Increasing Equilibrium Moisture Research Articles

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

This study investigates lignin's influence on the hygroscopic behavior of poplar wood. Delignification was achieved using an acidic NaClO2 solution, and digital image correlation (DIC) was employed to measure strain distribution during shrinking and swelling across relative humidity (RH) ranging of 0% to 97%. Results showed that lignin removal increased equilibrium moisture content (EMC) by up to 3.6% in samples with 27% lignin reduction. Strain analysis revealed significant radial strain differences between earlywood and latewood, with tangential strain suppressed by wood rays. Increased porosity and cellulose slippage were observed following lignin removal, and samples with the highest lignin removal rate exhibited reduction exhibited over 58% greater εxx and over 43% greater εyy compared to untreated wood. These effects were most pronounced in latewood and regions distant from wood rays, where stress concentrations occurred. Delignification-induced cell wall thinning amplified the wood rays' inhibitory effect on anisotropic deformation during shrinking，enhancing the contrast between isotropic deformation in latewood and anisotropic deformation in earlywood during swelling. These findings provide insights into lignin's role in wood-water interactions, supporting the optimization of wood modification techniques.

Physical, chemical, and rheological properties of flour from accessions of Frafra potato (Solenostemon rotundifolius)

Frafra Potato (FP) is a climate-smart crop facing extinction in the tropical regions of Africa due to inadequate information about its properties. This study determined the physicochemical, functional, and rheological characteristics of flours from ten FP accessions to gauge their suitability for culinary purposes. The flour yield from FP tubers ranged from 59.3 % (E134) to 69.3 % (E111). While FP flours (FPF) exhibited consistent colour across accessions, variations in paste clarity were noted, ranging from 5.2 % (E145 and Maa-Lana) to 8.6 % (WAAPP). The least gelation concentration varied from 8 % (WAAPP) to 12 % (E 82, 111, 132, 134, 145). Released accessions showed higher protein and ash content than unreleased ones. Mineral composition differed significantly among accessions, including iron, calcium, zinc, and phosphorus, each with varying bioavailability percentages. Vitamin A content also varied across accessions. Proteins common in tuber crops, such as lipoxygenase, patatin, sporamin, tarin, and protease inhibitors (Bowman-Birk PIs), were identified in FPF. Amino acid analysis revealed nineteen amino acids, including seven essentials. FPF characteristics included a bulk density of 0.9 g/ml, oil and water binding capacities of 3 g/g and 1.3 g/g respectively, a pH of 6.4, and titratable acidity of 0.5. All FP flours displayed standard non-Newtonian behaviour, exhibiting pseudoplastic properties. They also showed a type II sigmoidal sorption curve, indicating increased equilibrium moisture content with higher water activity. Moisture sorption studies predicted a safe storage maximum allowable moisture content. These findings have practical implications for flour packaging and storage. The study underscores the culinary potential of Frafra potato and its role in addressing food and nutrition security in Ghana and Sub-Saharan Africa.

Einkorn (Triticum monococcum L.) and nectarine flour mixture - antioxidant activity, microbiological and sorption characteristics

The current paper presents the initial scientific research on a new enriched flour mixture with nectarine powder, comprising physicochemical parameters, antioxidant capacity, microbiological load, and sorption characteristics data. A mixture of 70% Einkorn flour and 30% fruit powder of Bulgarian origin as a functional food supplement was blended. The presence of bioactive components was proved by the in vitro analysis of antioxidant activity through DPPH, ABTS, FRAP, and CUPRAC methods. The microbiological indicators, the total count of mesophilic aerobic and facultative anaerobic microorganisms, yeasts and molds, Escherichia coli, Salmonella spp., coagulase-positive staphylococci and coliforms, were within the permissible norms and no presence of pathogenic microorganisms, were detected in the flour mixture. Adsorption and desorption processes were studied at 10, 25 and 40°C and aw = 0.112-0.868 following static gravimetric methods. The obtained S-shaped equilibrium sorption isotherms confirm the constant trend that with increasing equilibrium moisture content, the temperature decreases in conditions of constant water activity. Based on the obtained sorption capacity data, a calculation of the monolayer moisture content was made using the linearization of the BET model. One of the modified three-parametric models of Oswin, Halsey, Henderson, and Chung-Pfost was selected as a suitable model for describing all sorption isotherms.

Evaluation of moisture diffusion in lignocellulosic biomass in steady and unsteady states by a dynamic vapor sorption apparatus

Abstract To examine the methodology for determining the moisture diffusion behavior of lignocellulosic biomass in steady and unsteady states (two stages of a sorption isotherm), the diffusion coefficients in the steady and unsteady states (D SS and D US) were investigated over a range of relative humidity (RH) from 10 to 90% using a dynamic vapor sorption (DVS) apparatus and a specifically designed cell kit. Thin samples with a thickness of 50 μm were prepared from three lignocellulosic biomasses, i.e. poplar, Chinese fir and moso bamboo. Based on Fick’s first and second laws, D SS and D US were determined. An increase in D SS or D US was observed with increasing equilibrium moisture content (EMC) or transient status, regardless of the lignocellulosic biomass species. The moisture-dependent D SS of poplar, Chinese fir and moso bamboo was similar to values previously reported. Chinese fir and moso bamboo exhibited the highest and the lowest D SS values, respectively, when the same EMCs were achieved. The results of this study revealed that D SS and D US of lignocellulosic biomass (even with limited dimensions) could be determined during a sorption isotherm in a wide humidity range. Furthermore, the results are helpful for simulating moisture transport behaviors in the fields of drying, paper packaging and wooden building maintenance.

How does delignification influence the furfurylation of wood?

To investigate the influence of delignification on wood furfurylation, poplar wood (Populus euramericana Cv.) was partly delignified prior to the impregnation of furfuryl alcohol (FA) at concentration of 25%. The observation by using scanning electron microscope (SEM) and confocal laser scanning microscopy (CLSM) showed that many intercellular spaces appeared in middle lamella and cell corners in the wood with 8.86% lignin loss (LL), after further furfurylation, these spaces were filled with polymerized furfural resin, which contributed to the more uniform distribution of modifier and larger bulking of cell wall in furfurylated wood with low lignin (LF) than furfurylated control (CF). The size distribution of mesopores increased after delignification but decreased after furfurylation, and the specific surface area was reduced over 20% for LF with about 50% total pore volume decrease compared with the control from the analysis of nitrogen adsorption. Lignin loss and chemical polymerization of furfural resin were confirmed but without chemical reaction between FA and cell wall components by both results of Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance (NMR). Delignification resulted in increased equilibrium moisture content (EMC) and dimensional instability, after further furfurylation, the EMC and dimensional changes of LF decreased and were lower than those of control by 16.3% on average, suggesting the availability of furfurylation in reducing moisture sorption and improving dimensional stability of low lignin content wood. The number of accessible hydroxyl groups in wood calculated by using Hailwood-Horrobin theory exhibited in the following order: LL > control > LF > CF. The results can potentially help with understanding the action of delignification in wood furfurylation, as well as providing information on the possibility of make sustainable use of wood products with degraded lignin by furfurylation.

Production of fuel pellets via hydrothermal carbonization of food waste using molasses as a binder

Hydrochar was produced from food waste under varying hydrothermal carbonization (HTC) conditions, and was pelletized using molasses and molasses/lime binders for fuel pellet production. The physico-chemical properties, density, mechanical properties, and water resistance, and combustion characteristics of the hydrochar pellets were investigated. The results indicated that molasses pellets and molasses/lime pellets exhibited increased compressive strength, density, and impact resistance due tothe “solid bridge” that formed from molasses recrystallization and agglomeration by lime. The hydrochar samples prepared at 230 °C and 260 °C, with long residence times of 8 h, showed excellent compressive strength and impact resistance index (IRI). Both molasses pellets and molasses/lime pellets exhibited slightly increased equilibrium moisture content (EMC), with the former showing a high water-resistance index (WRI) in the immersion test. Thermogravimetric analyses indicated that the molasses pellets had a lower ignition temperature and higher combustion interval than those of the molasses/lime pellets.

Thermodynamic properties of water desorption in lettuce seeds

Knowledge of the movement of water molecules inside material is important for the study of interactions between water and chemical components of agricultural products. The thermodynamic properties calculation reports this need, being the source of information to design drying equipment, calculate the energy required in this process and evaluate the physical phenomena that occur on the food surface. Given the importance of the subject, the objective of this study was to determine the thermodynamic properties of the water desorption process in lettuce seeds. Lettuce seeds had an initial moisture content of 9.3% (d.b.). The equilibrium moisture content of seeds was determined by static gravimetric method at different temperatures (10, 20, 30, 40 and 50 ± 1 °C) and relative humidity values (between 11 and 96%). Experiments were conducted in triplicate. It was observed that, with increasing equilibrium moisture content, there was a reduction in the energy required for evaporation of water in lettuce seeds, with values of integral isosteric heat of desorption in the water content range 2.1 to 21.2% (d.b.) which varied from ‘4164.89 to 2477.43’ kJ kg-1. With increasing equilibrium moisture content there was a decrease in differential entropy, resulting in lower demand for mobility of water molecules. The Gibbs free energy also decreased with increasing equilibrium moisture content and was positive for all temperatures studied, showing non-spontaneity of water desorption in the seeds. The enthalpy-entropy compensation theory was has been satisfactorily applied to the sorption phenomenon and the water desorption process in lettuce seeds was controlled by enthalpy.

Cornstarch-Gelatin Films: Commercial Gelatin Versus Chromed Leather Waste Gelatin and Evaluation of Drying Conditions

In this work, gelatin extracted from chromed leather waste (CLW) was used with cornstarch and glycerol to produce polymeric films. These films were compared with commercial gelatin ones. Gelatin from CLW presented a more pronounced plasticizer behavior than commercial gelatin. It may have occurred due to its lower molar mass, due to the presence of free amino acids from the partial degradation of the protein polypeptide chain during CLW gelatin extraction, and/or due to the presence of high salts content. The high drying temperature (40 °C) made the drying process faster than the starch retrogradation process. It resulted in the reduction of films crystallinity and tensile strength, and in the increase of elongation at break. It also increased equilibrium moisture content, as indicated by water sorption isotherms. FTIR spectra indicated that the absorption bands of cornstarch and CLW gelatin films are the same ones found for films of these materials when not combined, which indicates the presence of a system with phase separation.

Moisture sorption isotherm of microencapsulated extra virgin olive oil by spray drying

Adsorption isotherms, at 4, 25 and 60 °C for microencapsulated extra virgin olive oil powder (MEVOP) prepared by rotor–stator homogenization (RSH) and ultrasonic homogenization (UH) methods before spray drying, were obtained using standard static gravimetric method. The sorption isotherms exhibited type III (J shape) behaviour. The sorption isotherms of MEVOP depended on temperature, chemical composition of particle surface and particle size of samples. The equilibrium moisture contents (EMC) decreased with increasing temperature. The sorption isotherm of MEVOP obtained with UH shifted up compared to that obtained with RSH because of the smaller particle size of MEVOP obtained with UH. The Guggenheim–Anderson–de Boer (GAB) model was the best fitting the experimental sorption data. Monolayer moisture contents of MEVOP were in the range of 0.036–0.079 kg H2O per kg d.s. All K values of MEVOP were higher than 0.89. C values of MEVOP obtained with RSH and UH method varied in range of 7.17–13.86 and 8.42–27.76, respectively. Net isosteric heat of sorption was evaluated using the Clausius–Clapeyron equation and differential entropy decreased with increasing moisture content. Gibbs-free energy decreased with increasing equilibrium moisture content. The spreading pressure increased with the rise in water activity for all temperatures.

Moisture Sorption-desorption Characteristics and the Corresponding Thermodynamic Properties of Carvedilol Phosphate.

Aims:Carvedilol phosphate (CDP) is a nonselective beta-blocker used for the treatment of heart failures and hypertension. In this work, moisture sorption–desorption characteristics and thermodynamic properties of CDP have been investigated.Materials and Methods:The isotherms were determined using dynamic vapor sorption analyzer at different humidity conditions (0%–90% relative humidity) and three pharmaceutically relevant temperatures (20°C, 30°C, and 40°C). The experimental sorption data determined were fitted to various models, namely, Brunauer–Emmett–Teller; Guggenheim-Anderson-De Boer (GAB); Peleg; and modified GAB. Isosteric heats of sorption were evaluated through the direct use of sorption isotherms by means of the Clausius-Clapeyron equation.Statistical Analysis Used:The sorption model parameters were determined from the experimental sorption data using nonlinear regression analysis, and mean relative percentage deviation (P), correlation (Correl), root mean square error, and model efficiency were considered as the criteria to select the best fit model.Results:The sorption–desorption isotherms have sigmoidal shape – confirming to Type II isotherms. Based on the statistical data analysis, modified GAB model was found to be more adequate to explain sorption characteristics of CDP. It is noted that the rate of adsorption and desorption is specific to the temperature at which it was being studied. It is observed that isosteric heat of sorption decreased with increasing equilibrium moisture content.Conclusions:The calculation of the thermodynamic properties was further used to draw an understanding of the properties of water and energy requirements associated with the sorption behavior. The sorption–desorption data and the set of equations are useful in the simulation of processing, handling, and storage of CDP and further behavior during manufacture and storage of CDP formulations.

Analysis of adsorption–desorption moisture isotherms of rosemary leaves

The moisture sorption isotherms data of rosemary leaves were investigated via the gravimetric static method at three different temperatures (30, 40 and 50°C). The sorption isotherms obtained were of sigmoid shape and of type II of Brunauer classification. From various mathematical models used for our experimental data, The GAB model best described the experimental data.The sorption data were analyzed for determination of monolayer moisture content (3.4–9.7%), and properties of sorbed water. Analysis of sorption isotherm by the model of the Yanniotis and Blahovec shows that the contribution of surface adsorption in relation to solution water at each water activity was higher in desorption than in adsorption The net isosteric heat of desorption and adsorption of the rosemary leaves ranged respectively from 1.77 to 47.37kJ/mol and from 0.85 to 26.86kJ/mol. The enthalpy–entropy compensation suggested that the sorption mechanism involved was enthalpy driven. The net integral enthalpy of adsorption and desorption decreased with increasing equilibrium moisture content.The integral entropy increased with moisture content, but was of negative value.

THERMODYNAMIC PROPERTIES OF WATER DESORPTION OF SOYBEAN BRAN

The differential and integral thermodynamic properties (enthalpy, entropy, Gibbs free energy, temperature isokinetic and spreading pressure) of soybean bran were determined. Experimental data obtained from the literature were adjusted appropriately by GAB equation (R2>0.95), whose parameters were used to estimate the thermodynamic properties of desorption of soybean bran. The differential enthalpy and entropy increased with decreasing equilibrium moisture content and the isokinetic temperature confirmed the linear chemical compensation between the enthalpy and entropy and the process was enthalpy driven. The spreading pressure increased with increasing water activity. The integral enthalpy decreased with increasing equilibrium moisture content, whereas the integral entropy increased, but negative values, reaching up to -0.02 kJ/mol.K.

THERMODYNAMIC PROPERTIES OF WATER DESORPTION OF SOYBEAN RAN

The diff erential and integral thermodynamic properties (enthalpy,entropy, Gibbs free energy, temperature isokinetic and spreadingpressure) of soybean bran were determined. Experimental dataobtained from the literature were adjusted appropriately by GABequation (R2>0.95), whose parameters were used to estimatethe thermodynamic properties of desorption of soybean bran.The diff erential enthalpy and entropy increased with decreasingequilibrium moisture content and the isokinetic temperatureconfi rmed the linear chemical compensation between the enthalpyand entropy and the process was enthalpy driven. The spreadingpressure increased with increasing water activity. The integralenthalpy decreased with increasing equilibrium moisture content,whereas the integral entropy increased, but negative values,reaching up to -0.02 kJ/mol.K.

Physical and Thermal Stability of Spray-Dried Swiss Cheese Bioaroma Powder

The effect of water content on the glass transition temperature of Swiss cheese bioaroma microencapsulated with a spray dryer was determined using differential scanning calorimetry (DSC) while mass loss was determined by thermogravimetric analysis (TGA). The sorption isotherm behavior was assessed at 15–45°C. Data were fitted with different sorption models. The bioaroma microparticles were produced via spray drying in a matrix with a 1:1 ratio (w/w) of maltodextrin 20DE and modified corn starch (Capsul). The isotherms displayed Type II behavior, and the best fit was obtained by the Guggenheim–Anderson–de Boer (GAB) model (coefficient of determination R² ≥ 0.98). The DSC analysis showed that the increased equilibrium moisture content caused a significant reduction in the Tg of the microparticles. The samples stored at intermediate humidity showed thermal stability and the samples with equilibrium moisture content of 17.92% showed a lower mass loss.

Formulation and physical properties of cyanate ester nanocomposites based on graphene

ABSTRACTWe report the thermal, mechanical, and diffusion properties of bisphenol E based polycyanurate nanocomposites with three forms of graphene derived from sequential processing of the same carbon nanostructure. Edge‐functionalized graphene nanoplatelets (GNP) were converted to graphene oxide (GO), then heated to produce thermally reduced graphene oxide (TRGO). All three reinforcements were individually mixed with the dicyanate ester of bisphenol E (LECy) at low loading levels and cured to form polycyanurate nanocomposites. GNP, with very low oxygen functionality, was incompatible with the cyanate ester, while the highly oxidized GO formed well‐dispersed (though not exfoliated) nanocomposites, with the TRGO forming a good dispersion on mixing but phase separating during cure. The addition of GO, and, to a lesser extent, TRGO, resulted in improved mechanical properties, particularly fracture toughness, with the addition of TRGO having a modestly negative effect on the glass transition temperature. Surprisingly, neither GO nor TRGO addition was effective at slowing down the diffusion of water in the polycyanurate, with the addition of both resulting in increased equilibrium moisture uptake. It thus appears that the trade‐off between dispersion and the required level of oxygen functionality acts in a manner to frustrate attempts at minimizing the permeation of water by addition of graphene‐based reinforcements. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 1061–1070

Water Absorption of Poly(lactic acid) Nanocomposites: Effects of Nanofillers and Maleated Rubbers

Injection-molded poly(lactic acid)/organo-montmorillonite (PLA/OMMT) and poly(lactic acid)/ nano-precipitated calcium carbonate (PLA/NPCC) were exposed to a water absorption test at 30°C for 70 days. The analysis was focused on the water diffusion kinetics and impact strength changes induced by the hydrolysis. The diffusion exponent (n) values of all the PLA samples are less than 0.5, indicating the Fickian diffusion model (case I) is obeyed. Adding nanofillers and maleated rubbers (SEBS-g-MAH or EPR-g-MAH) increased equilibrium moisture content but decreased diffusion coefficient values of PLA. The recoverability and retention-ability of the maleated rubbers toughened PLA/OMMT and PLA/NPCC after water absorption are excellent.

Preparation and characterization of extruded thermoplastic zein–poly(propylene carbonate) film

The novel film mainly composed of zein and poly(propylene carbonate) (PPC) was developed to study its feasibility as an alternative to petroleum-based plastics for food or non-food packaging, in combination with the acetone-pretreatment along with extrusion process using a conical twin-screw extruder. The effects of film formulation (the ratio of corn–zein to PPC, and plasticizer concentration) on physicochemical properties of extruded films were investigated. The results indicate that the addition of PPC with an appropriate concentration could improve the tensile strength and water resistance of the extruded zein–PPC film. In addition, PPC has a minor role in the film transparency and in contrast, the film transparency is highly dependent on the concentration of glycerol. Moreover, different models were used to describe the relationship between the tensile strength and humidity conditions. The Halsey model was identified as an ideal model perfectly fitting the experimental data, suggesting that the tensile strength of zein–PPC film was decreased with increasing equilibrium moisture content (EMC) of films. Scanning electron microscopy (SEM) revealed that the extruded film consisted of a single phase and also, the presence of PPC has a significant impact on the internal and external structures of the films. Furthermore, the results obtained from thermogravimetric analysis (TGA) showed the improved thermal stability of extruded zein–PPC film when compared to either the pure PPC or zein film. In conclusion, zein–PPC film could be considered a promising candidate to replace conventional petroleum-based plastic used in composite for packaging applications.

Moisture Sorption Isotherms and Net Isosteric Heats of Sorption of Green Soybean

Abstract Moisture sorption isotherms of green soybean seeds were determined by static gravimetric method and water activity ranging from 0.11to 0.94 at 20, 30 and 40°C. The optimal sorption model of green soybean was determined by using nonlinear regression method. Modified BET multilayer sorption theory model parameters at different temperatures were calculated, isosteric sorption heat was derived by the water activity sorption isosteric model. Results indicated that sorption isotherms were belong to type III behaviour, a notable hysteresis effect was observed, Green soybean monolayer saturated sorption capacity was greater in desorption process than that of adsorption. The monolayer saturated sorption capacity decreased with increasing temperature, while the number of multilayer had a reverse trend with the monolayer saturated sorption capacity, the optimal sorption isotherm model for green soybean is Halsey model, The thermodynamic parameters including net isosteric heat of adsorption and desorption calculated at 40°C were 105.2-1865.4 kJ/kg and 111.62-1939.0 kJ/kg with equilibrium moisture content between 5% and 32% (d.b.), respectively. The net isosteric heat of sorption decreased with increasing equilibrium moisture content.

Thermodynamic analysis of sorption isotherms of cassava (Manihot esculenta).

Sorption isotherms of cassava were determined experimentally using a static gravimetric method at 30, 45 and 60°C and within the range of 0.10-0.90 water activity. At a constant water activity, equilibrium moisture content decreased with increasing temperature. The equilibrium moisture content increased with increasing water activity at a given temperature. The experimental results were modelled using seven sorption models using non-linear regression technique. Results demonstrated that the GAB model adequately predicted equilibrium moisture content of cassava for the range of temperatures and water activities studied. The thermodynamic functions such as net isosteric heat of sorption, differential entropy of sorption, net integral enthalpy and entropy were evaluated to provide an understanding of the properties of water and energy requirements associated with the sorption behaviour. Net isosteric heat and differential entropy decreased with increasing equilibrium moisture content. The net integral enthalpy decreased while net integral entropy increased with increasing equilibrium moisture content. Net integral entropy was negative in value. All thermodynamic functions were adequately characterised by a power law model. The point of maximum stability was found between 0.053 and 0.154kg water/kg db for cassava.