Equilibrium Moisture Content Research Articles

Development of Moisture Sorption Isotherm and Mathematical Modeling of Finger Millet (Eleusine coracana)

In the literature, only a limited number of studies have explored the sorption characteristics of finger millet-based products.Moisture sorption isotherms provide information on the interaction between food and the storage environment. The sorption isotherms of finger millet based food product were studied with dynamic vapor sorption method, isopiestic Method and static gravimetric methods at different temperatures ranging from 25–70◦C with humidity ranges from 5-100%. Additionally, no research has been conducted on whole grains concerning their storage for further processing. This study deals with the sorption properties of whole finger millet grains. Methodically, the equilibrium moisture content of whole finger millet grains was determined by the dynamic humidity chamber method. The Guggenheim–Andersen–de Boer (GAB), Brunauer–Emmett–Teller (BET), Henderson, and Halsey sorption models were applied to describe the relationship between detected water activity and equilibrium moisture content. The study was conducted at three different temperature levels of 25◦C, 30◦C, and 35◦C. The relative humidity ranged from 10% to 90%, with an increment of 10%. Thevalue of average R2 for each model is 0.9103, 0.7226, 0.9123 and 0.8853, respectively. Furthermore, a new mathematical model incorporating exponential and power-law (nonlinear) relationships was developed, achieving an average R2 value of 0.9720. Furthermore, this study validates the developed mathematical model for fitting sorption isotherms across different millet varieties and temperature levels. Experimental data from EX-BORNO millet were utilized for model validation. The results demonstrate high accuracy, with the coefficient of determination R2 values for adsorption at 30°C, 40°C, 50°C, 60°C, and 70°C recorded as 0.976, 0.968, 0.963, 0.951, and 0.977, respectively. Similarly, the R2 values for desorption at these temperatures were 0.978, 0.970, 0.963, 0.954, and 0.963. These findings confirm the robustness of the developed model in capturing moisture sorption behavior, providing a reliable tool for optimizing storage and processing conditions for millet. The developed mathematical model enhances the accuracy of moisture equilibrium predictions, facilitating the development of improved storage systems and drying strategies. These findings contribute to extending the shelf life and optimizing the processing efficiency of finger millet grains in the food industry. Additionally, this study offers a comprehensive analysis of the moisture sorption behavior of whole finger millet grains.

RESEARCH OF SORPTION OF COMPOSITES BASED ON MUNICIPAL SOLID WASTE AND BIOMASS

Abstract. Municipal solid waste disposal is one of the main problems worldwide. Among the technologies for the energy use of municipal solid waste, the most common and one of the most efficient is the tech-nology of incineration of this waste in cogeneration plants for the production of electricity and heat. The production of highly effi-cient composite fuels based on municipal solid waste is of considera-ble scientific interest because it requires the development of appro-priate energy-saving technologies. The creation of fuels based on municipal solid waste and biomass allows to reduce CO2 emissions during combustion. When incinerating municipal solid waste with high humidity, most of the energy will be spent on drying it. There-fore, it is advisable to dry solid waste. However, the drying stage is characterized by high energy consumption. Therefore, the paper first considers the study of sorption of fuels based on municipal solid waste and biomass. Sorption studies make it possible to determine the equilibrium moisture content to which drying should be carried out and will further reduce energy consumption for the process. The study to determine the equilibrium moisture content of composite fuels depending on the relative humidity of the air used the Van Bamelen strain (static) method. As a result of the research, it was determined that the moisture content of the fuel does not exceed the standard. At the same time, it was found that the addition of a large amount of polyethylene reduces the equilib-rium humidity. Storage of the composite at a relative humidity of 60 % for fuel composition 1 with a polyethylene content of 40 % is 4.5 %; for fuel composition 2 – 4.9 %; for fuel composition 3 – 6.3 %. Bibl. 30, fig. 5, tab. 2.

Free shrinkage characteristics of Eucalyptus urophylla × E. grandis wood prone to collapse

Abstract Free shrinkage is a natural characteristic of wood during drying, occurring when the moisture content (MC) drops below the fiber saturation point (FSP). However, achieving complete free shrinkage in practical processes is challenging due to drying stresses from varying rates between the surface and core layers. Eucalyptus wood is particularly prone to collapse above the FSP, complicating the free shrinkage process. This study investigates the free shrinkage characteristics of 2-mm thick Eucalyptus urophylla × E. grandis specimens, both sliced along the fiber direction and split tangentially (layered). The findings are as follows: Layered specimens exhibited significant shrinkage ratios (5.7–6.7 %) and equilibrium moisture content (EMC) values (19.0–22.7 %), which can be attributed to the differing anatomical structures across layers. In contrast, sliced specimens did not display a MC gradient during drying, but their shrinkage was somewhat constrained by adjacent layers. Consequently, layered specimens had fewer radial and tangential restrictions, allowing more pronounced unrestricted shrinkage. Also, the slight collapse in smaller sliced specimens had a negligible impact on free shrinkage. To achieve free shrinkage without collapse, it is essential to use small-sized specimens in both fiber and radial directions while maintaining low temperatures and high relative humidity (RH) conditions.

Influence of moisture on the identification of tropical wood species by NIR spectroscopy

Abstract Solutions for species discrimination are important for monitoring native timber harvesting. Near-infrared (NIR) spectroscopy has shown promise for identifying wood species in real time. The influence of moisture content on the model’s performance for classifying wood is not well known. The objective was to evaluate the effect of wood moisture on the predictive capacity of the models for species discrimination based on NIR spectra using a benchtop and a portable spectrometer. First, NIR signatures were collected on the radial face of wood specimens at equilibrium moisture content (EMC) of 11 native species from Amazonia using both equipments. After saturation, new spectra were collected at the maximum moisture condition and subsequently at every 10 % of the water mass loss during drying. Partial least squares discriminant analysis (PLS-DA) was developed to discriminate the timber species according to their spectral signatures. Principal component analysis of the spectral data obtained in EMC was able to discriminate the species depending on the density gradient of the specimens. Moisture had no significant impact on the spectral signal. The PLS-DA models successfully classified unknown wood samples by species with over 91 % accuracy, regardless of moisture content. Both NIR devices show strong potential for use in forest inspections.

Assessment of torque performance during screwing in beech plywood reinforced with glass fiber in phenol-formaldehyde resin

This study aimed to develop plywood, which is generally used as a building material in outdoor areas, by adding low-cost glass fiber and to examine some physical and mechanical properties of the developed plywood. For this, beech veneers (600 × 600 mm dimension, 2 mm thickness in 3% to 5% humidity) were glued with phenol-formaldehyde adhesive at the levels of 10%, 20%, and 30% by adding powdered e-type glass fiber in two different sizes (25 µm and 10 µm) to produce seven-layer beech plywood. Density, equilibrium moisture content, thickness swelling, tensile-shearing, and tensile-perpendicular to the surface were evaluated on test samples cut from the beech plywood in 50 × 50 mm dimension, and screwing torque values were carried out on test samples cut in 500 × 50 mm dimensions. Two-factor analysis of variance (ANOVA) was performed separately for the tests above. Results indicated that in cases where interactions between the glass fiber size and ratio were significant at the 0.05 significance level, the least significant difference value (LSD) analysis of the interaction was performed. According to LSD results, the tensile strength perpendicular to the surface decreased as the glass fiber ratio was increased.

Experimental Investigation of Standardized Conditioning and Representative Accelerated Drying Protocols Impact on Concrete Spalling

Experimental Investigation of Standardized Conditioning and Representative Accelerated Drying Protocols Impact on Concrete Spalling

Quality evaluation of dried tomato fruit and optimization of drying conditions using a modified solar dryer integrated with an automatic solar collector tracker.

In the current study, a modified solar dryer (SD) integrated automatic solar collector tracker (ASCT) was used for drying tomato fruit (TF) at three slice thicknesses of 4, 6, and 8mm on both drying systems at three air speeds of 1, 1.5, and 2m/s until reaching the equilibrium moisture content. Where the comparison study was conducted between the ASCT, and another SD integrated with a fixed solar collector (FSC). The obtained results of the current study showed that the maximum solar intensity and ambient air temperature during the test period were 900 W/m2, and 43.6°C, respectively. As well as the highest efficiency of the PV system was 16.69% at the same time. On the other hand, the height, greatest diameter and smallest diameter of the TF used in the current study ranged between (4.6 and 5.2cm), (3.5 and 4.2cm), and (3.4 and 4.1cm), respectively. As well as both the athematic and geometric diameters ranging between 3.87 and 4.47cm and 2.26 and 2.38cm, the sphericity values of tomatoes tend to have a round shape. In addition, the obtained results that there was no significant effect of the hot air velocities on the drying time, but the final moisture content (MC) decreased with increasing the hot air velocities. The lowest final MC was 6%, and it was recorded with a slice thickness of 4.0mm that dried on SD integrated with ASCT. Additionally, color analysis showed that, the darkest tomato slices were dried on the SC integrated with FSC at a hot air velocity of 1.0m/s. Meanwhile, the intensity of red and yellow colors significantly increased after drying with the SD integrated with ASDT. Furthermore, the chemical analysis of the dried tomato slices showed that the highest rehydration ratio of 4.43kg water/kg dry matter was obtained for the dried tomato slices dried on SD integrated with ASCT at a hot air velocity of 1.5m/s and a slice thickness of 8.0mm. As well as the highest values of pH were monitored on the dried tomato slices on ASCT in comparison to the other tomato slices dried on FSC. Also, the highest ascorbic acid content recorded was 141mg/100g (d.b.) in tomato slices with an 8.0mm thickness, dried using SD combined with FSC at an air velocity of 2m/s. After drying, the total phenols content increased in all dried tomato samples but decreased with lower hot air velocities.

Investigating the Moisture Sorption Behavior of Biscuits under Controlled Humidity Conditions

Biscuits are ready-to-eat foods that are traditionally prepared mainly with wheat flour, fat, and sugar. In this study, the efficacy of temperature and humidity on the equilibrium moisture content (EMC) of biscuits was explored. The EMC was determined by static method at four different temperatures (20, 30, 40, and 50ºC) and five levels of relative humidity (20.1 to 93.2%). The equilibrium moisture content of the biscuit varied from 4.60 to 23.57% (dry basis) within the experimental range of temperatures and relative humidity. The EMC increased with the increase in relative humidity while EMC slightly decreased with the increase in temperature. The observed data was fitted to four selected EMC-ERH models. These models were modified-Henderson, Chung-Pfost, Halsey and Oswin. Based on statistical analysis, the modified Chung- Pfost model represented the experimental data more closely over the entire experimental range of temperature and relative humidity.

Physical-Chemical and Nutritional Assessment of Elionurus muticus (Spreng.): An Underutilized Medicinal and Aromatic Plant from South America.

Elionurus muticus (Spreng) Kuntze, commonly known as "espartillo", is a South American plant with a rich history of traditional use as an aromatic and medicinal infusion. The essential oil (EO) composition of E. muticus has garnered significant attention in recent decades due to its citrus aroma and antimicrobial properties. However, comprehensive investigations into its nutritional profile, bioactivity, and moisture behavior have been scarce. This study aimed to comprehensively characterize espartillo leaves, uncovering valuable insights for potential agro-industrial applications. Our findings revealed a rich nutritional profile. Espartillo leaves demonstrated a high dietary fiber content (29.5%), alongside moderate levels of carbohydrates (6.2%), and a low-calorie profile (49kcal/100g). The essential oil yield was 0.97%, predominantly composed of neral (35.3%) and geranial (43.8%). Furthermore, the leaves extracts exhibited significant levels of total phenolic compounds (42.9-65.0 mgAGE/g), and flavonoids (11.8-13.1 mgQE/g), demonstrating potent antioxidant activity comparable to the synthetic antioxidant BHT. The equilibrium moisture content of espartillo leaves was accurately described by the Oswin equation at lower temperatures (25 and 30°C) and the Henderson model at higher temperatures (40 and 50°C). These findings position espartillo as a promising natural source of aromatics, dietary fiber, and bioactive compounds with potential applications in food and pharmaceutical industries. Further research exploring the incorporation of espartillo leaf extracts into functional foods and nutraceuticals is warranted.

Analysis of Machine Learning Algorithms for the Computer Simulation of Moisture Sorption Isotherms of Coffee Beans

Abstract Digital twin–based machine learning (ML) techniques can improve the control of the storage conditions of dried products, strengthening the classical water sorption isotherm–based approach by including additional process variables. In this study, water sorption isotherms of dried parchment and green coffee beans were experimentally determined at 25, 35, and 45 °C using the dynamic dew point (DDI) method. Experimental data (both coffee bean types and temperatures) were simultaneously modeled by means of three ML techniques, support vector machine (SVM), random forest (RF), and artificial neural networks (ANN), with 75% of data used for model training and 25% for validation. The hyperparameters were identified by minimizing the mean square error (MSE). The ML model’s accuracy was addressed by a multiway ANOVA on the mean relative error (MRE), the coefficient of determination (R 2), and the computation time (CT). The sorption isotherms were significantly (p-value < 0.05) affected by the type of coffee and the temperature. The SVM model provided the best fit (MRE < 1% and R 2 > 99%) in a reasonable CT (< 13 s). These results revealed the potential of ML models as a robust tool for the fast prediction of the equilibrium moisture content, including additional variables such as the type of coffee stage (dried parchment or green) and temperature; this paves the way for their industrial-level implementation to assist storage management.

Thin-layer modeling, drying parameters, and techno-enviro-economic analysis of a solar dried salted tilapia fish fillets

This study focused on the development of an indirect forced solar dryer that incorporates a three-sided flat plate solar collector (TSFPSC) specifically designed for increasing thermal efficiency, and the system used for drying salted tilapia fish fillets (STFF). The investigation analyzed three fillet thicknesses—4 mm, 8 mm, and 12 mm, employing both open sun drying (OSD) and the developed solar dryer (DSD), with a constant airspeed of 0.5 m/s. The research additionally developed thin-layer drying models (TLDM), assessed drying parameters, and performed an extensive techno-enviro-economic analysis. Results showed that the initial and final moisture content (MC) (w.b. %) of the STFF were 74.83 and 18.84%, respectively, and reached the equilibrium MC after 16–20.5 h for the DSD and 30–36 h for the OSD, which means the drying time reduced by about 53.3%, and 61.11% compared with the OSD. This reduction in drying time demonstrates the effectiveness of the developed solar dryer. The effective moisture diffusivity (EMD) of different STFF samples at both drying systems were 0.51 × 10–10 to 9.16 × 10–10 m2/s. In addition, all eleven basic TLDM were applied to predict the drying behavior of STFF during the drying process, while the combined Two-Term and Page model had the best fitting for the OSD system, and the modified Midilli II model and combined Two-Term and Page model had the best fitting for the DSD system. In terms of economic analysis, the annual capital and investment costs were calculated to be $22.458 and $21.334, respectively. Additionally, the environmental analysis indicated an energy payback (EP) period of 1.59 years, with a net CO2 mitigation of 14 tons realized over the operational lifetime of the DSD.

Equilibrium Moisture Effects in Silica Gel Adsorption/Desorption

This research involves a numerical analysis focused on examining how the initial moisture content and equilibrium moisture content affect a Regular Density (RD) silica gel-packed bed, in terms of the composite mass and heat transfer dynamics during the adsorption and desorption processes. The detailed interaction between the air and the desiccant material is thoroughly represented through the development of the governing drying kinetics, mass conservation, and energy conservation equations, thereby establishing a solid mathematical foundation to clarify these essential processes. All numerical simulations are meticulously executed using the Finite Volume Element method, allowing for a detailed analysis of the mass and heat transfer phenomena within the RD silica gel-packed bed. The utilization of this advanced computational technique enables a deeper understanding of the complex interactions between the moisture content and transfer process efficiency in the desiccant system. This research culminates in the development of correlations that serve as predictive tools. An accurate estimation is facilitated by both the removal/addition of humidity from/to the air and the maximum enthalpy released/absorbed by the RD silica gel medium throughout the adsorption and desorption phases. These correlations, rooted in the equilibrium and initial moisture content of the RD silica gel medium, provide valuable insights into optimizing the performance and efficiency of desiccant systems in various operating conditions. There are intricate relationships between moisture content and transfer processes. This study contributes to advancing the understanding of desiccant systems, paving the way for more efficient and sustainable air treatment technologies.

Hygrothermal Properties of Tibetan Paper: The Effects of Air Pressure and Printed Scriptures

Hygrothermal Properties of Tibetan Paper: The Effects of Air Pressure and Printed Scriptures

Effect of delignification on shrinking and swelling of poplar wood assessed using digital image correlation technique.

Effect of delignification on shrinking and swelling of poplar wood assessed using digital image correlation technique.

Application of ultraviolet radiation type C and pretreatments as an emerging and innovative technology for unripe bananas drying: Kinetic and diffusive study, color, and microstructure.

Application of ultraviolet radiation type C and pretreatments as an emerging and innovative technology for unripe bananas drying: Kinetic and diffusive study, color, and microstructure.

Adsorption isotherms in roasted specialty coffee (Coffea arabica L.): Dataset and statistical tools for optimizing storage conditions and enhancing shelf life.

This work presents a comprehensive dataset of adsorption isotherms and infrared spectral data for roasted specialty coffee (Coffea arabica L.). The dataset includes adsorption isotherms for whole roasted beans and ground coffee at medium (850 µm) and fine (600 µm) particle sizes. Adsorption isotherms were experimentally determined using the Dynamic Dewpoint Isotherm (DDI) method, considering a water activity range from 0.1 to 0.9 and temperatures of 25, 35, and 45 °C. Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy was used to characterize the coffee samples spectrally. The dataset also provides two calibrated sorption models: Peleg and Double Logarithm Polynomial (DLP), which are highly suitable for practical applications, allowing users to predict the equilibrium moisture content of coffee as a function of water activity, temperature, and coffee type (whole beans or ground coffee). These tools offer valuable insights for researchers, coffee producers, and decision-makers in computing critical parameters related to roasted specialty coffee's shelf life, determining optimal packaging materials, and understanding the hygroscopic properties of coffee. The calibrated models could be used to optimize coffee storage processes and improve the understanding of water sorption behavior in different particle sizes. The dataset compiles the experimental adsorption isotherms and infrared spectra in Excel sheets according to the experimental conditions and replicates. Furthermore, this dataset includes different MATLAB® R2023a (The MathWorks Inc., Natick, MA, USA) files where the models have been calibrated with the experimental adsorption isotherms using the "Curve Fitting" tool and are available for their use in the coffee industry.

Mathematical modeling of water sorption isotherms in specialty coffee beans processed by wet and semidry postharvest methods

This study investigates the experimental assessment and mathematical modeling of the water sorption isotherms in dried specialty coffee beans processed by wet and semidry postharvest methods. The wet and semidry sorption isotherms were experimentally obtained over a range of water activities between 0.1 and 0.85 at temperatures of 25, 35, and 45 °C using the dynamic dew point method (DDI). Mathematical modeling was conducted to describe the influence of water activity, temperature, and postharvest method on the equilibrium moisture content. Twelve conventional sorption equations and four machine learning techniques were employed for modeling, using 75% of the experimental data for training and 25% for validation. The selection of the best model was carried out via multifactor Analysis of Variance (ANOVA). Experimental results showed that wet and semidry coffee beans exhibited a type II S-shaped isotherm (Brunauer–Emmett–Teller classification) and a significant (p < 0.05) influence of temperature on sorption curves. Additionally, the mucilaginous coating found in semidry coffee beans provided a protective role against water sorption. The Support Vector Machine (SVM) model provided the best fit for describing the sorption isotherms (mean relative error, MRE < 1% and adjusted coefficient of determination, R2adj > 99%), demonstrating its robustness in predicting the equilibrium moisture content as a function of water activity, temperature, and postharvest processing method. This mathematical model could serve as a virtual representation of the storage process, facilitating real-time decision-making to enhance coffee quality management during storage.

Technical and economic analysis of a specific spruce wood material drying process

The presented work reveals the technical and economic analysis of a spruce wood material drying process, for a specific installation. The analysis is made of the drying process of spruce timber, where the amount of initial moisture content is 60% and the equilibrium moisture content is 12%. The baseline technological process is considered for the existing installation with a wood burning boiler, used for heat supply source. Three different heat source options were further suggested and analysed, for the wood drying process optimization: implementation of natural gas boiler, electric boiler and high temperature heat pump installation. The calculations for each of them were performed at a heat output of 100 kW and a drying temperature regime of 90/75°C. The results show that only the annual energy costs of the option with a heat pump system are lower than the base case, with the cash savings amounting to USD 4,884/year, payback period of 9.47 years and 99.93 t/year CO2 emissions. The specific energy consumption in this optimal suggested case is 0.139 kWh/kg.

EVALUATION OF MOISTURE SORPTION ISOTHERM FOR SHEA NUTS, VITELLARIA PARADOXA

HighlightsEquilibrium moisture content models were assessed for shea nuts.The Modified Halsey and Modified Oswin EMC/ERH models were found to be most appropriate in describing the sorption behavior of shea nuts.Critical moisture content for storage of shea nuts in the Sahel region was determined to be 5.08% to 6.68%.The study provided a basis for developing a calibration equation for a commercially available, hand-held, low-cost moisture meter for adoption in the shea nut value chain.Abstract. Shea nuts (Vitellaria paradoxa) are prone to mold deterioration during post-harvest handling, drying and storage. Evaluating the moisture sorption characteristics provides the basis to better understand their drying and storage behavior for prevailing climatic conditions during growing, harvesting and storage periods in shea-producing communities. Thus, this study sought to evaluate the moisture sorption isotherm of whole shea nuts across a temperature range of 20°C to 35°C, as is typical in the Sahel region. A series of goodness-of-fit indices were assessed to evaluate five moisture sorption models. The Modified Halsey and Modified Oswin EMC/ERH models were found to be most appropriate in describing the sorption behavior of shea nuts. The critical moisture content determined at 0.65-0.70 water activity across the 20°C to 35°C temperature range was 5.08% to 6.68%. Therefore, this study provided a recommendation for the safe storage moisture content of shea nuts and a basis for developing a calibration equation for a commercially available, hand-held, low-cost moisture meter to monitor effective drying, safe storage, and improved handling in the shea nuts value chain. Keywords: Keywords.,Equilibrium moisture content, Post-harvest handling, Safe storage moisture content, Shea nuts, Sorption isotherm.

Equilibrium moisture content of horseradish

The equilibrium moisture content of horseradish (Armoracia rusticana) at 20°C was determined experimentally using the tensiometric method. Mathematical relationships describing sorption and desorption isotherms for relative humidity from 0 ÷ 90 % were obtained. The equilibrium moisture content of the product was also determined analytically for higher temperatures - 40°C, 60°C and 80°C, using the Pass-Slepchenko`s method. The results have been summarized and presented in both graphical and tabular form.