Studies on equilibrium moisture absorption of kappa carrageenan (original) (raw)
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Determination and Modelling of Moisture Sorption Isotherms of Chitosan and Chitin
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Effect of maltodextrin addition on moisture sorption properties of khoa
International Journal of Dairy Technology, 2008
Khoa is a popular traditional Indian milk product. It is used as the base material for preparation of variety of popular sweetmeats. The shelf life of this product is limited due to its high water activity (> 0.96). In the present investigation, an attempt was made to lower the a w of khoa (25.62% moisture, 31.25% fat, 18.21% protein, 3.65% total ash and 21.29% lactose) by using maltodextrin (DE-16) as a humectant (concentration: 0, 2, 5 and 10%; wt/wt). It was observed that the desorption curves of the product exhibited a sigmoid shape corresponding to type II, typical of many foods. At higher concentrations of maltodextrin, the isotherms shifted to the left compared to control. Among the several models chosen to test the fitness of sorption data, Guggenheim, Anderson and De Boer (GAB) and modified Mizrahi models showed the best fit as indicated by the smallest percentage root mean square values. The monolayer moisture content increased with increasing maltodextrin level, the range being 2.85-3.29 and 3.03-3.81 g/100 g solids for the two models, respectively. Caurie's slope also increased from 0.38 to 0.44, whereas nonfreezable water decreased from 4.98 to 4.01% as the maltodextrin level increased from 2 to 10%. Other critical water sorption parameters such as number of adsorbed monolayers, density of sorbed water and surface area of sorption were also obtained.
Moisture sorption properties of chitosan
LWT - Food Science and Technology, 2010
The moisture equilibrium isotherms of chitosan were determined at 20, 30, 40, 50 and 60 C, using the gravimetric static method. Experimental data were analyzed by the GAB, Oswin, Halsey and Smith equations. Isosteric heat and differential entropy of sorption were determined from the GAB model using the Clausius-Clapeyron and Gibbs-Helmholtz equations, and pore size distribution was calculated by the Kelvin and Halsey equations. The GAB and Oswin equations showed best fit to the experimental data with R 2 z 99% and low mean relative deviation values (E% < 10%). Monolayer moisture content values (from 0.12 to 0.20 kg kg À1 ) and water surface area values (from 450 to 700 m 2 g À1 ) decrease with increasing temperature. Isosteric heat and differential entropy of sorption were estimated as a function of moisture content. The Kelvin and Halsey equations were adequate for calculation of pore size distribution, which varied from 0.5 to 30 nm.
Effect of temperature on moisture desorption isotherms of kheer
LWT - Food Science and Technology, 2005
Desorption isotherms of kheer, a rice based partially heat concentrated and sweetened Indian milk dessert, were obtained in the temperature range of 10-40 C. The desorption curves exhibited sigmoid shape corresponding to type II, typical of many foods. There was generally a negative temperature effect on EMC at low a w ; but curves at 25 C and 40 C showed inversion above water activity of 0.60 implying a higher equilibrium moisture content at higher temperature. Of the five sorption models tested, the GAB model gave the best fit at all the three temperatures. Besides monolayer moisture, properties of sorbed water viz. number of adsorbed monolayers, bound or nonfreezable water, density of sorbed water and surface area of sorption were also obtained. Isosteric heat of sorption obtained by applying Clausius-Clapeyron equation decreased exponentially with the increasing moisture content.
Bulletin of the National Research Centre
Background Karaya gum is heavily acetylated polysaccharide and used for medicinal purposes as a bulk-forming laxative. It is also used in the paper and textile industries as well as food stabilizer. So its moisture sorption behavior study is important. The moisture sorption isotherms of karaya gum were investigated at four experimental temperatures (30, 40, 50 and 60 °C) under the water activities range from 0.10 to 0.95 using static gravimetric method. Results Maximum value of equilibrium moisture content (EMC) of karaya gum (39.7%, db) was noted with the set of highest water activity (0.92) at lowest temperature (30 °C) and minimum value of EMC (2.5%, db) with lowest water activity (0.11) at highest temperature (60 °C). The sorption data were fitted with GAB, Iglesias and Chirife, Caurie, Halsey and BET models. The adequacy of the sorption isotherm models were observed statistically using goodness of fit parameters. The well-known GAB model best interpreted the equilibrium data in...
Journal of Food Engineering, 2005
Moisture sorption isotherms of cowpea (Vigna unguiculata L. Walp), powdered cowpea and protein isolate of cowpea at 10, 20 and 30°C were derived. The sorption data were treated according to many well-known sorption isotherm equations. The goodness of fit was evaluated on the basis of criteria such as the mean relative deviation modulus, coefficient of determination and standard errors of models. It was found that the GAB model was the most satisfactory model for representation of the sorption data. Monolayer moisture contents (M 0) were determined from the GAB and the BET equations. The temperature dependence of M 0 was examined. Heats of sorption data were evaluated using the Clausius-Clapeyron equation. An attempt was made to determine the moisture contribution of the protein component of cowpea to the total moisture content.
Journal of Food Process Engineering, 2003
A thermodynamic approach was used to interpret the experimental adsorption anddesorption isothenn data forpotato starch gel. Cainrhtion of the thermodynamic properties (differential enthalpy, integral enthalpy. differential entropy and integral entropy) provides an understanding of the properties of water and energy requirements associated with the sorption behavior. Isosteric heats (differential enthalpies) were calcukated through direct use of moisture isotherms by applying the Clausius-Clapeyron equation. The differential enthalpy and entropy decreased with increasing moisture content and were adequately characterized by an exponential model. A plot of differential heat versus entropy satisfled the enthalpy-entropy compensaion theory. The spreading pressure increased with increasing water activity, and decreased with increasing temperature. The net integral enthalpy increased with moisture content to a maximum value (around the monolayer moisture content) and then decreased. In a reverse manner, the net integral entropy decreased with moisture content to a minimum value and then increased.
Modelling and Simulation in Engineering, 2014
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.
Pakistan Journal of Chemistry, 2014
This work describes moisture sorption behavior and water vapor permeability of gluteraldehyde-crosslinked Carrageenen/polyvinyl alcohol (Carr/PVA) films. The moisture uptake has been studied under various relative humidity (RH) and the data obtained has been interpreted in the terms of various isotherm models such as GAB, Oswin and Halsey models. The moisture permeability through the films has been characterized in the terms of various parameters like water vapor transmission rate (WVTR), permeance (P) and Water vapor permeability (WVP). It was found that these parameters are greatly affected by the degree of crosslinking of the films. Finally, the model drug Gentamycin Sulphate was loaded in to the films and its release was monitored kinetically in the physiological buffer (PF) at 37 0 C. The films exhibited diffusion controlled release mechanism.
Moisture Sorption Studies of Kamsa
European Journal of Engineering Research and Science
The study was aimed at establishing storage stability indices of a traditional smoke dried product kamsa, produced from beef. The sample was produced using a standardized method and stored over a period of six months. Data for sorption studies was generated between the temperature ranges of 33.8oC to 50oC for adsorption and desorption using the gravimetric method. The data was analyzed using the Guggeinheim Anderson de Boer (GAB) and the Brunaeur Emmett Teller (BET) model equations. A nonlinear regression analysis method was used to evaluate the constants of the sorption equations. From the results using the GAB model, the monolayer moisture content (Mo) decreased from 0.021 to 0.008gH2O/g solids; the value of the constant K, increased from 0.587 to 1.052; and the value of CG decreased from 2.481 to 2.154. For desorption, the value of Mo decreased from 0.021 to 0.004g H2O/g solids; K increased from 0.587 to 1.035; CG increased from 2.173 to 2.646. The model gave low percent standard...