Guggenheim Anderson De Boer Research Articles

Moisture sorption isotherm and shelf‐life prediction of anticaking agent incorporated spray‐dried soursop (Annona muricata L.) powder

AbstractThe moisture sorption isotherm (MSI) and shelf lives of soursop powders that had been incorporated with two commercial anticaking agents, calcium silicate (CS) and tricalcium phosphate (TCP), and inserted into aluminum laminated polyethylene pouches under room (RT, 25 ± 1°C) and elevated (ET, 38 ± 1°C) temperature, maintained at 93 ± 1% RH, were investigated. The powder possessed a Type III Brunauer's classification isotherm curve. The monolayer moisture content (Mo) was 0.023 ± 0.001 g H2O/g ds. A combination of low mean relative percent deviation modulus, E (2.18–3.75%), small sum of square residual, SSR (1.03 × 10−5–8.51 × 10−6), and high coefficient of determination (R2 > .99) indicating the moisture sorption data was sufficiently good fit using GAB model. Powder without anticaking agent stored at ET has the shortest estimated shelf life (~86 days) while 1.0 g/100 g TCP stored at RT exhibited the longest shelf life (~316 days). This study demonstrated that the incorporation of anticaking agents is effective to maintain the quality of powder by extending the shelf life by lowering moisture adsorption. The acceptability of reconstituted soursop powder based on hedonic test showed the scores for all attributes were higher than six.Practical applicationsUp to date, limited information describes the preservative effect of anticaking agents throughout the storage period. Hence, this work provides an insight to look into detail of how the incorporation of anticaking agents improve or retain the quality of the dried powder especially the moisture sorption isotherm (MSI) behavior. To achieve this, enzymatic pre‐treated spray‐dried powder was incorporated with anticaking agent. MSI was carried out and the behavior was determined by fitting the data into Guggenheim–Anderson–de Boer (GAB) model. Prediction of shelf life was studied by considering the critical moisture content (X c), which is the moisture content of powder that undergoes transition changed. The outcome of this work was expected to be beneficial to food powder industry to comprehend the protective effect of anticaking agents as a functional additive. Production of anticaking agent treated spray‐dried soursop powder was expected to broaden its potential applications as functional ingredient.

Sorption equilibrium moisture and isosteric heat of cold plasma treated milled rice

Abstract To promote industrial adoption of cold plasma as a sustainable and safe processing technology for rice, data on equilibrium moisture content (EMC) for cold plasma treated milled rice of five Chinese varieties were collected by a gravimetric method at 11–96% equilibrium relative humidity (ERH) and a temperature range of 15–35 °C. Nine models were fitted well to the sorption data, with the modified Guggenheim–Anderson–deBoer equation (3-MGAB), modified Henderson equation (MHE), and a polynomial equation being the best fits. At a constant ERH, the EMC was negatively correlated with temperature, whereas there was a strong effect of temperature on the sorption isotherms of the milled rice. Initially, the isosteric heats of sorption for the cold plasma treated rice decreased rapidly with increasing sample moisture content (MC); however, when MC was higher than 15% of the wet basis (w.b.), further increases in MC caused a slight decrease in heat sorption values. The heat of vaporization of the milled rice approached the latent heat of pure water at a moisture content of ~17.5% w.b., which was ~2500 kJ/kg. The isosteric heat of sorption values of the milled rice predicted by the modified Chung-Pfost equation (MCPE) and MHE models negatively correlated with temperature. At 70% ERH, the safe-storage MC of the cold plasma treated rice were ≤14.5% w.b. at 25 °C. In comparison to the untreated milled rice, the cold plasma treated rice with 120 W for 20 s and 60 s significantly decreased the water contact angle and increased kernel broken index, without significantly changing the appearance quality of milled rice. The cold plasma treated rice with 120 W-20 s had insignificantly higher EMC than that of 120 W-60 s at the studied temperature range. This study demonstrates that helium cold plasma treatment insignificantly changed hygroscopic property of milled rice whilst maintaining the appearance quality.

Evolution of surface micro-structure and moisture sorption characteristics of spray-dried detergent powders

The role of water is critical to the solid state behaviour of complex formulated products such as spray-dried detergent powders. Understanding changes in water sorption behaviour due to interactions within the solid allows the influence of water sorption on the surface micro-structure to be better elucidated. This work investigates the effect of relative humidity (RH) on the micro-structural evolution and moisture sorption behaviour of model detergent powders containing the sodium salt of linear alkylbenzene sulphonate (NaLAS) and sodium sulphate. Scanning electron microscopy showed significant changes to surface morphology when the powders were exposed to 75% RH. However, the addition of sodium silicate to the formulation made the powders more susceptible to humidity-induced morphological changes. Surface crystal growth was seen at 54% RH and dramatic changes in structure were seen at 75% RH due to the emergence of the hydrated phase of sodium sulphate, i.e. mirabilite, which was confirmed by the X-ray diffraction. These differences are thought to be due to the increased hygroscopicity and water mobility conferred by the silicate and observed via sorption isotherm measurements and FTIR analysis, which suggest a change in structure due to a moisture-induced glass transition. Considerable differences in moisture absorption were observed between samples produced from the slurries differing in water content, highlighting the importance of micro-structure on moisture sorption behaviour. The experimental sorption isotherms were fitted to three mathematical models: Brunauer-Emmett-Teller (BET), Guggenheim-Anderson-de Boer (GAB) and Oswin. In nil-silicate powders, all three models presented a good fit to the experimental data with R2 ∼ 99%. However, in silicate containing powders, the GAB and Oswin fits were unsuccessful; the influence of the phase transition on the isotherm not being captured by the models.

Moisture sorption isotherm and thermal characteristics of freeze-dried tuna

Water activity is considered an important factor in assessing the stability of food. Understanding the relationship between water activity and equilibrium moisture content (moisture sorption isotherm) benefits food processing in terms of modeling of drying and estimation of shelf life. In addition, glass transition helps to quantify molecular mobility which helps in determining the stability of food. The aim of this study was to determine the moisture sorption isotherm and thermal characteristics of freeze-dried tuna. These characteristics will help in determining the monolayer moisture and glassy state of the product, at which food is considered most stable. Moisture sorption isotherm at 20°C and thermal characteristics (over a wide temperature range i.e. from -90 to 250 °C) of freeze-dried tuna flesh were measured. Isotherm data were modeled by BET (Brunauer-Emmett-Teller) and GAB (Guggenheim-Anderson–De Boer) models. The GAB and BET monolayer water values were determined as 0.052 and 0.089 g g -1 dry-solids (dry-basis), respectively. In the case of samples at moisture contents above 0.10 g g -1 (wet basis), DSC (Differential Scanning Calorimetry) thermograms showed two-step state changes (i.e. two glass transitions), one exothermic peak (i.e. molecular ordering) and another endothermic peak (i.e. solids-melting). However, the sample at moisture content of 0.046 g g -1 showed three-step state changes (i.e. three glass transitions). The multiple glass transition could be explained by the natural heterogeneity of tuna flesh and inhomogeneity due to molecular incompatibility of the different compositions. The moisture content did not affect the first glass transition temperature nor the exothermic peak (p>0.05), whereas the third glass transition temperature decreased (i.e. plasticized) with increasing moisture content (p<0.05). The solids-melting peak temperature decreased, and enthalpy increased with decreasing moisture content (p<0.05).

Moisture sorption isotherm and thermal characteristics of freeze-dried tuna

Water activity is considered an important factor in assessing the stability of food. Understanding the relationship between water activity and equilibrium moisture content (moisture sorption isotherm) benefits food processing in terms of modeling of drying and estimation of shelf life. In addition, glass transition helps to quantify molecular mobility which helps in determining the stability of food. The aim of this study was to determine the moisture sorption isotherm and thermal characteristics of freeze-dried tuna. These characteristics will help in determining the monolayer moisture and glassy state of the product, at which food is considered most stable. Moisture sorption isotherm at 20°C and thermal characteristics (over a wide temperature range i.e. from -90 to 250 °C) of freeze-dried tuna flesh were measured. Isotherm data were modeled by BET (Brunauer-Emmett-Teller) and GAB (Guggenheim-Anderson–De Boer) models. The GAB and BET monolayer water values were determined as 0.052 and 0.089 g g-1 dry-solids (dry-basis), respectively. In the case of samples at moisture contents above 0.10 g g-1 (wet basis), DSC (Differential Scanning Calorimetry) thermograms showed two-step state changes (i.e. two glass transitions), one exothermic peak (i.e. molecular ordering) and another endothermic peak (i.e. solids-melting). However, the sample at moisture content of 0.046 g g-1 showed three-step state changes (i.e. three glass transitions). The multiple glass transition could be explained by the natural heterogeneity of tuna flesh and inhomogeneity due to molecular incompatibility of the different compositions. The moisture content did not affect the first glass transition temperature nor the exothermic peak (p&gt;0.05), whereas the third glass transition temperature decreased (i.e. plasticized) with increasing moisture content (p&lt;0.05). The solids-melting peak temperature decreased, and enthalpy increased with decreasing moisture content (p&lt;0.05).

ADSORPTION ISOTHERMS OF KIWIFRUIT DRIED BY DIFFERENT DRYING METHODS

The aim of this study was to determine the moisture adsorption isotherms of kiwifruit dried by hot air, vacuum and freeze drying methods. Equilibrium moisture contents (EMC) of dried kiwifruits were obtained by using the standard gravimetric method at two different temperatures (25 and 45°C) within a range of water activities from 0.112 to 0.936. The adsorption isotherms of dried kiwifruits decreased with increasing temperature and exhibited type III behavior. Six different isotherm equations (GAB (Guggenheim-Anderson-de Boer), BET (Brunauer-Emmett-Teller), Oswin, Henderson, Halsey and Peleg) were employed to describe the experimental adsorption isotherm data. Adsorption data obtained at both 25 and 45°C for vacuum dried samples and data obtained at 45°C for hot air and freeze dried samples were best represented by Peleg equation. For the samples dried by hot air and freeze drying, GAB equation gave the best description of the experimental data obtained at 25°C.

Experimental and numerical simulation of water adsorption and diffusion in shale gas reservoir rocks

Despite the success of deep horizontal drilling and hydraulic fracturing in yielding large production increases from unconventional shale gas reservoirs, uncertainties associated with basic transport processes require understanding in order to improve efficiency and minimize environmental impacts. The hydraulic fracturing process introduces large volumes of water into shale gas reservoirs, most of which remains unrecoverable and interferes with gas production. In this study, the water adsorption and diffusion measurements of the Longmaxi Formation shale were conducted at 30℃ and 50℃for relative humidities from 11.1% to 97.0%. Based on the experiment, a computational model based on the Maxwell-Stefan diffusion equation was constructed to analyze water adsorption and diffusion in shale rocks, and the Guggenheim-Anderson-de Boer (GAB) isotherm for gas adsorption was included in the model. The results show that water adsorption isotherms of shales belong to type II curve, including the monolayer, multilayer adsorption and capillary condensation, and the GAB model can be used to describe the water adsorption process in shale rocks. With the increasing of relative pressure, the water adsorption of shale increases, and the organic carbon content and temperature strengthen the water adsorption in shale. The capillary pressure can reach the order of several hundreds of MPa after the hydraulic fracturing process, and it results in a large amount of fracturing fluid retained in shale gas reservoirs. Furthermore, the simulations of water adsorption and diffusion in shale rocks is less than the experimental value, which further indicates that capillary condensation occurs in shale rocks. Cited as : Shen, W., Li, X., Cihan, A., Lu, X., Liu, X. Experimental and numerical simulation of water adsorption and diffusion in shale gas reservoir rocks. Advances in Geo-Energy Research, 2019, 3(2): 165-174, doi: 10.26804/ager.2019.02.06

Experimental Determination of Moisture Sorption Isotherm of Fecal Sludge

Dewatering and drying of fecal sludge (FS) is a key treatment objective in fecal sludge management as it reduces volume (thereby reducing emptying frequency and associated transportation costs), inactivates pathogens, and is beneficial and/or necessary to resource recovery activities such as composting and combustion as fuel. However, studies on dewatering performances of FS are limited. The physical water distribution of such matrices is not fully understood, limiting the progress in the development and optimization of FS dewatering technologies. The objective of this study is to present a gravimetric method intended to assess the dewatering characteristics and associated modelling of FS through moisture sorption isotherms. Samples were placed in airtight jars containing different saturated salt (NaOH, CaCl2, NaCl, KCl, K2SO4) solutions to reproduce a range of relative humidity values (6 to 97%). Results confirmed the achievement of characteristic sigma-shaped moisture sorption isotherms with increasing moisture adsorption at higher values of relative humidity. Furthermore, experimental data best fit the three-parameter Guggenheim–Anderson–de Boer (GAB) model. This method can be replicated to contribute critical data about the characterization of fecal sludge, a seriously under-researched matrix.

Measurement of effective diffusion coefficients in dairy powders by confocal microscopy and sorption kinetic profiles

Abstract A new method for the visualisation and determination of local diffusion coefficients in dairy powders is described based on real-time visualisation of penetration of fluorescent dyes into individual particles of spray-dried dairy powders including skim milk powder, milk protein concentrate and whey protein isolate. The rehydration process was controlled by adding polyethylene glycol (PEG) as a viscosity modifier to the aqueous phase in ratios of 1:0, 1:1, 1:3 and 1:4 aqueous rhodamine to PEG, respectively. Real-time effective diffusivity values were obtained from analysis of confocal laser scanning microscope images. Particle size was measured optically. Results indicated that for all dairy powders, rehydration rates were highly dependent on particle size. Effective diffusivity increased linearly with increasing particle size and average effective diffusivity of the liquid phase was calculated for all particle size distributions using this dependence. The Guggenheim-Anderson-de Boer (GAB) water sorption relationship was used to model water sorption isotherms over a broad range of water activities. Vapour phase systems had significantly higher effective diffusivity than liquid phase systems. The results obtained by this new method is broadly in agreement with previously published works, suggesting this new method may be used to measure the hydration of individual powder particles.

Influence of Plasticizers in Enzymatic Degradation and Water Resistance of Starch Foam Trays Obtained by Thermal Expansion

Biodegradability and water resistance of cassava starch trays with different plasticizers [glycerol, sorbitol and polyvinyl alcohol (PVA)] were investigated. The degradability was tested by exposure at two amylolytic enzymes of microbial origin, one of them commercial (Termamyl®) and the other obtained in laboratory by the submerged cultivation of the fungus Penicilium echinulatum. The extent of degradation was analyzed by the percentage of weight loss and the concentration of released reducing sugars. The results showed that the packaging was sensitive to the action of the enzymes, because it was observed an increase in the concentration of reducing sugars in the first hours of reaction and percentages of weight loss near 90%. Water resistance was measured by solubility, contact angle and moisture sorption isotherms, with adjustment of the experimental data to mathematical models of Guggen-heim, Anderson de Boer (GAB), Brunauer–Emmet–Teller (BET), Oswin and Jaafar. Trays containing PVA addition showed less solubility, with greater contact angle and lower equilibrium moisture (in aw 0.98). The mathematical models of GAB and Oswin reproduced the best fit to the experimental data of the isotherms. The starch trays showed biodegradability independent of the material used as plasticizer.

Study of sorption isotherm and isosteric heat of Kepok Banana (Musa paradisiaca F.) slice

Kepok banana (Musa paradisiaca F.) is an abundant commodity in Indonesia. This commodity is a kind of horticulture that has high risk to be defect and damage, moreover if it is handled with poor of post-harvest technology, it makes the economic value of this commodity comes low. The processing is needed in order to preserve quality and to improve economic value. Kepok banana contains high amylose and starch around 29.50% so it is suitable to be processed as flour. The critical step of flour processing occurs in the drying process of banana slices so this research focused on slices form. Two important factors of drying process are the equilibrium water content and water activity (aw). The relationship between moisture content and aw at constant temperature is known as Moisture Sorption Isotherm (MSI). The MSI of Kepok banana slice was experimented by static gravimetric method with 5 types of saturated salt in aw range of 0.05-0.90 at 30°C, 40°C, and 50°C. It was tested by BET (Braunauer, Emmet and Teller), Smith, Oswin, Caurie, and GAB (Guggenheim-Anderson-de Boer) model. Then the isosteric heat was calculated using the Clausius-Clapeyron equation. The results showed that the equilibrium moisture content at constant temperature increases with increasing of aw value, while at constant aw equilibrium moisture content decreases with increasing temperature. The most appropriate model in describing the characteristics of MSI Kepok banana slices is GAB model and is classified in type II. In addition, the isostreric heat for desorption is higher than adsorption.

Moisture Sorption Isotherms and Isosteric Heats of Sorption of High-Pressure Treated Paulownia Wood under Different Storage Conditions

Abstract. Understanding of moisture sorption isotherms (MSI) is critical for predicting the stability of wood during handling, transport, and storage. The aim of this study was to evaluate the adsorption and desorption isotherm characteristics of high-pressure (HP) treated paulownia wood and to identify the best-fitting model to describe its sorption behavior. The equilibrium moisture contents (EMCs) of HP-treated paulownia wood were obtained using a static gravimetric method under different storage conditions: three temperatures (20°C, 30°C, and 40°C) and five water activity (aw) levels (0.32 to 0.95). Results showed that HP parameters did not significantly affect the MSI trend of treated groups. Eight modified models (modified Chung-Pfost, modified Henderson, modified Oswin, modified Halsey, Chen-Clayton, Guggenheim-Anderson-de Boer (GAB), simply modified GAB, and Peleg) were fitted to the experimental data. The Chen-Clayton model (temperature-dependent) produced randomized residuals and the best prediction performance for both adsorption and desorption among all models. Net isosteric heat of adsorption and desorption decreased from 7.55 to 4.84 kJ mol-1 and from 18.1 to 12.2 kJ mol-1, respectively, with an increase in EMC from 7.5% to 10%. The isosteric temperature (Tß) was 352 K for adsorption and 335 K for desorption, between which all the adsorption and desorption reactions proceeded at the same rate. All thermodynamic functions were adequately characterized by a power law model. Keywords: Equilibrium moisture content, High-pressure treatment, Modeling, Moisture sorption isotherm, Paulownia wood, Temperature, Thermodynamic analysis.

Determination of Moisture Sorption Isotherm of Crosslinked Millet Flour and Oxirane Using GAB and BET

Epoxy resin was prepared by crosslinking epoxidized oil and millet flour. The reaction was carried out at three different temperatures (25, 40, and 55°C) and zinc chloride levels (1, 2, and 3%). Moisture sorption isotherms were determined at 0.1 to 0.9 water activity (aw) using a gravimetric sorption analyzer (Q 2000). The sigmoidal shape (type II) of the resin isotherms exhibited lower equilibrium moisture content (EMC) at higher temperature. The experimental data were modeled using GAB (Guggenheim–Anderson–de Boer) and BET (Brunauer–Emmett–Teller). The EMC of the resin was significantly lower than that of the flour, which could be attributed to the decrease in the number of water-binding sites due to the creation of dense areas during crosslinking. The low root-mean-square error (RMSE) indicates that GAB and BET were suitable for predicting the water sorption isotherm for millet flour resin. The heat of sorption of the resin was large at low moisture content and increased at higher relative humidity. It is recommended that millet flour resin be used at relative humidity below 60%.

Water sorption and stickiness of spray‐dried grape juice and anthocyanins stability

In this study, grape juice powders from cultivar BRS Violeta was produced through spray drying. The influence of water activities on physical–chemical properties of powder, and the light stability of anthocyanins microcapsules were investigated. Evaluations of sorption isotherms, stickiness, and light stability of the anthocyanins microcapsules were carried out throughout 90 days. Blends of soy protein/maltodextrin and whey protein/maltodextrin in different concentrations and proportions were used as carrier agents. The Brunauer–Emmett–Teller and Guggenheim–Anderson–de Boer models were fitted to data of water adsorption, and the curves were classified as type II. The compression force was strongly dependent on water activity. The encapsulation matrix formulated with 10% soy protein and applied at CACof 1.25 g carrier agent/g soluble solids of the juice (1SM) resulted in the less hygroscopic powder, with a higher compression force, lower stickiness, and better anthocyanin protection, consequently presenting lower total color differences during storage. PRACTICAL APPLICATIONS: This study shows the influence of water activities on the characteristics of spray‐dried grape juice and in the stability of microcapsules. The microcapsules of BRS Violeta grape juice present high amounts of anthocyanins and, therefore, can be used as a natural colorant or as a food additive due to their antioxidant properties. It is important to know the influence of moisture and stickiness on the powders’ properties, because these factors affect the processability, handling, and stability of microcapsules, possibly reducing the product quality. Knowing the physical–chemical properties of the microcapsules formulated with different carrier agents is very important in order to ensure longer shelf life, thus enabling a variety of applications both in the food and the pharmaceutical industry.

Effects of lipids on the water sorption, glass transition and structural strength of carbohydrate-protein systems

Encapsulant systems are gaining wide practical interest due to their functional and nutritional properties. This paper was focusing on understanding structural relaxations in that systems near glass transition temperature. Freeze-dried trehalose-whey protein isolate-sunflower oil systems with various ratios of the last were used as a carbohydrate-protein-lipid food model. The Guggenheim-Anderson-de Boer (GAB) water sorption relationship was used as a tool to model water sorption isotherms. The glass transition temperature was obtained by differential scanning calorimetry (DSC). Structural α-relaxation temperatures were measured by dynamical mechanical analyses (DMA), dielectric analysis (DEA) and combined to cover a broad range for strength assessment. The microstructure was characterized by optical light microscopy, confocal laser scanning microscopy and scanning electron microscopy. The C1 and C2 constants for Williams-Landel-Ferry (WLF) equation and structural strength parameter were calculated for each system. The effect of sunflower oil and water contents on strength of carbohydrate-protein system was analyzed. Strength shows decreasing with increasing of lipid concentration in the mixtures and more complex dependence on the water content in a system.

Nanoscale hygromechanical behavior of lignin

The nanoscale hygromechanical behavior of lignin is presented in this work. Three atomic force microscopy experimental methods were used to correlate moisture sorption of lignin to its mechanical behavior. First, sorption isotherms were established using cantilever mass sensing and subsequently predicted using the Guggenheim–Anderson–de Boer model. The sorption isotherms of lignin particles followed a repeatable and cyclic trend reaching a maximum moisture content of ≈ 17% at ≈ 79% relative humidity (RH). Second, 3D nanomechanical contrast images were obtained using contact resonance force microscopy (CR-FM) to observe the hygromechanical response of lignin over three RH cycles. Finally, force volume mapping and the Hertz model were used to compute the elastic modulus of lignin as a function of moisture content. As RH increased, CR-FM measurements revealed initial topographical heterogeneity, as well as notable surface softening, especially in initially smooth domains. The average elastic modulus of the smooth domain decreased from 9.0 to 4.3 to 2.4 GPa as the moisture content increased from 0.024 to 9.1 to 17.3%, respectively. Cyclic measurements confirm that the elastic modulus of lignin rebounds upon moisture desorption.

Moisture Sorption Isotherm Characteristics of Fermented Cassava Flour By Red Yeast Rice

This study aims to study the characteristics of moisture sorption isotherm of fermented cassava flour by red yeast rice at various fitting models and to determine the best fit model. Samples were analyzed at 303K, 308K, and 313K and equilibrium relative humidity (ERH) from 10%-99% using the gravimetric method. The experimental data were fitted into five equations, e.g., Guggenheim-Anderson-de Boer (GAB), Henderson, Halsey, Oswin, and Chen-Clayton model. The best-fitting model was analyzed using Mean Relative Determination (MRD) analysis. The results showed that the GAB model was the best fitting model for 303K and 308K with MRD coefficient 1.98% and 3.11%. Henderson model was the best fit model for 313K with MRD coefficient 3.32%.

Adsorption of Difluoromethane (HFC-32) onto phenol resin based adsorbent: Theory and experiments

Adsorption and desorption of difluoromethane (HFC-32) onto newly developed phenol resin based adsorbent (SAC-2) have been measured experimentally for the isotherm temperatures ranging from 30 °C to 130 °C and pressure up to 3 MPa. A magnetic suspension balance based adsorption measurement unit is used to measure adsorption uptake gravimetrically. The presented SAC-2/HFC-32 pair has adsorption uptake as high as 2.23 kgref/kgads (excess adsorption) and 2.34 kgref/kgads (absolute adsorption) at 30 °C and 1.67 MPa. To the best of our knowledge, it is the highest HFC-32 adsorption capacity onto any adsorbent available in the literature. The experimental data of adsorption/desorption isotherms show that there is no hysteresis for the studied pair. The data have been fitted with Tóth; Dubinin–Astakhov (D–A); and Guggenheim, Anderson, De-Boer (GAB) adsorption isotherm models. The parameters of adsorption isotherm models are optimized by nonlinear optimization technique. The D–A model fits the experimental data precisely as compared to other models. In addition, numerical values of isosteric heat of adsorption have also been extracted by means of Clausius–Clapeyron equation using adsorption isotherm models.

Sorption isotherm modeling of “gaplek” flour fortified by protein from red bead tree flour

The objective of the study is to determine the characteristic of moisture sorption isotherm from "gaplek" flour fortified with protein from red bead tree flour using various modeling and being observed from the monolayer moisture content and its absorption types. This research used 5 salt solutions and storage temperature of 298K, 308K, and 318K. The models used were Brunauer-Emmet-Teller (BET), Guggenheim-Anderson-de Boer (GAB) and Caurie model. The monolayer moisture content was around 5.07 – 8.53% db. kb value of GAB model was around 0.5941-0.6252. c value of GAB model was around 16.0588-23.4111. C value of BET was around 32.7241-306.5000. Whereas the c value in Caurie model was around 1.1419-1.2769. The equilibrium and monolayer moisture content on ‘gaplek" flour fortified with protein from red bead tree flour was decreasing as the temperature going up. GAB constant value indicated that the process of moisture absorption on the "gaplek" flour fortified with protein from red bead tree flour categorized in type II.

Moisture sorption isotherms and thermodynamic properties of sorbed water of chironji (Buchanania lanzan Spreng.) kernels at different storage conditions

Moisture sorption isotherms of chironji kernels were determined at 25, 35 and 45 °C over a water activity range of 0.11–0.93. Three sorption models i.e., Guggenheim–Anderson–de Boer (GAB), Brunauer–Emmett–Teller (BET) and Caurie were evaluated to find out their fitness to the sorption data. Thermodynamic properties of sorbed water were analyzed over the selected range of water activity and temperature. The result showed that the sorption isotherms reflected Type II BET sorption characteristics with a clear hysteresis at the temperatures. Of the three models, GAB and Caurie models were found superior predicting the sorption of chironji kernels over the entire range of water activity values. The monolayer moisture content values calculated by the best-fitted GAB and Caurie model for adsorption were 9.86 and 6.31%, 8.023 and 6.18%, 6.90 and 5.97% (db) and for desorption were 6.53 and 6.01%, 5.85 and 5.68%, 4.21 and 5.60% (db), respectively at 25, 35 and 45 °C. The value of isosteric heat decreased with increasing moisture content and approached the latent heat of pure water. Sorption entropy increased with increasing moisture content and decreased gradually with increase in moisture content. The spreading pressures, for both adsorption and desorption, increased with increasing water activity at the three selected temperatures.