Oswin Model Research Articles

Adsorption Isotherms and Vaporization Latent Heat of Malagueta Pepper Seeds

The aim of this study was to determine and model malagueta pepper seeds’ adsorption isotherms, as well as to estimate the vaporization latent heat released during adsorption process. Hygroscopic balance moisture contents were determined by static method, using six saline solutions and three temperatures. Clausius- -Clapeyron equation used to calculate malagueta pepper seeds vaporization latent heat. From obtained results, it was concluded that temperature increase promotes malagueta pepper seeds moisture content reduction, in constant water activity. The Modified Oswin model properly adjusted to the experimental data, satisfactorily representing pepper seeds adsorption isotherms. The energy released during the adsorption process, represented by vaporization latent heat, increases with moisture content reduction, ranging from 2762.92 to 2495.56 kJ kg -1 for moisture contents from 0.056 to 0.134 (db).

Sorption isotherms modeling approach of rice-based instant soup mix stored under controlled temperature and humidity

Moisture sorption isotherms of rice-based instant soup mix at temperature range 15–45°C and relative humidity from 0.11 to 0.86 were determined using the standard gravimetric static method. The experimental sorption curves were fitted by five equations: Chung-Pfost, GAB, Henderson, Kuhn, and Oswin. The sorption isotherms of soup mix decreased with increasing temperature, exhibited type II behavior according to BET classification. The GAB, Henderson, Kuhn, and Oswin models were found to be the most suitable for describing the sorption curves. The isosteric heat of sorption of water was determined from the equilibrium data at different temperatures. It decreased as moisture content increased and was found to be a polynomial function of moisture content. The study has provided information and data useful in large-scale commercial production of soup and have great importance to combat the problem of protein-energy malnutrition in underdeveloped and developing countries.

Finite Element Simulation of Shelf Life Prediction of Moisture-Sensitive Crackers in Permeable Packaging under Different Storage Conditions

A finite element method (FEM) approach using COMSOL Multiphysics software was presented to solve unsteady-state moisture diffusion differential equations and predict the shelf life of crackers based on critical moisture content obtained by sensory evaluation. The crackers' moisture contents were given as a function of storage time, environment conditions (temperature and relative humidity) and the package materials. Classical Oswin model was used to fit the moisture sorption data at four different temperatures. Effective moisture diffusivity of crackers as a function of moisture content and temperature were investigated. In addition, the relationship of moisture permeability coefficient and temperature of two selected packaging films, low-density polyethylene (LDPE) and cast polypropylene (CPP) film, was determined based on Arrhenius equation. The crackers were packaged in LDPE and CPP packaging pouches, and stored at four different conditions to simulate actual storage conditions and determine the shelf life experimentally. There was a good agreement between experimental results and finite element predictions for moisture-sensitive crackers subjected to different storage and packaging conditions. Practical Applications This paper describes the shelf life prediction of crackers using a simulation model based on unsteady-state Fickian diffusion of moisture through the food. The temperature effect on the moisture sorption, moisture diffusivity of foods and the moisture permeability coefficient of packaging films are considered. The food product's moisture content was simulated using COMSOL Multiphysics as a function of storage time under different storage conditions and packaging film. The finite element simulation provides a powerful support tool for shelf life estimation and packaging development.

Kinetics and Equilibrium Isotherms of Water Vapor Adsorption/Desorption in Cement-Based Porous Materials

The kinetics and equilibrium of water vapor adsorption/desorption isotherm (WVSI) are fundamental information for solid–moisture interaction in the microstructure of cement-based porous materials (CBPM). This paper presents firstly the experimental data for WVSI of CBPM with a ternary binder. Mass changes in specimen are recorded in sorption tests for materials with different aggregate contents and water-to-binder (w/b) ratios under controlled ambient relative humidity. Both the sorption equilibrium and sorption kinetics are investigated through some established physical models, and the corresponding intrinsic parameters of moisture sorption are determined. For sorption kinetics, the mass change during sorption is interpreted through Elovich model, power model and pseudo-first-order and pseudo-second-order models. The mass change in sorption occurs mainly in the first 40 days, and the pseudo-second-order model shows the best adaption to all adsorption/desorption processes. For sorption equilibrium, Guggenheim–Anderson–de Boer (GAB), modified Halsey and Oswin models are used to interpret the moisture sorption capacity. The hysteresis between adsorption and desorption processes is attributed, respectively, to the mechanisms of snap-through, energy instability and pore constrictivity for low, middle and high relative humidity ranges. From the analysis, it is found that (1) through the interpretation of pseudo-second-order model the moisture sorption kinetics can be controlled by the sorption between the water molecules and the pore wall in addition to vapor diffusion; (2) the sorption capacity is sensitive to aggregate content and w/b ratio; incorporating aggregates, decreasing w/b ratio and increasing humidity gradient tend to decrease the sorption capacity of CBPMs; (3) the sorption isotherm hysteresis is well described by GAB-H model, both the extent of hysteresis and the energy constant related to pore surface tension showing clear correlation with the aggregate content and w/b ratio of CBPMs.

Investigation and modeling of moisture sorption behaviour of rice starch/carboxymethyl chitosan blend films

The biopolymer films from rice starch (RS) and carboxymethyl chitosan (CMCh) were developed by solution casting. The effect of the ratios of rice starch to CMCh (100:0, 88:12, 67:33, 50:50, 33:67, 12:88 and 0:100) on water barrier properties and moisture sorption isotherm of blend films was studied. Water vapor permeability of rice starch film and CMCh film were 4.8 and 9.1 g.mm/m2.mHg.day, respectively, while those of the RS/CMCh blend films ranged between 5.0 and 9.1 g.mm/m2.mHg.day. The sorption isotherm of RS/CMCh blend films was determined at 25°C. The sorption behaviour of RS/CMCh blend films could be categorized as type II and type III isotherms. The highest equilibrium moisture content (63.5 g water/100 g dry solid) was obtained in the CMCh film at aw of 0.87. For further application of sorption isotherm data, the moisture sorption characteristic of the films can be predicted using empirical models. Lewicki, Peleg, Guggenheim-Anderson-deBoer (GAB), Brunauer-Emmett-Teller (BET), and Oswin models were tested to fit the experimental data. The Peleg equation showed the best fit to the experimental data of the RS/CMCh blend films with r2 ∼ 0.997 and the lowest % RMS of 6.2-44.3.

Adsorption isotherms of hog plum (Spondias mombin L.) pulp powder obtained by spray dryer

Food sorption isotherms are highly important to predict drying time and storage conditions of a product. Current assay evaluates the behavior of adsorption isotherms of hog plum powder obtained by spray-dryer, through mathematical models. GAB, BET, Henderson and Oswin models were adjusted to the experimental data at 25, 30, 35 and 40oC. The BET model best adjusted to the atomized hog plum for all temperatures tested, with an error ranging between 8.45 and 11.17%. The coefficient of determination (R 2 ) had rates higher than 0.9900 for all the adjusted models. The behavior of hog plum powder adsorption isotherms was classified as Type III.

Modeling the equilibrium moisture content (EMC) of Miscanthus sinensis, miscane, energy cane, and energy sorghum

Understanding of moisture sorption isotherms of bioenergy crops is critical to monitoring their stability and quality during harvest, handling, transportation, and storage. Relationships between the moisture content (EMC) and equilibrium relative humidity (ERH) of four biomass crops – Miscanthus sinensis, miscane, energy cane, and energy sorghum – were determined at 15, 25, and 35°C. Type II and type III isotherm characteristics were observed in all samples. The Henderson, modified Henderson, modified Chung-Pfost, modified Halsey, modified Oswin, and modified GAB models were applied to the individual energy crop’s sorption isotherm data and a global isotherm model for the four energy crops was developed. Results showed that the modified Oswin model best fit the sorption behavior of the individual crops (0.974⩽R2⩽0.997 and 0.72% wet basis (w.b.)⩽standard error (SE)⩽1.91% w.b.) and for a global isotherm model of these crops (R2=0.973 and SE=1.96% w.b.). When the soluble sucrose content (0.00–15.9%) of the energy crops were included the global isotherm model based on the modified Oswin equation, overall performance improved (R2=0.979 and SE=1.75% w.b.).

Moisture adsorption of sprouted bambara groundnut flour (Vigna subterranean)

This study investigated the moisture adsorption characteristics of sprouted Bambara groundnut (Vigna subterranean). The adsorption isotherm for sprouted Bambara groundnut was determined and studied at room temperature (27±2 °C) using the static gravimetric method. Samples were equilibrated in desiccators containing tetraoxosulphate (VI) acid solution of known relative humidity varied from 20%, 30%, 40% and 50%. The moisture content was then calculated using the data of initial moisture content and the amount of moisture gained or lost at equilibrium. The desiccators were made into each relative humidity and were studied at room temperature (27±2 °C). The plot of equilibrium moisture content against water activity at 20%, 30%, 40% and 50% for adsorption process gave a sigmoidal shaped isotherm curve. The equilibrium moisture content value increased with water activity. The Henderson and Oswin models gave the best fit and could be used to present the moisture adsorption isotherm of sprouted bambara groundnut flour for water activity content range of 0.2 to 0.5.

Adsorption thermodynamics of sugarcane (Saccharum officinarum L.) powder obtained by spray drying technology

Background: Sugarcane is one of the world’s largest crop. It grows in the tropical and subtropical regions, and its harvest provides 80% of the world’s sugar. In Latin America unrefined cane sugar is widely available and much less expensive than refined sugar. Sugarcane is a crop of great interest in Colombia due to the economic impact on the rural population and its application as sweetener agent. The poder of sugarcane (Saccharum officinarum L.) is widely used as a raw material in a wide range of industries such as foods, pharmaceutical, cosmetic and chemical. Objectives: The aim of the research work was the evaluation of the adsorption thermodynamics of sugarcane powder obtained by spray drying technology. Methods: The adsorption isotherms of sugarcane powder were evaluated at temperatures of 4 ± 0.1, 20 ± 0.2 and 30 ± 0.3 °C and its thermodynamic properties such as Gibbs free energy (G), differential heat of adsorption (ΔH) and differential entropy (ΔS) were calculated as a function of moisture content. Experimental data of adsorption isotherms were fitted to the GAB (Guggenheim – Andersen - de Boer), BET (Brunauer – Emmett - Teller), Henderson, Caurie, Smith, Hasley, Peleg, and Oswin models. Results: The results showed a type-II sigmoidal behavior, with temperature having a statistically significant effect. The GAB equation showed a better fit to the experimental data modeling (0.11≤aw≤0.87) although all models showed validity and goodness of fit to the experimental data. The net isosteric heat increased to a maximum value (57 kJ mol-1) and then decreased with the increase in moisture content. Conclusions: The sugarcane powder with maltodextrin, obtained by spray drying got low adsorption thermodynamic stability, as it required very low energy to occur this phenomenon, being obtained the maximum net isosteric heat when moisture content of 4.7% (d.b). This value is within the range of the monolayer moisture content found in the GAB and BET models.

Hygroscopic properties of solid agro-industrial by-products used in solid-state fermentation

One of the main drawbacks in operating solid-state fermentation (SSF) bioreactors is the reduction in moisture content (MC) of the solid phase due to microbiological and physicochemical issues. Therefore, heat and mass transfer models require hygroscopic information concerning the solid substrate. This contribution addresses the study of the sorption isotherms of sugarcane bagasse (SCB) and wheat bran (WB) obtained using the static gravimetric method, with temperature and water activity as the controlled variables. The Oswin model was selected to construct the sorption isotherm for SCB, and the Halsey model, modified in the present study, for WB. The Bates and Watts curvature measurements and the Box parameter bias were used to analyze the nonlinear behavior and assess the goodness of the fitting process. Fermentative assays were carried out in glass flasks for the production of endoglucanase employing the fungus Myceliophthora thermophila I-1D3b, controlling the environmental water activity, in order to assess the influence of the loss of moisture from the solid phase on fungal metabolic activity.

Impact of Swell-Drying Process on Water Activity and Drying Kinetics of Moroccan Pepper (Capsicum annum)

The impacts of total hot air drying (THD) and the swell-drying process (SD), which is hot air drying coupled with an instant controlled pressure drop DIC process, on the drying kinetics and adsorption isotherm behavior, were determined in the case of Moroccan peppers. Drying kinetics were studied through a model that takes into account the starting accessibility and the internal diffusion model with Fick's law. Adsorption experimental data were obtained by using the gravimetric method at 25, 40, and 50°C. Data were fitted to the GAB, Halsey, and Oswin models. Studied responses were: effective diffusivity (Deff), starting accessibility (δWs), monolayer moisture content (Xm), specific surface area (σ), internal porosity (ϵ), and microstructure. Mean relative percentage deviation (E) and root mean square (RMS) were used to evaluate the fitting of models. Results showed that: pepper adsorption isotherms followed the type II isotherm curve;the equilibrium moisture content (Xeq) depended on the temperature and the drying method; the GAB and Halsey models fitted well the experimental data; at selected conditions of the DIC treatment (0.35 MPa and 5 s), the monolayer moisture content (Xm), the specific surface area (σ), and the internal porosity values were higher than those of THD samples; the DIC process intensified the drying operation, by increasing the effective diffusivity and the starting accessibility. Although the DIC process improves the drying kinetics, this behavior could be ignored related to a higher aw. This study shows that, thanks to the new expanded structure obtained by the DIC process (higher porosity), the adsorption capacities of products are improved (aw is reduced). Thus, the SD process improves both the drying operation and the stability of dried pepper products.

Modeling Soil Water Retention Curves in the Dry Range Using the Hygroscopic Water Content

Accurate information on the dry end (matric potential less than −1500 kPa) of soil water retention curves (SWRCs) is crucial for studying water vapor transport and evaporation in soils. The objectives of this study were to assess the potential of the Oswin model for describing the water adsorption curves of soils and to predict SWRCs at the dry end using the hygroscopic water content at a relative humidity of 50% (θRH50). The Oswin model yielded satisfactory fits to dry‐end SWRCs for soils dominated by both 2:1 and 1:1 clay minerals. Compared with the Oswin model, the Campbell and Shiozawa model combined with the Kelvin equation (CS‐K) produced better fits to dry‐end SWRCs of soils dominated by 2:1 clays but provided poor fits for soils dominated by 1:1 clays. The shape parameter α of the Oswin model was dependent on clay mineral type, and approximate values of 0.29 and 0.57 were obtained for soils dominated by 2:1 and 1:1 clays, respectively. Comparison of the Oswin model combined with the Kelvin equation, with water potential estimated from θRH50 (Oswin‐KRH50), CS model combined with the Arthur equation (CS‐A), and CS‐K model, with water potential obtained from θRH50 (CS‐KRH50) indicated that for soils dominated by 2:1 clay minerals, the predictive ability of the Oswin‐KRH50 model was comparable to the CS‐KRH50 model in which θRH50 was the input parameter but performed better than the CS‐A model where clay content was the input parameter. The Oswin‐KRH50 model also has the potential for predicting dry‐end SWRCs of soils dominated by 1:1 clays.

Avaliação físico-química e comportamento higroscópico de goiaba em pó obtida por spray-dryer

The guava is one of the most popular tropical fruits, being highly accepted all over Brazil. Many food products can be made from the fruit, such as jams, jellies, liquors and many types of juice. Given the above, the objective of this research was to characterise atomised guava pulp as to its physicochemical composition, and assess its hygroscopic behaviour by means of adsorption isotherms employing different mathematical models. The physicochemical analyses, carried out on both the whole guava pulp and on the atomised guava powder, were: moisture; pH; acidity; soluble solids and ascorbic acid, giving the following results respectively: 88.57-5.69 %; 3.76-3.88, 0.43-0.24 mg 100 g-1; 8.43 to 93.00 ºBrix and 2.77-3.79 mg 100 g-1. The adsorption isotherms were constructed adjusting the experimental data to the mathematical models of GAB, BET, Henderson and Oswin. The Henderson model presented the best fit to the atomised guava powder for all temperatures tested, presenting an error ranging from 09.93 to 12.09% and a correlation coefficient ranging from 0.9900 to 0.9934.

볶음온도에 따른 옥수수 분말의 흡습특성

The moisture sorption isotherms of corn powder prepared from corn kernels roasted for 20 min at 160, 180, 200, 220, and 240°C were determined at 20°C using the static gravimetric method over the range of water activities (aw) of 0.11~0.90. The moisture sorption isotherms showed a typical sigmoid shape, and the equilibrium moisture content tended to increase with increasing aw, and increased sharply at above 0.75 aw. At above 0.53 aw, the equilibrium moisture content of the roasted corn powder increased with the increase in the roasting temperature. Six mathematical models (Bradley, Caurie, Halsey, Henderson, Kuhn, and Oswin) were used to fit the experimental data. The Oswin, Caurie, Henderson, and Halsey models were found to have suitability for describing the sorption curves, and the Oswin model was the best fit model for all the roasting temperatures. Concerning the monolayer moisture content, the Guggenheim-Anderson-Boer (GAB) equation showed high significance. The monolayer moisture content increased as the roasting temperature was increased, to 0.043 and 0.053 kg H2O/kg solids in the corn powder roasted at 180°C and 240°C, respectively. These results suggest that the roasting temperatures of the corn kernels affected the moisture sorption characteristics (20°C) of the corn powder.

Mathematical Modeling of Moisture Sorption Isotherms and Determination of Isosteric Heats of Sorption ofZiziphusLeaves

Desorption and adsorption equilibrium moisture isotherms ofZiziphus spina-christileaves were determined using the gravimetric-static method at 30, 40, and 50°C for water activity(aw)ranging from 0.057 to 0.898. At a givenaw, the results show that the moisture content decreases with increasing temperature. A hysteresis effect was observed. The experimental data of sorption were fitted by eight models (GAB, BET, Henderson-Thompson, modified-Chung Pfost, Halsey, Oswin, Peleg, and Adam and Shove). After evaluating the models according to several criteria, the Peleg and Oswin models were found to be the most suitable for describing the sorption curves. The net isosteric heats of desorption and adsorption ofZiziphus spina-christileaves were calculated by applying the Clausius-Clapeyron equation to the sorption isotherms and an expression for predicting these thermodynamic properties was given.

Investigation of moisture sorption behavior of soluble sodium caseinate

Casein is a potential food protein, used in a number of food applications. In this work, moisture sorption isotherms of casein were determined at 10, 20 and 30 o C under different relative humidity in the range of 12 to 98 percent using gravimetric method. The equilibrium moisture uptake data were interpreted with the help of three well-known sorption isotherm models namely, (GAB, Halsey and Oswin models) using non-linear least square method. The experimental moisture uptake data were best interpreted by GAB model. The monolayer moisture content X m was found to vary from 54.08 x 10 -3 to 10.48 x10 -3 kg kg -1 (db) for a temperature rise from 10 to 30 o C, thus indicating negative temperature dependence. The Clausius-Clapeyron equation was used to determine the isosteric heat of sorption (q st ). The uptake data was also used to determine isokinetic temperature T β (315.9 K) and harmonic mean temperature T hm (292.8 K). The enthalpy-entropy compensation theory indicated that moisture sorption process was enthalpy driven.

<b>Hygroscopic behavior of freeze-dried papaya pulp powder with maltodextrin</b> - doi: 10.4025/actascitechnol.v36i1.17499

The sorption isotherms describe the relationship between water activity and equilibrium moisture content of foods at a certain temperature. This work was carried out to study the hygroscopicity of freeze-dried papaya pulp powder with maltodextrin at different concentrations using sorption isotherms constructed at 25° C. Three formulations of freeze-dried powders were prepared, papaya pulp powder, papaya pulp powder with maltodextrin 5% (w w -1 ) and papaya pulp powder with maltodextrin 15% (w w -1 ). In order to adjust the adsorption isotherms data, mathematical models of GAB, BET, Henderson and Oswin were used. The GAB model showed the best fit for all samples. The addition of maltodextrin increased the amount of water in the monolayer and reduced the hygroscopicity of the powders

Comportamento das isotermas de adsorção do pó da polpa de manga liofilizada

A qualidade e a vida útil dos pós de frutas dependem de seus teores de água e da maneira como esta se encontra ligada ao alimento. O comportamento higroscópico de alimentos em pó pode ser avaliado através de suas isotermas de sorção. O objetivo deste trabalho foi avaliar modelos matemáticos para representação da isoterma de sorção do pó de manga liofilizada e avaliar as características físico-químicas da polpa de manga in natura e seu pó liofilizado. Foram feitas as análises de umidade, pH, sólidos solúveis, acidez total titulável, ácido ascórbico e cor. Os modelos matemáticos ajustados aos dados experimentais foram BET, GAB, Henderson e Oswin nas temperaturas de 25, 30 e 35 °C. O melhor ajuste aos dados experimentais foi obtido pelo modelo de GAB. O modelo de GAB apresentou erros médios de 4,092 a 5,175% e valores de R entre 0,9986 a 0,9993 para as temperaturas estudadas. As isotermas do pó da polpa de manga liofilizada apresentaram formato característico do tipo III.

Prediction Modeling for Moisture Sorption Isotherms of Rice Starch/Carboxymethyl Cellulose from Durian Rind Blend Films

Rice starch/carboxymethyl cellulose from durian rind (RS/CMCd) blend films were prepared by solution casting. The effect of different ratios between rice starch and CMCd (100:0, 88:12, 67:33, 50:50, 33:67, 12:88 and 0:100) on moisture sorption isotherm of blend films was investigated. The sorption isotherm of RS/CMCd blend films was determined at various relative humidity (RH) at 25°C. The isotherm curves revealed that the highest equilibrium moisture content (EMC) was obtained from CMCd film, at aw=85. Knowledge of sorption isotherms is important to predict the moisture sorption properties of the filmsviamoisture sorption empirical models. The Lewicki, Peleg, Guggenheim-Anderson-deBoer (GAB), BrunauerEmmettTeller (BET), and Oswin models were tested to fit the experimental data. The root mean squares percentage error (%RMS) of Lewicki, Peleg, GAB, BET and Oswin was in the range of 5.3-83.1, 2.2-20.0, 6.9-20.2, 3.4-26.4 and 4.7-41.2, respectively. The Peleg model was found to be the best fitted model for RS/CMCd blend films.

Modeling of the Equilibrium Moisture Content (EMC) of Switchgrass

<abstract><title><italic>Abstract.</italic></title> Moisture sorption isotherms of milled switchgrass (Panicum virgatum) were developed to provide guidelines for proper storage and drying of biomass. Samples were stored for a minimum of 8 days inside incubators set at 15°C, 25°C, or 35°C at different relative humidities, ranging from 16% to 88%. Equilibrium moisture content (EMC) data were fitted with the Henderson model and modified versions of the Chung-Pfost, Guggenheim-Anderson-deBoer (GAB), Halsey, Henderson, and Oswin models. The modified GAB model (R² = 0.99; SE = 0.58% d.b.) followed by the modified Henderson model (R² = 0.99; SE = 0.68% d.b.) produced randomized residuals and the best fit for milled switchgrass. The results have practical applications in the handling, drying, storage, and transportation of switchgrass to ensure that quality deterioration and spoilage by microorganisms are minimized.