Oswin Model Research Articles

Drying kinetics of tobacco strips at different air temperatures and relative humidities

The effects of air temperature and relative humidity (RH) on the drying kinetics of two kinds of flue-cured tobacco strips (C3F and B3F) were studied using a thermogravimetric device in this work. The drying experiments were carried out with drying air temperatures of 60, 70, 80, and 90 °C and RH values of 0, 10, 20, 30, and 40% at a constant airflow. Taking the effect of RH into consideration, a modified Arrhenius-type equation of diffusivity was proposed. In addition, comparing five thin-layer drying models and five equilibrium moisture content models to describe the drying kinetics and the desorption isotherms of tobacco strips, high coefficients of determination (R2) and low reduced Chi-square (χ2) and residual sum of squares (RSS) values indicated that the Logarithmic model and the Modified Oswin model appeared to be the most suitable for predicting the moisture ratio and the moisture desorption relationship of tobacco strips. The effective moisture diffusion coefficient under different temperatures and RHs ranged from 1.68 × 10−11 to 6.81 × 10−11 m2 s−1 for C3F and from 1.62 × 10−11 to 6.68 × 10−11 m2 s−1 for B3F. A modified Arrhenius-type equation with an RH term was found to be effective for describing the drying behavior of two flue-cured tobacco strips, and the activation energy (Ea) values were 34.6 and 35.2 kJ mol−1 for C3F and B3F, respectively.

Mathematical modeling of drying the pulped coffee (Coffea arabica l.) at different air conditions

The aim of the study was to describe the drying kinetics of washed coffee (Coffea arabicaL.) and evaluate the best mathematical model to fit the experimental drying data conducted with different air humidity (40 %, 50 %, and 60 %) and temperatures (23 °C, 40 °C, and 60 °C). The fruit shakes were standardized washing, separation, and manual selection of green coffees, pass cane, and green buoy. Then, approx. 150 L of coffee cherries were pulped and taken directly to the yard. Drying the washed coffee was completed in a mechanical dryer and yard. The obtained results showed that the different conditions of the ambient air significantly influenced the processes of drying pulped coffee. The water content of the hygroscopic equilibrium of pulped coffee is directly proportional to the water activity and relative humidity, decreasing with increasing temperature, for the same value of equilibrium relative humidity. The Oswin model was best represented by the hygroscopicity of the pulped coffee, while the Midilli model shows the best fit to describe the drying curves of the washed coffee. The effective diffusion coefficient increases with increasing temperature of the drying air and reducing of relative humidity, being described by the Arrhenius equation. The aim of the study was to describe the drying kinetics of washed coffee (Coffea arabica L.) and evaluate the best mathematical model to fit the experimental drying data conducted with different air humidity (40 %, 50 %, and 60 %) and temperatures (23 °C, 40 °C, and 60 °C). The fruit shakes were standardized washing, separation, and manual selection of green coffees, pass cane, and green buoy. Then, approx. 150 L of coffee cherries were pulped and taken directly to the yard. Drying the washed coffee was completed in a mechanical dryer and yard. The obtained results showed that the different conditions of the ambient air significantly influenced the processes of drying pulped coffee. The water content of the hygroscopic equilibrium of pulped coffee is directly proportional to the water activity and relative humidity, decreasing with increasing temperature, for the same value of equilibrium relative humidity. The Oswin model was best represented by the hygroscopicity of the pulped coffee, while the Midilli model shows the best fit to describe the drying curves of the washed coffee. The effective diffusion coefficient increases with increasing temperature of the drying air and reducing of relative humidity, being described by the Arrhenius equation

The Effect of Moisture on Cellulose Nanocrystals Intended as a High Gas Barrier Coating on Flexible Packaging Materials

Cellulose nanocrystals (CNCs) exhibit outstanding gas barrier properties, which supports their use as a biobased and biodegradable barrier coating on flexible food packaging materials. As highly hydrophilic biopolymers, however, CNCs have a strong sensitivity to water that can be detrimental to applications with fresh foods and in moist conditions due to the loss of barrier properties. In this work, the oxygen and water vapor permeability of polyethylene terephthalate (PET) films coated with CNCs obtained from cotton linters were measured at varying levels of relative humidity, both in adsorption and desorption, and from these data, the diffusion and solubility coefficients were estimated. Therefore, the characterization of CNCs was aimed at understanding the fundamentals of the water-CNCs interaction and proposing counteractions. The CNCs’ moisture absorption and desorption isotherms at 25 °C were collected in the range of relative humidity 0–97% using different techniques and analyzed through GAB (Guggenheim-Anderson-de Boer) and Oswin models. The effects of moisture on the water status, following the freezable water index, and on the crystal structure of CNCs were investigated by Differential Scanning Calorimetry and by X-ray Powder Diffraction, respectively. These findings point to the opportunity of coupling CNCs with hydrophobic layers in order to boost their capabilities as barrier packaging materials.

Effect of Storage Conditions on Moisture Sorption of Mixed Biomass Pellets

The aim of this paper was to study the moisture sorption characteristics of mixed biomass pellets. The pellets were developed using a mixture of woody (spruce or pine) and agricultural (reed canary grass or hay) biomass with a ratio of 1:1. The pellets were stored in a controlled environment until reaching the equilibrium moisture content. The temperature of the controlled environment was varied between 15 and 25 $$^{\circ }\hbox {C}$$ and relative humidity between 20 to 90%. The experimental results showed this temperature range had no effect on the moisture sorption isotherms. However, the equilibrium moisture content at higher relative humidity was found dependent on the type of the material and was higher for spruce-hay pellets compared to the other tested pellets. Oswin, Guggenheim-Anderson-de Boer, Henderson and Peleg models were tested for the prediction of the moisture isotherms. With a coefficient of determination varying between 0.998 and 0.995, a standard error between 0.054 and 0.071 and chi-square error ranging between 0.009 and 0.015, Oswin model was found more suitable to predict the moisture sorption isotherms of all biomass pellets. This result was further confirmed using the residuals plot, showing a more uniform distribution for Oswin model compared to the other models.

Desorption isotherms of Lactuca sativa seeds

ABSTRACT Lactuca sativa seeds are highly sensitive to climate conditions; thus, they should be stored securely to maintain their qualitative and quantitative characteristics. Studies on hygroscopicity aim to decrease possible changes in agricultural products under specific environmental conditions. Accordingly, this study aims to develop an appropriate mathematical model to represent the desorption isotherms of Lactuca sativa seeds. The hygroscopic equilibrium was achieved using a static-gravimetric method at temperatures of 10, 20, 30, 40 and 50 °C and water activity in the range 0.11-0.96. Six mathematical models were fitted to the experimental data of the equilibrium moisture content of Lactuca sativa seeds. The best model was chosen based on the determination coefficient (R2), magnitude of mean relative error (MRE), standard deviation of the estimate (SDE), and analysis of residue distribution. The modified Oswin model best represented the hygroscopicity of the Lactuca sativa seeds, with values of 8.02% and 0.55 for the MRE and SDE, respectively; moreover, the residual values were randomly distributed. The shape of the isotherms of the Lactuca sativa seeds estimated using the modified Oswin model is sigmoidal, which is characteristic of a type II curve.

Air drying modelling of Mastocarpus stellatus seaweed a source of hybrid carrageenan

Water sorption isotherms from 5 up to 65 °C and air drying kinetics at 35, 45 and 55 °C of Mastocarpus stellatus seaweed were determined. Experimental sorption data were modelled using BET and Oswin models. A four-parameter model, based on Oswin model, was proposed to estimate equilibrium moisture content as function of water activity and temperature simultaneously. Drying experiments showed that water removal rate increased significantly with temperature from 35 to 45 °C, but at higher temperatures drying rate remained constant. Some chemical modifications of the hybrid carrageenans present in the seaweed can be responsible of this unexpected thermal trend. Experimental drying data were modelled using two-parameter Page model (n, k). Page parameter n was constant (1.31 ± 0.10) at tested temperatures, but k varied significantly with drying temperature (from 18.5 ± 0.2 10−3 min-n at 35 °C up to 28.4 ± 0.8 10−3 min-n at 45 and 55 °C). Drying experiments allowed the determination of the critical moisture content of seaweed (0.87 ± 0.06 kg water (kg d.b.)−1). A diffusional model considering slab geometry was employed to determine the effective diffusion coefficient of water during the falling rate period at different temperatures.

Hygroscopic trend of lyophilized ‘mangaba’ pulp powder

ABSTRACT Mangaba is a widely-consumed fruit in the Northeast of Brazil, which is usually exploited through extractivism. This fruit is rich in various nutrients, especially in vitamin C, with pleasant taste and aroma. The lyophilization process transforms these fruits into amorphous powders, which must be analyzed regarding their properties and hygroscopic trend. Thus, the objective of this study was to characterize and evaluate the physico-chemical properties of adsorption isotherms of the lyophilized ‘mangaba’ pulp powder, with addition of maltodextrin (DE 20). The pH, titratable acidity, soluble solids, ascorbic acid and water activity were analyzed. Regarding the isotherms, the mathematical models of GAB, BET, Oswin, and Henderson were used at temperatures of 25, 30, 35 and 40 °C. The obtained powder presented pH of 3.14, titratable acidity of 1.95 mg of citric acid 100g-1 of powder, soluble solid contents of 99 ºBrix, ascorbic acid content of 55.97 mg 100g-1 and water activity of 0.16. Henderson was the mathematical model that best fitted the data of the adsorption isotherms at the four evaluated temperatures, with average errors ranging from 5.76 to 9.70% and R2 from 0.9974 to 0.9995.

Quantitative and mechanistic analysis of impact of novel cassava-assisted improved processing on fluid transport phenomenon in humidity-temperature-stressed bio-derived films

Bio-derived films’ realistic performance integrity is ascertained by their resilience in highly-stressful storage conditions, a function of its ability to respond timely and manages fluid barrier appropriately. Bio-derived films’ moisture and temperature sensitivity often posed mass transport challenges, thus decreasing their lifespan. Quantifying bio-derived film mass transport behaviour has been limited to mass transfer representations, which can be imperfect to understand fully mass transport phenomenon. This study reported quantitative and mechanistic analysis of fluid-phase mass transport phenomenon in Simultaneous Release Recovery Cyanogenesis-produced intact bitter cassava (IBC) bio-derived films under stressful conditions. Films were tested for solvent solubility, swelling ratio, sorption and permeability to water vapour and oxygen at 10–40°C and 10–95% RH. Film’s structural alterations were characterised by their thermal and chemical properties. Modified-BET, Peleg, Oswin models best described sorption data. Temperature-dependence of film water vapour permeability was simulated best by Arrhenius model, while oxygen permeability was influenced highly by crystallinity and RH. Non-organic and organic film-solvent diffusion followed case II and Fickian diffusional patterns respectively. Solvents induced structural changes in IBC films with concentration-dependent diffusion. Cassava bio-derived films’ integrity will depend on the host environment, thus maximum care should be ensured to minimise environment impact during applications. Nonetheless, IBC films hold potential as biomaterials for broad range product use.

Cost-effectiveness of a specialised medium secure personality disorder service

IntroductionThe Oswin unit located in the North East of England is commissioned primarily for offenders screened on the offender personality disorder (OPD) pathway based on measures of personality disorder being linked to moderate to high risks to other persons.ObjectivesThe Oswin Unit was re-designed in early 2014 meeting commissioning specifications to meet objectives based on access, measuring quality and reducing. The primary objective of this pathway is to ensure personality Disorder offenders have access to “community-to-community”, joint-up care and monitoring of risks. The Oswin unit implemented a re-designed service offering individuals formulation based assessments and risk management embedded in the OPD pathway. The overall objective of this project is to evaluate the effectiveness and risk amelioration of this hospital-based service.AimAs part of a broader service development and evaluation project, the cost-effectiveness of the current model of the unit was compared to that of the unit prior to the redesign of the service.MethodCollection of data on number of admission and length of stay and calculation of expenses per capita. Retrospective analysis of costs of care.ResultsAnalysis of comparative figures post-implementation of this new model of care found 41% more episodes of care. Cost-analysis indicated a saving of £200,000.ConclusionThe new Oswin Model meets commissioning objectives in offering access to hospital-based care and focused treatments for prisoners ‘stuck’ in prison pathways. This finding led to further investigation using thematic measures of quality of care to evaluate the effectiveness of this service and risk amelioration.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Equilibrium sorption isotherms of Moringa oleifera leaves at different temperatures

Adsorption and desorption isotherms for Moringa oleifera leaves were investigated using concentrated H2SO4 solutions to vary the micro-climate over different temperatures (27, 32, 37°C) and water activity (aw) (0.1–0.8). Plots of equilibrium moisture content (EMC) against aw were used to generate isotherm curves, local isotherm (Li) concept and stability. The experimental data obtained were compared with four widely recommended models in the literature for food sorption isotherms [GAB, modified GAB (MGAB), modified Oswin (MOE) and OSWIN models]. Results obtained showed that the moisture sorption isotherms were sigmoidal in shape and were influenced by temperature. The four sorption models adequately predicted the adsorption and desorption isotherms for Moringa oleifera leaves at the evaluated temperatures, with R2 values between 0.980 and 0.998. The sequence in which the evaluated models effectively fitted the moisture sorption, were GAB, MGAB, MOE and OSWIN models, with GAB being the best. While the GAB model was most suitable for fitting the adsorption [Mean square error (MSE = 183.08), standard error of estimate (SEE = 549.24), R2 = 0.980)], MGAB was better for desorption isotherm [(MSE = 141.950), SSE = 425.86), R2 = 0.998] of Moringa oleifera leaves under practical storage temperature and water activity used in this study.

Moisture Adsorption Studies on Soy - Mumu Supplemented with Moringa Leaf Powder

Moisture adsorption Studies was carried out on Soy-mumu, a Nigerian cereal-based food product supplemented with 0, 10, 15 and 20% Moringa leaf powder at four different temperatures(20°C, 30°C, 40°C and 50°C) using the standard static gravimetric method. The different blends of Soy-mumu products were subjected to water activities of 0.1 – 0.957 for each of the four temperatures (20°C, 30°C, 40°C and 50°C) and data obtained were analysed using Oswin, Henderson and GAB models while thermodynamics of moisture transfer were estimated using Clausius-Clapeyron and kinetic compensation equations. The moisture adsorption isotherms were sigmoid in shape (type II). The equilibrium moisture content (EMC) of the Soy-mumu products increased with increase in water activity at constant temperature and were lower as the temperature increased at constant water activity. The sorptive capacity of Soy-mumu products increased with increasing levels of Moringa leaf powder supplementation and exhibited higher isotherms. Using the percent root mean square of error (% RMS), Oswin model gave the best fit for describing the adsorption isotherms of the Soy-mumu products while GAB and Henderson models fitted poorly (<10% RMS). Monolayer moisture content (Mo) and surface area (So) of adsorption decreased with increase in temperature. The GAB monolayer moisture contents were higher than BET monolayer moisture contents. The isosteric heat of sorption generally decreased as the moisture content increased. The maximum isosteric heat (ΔHst) was 14.1928; 14.19288; 37.0272 and 57.9120kj/mol for samples that were supplemented with 0, 10, 15 and 20% Moringa leaf powder respectively. The enthalpy-entropy compensation theory is suitable for describing the moisture adsorption phenomenon of the Soy-Mumu products.

English

One of the meat products in East Nusa Tenggara is called “se’i”, commonly made from beef, pork, deer meat, and recently have been developed using fish meat. Moisture Sorption Isotherm (MSI) is an important characteristic of food which is almost affected to aspect of the dehydration process and storage stability of the dried product. The aims of this study are to produce tuna se’i using liquid smoke with different concentrations, and to determine the MSIs using a constant relative humidity camber. In this method, water content of samples are allowed to equilibrate in a closed chamber with a salt solution which produces a desired relative humidity. Tuna se’i were made from two part of the tuna meat, that is, dorsal and belly. Five liquid smoke concentrations were used to dip the meats, that is, 1.0, 1.2, 1.4, 1.6 and 1.8%. The results show higher water conten in se’i from dorsal and the lower in se’i made from belly. The equilibrium moisture conents for samples in lower RHs ( 54%) ranged between 11.12 and 75.65% (db). Using five models equations, Oswin models shown best fit values of regression coefficients, with ranges value of relatife determination, 4.81 to 9.89, and MSI curves were sigmoid. From the MSI curves, can be conclude that tuna se’i need a packaging for storage in ambient temperature specially RHs above 50%. Key words: Liquid smoke, se’i, moisture sorption isotherm (MSI), equilibrium moisture content.

Bean grain hysteresis with induced mechanical damage

ABSTRACT This study aimed to evaluate the effect of mechanical damage on the hysteresis of beans with induced mechanical damage under different conditions of temperature and relative humidity. Beans (Phaseolus vulgaris L.) harvested manually with 35% water content (w.b.) were used. Part of this product was subjected to induced mechanical damage by Stein Breakage Tester and controlled drying (damaged and control sample), for sorption processes. The sorption isotherms of water were analyzed for different temperature conditions: 20, 30, 40 and 50 oC; and relative humidity: 0.3; 0.4; 0.5; 0.7 and 0.9 (decimal). Equilibrium moisture content data were correlated with six mathematical models, and the Modified Oswin model was the one that best fitted to the experimental data. According to the above mentioned isotherms, it was possible to observe the phenomenon of hysteresis of damaged and control samples, and this phenomenon was more pronounced in control ones.

Moisture Sorption Isotherms of Yogurt Powder Containing Candied Chestnut Puree

Yogurt powder was produced by freeze drying and with added candied chestnut puree at ratios of 5, 10, and 20 % by weight. Moisture sorption isotherms of yogurt powder samples, plain (YP), and containing 5, 10, 20% candied chestnut puree (CCP) were determined at 25°C using the standard, static-gravimetric method. The experimental adsorption data of yogurt powders at 25°C were fitted to 14 sorption equations which are most widely used to fit experimental sorption data of various food materials. The parameters of the sorption models were estimated from the experimental results by using the nonlinear regression analysis. The GAB model gave the closet fit to the sorption data of freeze dried yogurt powders with candied chestnut puree at 25°C. BET, Ferro Fanton, Henderson, Halsey, Oswin and Modified Oswin models are also acceptable for describing the adsorption isotherms for freeze dried yogurt with candied chestnut puree at 25°C.

Modelling the effect of temperature on the water sorption isotherms of chitosan films

The interaction of the water molecules from the environment with foods and other materials can be evaluated using sorption isotherms. Films and biodegradable films are susceptible to changes in their functional characteristics due to adsorbed water. The amount of moisture that biodegradable films can adsorb depends on the temperature, relative humidity of the storage area and chemical composition. Several mathematical models can be used to describe the behavior of sorption isotherms in biodegradable films and some of them have been modified to include the temperature parameter into the equation. In this research, the original and modified BET, GAB, Halsey, Henderson and Oswin models were assessed to determine their suitability describing the behavior of moisture adsorption isotherms of chitosan films at 15, 20, 25 and 30 °C. The modified models of GAB, Oswin and Halsey gave the best fit to the experimental sorption data of the chitosan films, with R2 values higher than 0.97 demonstrating that those models describe better the sorption isotherms at the temperatures studied.

Moisture desorption isotherm, diffusivity and finite element simulation of drying of macadamia nut (Macadamia integrifolia)

This paper presents moisture diffusivity, equilibrium desorption isotherm and finite element simulated drying of macadamia nut. In order to create the desorption isotherm, the equilibrium moisture content was determined by using the gravimetric method. The Modified Oswin model fitted the best experimental data and is satisfactory for the prediction of the moisture desorption isotherm of macadamia nuts. The thin layer drying experiments of the kernel and shell of the macadamia nuts were conducted at a temperature of 40°C, 50°C and 60°C and relative humidity of 10%, 20% and 30%. The moisture diffusivity of the kernel and shell of the macadamia nut was determined by minimizing the sum of square of the deviation between the predicted and the experimental moisture contents values during the thin layer experiments. The diffusivity of the kernel and shell was expressed as functions of temperature using the Arrhenius type equation and the moisture diffusivity of the kernel was higher than that of the shell of the macadamia nuts. A two-dimensional finite element drying model of macadamia nut was developed and this model predicted reasonably the moisture contents during drying. The model can be used to reveal spatial and temporal changes in moisture content inside the macadamia nut.

Moisture sorption isotherm characteristics of Hemerocallis Fulva and Cymbopogon

AbstractThe moisture sorption isotherms of Hemerocallis Fulva and Cymbopogon are measured by the static gravimetric method at 25, 35, and 45 °C over a water activity range of 0.09 to 0.95 using standard saturated salt solutions. The sorption isotherms of H. fulva and Cymbopogon display type III (J‐shaped) and type II (nearly sigmoid shapes) isotherms. In addition, the adsorption and desorption data of H. fulva and Cymbopogon fit well with the White &amp; Eiring model and the Oswin model, respectively. The Brunauer–Emmett–Teller equation is applied to determine the monolayer moisture content, and the surface area of a monolayer was calculated. The values of the net isosteric heat of sorption are found to increase with decreases in the equilibrium moisture content. Moreover, the net isosteric heat of desorption is higher than that of the adsorption heat. Copyright © 2016 Curtin University of Technology and John Wiley &amp; Sons, Ltd.

Water adsorption isotherms and thermodynamic properties of cassava bagasse

Losses of food industry are generally wet products that must be dried to posterior use and storage. In order to optimize drying processes, the study of isotherms and thermodynamic properties become essential to understand the water sorption mechanisms of cassava bagasse. For this, cassava bagasse was chemically analyzed and had its adsorption isotherms determined in the range of 293.15–353.15K through the static gravimetric method. The models of GAB, Halsey, Henderson, Oswin and Peleg were fitted, and best adjustments were found for GAB model with R2>0.998 and no pattern distribution of residual plots. Isosteric heat of adsorption and thermodynamic parameters could be determined as a function of moisture content. Compensation theory was confirmed, with linear relationship between enthalpy and entropy and higher values of isokinetic temperature (TB=395.62K) than harmonic temperature. Water adsorption was considered driven by enthalpy, clarifying the mechanisms of water vapor sorption in cassava bagasse.

Hygroscopic behavior of lyophilized acerola pulp powder

ABSTRACT Powder products are characterized by their practicality and long life. However, fruit powders have high hygroscopicity and tend to agglomerate due to its hydrophilic nature. The isotherms of equilibrium moisture content apply to the study of dehydrated food preservation potential. Acerola is a nutritionally rich fruit, with great economic and industrial potential. The objective of this study was to analyse acerola powder adsorption isotherms obtained by lyophilization and characterize the powder obtained from lyophilized acerola pulp. Analysis of hygroscopicity, solubility and degree of caking were performed. Isotherms were represented by the mathematical models of GAB, BET, Henderson and Oswin, at temperatures of 25, 35 and 45 °C. According to the results, the obtained powder showed hygroscopicity of 5.96 g of absorbed water 100g-1 of solids, solubility of 95.08% and caking of 14.12%. The BET model showed the best fit to the adsorption isotherms of the acerola pulp powder obtained by lyophilization. The obtained isotherm was of type III, with a "J" shape. There was an inversion of the effect of temperature on the isotherms of acerola powders.

Moisture sorption isotherms and storage study of spray dried tamarind pulp powder

Moisture adsorption isotherms and storage study of spray dried tamarind pulp powder were evaluated in this work. Adsorption isotherms of tamarind pulp powder were determined at four different temperatures (20, 30, 40 and 50°C) using a gravimetric technique. The sorption isotherms were found to be typical type II sigmoid. The experimental data obtained was fitted to several mathematical models viz. two-parameter (BET, Oswin, Smith, Caurie, and Iglesias and Chirife), and three-parameter (GAB) relationships. A non-linear least square regression analysis was used to evaluate the model constants. The GAB followed by Oswin model best fitted the experimental data. Changes in physicochemical properties of tamarind pulp powder were evaluated during storage (at 0, 1, 2, 3, 4, 5 and 6months), using three different packaging materials (low density polyethylene, LDPE; aluminum laminated polyethylene, ALP and glass). Color parameters, moisture content, titratable acidity, bulk density and flowability of the powder varied to different extent during storage, depending on the type of packaging material used. Compared to other packaging materials, powder packed in LDPE showed considerable changes in physicochemical properties during storage. The magnitude of the change in physicochemical properties of the powder measured during storage suggests that glass is best for long term storage of tamarind pulp powder.