Oswin Model Research Articles

Simulation of Storage Conditions of Mixed Biomass Pellets for Bioenergy Generation: Study of the Thermodynamic Properties

Experimental and mathematical modeling of the moisture sorption isotherms for biomass pellets during storage is performed in this study. The tested pellets are a mixture of 50% wood: spruce or pine, and 50% switchgrass agricultural biomass. Storage conditions, i.e., temperature and humidity, are tested by varying the environment conditions in a conditioning chamber. The experimental results show that the moisture sorption isotherms are not affected by the temperature. Nevertheless, the equilibrium moisture content depends on the kind of the tested pellets. Mathematical modeling of the experimental isotherms is performed using four common models: the Oswin, GAB, Henderson and Peleg models. The Oswin model is defined as the most appropriate model to predict the moisture sorption isotherms of the spruce–switchgrass pellets. It presents a coefficient of determination equal to 0.998, a standard error around 0.049 and a chi-square approaching 0.007. On the other hand, Henderson and GAB models show the best results for pine–switchgrass pellets, with a coefficient of determination varying between 0.998 and 0.997, a standard error range 0.054–0.065 and chi-square error between 0.008 and 0.009. The thermodynamic properties, which include the net isosteric of heat and the entropy changes of sorption, are also determined for all tested samples.

Determination of thermophysical and desorption properties of elephant foot yam using composition based and fast sorption method

In the present work, thermophysical properties (thermal conductivity, specific heat, density and thermal diffusivity), and sorption properties (water activity and total isosteric heat of desorption) of elephant foot yam (EFY) tuber crop are determined at different temperatures. EFY is a widely consumed tuber crop which is mainly grown in tropical and subtropical regions of Southeast Asian countries. The thermophysical properties are determined using composition and temperature based thermophysical property models for each constituent in conjunction with the constituents present in the food material. Two different methods - gravimetric and fast sorption have been used for determining the sorption properties of EFY. Three sorption models are used to find the best model which describes the experimental sorption behaviour of EFY. It is found that all thermophysical properties increase with temperature except the density of the EFY. The sorption behaviour of EFY is observed as sigmoid shape for all temperatures which comes under II type of sorption isotherm. GAB model is found to be the best model followed by BET and OSWIN model to describe the desorption isotherm of EFY. The total isosteric heat of desorption of EFY drastically increases at lower moisture content as compared to higher moisture content of EFY.

Sorption Isotherm of Corn Chips Made from Blends of Corn Flour and Bambara Groundnut Nut Flour

The adsorption equilibrium moisture contents of corn chips (kokoro) made from blends of maize flour and Bambara nut flour was investigated by measuring water activities at 27°C, 37°C and 40°C using the static gravimetric method. Sorption isotherms followed a type II shape in water activities range from 0.10 - 0.80 showing characteristics of most biological tissues. Five isotherm model equations were used which are BET, GAB, Oswin, Halsey and Henderson. The experiments were performed using polythene packaging and exposed petri dishes. The samples were weighed at two days interval until equilibrium was attained when three identical measurements were obtained. The equilibrium moisture content (EMC) decreased with increase in temperature at constant water activity and polythene packaging had lower EMC compared to petri-dishes. Oswin and Henderson model were best fit at 27°C with RSS = 1.929×10^-5, SEE = 0.00011, R² = 0.99531 and RSS = 0.001192, SEE = 0.00011, R² = 0.9807 for polythene and petri-dish respectively. Oswin model was best fit for both storage conditions at 37°C and 40°C. The monolayer moisture content at the three temperatures ranged from 0.0193 - 0.0752 and the general model observed for this study that could predict the sorption behavior of Bambara-corn chips was Oswin model.

Desorption of the Exotic Fruit Jujube (Ziziphus Jujube Mill) of Bulgarian Origin

The present study determined the physico-chemical parameters of the exotic fruit jujube (Ziziphus jujube mill) of Bulgarian origin – pH of 4.62, refractometric dry matter of 31.6 %, dry matter (in weight) of 36.78 %, TTA (total titratable acidity) – citric acid – of 0.67 %, 0.70 % malic acid, 65.95 % moisture, 0.78 % fibre, 1.41 % protein, 23.65 % carbohydrate, 0.24 % fat and energy value of 428.44 kJ/102.4 kcal. Equilibrium moisture content and monolayer moisture content were established for desorption concerning eight water activities in the 0.1 0.9 range and the temperatures of 10 °С, 25 °С and 40 °С. The coefficients of the modified Oswin, Chung-Pfost, Halsey and Henderson models were obtained statistically. The modified Halsey model is recommended as a description of the desorption isotherms of jujube (Ziziphus jujube mill) since it corresponds to the criteria for model assessment and suitability. Via BET model linearization, the values of the monolayer moisture content for desorption at the temperatures of 10 °С 5.41 % d.b., 25 °С – 4.65 % d.b. and 40 °С 5.08 % d.b were determined.

Sorption isotherms of tobacco (Nicotiana tabacumL.) seeds

The moisture sorption capacity of tobacco seeds is decisive for their safe long-term storage; therefore, the analysis of the sorption isotherms, in a wide temperature and water activity range, is essential for seed quality maintenance in storage. In this study, the equilibrium sorption isotherms of tobacco (N. tabacumL.) seeds, “Kroumovgrad 90” variety of Oriental tobacco, were determined. The experimental data were obtained by the static gravimetric method at different temperatures and water activities. Sorption isotherms showed a typical Type II sigmoidal profile, with a significant hysteresis effect and a decrease of seed sorption capacity with the increase of temperature. The best fitting with tobacco seed sorption isotherms were the modified Chung-Pfost (desorption) and Oswin (adsorption) models. The monolayer moisture content, important for the safe storage of tobacco seeds, was also determined. The outcomes from the study might be of practical use in tobacco seed conditioning and storage design.

Effect of particle size and temperature on the hygroscopic behaviour of cassava flour from dry group and storage time estimation

ABSTRACT The cassava flour from dry group is marketed and consumed under three different particle sizes (coarse, medium and fine), mostly in the North and Northeast regions of Brazil. Thus, as a contribution to the packaging, storage and handling of this type of flour, moisture sorption isotherms were made at 25°C, 35°C and 45°C, for three different particle sizes. Five mathematical models were fitted to the moisture sorption data and the isosteric heat of sorption (Qst) was calculated. The sorption isotherms indicated that the particle size did not interfere on the product’s hygroscopicity and moistures below 9.55 g H2O/100 g ensures the product’s microbiological stability when stored between 25°C and 45°C. The Oswin model displayed the best fit and the Qst values indicated that great amount of energy is involved in the product’s drying process. The storage time of the product was estimated in 136 days.

Determination of Moisture Sorption Isotherms of Rice and Husk Flour Composites

HighlightsMoisture sorption isotherms of rice and husk flour composites were determined.Adsorption isotherms were best modeled by the Chung-Pfost and Oswin equations.Desorption isotherms were best modeled by the Polynomial and Chung-Pfost equations.The Modified Oswin model was the best for both adsorption and desorption.Abstract. Empirical models describing isotherms specifically for adsorption and desorption have not been described for rough rice and husk flour composites. Such models are vital for process control and monitoring operations which use rice husk and rice flours or their mixtures for food or material processing. The current study was undertaken to determine the moisture sorption isotherms of rice husk flour, rough rice flour and their mixtures subjected to different temperature levels. Effects of rice husk flour to rough rice flour ratio of 0:1 (0.0%), 1:49 (2.0%), 1:16 (5.9%), and 1:0 g/g (100.0%) on rough rice moisture isotherms at temperature levels of 20°C, 40°C, and 60°C were investigated. The dynamic dewpoint isotherm technique (DDI) was used to generate accurate isotherms. Several empirical models were tested to fit the experimental EMC data. All the isotherms showed typical sigmoidal type 2 shapes. The equilibrium moisture content (EMC) over equilibrium relative humidity (water activity) ranging from 10% to 95% showed temperature dependence. Hysteresis was evident for all samples, with a decreasing level at a higher temperature. Rice husk flour to rough rice flour ratio, as a factor, showed a significant effect on the EMC of rough rice. The EMC decreased with an increase in rice husk flour levels. Chung-Pfost and Oswin were the two best models for describing adsorption isotherm, and Polynomial and Chung-Pfost were the best models for fitting the desorption isotherm. Modified Oswin model was the best model amongst the two-variable models for describing both adsorption and desorption isotherms. Keywords: Empirical models, Equilibrium moisture content, Rice husk flour, Rough rice flour, Sorption isotherms.

Shelflife Estimation of Seaweed Dodol in OPP Packaging by Using Accelerated Shelf Life Test Method

AbstracThis research is carried out due to the limited information on the shelf-life of food product in Indonesia, especially in South Sulawesi. In addition, there is no sufficient information on the self-life of packed seaweed dodol which produced by using scientific method. Seaweed dodol has a high economic value. The objective of this research was to estimate the self-life of seaweed dodol which is produced in traditional scale (micro, small, and middle scale bussiness) using the scientific method. Accelerated Shelf Life Testing (ASLT) Method is one of methods used in determining the shelf life of seaweed dodol based on critical water content and graining as indicators of quality deterioration. The isotermic sorption model of products was obtained from isotermic sorption curve formed from the relationship between the values of water activity (aw) and the equilibrium moisture content (Me). Moreover, five different models of isotermic sorption were tested. They were Hasley, Chen-Clayton, Henderson, Caurie, and Oswin model. The results showed that the Henderson model was the appropriate model in describing the isotermic sorption phenomena at seaweed dodol with the Mean Relative Deviatian (MRD) of 1.4. By integrating the critical moisture content (Mc), packing permeability (OPP), sample weights (Ws), the surface area of packing (A) and the saturated vapor pressure (Po) into the equation Labuza, the self-life of seaweed dodol at temperature of 30 °C and RH of 78% was 56 days.

EFFECT OF TEMPERATURE ON DESORPTION ISOTHERMS FOR BEEF

Desorption isotherms of beef were determined by the standard static gravimetric technique, based on theuse of saturated salt solutions with water activities from 0.05 to 0.9. Equilibrium moisture content ofeach sample at different temperatures and water activities were determined. The stable moisture contentfor meat during drying was also established. The GAB, BET and Oswin models were used to fit theexperimental sorption data. Non-linear regression analysis was performed to estimate model parametersand fitting quality evaluated using the Coefficient of determination (R2) and the standard error ofestimate (SEE). The equilibrium moisture content decreased with increase in temperature at constantwater activity and increased with increase in water activity at constant temperature. The criticalmoisture was 10-20 % (d.b). The high values of R2 and low values of SEE for the GAB and Oswinmodels indicated that these models gave the best fit for the desorption data of beef

Hygrothermal Characterization of Compressed and Cement Stabilized Earth Blocks

Sustainable construction has become a real issue in Algeria and in the whole world. The compressed and cement stabilized earth blocks remain among the materials that contribute to a healthy, ecological and sustainable environment, as well as a source of interior comfort. In this work, an experimental investigation is performed on hygrothermal characterization of Compressed and cement Stabilized Earth Blocks with a moderate portion of 6%. The characterization of sorption isotherms was performed according to the “gravimetric” method in a temperature of 23 °C and relative humidity ranging from 9% to 99%.Twelve models were used to adjust the sorption isotherms of cement stabilized earth blocks. Therefore, only OSWIN model yielded a good result with a relative error experimented with a mean relative error less than 10%. In this work, the thermo-hydric characterization includes thermal conductivity, specific heat, and water vapor permeability.

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.

Determination of Desorption Isotherms of Potato Using Gravimetric Method and Fast Isotherm Method

The desorption isotherms of potato (Solanum tuberosum) were determined for a range of temperature 30–60 °C using gravimetric and fast isotherm method over the range of relative humidity 5–85%. The objective of this work is to investigate and document the best practice to perform experiments using both these two methods. The desorption isotherms obtained from the gravimetric method were fitted using three models: GAB, BET, and Oswin. A nonlinear least-square regression analysis was used to evaluate the constants of the three isotherm models. The goodness of the fit was determined by two statistical parameters: standard error and correlation coefficient. GAB model was found to be competent to describe desorption isotherms of potato followed by BET and Oswin model. Also, the sorption behavior of potato obtained from the fast isotherm method was validated to the standard gravimetric method.

Hygroscopic behavior of acerola powder obtained by spray-drying

Acerola is a tropical fruit characterized by a high content of vitamin C. The food sorption isotherms reflect the way that the water binds to the food. This study aimed to fit mathematical models to the adsorption isotherms of the acerola pulp powder obtained by spray-drying, and. It was used acerola pulp containing 17.1% (m m -1 ) maltodextrin, and a spray-dryer with drying air temperature of 154°C. The mathematical models of GAB, BET, Henderson, and Oswin were applied to determine the isotherms, using temperatures of 25, 35 and 45°C. The hygroscopicity, degree of caking and solubility analysis were performed to characterize the powders. The powder showed hygroscopicity of 5.18, degree of caking of 3.67 and solubility of 94.88%. The evaluated mathematical models showed mean relative errors ranging from 10.18 to 29.13% and a coefficient of determination (R 2 ) ranging from 0.939 to 0.977. At 25°C, the Oswin model was the best fitted, whereas at 35 and 45°C the best fitting was obtained by the Henderson model. Type III (J-shape) isotherms were obtained, typical of high-sugar foods. The powder showed a low hygroscopicity and degree of caking in addition to a high solubility.

Sorption Characteristics of Cocoyam (Colocasia Esculenta) at Different Temperatures

The exploitation of cocoyam (Colocasia esculenta) for food is limited to direct consumption of primary products which often result in huge post-harvest losses. This study reports the development and storage of flour from cocoyam with the intent of establishing suitable storage conditions for its storage. Fresh cocoyam corms obtained from the Federal University of Technology (FUTA) Research Farm, were peeled, washed, sliced, oven-dried and then milled into the powder. Insights into the is essential to maintain Good keeping quality of food materials is a function of the relationship between their air relative humidity (expressed as water activity (aw)) and equilibrium moisture content. The gravimetric method was used to determine the adsorption isotherms of cocoyam flour. In the range of temperature (20 - 40 oC) and aw (0.10 - 0.80) typical of the tropical environment, different concentrations of concentrated acid (H2SO4) solutions were used to vary the condition of the research area. The experimental data were compared with six widely recommended models for food sorption isotherms (GAB, BET, Oswin, modified Oswin, Hasley & Smith). The plot of moisture sorption isotherms also resulted in a sigmoidal shape which is influenced by temperature variation. Generally, the Modified Oswin model was found most suitable to describe the sorption isotherm of cocoyam flour.

Influence of the temperature and granulometry on the hygroscopic behavior of tapioca flour

ABSTRACTThe morphological difference between two types of tapioca flour motivated this research, which aims to evaluate the hygroscopic behavior of these products via moisture sorption isotherms (MSI). The MSI of the products were obtained at 25°C, 35°C, 45°C, and 55°C and the experimental data were fitted at seven mathematic models that concern the effect of temperature. MSI had type-II behavior and hysteresis were observed between the moisture adsorption and desorption isotherms, whose magnitudes decreased with higher temperatures. According to adsorption, the two flour are microbiologically stable if they have moisture below 11% and they are less susceptible to becoming moist if they are stored at relative humidity below 70%. The MSI indicated that the tapioca flour more expanded is more hygroscopic and with higher moisture decreases as temperature increases, suggesting distinct storage conditions for the two flour. The modified Oswin model had a good fit to the sorption data.

<b>Statistical evaluation of models for sorption and desorption isotherms for barleys

This study presents a novel approach to evaluate water sorption and desorption isotherm modeling consisting in statistical evaluation of the fit followed by the ranking of the models. Water sorption and desorption isotherms for BRS Elis and BRS Caue barley cultivars were evaluated at 40, 50, and 60°C. Data were analyzed by the GAB, Freundlich, Halsey, Henderson, Langmuir, Oswin, and Smith models. The BET model was also fitted to determine the moisture content. All models were submitted to five tests to determine whether the model was statistically significant. Then, the models were ranked using corrected Akaike information criterion. At all temperatures, the equilibrium moisture content increases as water activity increases and temperature decreases. Data showed no hysteresis in both cultivars. The statistical parameters evaluated indicate the goodness of the fit for all models except for the GAB model for BRS Elis cultivar at 60°C. The analysis with the corrected Akaike information criterion revealed that the Oswin and Henderson models showed best results at 40 and 50°C for both cultivars studied. At 60°C, the Freundlich model was the best for both cultivars. For both cultivars, the value of isosteric heat decreases with an increase in moisture content.

보리의 평형함수율/평형상대습도에 관한 연구

Desorption equilibrium moisture content (EMC)/equilibrium relative humidity (ERH) experiments were performed on two cultivars (Sae naked and Hin-chal naked) of barley (Hordeum vulgare L.) at 5, 15, 25, 35, and 45℃ for moisture contents between 9.51 and 29.13%,db. The method employed involved measuring the ERH of air in contact with the grain under static conditions, using an electronic hygrometer. The effects of temperature and moisture contents were investigated, and the measured values were fitted to the modified Henderson model, the modified Chung-Pfost model, the modified Halsey model, the modified Oswin model, and the modified GAB model. The ERHs of barleys decreased with decreasing moisture content and temperature, and the EMCs increased with decreasing temperature and increasing relative humidity. The increase in moisture content with increasing relative humidity at a given temperature is not linear: the moisture content increased rapidly at high relative humidities, and the differences between ERH values at different temperature (5-45℃) were insignificant at high relative humidity (>80%). The effect of the cultivars on EMC/ERH was insignificant at the same temperature. The modified Halsey model was found to be the best in describing the EMC/ERH of barleys.

Sorption isotherms and isosteric heat estimation of purple cactus pear (Opuntia stricta) juice embedded in gelatin–maltodextrin matrix

AbstractMoisture sorption isotherms of microencapsulated juice from purple cactus pear were determined at different temperatures (15, 20, and 30 °C) in water activity (aw) range from 0.112 to 0.976. The experimental data were correlated to GAB, BET, Caurie, Smith, Henderson, Bradley, Kuhn, and Oswin models. The obtained isotherms present a sigmoid shape Type IV. The models of Smith, Kuhn, and Oswin were found as the most suitable (EMR < 10%). The isosteric heat (Qst) decreased with the increase in moisture content obtaining the maximum and minimum values of 14.84 and 5.60 kJ/mol, respectively, for moistures between 10 and 70%.Practical applicationsToday, the food industry is looking for new storage procedures for the preservation of bioactive compounds contained in fruits. Until now, many native Mexican fruits have not been processed in agro‐food industry, for example, purple cactus pear (Opuntia stricta) fruit, which is one of the natural products not widely processed. There is strong evidence that such fruit contains antioxidants, natural pigments, and phenolic compounds. The conservation of the bioactive compounds can be carried out by embedding the juice into a biodegradable matrix. We first propose the encapsulation of the juice through using the gelatin–maltodextrin composite as wall material. Then, the characterization of the dried product by determining the sorption isotherms can be useful to predict the optimum storage conditions, life prediction, and packaging design of this type of products.

Moisture sorption isotherms and isosteric heat of sorption of Tunisian clay product

The aim of this study was to determine the adsorption and desorption isotherms of Tunisian clay product at different temperatures with a water activity varying from 10.95 to 97% using the statistic gravimetric method, which is an important step to evaluate its hygroscopic character. It was found that when temperature increases, clay material becomes less hygroscopic due to physical and/or chemical changes in product. Ten mathematical models were used to fit experimental data of sorption isotherms. The fitting of the model to experimental data was evaluated with the correlation coefficient (R2) and the root mean square error (RMSE). The Oswin model was determined to be the best model for describing experimental data of adsorption and desorption in the investigated ranges of temperature and water activity. The net isosteric heat of sorption determined from sorption isotherms estimated from Oswin model and using Clausius-Clapeyron equation decreased continuously with increasing the equilibrium moisture content.

Effect of homogeneous static magnetic treatment on the adsorption capacity in maize seeds (Zea mays L.).

In order to analyze the treatment of seeds with homogeneous static magnetic field on the water adsorption process, an experimental-theoretical study of hygroscopic equilibrium in maize seeds (Zea mays L. cv. ICAV305) was carried out. Four treatments with magnetic induction of 80.0, 120.0, 160.0, and 200.0 mT were applied for 10 min, and there was a control group without treatment. The doses were selected because they showed a decrease in mean germination time. Treated seeds were subjected to an environment with a stable temperature of 30.0 °C ± 0.1 °C and atmospheres of different relative humidity (h), using eight salt solutions saturated with water activity between 0.216 and 0.970. Curves were adjusted using the D'Arcy-Watt and modified Oswin models. It was found that the magnetic treatment of seeds affects adsorption, and the 200 mT-10 min one was the most significant in affecting the mechanisms of adsorption of water, and increasing the number of adsorption sites connected to weak binds with D'Arcy-Watt's adjustment. Using the Oswin model for simulation, we verified that the magnetic stimulus affected the enthalpy of adsorption and the mechanism of incorporation of water vapor molecules to the structure of seminal cover. These results show that the magnetic pre-treatment of seeds has an effect on a seed's specific biophysical and physiological processes in the early stages of germination. Bioelectromagnetics. 39:343-351, 2018. © 2018 Wiley Periodicals, Inc.