in a consistent way, which allows for coupled heat-diffusion problems to be solved. Three different models are derived, generalizations of the classic Oswin and Henderson isotherm models and a new model denoted LW. Experimental data from the literature is used to evaluate and compare model performance to the GAB model, and it is shown that generalizations of the classic Oswin, Henderson isotherms and the new LW model perform well. [ABSTRACT FROM AUTHOR]

Wood is widely considered to be a green and renewable building material. However, many of the challenges to using wood as an engineering material arise from the shrinkage and swelling behaviors during moisture content (MC) loss or gain. In this study, the shrinkage behavior of Queensland peppermint (Eucalyptus exserta F. V. Muell) wood was investigated at the macroscopic and cellular levels, and the interdependence between the two levels was explored. Results revealed that the tangential shrinkage of 2% and radial shrinkage of 1% was observed as MC decreased from about 60% to 32% in the macroscopic level. The most obvious anisotropic shrinkage was presented at the MC region of 32–22%, and the ratio of T/R was ranged from 1.6 to 1.75 below the fiber saturation point. At the cellular level, a considerable shrinkage was observed at MC of 42%. The cell wall was shrunk, but the lumen in radial (TR plane) was expanded with MC loss. The shrinkage of the total wood cell showed a linear relationship with MC. The shrinkage ratio of T/R was maintained around 1.5 below the fiber saturation point, indicating that the MC states have little effect on the anisotropic shrinkage. Besides, the shrinkage value at the macroscopic level was slightly smaller than the cellular level, but the anisotropic shrinkage showed an opposite trend. [ABSTRACT FROM AUTHOR]

A CT-scanner was used to scan 25 mm thick radiata pine boards during drying at 90 °C dry-bulb and 60 °C wet-bulb temperatures. Twenty transverse sections spaced by 10 mm along the length of the boards were CT-scanned six times during drying, and an elastic image registration technique was used to transform the CT-scanned images into moisture content profiles. The resulting images suggested that moisture content distributions did not always resemble diffusion-like moisture transfer mechanism, so common assumptions based on moisture content gradients as the main driving force for wood drying may not always be enough to explain the development of wet and dry zones coexisting below and above fiber saturation point. This paper discusses these findings based on both experimental CT-scanner data and the theory of water potential, which it is argued provides a more complete description of driving forces in wood drying. [ABSTRACT FROM AUTHOR]

Moisture content (MC) is an important indicator for evaluating the quality of agricultural products during drying. The rapid detection of MC helps to realize optimization of the configuration and online adjustment of drying process parameters, ensuring the quality of the final product and achieving green and efficient drying. As an effective tool for rapid and nondestructive detection of agricultural product quality, the use of hyperspectral/multispectral image (HSI/MSI) for MC evaluation of agricultural products/food during drying has been extensively studied. However, how to extract effective features from HSI/MSI and build a function relationship between these features and MC is still a challenging problem. The main work of this study is to develop a convolutional – long short term memory(C-LSTM) prediction model for MC evaluation of drying agricultural products based on HSI/MSI. The proposed C-LSTM model uses the convolution module to automatically extract the features of the HSI/MSI, and applies LSTM to explore the correlation information between the features extracted from each wavelength and the MC, thus finally realize the accurate prediction of MC. The carrot slices were dried with different drying time by using two different drying equipment (electric thermostatic drying oven drier and radio frequency- hot air drier (RF-HAD), and MSI of dried samples, covering the spectral range of 675–975 nm, were collected using multispectral imaging system based on a single shot. The best prediction results were achieved by C-LSTM models, with Rp of 0.966, RMSEP of 0.079(%) and RPD of 3.734 for oven drier, and Rp of 0.965, RMSEP of 0.085(%), and RPD of 3.604 for RF-HAD, compared to other four traditional models and LSTM model. The experimental results indicated that C-LSTM model is a potential modeling method for MC detection of agricultural products based on HSI/MSI. [ABSTRACT FROM AUTHOR]

This work aimed to clarify the influencing factors and mechanism of the moisture re-adsorption characteristics of dried lignite through a combination of experiment and simulation. By using the self-built experimental system, the effects of extrinsic environment and lignite's inherent properties on moisture re-adsorption characteristics were investigated. Mercury intrusion method was used to determine the pore structure and Fourier transform infrared spectroscopy was used to analyze the distribution of surface functional groups. Then, based on the quasi second-order kinetic model, the rate constant of moisture was calculated. Experimental results revealed that pore size and oxygen-containing functional groups are the main influencing factors. A close correlation between porosity and rate constant was observed. With the help of molecular dynamics simulation, moisture is found to be more easily adsorbed on carboxyl groups compared to hydroxyl groups. In the light of thermodynamics analysis and Dent model, the effect of extrinsic environment on moisture re-adsorption was examined. In low-humidity environment, humidity is the decisive factor for moisture equilibrium content, while it is temperature in high-humidity environment. The result of this paper will provide a systematic understanding of moisture re-adsorption of dried lignite. [ABSTRACT FROM AUTHOR]

Because of a lack of reliable models to predict the water activity (aw) of H2SO4 solutions, the standard sulfuric acid solution (SSL) method requires a periodic check and adjustment of the acid concentration to ensure that equilibrium will be reached at a predetermined aw point. To establish a reliable equation describing the aw of H2SO4 solutions, five molecular activity models, i.e. nonrandom two-liquid (NRTL), Wilson, universal quasi-chemical (UNIQUAC), modified NRTL-1 (M-NRTL 1) and modified NRTL-2 (M-NRTL 2), were introduced and compared in this study. Each of the models was applied to the 542 literature vapor-liquid equilibrium data points of H2SO4 solutions. The results showed that the NRTL model was the best with respect to its accuracy and simplicity. This NRTL model significantly simplified the implementation of the sulfuric acid solution method for MSI measurements. Excellent agreement was found between this simplified SSL method and the conventional saturated salt solution (SSS) method for MSI measurements of both microcrystalline cellulose (MCC) and apples at 25 °C. Therefore, this newly improved SSL method, based on the NRTL model, could be an inexpensive, convenient and reliable alternative to the conventional SSS method in food MSI measurements in the future. The NRTL model can accurately predict the aw of H2SO4 solutions. The NRTL model can significantly simplify the known sulfuric acid solution (SSL) method. This improved SSL method is valid and reliable for use in MCC and apples. A working table of the aw of H2SO4 solutions was developed for ease of use. [ABSTRACT FROM AUTHOR]

H2SO4 and glycerol solutions are two commonly used unsaturated solutions for humidity control in moisture sorption isotherm (MSI) experiments. In a previous study, we reported an accurate water activity (aw) model for H2SO4 solutions for use in MSI measurements. The current study aimed to construct a reliable aw model of glycerol solutions and apply it to MSI measurements. Our research showed that the Wilson model could accurately predict aw of glycerol solutions, with a root mean square deviation of 0.0096 aw, in the concentration range of 9.47–99.62% glycerol by mass and in the temperature range of 0–100 °C. This aw model considerably simplified the conventional glycerol solution (GSL) method. Finally, the reliability of this simplified GSL method was tested by comparing with the standard saturated salt solution method for MSI measurements of microcrystalline cellulose and apple at 25 °C. This proposed GSL method, based on the Wilson model, might be a reliable, safe, and inexpensive alternative method for MSI measurements in food areas in the future. The Wilson model can precisely predict aw of glycerol solutions. The Wilson model can remarkably simplify the known glycerol solution (GSL) method. The simplified GSL method is reliable and applicable for use in microcrystalline cellulose and apples. A working table of aw of glycerol solutions was generated for convenience of use. [ABSTRACT FROM AUTHOR]

Moisture removal during bio-drying with an auto-controlled aeration system was investigated under four combined aeration strategies for a set range on exhaust gas temperature and air-flow direction. The exhaust gas temperature was kept stable within the set range by varying the air-flow rate under upward aeration, although there was a horizontal temperature gradient in the waste layer, irrespective of air-flow direction. This aeration system enhanced drying performance such that 74.7% of initial moisture weight was removed for 14 days, on average. Moreover, inversion of the air-flow direction induced as much uniformity of the vertical moisture distribution as turning the waste matrix. We evaluated moisture removal in the bio-drying process in terms of performance and efficiency and confirmed that the air-flow rate significantly affected both indicators. To achieve rapid and efficient moisture removal during bio-drying, it is important to control the air-flow rate in response to the exhaust gas temperature to fully utilize metabolic heat for evaporation. [ABSTRACT FROM AUTHOR]

Shrinkage is an important factor affecting the final quality of Radix Paeoniae Alba (RPA) slices during drying processes. In this study, drying experiments were carried out to determine the effect of the initial drying of roots on RPA slice shrinkage. The RPA root was initially dried to an initial moisture content (M0) and then cut to slices that were sequentially dried to the targeted final moisture content to decrease the shrinkage symptoms of RPA slices. In this approach, M0 should be high enough to easily slice the roots without being cracked and as low as possible to decrease the deformation of the slices during the final drying. Results showed that the shrinkage ratio of the RPA slices decreased with the decrement of M0 and the increment of drying temperature (T). At a high T (70 °C), high M0 (up to 0.45 d.b.) could be effectively used to slice and dry RPA roots with less shrinkage in the final product, whereas at a low T (50 °C), low M0 (≤ 0.35 d.b.) should be used. A 3D model with moving boundary was also developed to simulate the drying and shrinkage process of RPA slices. Simulation results showed that the model successfully predicted the moisture content and temperature of RPA slices and simulated their shrinkage behavior during drying, with reasonable accuracy. [ABSTRACT FROM AUTHOR]

The moisture content of tobacco, as an important characteristic which should be kept at a desired level to maintain consistent product quality in drying process, is difficult to perform the direct measurement and anomaly detection due to its large delay in actual process. Therefore, an intelligent real-time detection method is an urgent and challenging task in ensuring the product quality. This paper proposes a time-domain raw data conversion method along with a novel deep learning architecture called multi-hierarchical convolutional neural network (MHCNN) for moisture prediction, in which the proposed architecture automatically learns multi-hierarchical features from transformed image-like data and simultaneously performs online prediction. Experiments are conducted on the real production data from the cigarette factory and the presented model performs well on overall testing dataset. Specifically, the MAE, RMSE and R2 of normal production batch can reach to 0.0131, 0.0244, and 0.9721 respectively, which are far superior to the estimation of experience and other alternatives. It demonstrates that the proposed online prediction strategy can simultaneously perform multi-hierarchical feature extraction and moisture online prediction with high precise to eliminate the detection delay for process optimization and control. [ABSTRACT FROM AUTHOR]

Lignite has great potential for use as one of the major sources for both energy and chemical feedstock. However, its high moisture content extremely restricts its use. The moisture re-adsorption of the dehydrated lignite has been studied increasingly in recent years. This review focuses on the issue of the high moisture re-adsorption capacity of lignite dehydrated using various drying techniques. Experimental and simulative studies on the effects of oxygen-containing functional groups, pores, and other factors on the moisture re-adsorption of the dehydrated lignites from different countries or districts and exploratory work on inhibiting the moisture re-adsorption of the dehydrated lignite are reviewed in detail. Of particular interest is a proposal for a mechanism of moisture re-adsorption on the dehydrated lignite. Additionally, future investigations on inhibiting the moisture re-adsorption of the dehydrated lignite are advised. [ABSTRACT FROM AUTHOR]

A hyperspectral imaging system was employed to develop a general model for monitoring moisture distribution of four types of vegetables undergoing microwave-vacuum drying (MVD). Partial least squares regression and least squares support vector machines were developed based on full and optimal wavelengths, while the multiple linear regression (MLR) was built from optimal spectral data. Genetic algorithm-MLR (GA-MLR) model with a determination coefficient in prediction of 0.974 and a root mean square error in prediction of 4.70% was used for the moisture content visualization of four MVD vegetables. Moisture distribution maps indicated a similar center drying pattern among different vegetables, while the conner effects occurred in celery stalks and spinach leaves. Additionally, evaluations of color changes of the vegetables using the computer vision system indicated a decrease of the browning index in dried carrot slices and celery stalks but an increase in potato slices and spinach leaves. [ABSTRACT FROM AUTHOR]

Since the loading of electrodes for Li-ion batteries with an excessive amount of moisture affects the performance of the cells, the moisture is partly removed in a post-drying process step. The drying time is thereby controlled by the amount of moisture that has to be removed as well as the mass transport kinetics of water. This mass transport kinetics is limited by various mass transport resistances, which in turn can be influenced by individual dryer settings. In this paper, we investigate water-based anodes for Li-ion batteries as well as selected materials, and distinguish between different possible mass transport resistances that affect the drying time. Determined diffusion coefficients can be used in future modeling of the post-drying process. Special consideration needs to be bestowed upon the mass transport of water in the polymeric binders, since earlier investigations revealed that the moisture uptake of the anodes is particularly caused by sodium carboxymethyl cellulose (Na-CMC). This high water uptake by the binder in water-based electrodes leads to a polymer film drying process within the porous structure of the electrode. The diffusion of water in layers of binder is particularly dependent on the concentration as well as the temperature of the binder. [ABSTRACT FROM AUTHOR]

With the development of optical and spectroscopy sensors, hyperspectral technology has been wildly used in the quality monitoring of food processing. Drying is one of the most commonly used processes in food processing. Moisture content (MC) and moisture distribution (MD) are very important in evaluating a drying technique and the quality of dried final products. This study aimed to investigate the feasibility of using hyperspectral data (387.1–1024.7 nm) to predict MC and realize visualization of MD during constant and intermittent drying, leading to determine the optimal drying in a nondestructive and convenient way. Two characteristic wavelength (CW) selected methods were established: regression coefficients (RC) and two-dimensional correlation spectroscopy (2 D-COS), resulting in 4 (405.7, 513.2, 606.9 and 967.1 nm) and 3 (402.3, 511.5 and 965.2 nm) CWs, respectively. The partial least-square regression (PLSR) models (FW-PLSR, RC-PLSR, and 2 D-COS-PLSR) for MC prediction were built using FW and CW. Comparing the performance of the models, RC-PLSR model was determined to be optimal (variable number = 4, RC2=0.9731, RCV2 = 0.9703, RP2=0.9662, RMSEC = 0.0335, RMSECV = 0.0355, RMSEP = 0.0353, and RPD = 5.5198). The visualization maps for MC and MD were generated by the optimized model, which revealed that the intermittent drying process of drying for 4 h with 1 h tempering could improve the product quality of scallops. This study proposed the method for predicting MC and MD and highlighted the potential of hyperspectral technology in the monitoring of constant and intermittent drying in scallop. [ABSTRACT FROM AUTHOR]

This work investigates how process control of moisture content in continuously operated convective dryers for particulate bio-materials influences the product's activity. As case study drying of baker's yeast in a fluidized bed dryer is considered. Superiority of controlled process operation over un-controlled operation with respect to uncertainties in the falling-rate drying period as well as process disturbances is demonstrated simulation studies. Furthermore, limitations in controllability of activity are pointed out and future actions are proposed. [ABSTRACT FROM AUTHOR]

The industrial utilization of natural bamboo has been plagued by cracking that are closely related to the relationship between the moisture content (MC) and drying shrinkage. To reveal the cracking mechanism, three relationships between environmental factors and drying rate (DR), MC and shrinkage strain, strain variation and cracking were investigated during the air seasoning (AS) of the 6-meter-long bamboo in free state. The DR decreased significantly affected by hygroscopicity, and a model considering hygroscopicity and environmental factors was proposed for estimating the DR. Natural bamboos were prone to cracking between 42% and 12% MC. The top cracking was earlier and more than other parts, which is caused by initial lower MC and absence of end diaphragm. There were significant differences in shrinkage strain between different tissues and sites. This work reveals the drying characteristics, the law of strain variation, and cracking mechanism in bamboo AS process, which is vital to the prevention and control of drying defects. [ABSTRACT FROM AUTHOR]

We experimentally report evaporation characteristics from leaf-like surfaces having low open (exposed) area ratio. Even at much lower (1–10%) exposed areas, higher transpiration rates (60–70% compared to a bare water source) are sustained by a leaf. We mimic stomata, tiny openings present on the leaves using holes punched on silicon wafers (SW). The leaf-mimics have different opening diameters, ranging from 50 μ m to 400 μ m , but nearly the same open area of ∼ 25 m m 2. The leaf-mimic with the smallest opening size was found to evaporate the most, while for the larger opening sizes it seems to decrease. In all the cases, evaporation ratio (ratio of the evaporation rate from the leaf-mimic to that of from a bare water surface at the same net incident radiation) increased with decreasing pore sizes; we compute this ratio based on three different definitions including one for the isothermal cases. In non-isothermal cases, we recognized that the variation in surface temperature led to nonlinear variation in the surface water vapor concentration. The effect of increased surface temperature, compared to a bare water surface in similar conditions, is missing in defining the evaporation ratios in previous approaches and thus we include it. [ABSTRACT FROM AUTHOR]

In this paper, the semi-theoretical kinetics equations were proposed and the electro-dewatering experiments of sludge were conducted to analyze the kinetics laws of electro-dewatering under constant voltage and constant current. The results showed that the decline rate of moisture content remained stable under constant current, while the decline rate of moisture content kept decaying in the operating mode of constant voltage. No matter in what kind of operating mode, the change in decline rate of moisture content was consistent with that of filtrate flow rate, both of which were essentially dependent on the current. The follow-up electro-dewatering tests under constant voltage were carried out by using three different kinds of sludge to understand the mechanism of electro-dewatering. The results showed that the main parameters that controlled the electro-dewatering behavior were measured current, conductivity and zeta potential of sludge. When treated at 30 V, sludge C reached the lowest moisture content, owing to its higher conductivity and zeta potential. However, the poorer electro-osmotic effect of sludge C led to its higher average unit energy consumption. By comparison, an increase of applied voltage was more effective for electro-dewatering process of sludge C but at the expense of higher energy consumption, while sludge A and B were more inclined to improve the electro-dewatering effect by extending the dewatering time. Finally, the derived equations were demonstrated by the experiments, which could provide guidance for the practical applications. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the storage stability of dried cranberry powders based on the moisture sorption isotherms and glass transition temperature (Tg). Microwave-vacuum dried (MWVD) and hot air convective dried (HACD) cranberry powders were kept at storage temperatures (TS) of 10, 20, 30 °C. Based on the coefficient of determination (R2 > 0.99) and percentage global relative square error (1.2 < GRSE < 3.7%) of the approximation it can be stated that Guggenheim–Anderson–de Boer (GAB), Lewicki and Peleg models well described the relationship between water activity (aw) and the equilibrium moisture content (EMC) of dried material. Storage temperature and drying method did not significantly influence the sorption isotherms of cranberry powders. The variations in Tg vs. aw and Tg vs. EMC were adequately predicted by Khalloufi, linear (R2 > 0.98; 1.8 < GRSE < 13.7%), square and Gordon–Tylor (R2 > 0.89; 18.0 < GRSE < 34.6%) models, respectively. The optimum aw, EMC and TS for storage of MWVD and HACD cranberry powders were 0.30, 0.056 g H2O·g−1 DM, ≤ -2.6 °C, and 0.30, 0.055 g H2O·g−1 DM and ≤ -0.7 °C, respectively. [ABSTRACT FROM AUTHOR]

Intermittent drying is considered as one of the alternative drying methods to save energy and improve product quality. In this study, low-field nuclear magnetic resonance (LF-NMR) has been used to evaluate the dynamics of the water mobility and distribution during the intermittent drying process. The results have shown that the first drying period of 1 hour is not effective to induce the moisture self-diffusion in the tempering period. After drying of 2 hours, the moisture transport in the tempering period became rapid and the changes reflected on T2 curve became visible clearly. The T2 values decreased gradually during drying, which indicated the reduced water mobility. As the tempering period progresses, the T2 continuously reduced and varied, which indicated the redistribution of water molecules during the tempering period. With the prolonged tempering time, the changes in T2 tended to be more stable, but it cannot reach equilibrium when there was concentration gradient. It was worth noting that A21 and A22 had an opposite trend during the intermittent drying process, indicating that the mobility of the bound water was increased during the intermittent drying. Effectively also when the samples were dried with the intermittent drying strategies, the vitamin C retention has increased by almost 50% relative to that of the continuous mode. [ABSTRACT FROM AUTHOR]

In food processing, drying is an important unit operation for preserving the product quality by moisture content reduction. However, some drying processes suffer from technical and economical drawbacks mainly related to low process efficiency, high energy cost, and product quality degradation. Drying food products using dehumidified air at low temperature is one of the smart options to solve the abovementioned problems. This review presents some challenges and opportunities for dehumidifying air to enhance the driving force for drying. The potential of some solid materials, namely zeolite, silica-based materials, activated carbons (ACs), and other biomass-based materials, as moisture adsorbents for air dehumidification in food drying applications is also discussed. This paper also comprehensively reviews the recent perspectives and emerging technologies in the development of efficient adsorbent materials for air dehumidification, moisture adsorption–desorption characteristics, and its potential for food drying application. Moreover, some crucial parameters for advancing the research and development of adsorptive dehumidification systems are criticized in this review paper. [ABSTRACT FROM AUTHOR]

Water migration plays an important role in the wheat-based products manufacture and is not only related to starch and gluten content, but also to the structure formed by gluten. Various gluten structure samples were constructed in powder and extrudate form. Density, moisture sorption isotherms, water migration rate, water binding energy of powders and extrudates were investigated. The average density of extrudates increased from 856 to 1321 kg m-3, which existed a linear relationship with starch content. The shrinkage of the starch displayed higher than that of gluten when the water activity change from 0.35 to 0.11. The monolayer moisture content (M0) of the starch was higher than that of gluten. Starch powder had a higher desorption rate and lower sorption rate than gluten, however, starch extrudate had higher sorption and desorption rates than gluten, for the extruded gluten has formed a network structure. The binding energy of the starch was higher than that of gluten, and which of all samples was close to zero when moisture content was greater than 20%. Those information on moisture migration behavior may guide to optimize the drying processing with balance of noodle quality, noodle yield, and energy consumption. [ABSTRACT FROM AUTHOR]

The moisture content of iron ore must be suitable for safe handling and transporting operations. Here, the characterization and drying kinetics of iron ore concentrates were presented and recommendations for the design of dryers were discussed. Pellet feed and sinter feed showed a high amount of fine particles (8-20% dp<10 mm) and a low pore volume (Vpore<10 mm). An ample period for drying at constant rate was observed (critical moisture around 5%), indicating that drying processes aiming at a moderate moisture reduction could be performed within this period. These findings contribute to the design of dryers and support economic operations. [ABSTRACT FROM AUTHOR]

The moisture content of iron ore must be suitable for safe handling and transporting operations. Here, the characterization and drying kinetics of iron ore concentrates were presented and recommendations for the design of dryers were discussed. Pellet feed and sinter feed showed a high amount of fine particles (8–20% dp<10 µm) and a low pore volume (Vpore<10 µm). An ample period for drying at constant rate was observed (critical moisture around 5%), indicating that drying processes aiming at a moderate moisture reduction could be performed within this period. These findings contribute to the design of dryers and support economic operations. [ABSTRACT FROM AUTHOR]

Drying is a simple but important method to utilize asparagus by-products for future use. We investigated the changes in LF-NMR spectra during the drying of various asparagus by-products including leaf, hard-stem and root. A shift of major peak in LF-NMR spectra toward left was noticed with the progress of drying. Also, a decrease in peak area for free water and an increase in peak area for strongly bound water were also observed until it reaches the safer level of moisture content. An end-point drying is the point when the material water activity is below 0.6, which was determined through the observation of a major peak at relaxation time below 1 ms. Correlation coefficient values suggested that both the moisture content and water activity were positively correlated with total peak area (0.892 to 0.991, and 0.860 to 0.975 respectively) and major peak area (0.876 to 0.987, and 0.900 to 0.963 respectively), while negatively correlated with the peak area for tightly bound water (-0.620 to -0.825, and -0.743 to -0.990, respectively). Since LF-NMR spectroscopy is quick and nondestructive method, in comparison to the conventional methods for moisture content or water activity, the observation of a major peak below 1 ms relaxation time indicated the drying end-point for these by-products. [ABSTRACT FROM AUTHOR]

Water migration plays an important role in the wheat-based products manufacture and is not only related to starch and gluten content, but also to the structure formed by gluten. Various gluten structure samples were constructed in powder and extrudate form. Density, moisture sorption isotherms, water migration rate, water binding energy of powders and extrudates were investigated. The average density of extrudates increased from 856 to 1321 kg m−3, which existed a linear relationship with starch content. The shrinkage of the starch displayed higher than that of gluten when the water activity change from 0.35 to 0.11. The monolayer moisture content (M0) of the starch was higher than that of gluten. Starch powder had a higher desorption rate and lower sorption rate than gluten, however, starch extrudate had higher sorption and desorption rates than gluten, for the extruded gluten has formed a network structure. The binding energy of the starch was higher than that of gluten, and which of all samples was close to zero when moisture content was greater than 20%. Those information on moisture migration behavior may guide to optimize the drying processing with balance of noodle quality, noodle yield, and energy consumption. [ABSTRACT FROM AUTHOR]

This study aimed to compare the moisture content (MC) uniformity of ginger slices subjected to microwave-vacuum drying (MVD) and hot-air drying (HAD) and discriminate MVD ginger slices from HAD ones (MC < 20 g/100 g) by NIR hyperspectral imaging (HSI). MC maps were visualized by a simplified partial least squares regression (PLSR) model with the determination coefficient in the prediction of 0.971. The hole effect of the semivariogram in MC maps indicated the moisture difference between the center and the edge. Furthermore, principal component analysis (PCA) of the semivariogram indicated a similar degree of moisture dissimilarity between MVD and HAD ginger slices with MC lower than 60 g/100 g. Partial least squares-discriminant analysis (PLS-DA) and support vector machines (SVM) classifiers were respectively applied to the datasets of spectral reflectance at full wavelengths and nine optimum wavelengths selected by PCA, and variances in E-W and N-S directions to build classification models. The highest correct classification rate (CCR) of 95.1% was achieved by applying PLS-DA or SVM to the dataset of full wavelengths, while CCR of 90.3% was obtained for SVM model based on the dataset of nine selected wavelengths, confirming the potential of HSI spectra for MVD and HAD ginger slices discrimination. [ABSTRACT FROM AUTHOR]

Hybrid mixture theory-based multiscale fluid transport equations were solved for drying of strawberries and carrots to predict the moisture transport during the process. The fluid transport equation was coupled with the selected product quality and nutritional attributes to predict changes in stress distribution, shrinkage, color parameters, and ascorbic acid/β-carotene content. The fluid transport equation includes a non-Fickian term that incorporates the effect of glass transition on moisture transport. A transformation between Eulerian and Lagrangian coordinates was used to include the moving volume effects due to shrinkage. Good agreements between the experimental and the predicted values of moisture content (RMSE ≤ 0.095, RMSE ≤ 0.579), color parameters (R2 ≥ 0.958, R2 ≥ 0.934), and volume changes (R2 ≥ 0.871, R2 ≥ 0.865) were obtained for strawberries and carrots, respectively. Drying in the vicinity of glass transition regime led to sharper moisture profiles, indicating non-Fickian transport. However, drying at temperatures higher than glass transition temperature of strawberries and carrots resulted in Fickian characteristics-round and smooth drying profiles for drying at 70 °C. Drying at higher temperature caused higher loss of quality attributes; it resulted in samples with lower color parameters and ascorbic acid or β-carotene content. Higher drying temperature resulted in greater shrinkage and deformation throughout the structure, leading to cracks and openings and faster degradation in quality attributes. The developed model would allow improving quality attributes and finding optimum processing conditions of strawberries and carrots. [ABSTRACT FROM AUTHOR]

In this study, the spin–spin relaxation time (T2) distributions of free water and bound water, as well as the moisture content (MC) profiles of MUF resin-impregnated poplar wood (Populous tomentosa) sample (RI) were investigated by low-field nuclear magnetic resonance, with the aim of providing insights into how MUF resin impregnation affects the moisture states and moisture transport in modified poplar wood during drying. The T2 curves demonstrated that the resin treatment did not increase the number of peaks in the T2 distributions, but affected the T2 value as compared to the control. Above the fiber saturation point (FSP), the T22 (corresponds to the free water in wood rays and wood fibers) of the RI sample exhibited an increase compared to the control, while the T23 (corresponds to the free water in the vessels) was almost unchanged. Below the FSP, a shorter T21 (corresponding to the bound water) of the RI sample was observed compared to the control. The drying curves and MC profiles indicated a significant difference in the moisture transport in the RI sample as compared to the control. The gradually cured resin system in the wood surface layer during drying provided a barrier for the transfer of water in the center layer toward to the surface, causing the resin curing reactions in the surface and core layers to be out of sync. Therefore, a more significant MC gradient was observed for the resin-impregnated sample. [ABSTRACT FROM AUTHOR]

Suitable fissures in kernels and the golden yellow color are the desired visual quality to evaluate germinated brown rice (GBR) subjected to drying processing. To improve the visual quality of GBR dried in a continuous microwave dryer, the effects of microwave intensity (1–5 W/g), air velocity (0–2 m/s), drying duration for per drying pass (2–10 min), and material layer thickness (4–12 mm) on the formation of visual quality of GBR in terms of fissure and color were investigated by using bench experiments and numerical modeling. The results showed that temperature and moisture content of the final dried GBR had high uniformity in the continuous microwave dryer, and most of the dried GBR kernels were in a "mild" (1–2 fissures in kernels) and "moderate" (3–4 fissures in kernels) fissure degree at the microwave intensity of 2–3 W/g. The increasing air velocity may weaken the effects of interior stress caused by moisture content gradients on fissures in GBR kernel. The chroma b*, representing the golden yellow color index of GBR, significantly (P < 0.05) increased with the microwave intensity and the drying duration for per drying pass of 4–6 min. The material layer thickness lower than 10 mm was suitable for the formation of golden yellow color appearance of GBR. The simulation results confirmed that microwave intensity had a positive effect on the formation of fissures for GBR in a continuous microwave dryer due to the rising stress along the short-axis direction of GBR kernel. The distribution of moisture content inside GBR kernel was relatively uniform under the microwave intensity lower than 3 W/g, and the higher moisture content gradients aggravated the evolution of fissures in kernels. Considering the desired visual quality of the final GBR, the appropriate microwave drying conditions of GBR were developed as microwave intensity of 2 W/g, air velocity of 1.0–1.5 m/s, drying duration of 6 min for per drying pass and 8 mm material layer thickness, which induced the generation of suitable fissures and the formation of golden yellow color for GBR under the continuous microwave dryer. This study may provide a preference for the industrial application of microwave drying of cereal materials such as GBR. [ABSTRACT FROM AUTHOR]

Electrohydrodynamic (EHD) drying is novel nonthermal technology exploiting high-voltage corona discharge for dehydration of heat-sensitive biomaterials. In this study, we investigated the effects of voltage, electrode geometry, air flow, humidity, and material thickness on drying rate of sliced white champignons. In most cases, drying rate of mushrooms was proportional to moisture content, which corresponds to diffusion-limited drying. Decrease of air relative humidity from 70 to 30% or introducing forced air flow 1.0 m/s significantly improved efficiency of EHD drying. Increase of emitters' density or thickness of mushroom slices negatively influenced drying rate. Effect of EHD on color was insignificant in contrast to forced air drying, which provoked significant browning. Energy, used in EHD drying, was negligibly small as compared to thermal drying. These results have been taken into consideration for up-scaling of the EHD drying. [ABSTRACT FROM AUTHOR]

Upon popping, corn kernels undergo substantial dehydration. Initial moisture content of the kernel, popping method and temperature determine the final quality, and physical characteristics of the flakes. In this work, corn kernels (Zea Mays var Everta) at different moisture contents were subjected to hot-air popping and quality, physical and morphometric parameters of the flakes were evaluated, and related with their microstructural features. The best moisture content for hot-air popping was 9.14%. Macro and microstructural examination and digital image analysis of the flakes showed that, at the macro level, the roughness of the different flakes, as given by their fractal dimension (FD), were similar among morphologies, whereas at the microscale, it was possible to differentiate between them. Additionally, at the macro-scale, for the different morphologies high correlations were found between areas and the linear dimensions (Feret or width)FD of evaluated flakes. Moreover, when using the FD of the microstructures as the exponent, high correlations were also observed, which confirms an analog multiscale behavior between the roughness of the flakes and their microstructures. [ABSTRACT FROM AUTHOR]

The moisture distribution changes in Chinese yam slices subjected to microwave freeze drying (MFD) were analyzed using low-field nuclear magnetic resonance (LF-NMR). During this process, the mutual transformation of the water binding state and moisture diffusion characteristics of Chinese yam were analyzed together with changes in the effective water diffusion coefficient, water content, drying rate and pore network structure. Notably, moisture migrated from a high to a low degree of freedom during the MFD process. The effective water diffusion coefficient and water migration velocity increased with increasing microwave power density, and the extent of the conversion of unbound to bound water also gradually increased. During the early stage of drying, moisture diffusion was mainly dominated by liquid phase diffusion. At later stages of drying, moisture diffusion shifted gradually from liquid phase diffusion to gas phase diffusion and was eventually dominated by the latter. [ABSTRACT FROM AUTHOR]

A new mathematical model, based on energy and mass conservation, to simulate grain aeration was developed. The developed model considered the sorption, desorption, and hysteresis of canola and the heat transfer in the normal direction to the airflow at the bin walls. The developed model was compared with a published model, which was verified by different research groups. The main difference between the new model and the published models was that the new model determined the isotherm status including hysteresis of the aerated canola by evaluating the vapor pressure. Canola temperature, RH, and moisture content measured during aeration inside grain columns were used to verify the developed model. The grain columns (0.2 m inner diameter, 1.5 m high) were filled with 11.8% moisture content (wet basis) canola and aerated at 0.00275 m/s superficial velocity with the air temperature of 10, 15, and 20 °C and relative humidity of 75 ± 10%. The developed new model did not over- or under-predict the moisture contents in most parts of the columns, and had a better prediction of canola moisture content than that of the published model. Including the hysteresis evaluation in the developed model notably increased the model prediction accuracy. [ABSTRACT FROM AUTHOR]

Effective moisture diffusivity provides an easy and expeditious route to understanding many moisture transport processes involving food materials. Instead of making the moisture diffusivity a parameter obtained from curve-fitting a given experimental data that severely restricts its predictive value for the different sets of conditions, a simple but mechanistic approach is provided that for its prediction uses very little empirical information. This approach is based on treating the food as porous media and using parameters such as relative permeability, porosity, tortuosity, and constrictivity. The parameters are predicted using well-known relationships. The model is a combination of liquid and vapor diffusion-weighted by the respective volumes present in the porous medium that provides effective moisture diffusivity. Our model is compared to a mechanistic model that is backboned by Kelvin's capillary pressure equation and experimental isotherms data. In addition, the prediction is thoroughly validated against available experimental data and the general understanding of liquid/vapor transport in porous media literature. The more mechanistic approach enables prediction over a broader range of moisture content and a greater range of food materials with acceptable RMSE compared to other literature models. [ABSTRACT FROM AUTHOR]

The strong physical effects of ultrasound can change the state of water in food. In order to study the effect of ultrasound on the microwave drying of apple slices, an ultrasonic online-assisted microwave vacuum drying (UOAMVD) device was designed. The curves of moisture content versus drying time, the change in dielectric constant and dielectric loss factor, and the flow characteristics of water molecules were obtained during microwave vacuum drying (MVD), microwave vacuum drying with the apple slices pretreated by ultrasound (MVDPU), and UOAMVD, was measured by a vector network analyzer and a low-field nuclear magnetic resonance and imaging analyzer. The differences in color and microporous structure of the different dehydrated products were determined. Compared with MVD and MVDPU, apple slices that underwent UOAMVD had a higher drying rate and improved drying uniformity, and the dielectric constant was significantly reduced. In addition, the color of the UOAMVD dehydrated samples was the closest to that of fresh apple slices, whereas the microporous structure was not obvious and there was granular starch overflow. UOAMVD significantly improved the microwave drying efficiency and quality of apple slices. This work provides a reference for enhancing the application of ultrasonic microwave combination drying. [ABSTRACT FROM AUTHOR]