scholarly journals Modelling the moisture sorption isotherms of Roselle (Hibiscus sabdariffa L.) in the temperature range of 5–35 °C

2013 ◽  
Vol 61 (6) ◽  
pp. 1769-1777 ◽  
Author(s):  
Jitka Langová ◽  
Donludee Jaisut ◽  
Ratiya Thuwapanichayanan ◽  
Charotorn Phowong ◽  
Jiří Štencl ◽  
...  
Keyword(s):  
Moisture Content ◽  
Water Sorption ◽  
Structural Changes ◽  
Sorption Isotherms ◽  
Moisture Sorption ◽  
Ambient Air ◽  
Point Of View ◽  
Hibiscus Sabdariffa ◽  
Adsorption And Desorption ◽  
Moisture Sorption Isotherms

Water sorption tests of Roselle (Hibiscus sabdariffa L.) carried out under laboratory conditions are presented together with mathematical analyses of the moisture sorption isotherms (MSI’s). Moisture equilibrium data for adsorption and desorption of water from Roselle powder were investigated at near ambient air temperatures in the range of 5 and 35 °C and water activity (Aw) ranging from 0.11 to 0.97. The manometric method has been used for water sorption tests. Models for MSI’s are exponential equations. Coefficients of determination are 0.998 and 0.996 (for adsorption and desorption at 5 °C, respectively), 0.998 and 0.999 (for adsorption and desorption at 20 °C, respectively), and 0.998 and 0.999 (for adsorption and desorption at 35 °C, respectively). The equilibrium moisture content (EMC) of Roselle samples increased with an increase of Aw at a constant temperature both for adsorption and desorption. Adsorption curve equates to desorption curve at higher temperatures of tests carried out. Critical values of EMC of samples tested corresponding to the Aw equal to 0.6 were between 13.401% moisture content wet basis (MC w.b.) and 15.934% MC (w.b.) for moisture adsorption and desorption, respectively. These values are useful for storing conditions optimisation from point of view microorganisms grow and structural changes analyses. Crystal structure changes were observed during adsorption and desorption in the microscope, too. It was found out glass transition in dependence on the water content of samples tested.

scholarly journals Moisture sorption isotherms of castor beans. Part 1: Mathematical modeling and hysteresis

2016 ◽  
Vol 20 (8) ◽  
pp. 751-756 ◽  
Author(s):  
André L. D. Goneli ◽  
Paulo C. Corrêa ◽  
Gabriel H. H. de Oliveira ◽  
Osvaldo Resende ◽  
Munir Mauad
Keyword(s):  
Moisture Content ◽  
Sorption Isotherms ◽  
Moisture Sorption ◽  
Environmental Condition ◽  
Adsorption And Desorption ◽  
Moisture Sorption Isotherms ◽  
Different Temperatures ◽  
The Difference ◽  
The Stability ◽  
And Storage

ABSTRACT Sorption isotherms are of great importance in post-harvest procedures, especially for predicting drying and storage, which help to establish the final moisture content of the product under certain environmental condition. Hysteresis is a phenomenon that occurs due to the difference between adsorption and desorption curves, which aids the evaluation of chemical and microbiological deteriorations, indicating the stability of stored products. Moisture sorption isotherms of castor beans were determined and hysteresis was analyzed. Static gravimetric technique at different temperatures (25, 35, 45 and 55 ± 1 °C) was used. Saturated salt solutions in the range of 37-87% ± 2% were utilized to create the required controlled relative humidity environment. Equilibrium moisture content data were correlated by different mathematical models and the Modified Halsey model presented good adjustment for the data, according to statistical procedures. Hysteresis between adsorption and desorption isotherms is present over the range of 0.2-0.9 of water activity, regardless of the temperature. This phenomenon decreases with temperature increase.

scholarly journals Water sorption properties of Dutch type semi-hard cheese edge in the range of common storing temperatures

2011 ◽  
Vol 59 (5) ◽  
pp. 203-208 ◽  
Author(s):  
Maria Carolina Soares Pereira ◽  
Jiří Štencl ◽  
Bohumíra Janštová ◽  
Václav Vlášek
Keyword(s):  
Moisture Content ◽  
Equilibrium Moisture Content ◽  
Pure Water ◽  
Free Water ◽  
Sorption Isotherms ◽  
Moisture Sorption ◽  
Water Evaporation ◽  
Adsorption And Desorption ◽  
Moisture Sorption Isotherms ◽  
Hard Cheese

Moisture sorption isotherms of Dutch type semi-hard cheese edge in the temperature range of 10–25 ºC and water activity (Aw) from 0.11 to 0.98 were determined using manometric method. The sorption curves had a sigmoid shape. The equilibrium moisture content (EMC) of cheese samples increased with an increase in Aw at a constant temperature both for water adsorption and desorption. An increase in temperature caused an increase in Aw for the same moisture content (MC) and, if Aw was kept constant, an increase in temperature caused a decrease in the amount of absorbed water. Critical values of equilibrium moisture content, corresponding to the Aw = 0.6, were between 11 % MC (w.b.) and 17 % MC (w.b.) both for moisture adsorption and desorption. Values of sorption heat were calculated from moisture sorption isotherms by applying the Clausius-Clapeyron equation. Values of the heat of desorption are higher than those of adsorption and the difference increases with the MC decrease. Heat of sorption decreased from 48.5 kJ/mol (~5.5 % MC w.b.) to the values approaching the heat of vaporization of pure water, free MC. The critical value for free water evaporation is about w = 27 % (w.b.) for the range of temperature 10–25 ºC.

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

2019 ◽  
Vol 62 (1) ◽  
pp. 105-114
Author(s):  
Xiuping Jiang ◽  
Xiuping Jiang ◽  
Huanhuan Li ◽  
Hosahalli S. Ramaswamy ◽  
Songming Zhu ◽  
...  
Keyword(s):  
High Pressure ◽  
Gravimetric Method ◽  
Sorption Isotherms ◽  
Moisture Sorption ◽  
Storage Conditions ◽  
Sorption Behavior ◽  
Adsorption And Desorption ◽  
Moisture Sorption Isotherm ◽  
Moisture Sorption Isotherms ◽  
Paulownia Wood

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.

scholarly journals Moisture Sorption Behaviour and Mould Ecology of Trade Garri Sold in South Eastern Nigeria

2014 ◽  
Vol 2014 ◽  
pp. 1-10 ◽  
Author(s):  
Tochukwu Samuel ◽  
J. Obeta Ugwuanyi
Keyword(s):  
Moisture Content ◽  
Water Activity ◽  
Central Africa ◽  
Sorption Isotherms ◽  
Moisture Sorption ◽  
Fungal Species ◽  
Temperature Dependent ◽  
Sorption Behaviour ◽  
Moisture Sorption Isotherms ◽  
West And Central Africa

Garri is a creamy white or yellow starchy grit produced by roasting to gelatinization and dryness of peeled, washed, mashed, and fermented dewatered cassava roots. It is the most important product of cassava in West and Central Africa. Mean moisture content of yellow and white garri was 11.11% and 10.81% within 24 hrs of sampling from the market, increasing to 17.27% and 16.14%, respectively, following 3 months of storage at room temperature. The water activity of samples varied from initial 0.587 to 0.934 following storage. Moisture sorption isotherms, determined by static gravimetric techniques at 20° and 30°C, showed temperature dependent BET Sigmoidal type II behaviour typical of carbohydrate rich foods but modulated very slightly by the content of palm oil. Equilibrium moisture content decreased with increase in temperature at constant water activity. A total of 10 fungal species belonging to the generaMucor,Penicillium,Cephalosporium,Aspergillus,Scopulariopsis,Rhizopus, and Paecilomyceswere identified, with range increasing with water activity of samples.

Equilibrium Moisture Content Models for Lafun

2008 ◽  
Vol 4 (2) ◽  
Author(s):  
Olusegun J Oyelade
Keyword(s):  
Moisture Content ◽  
Equilibrium Moisture Content ◽  
Adsorption Isotherms ◽  
Gravimetric Method ◽  
Sorption Isotherms ◽  
Moisture Sorption ◽  
Keeping Quality ◽  
Moisture Sorption Isotherms ◽  
Process Operation ◽  
The Relationship

Insights into the relationship between the air relative humidity (water activity (aw)) and equilibrium moisture content of food materials is essential to maintain good keeping quality and optimize process operation. The adsorption isotherms for cassava flour (lafun) were investigated with the static gravimetric method. Concentrated acid (H2SO4) solutions were used to vary the micro-climate in the study and presented in an easy-to-use template-like format over the range of temperature (27- 40oC) and aw (0.10-0.80) usually experienced in the tropical environment. The experimental data were compared with five widely recommended models in the literature for food sorption isotherms (GAB, modified GAB, modified Oswin, modified Henderson & modified Chung-Pfost). The moisture sorption isotherms were sigmoidal in shape and were influenced by temperature. The modified Oswin model was found to be most adequate whilst the modified GAB appears not suitable to model the adsorption isotherms for lafun.

scholarly journals Drying kinetics and determination of water sorption isotherms of corn

2017 ◽  
Vol 15 (2) ◽  
Author(s):  
J Roy ◽  
MA Alim ◽  
MN Islam
Keyword(s):  
Moisture Content ◽  
Sorption Isotherm ◽  
Water Sorption ◽  
Sorption Isotherms ◽  
Moisture Sorption ◽  
Drying Kinetics ◽  
Drying Time ◽  
Moisture Sorption Isotherm ◽  
Water Sorption Isotherm ◽  
Monolayer Moisture

The study was carried out for the purpose of determining the drying kinetics as well as moisture sorption isotherm of hybrid-81 corn. Corn at about 31% moisture content (wb) was dried in a forced convective hot air cabinet dryer at different drying conditions, such as variable air dry bulb temperature (40°C, 50°C and 60°C) and loading density (3.56 kg/m2, 7.12 kg/m2, and 10.68 kg/m2) as well as in shining sun at different layers (3.56 kg/m2, 7.12 kg/m2, and 10.68 kg/m2). The water sorption isotherm of the dried corn was developed using vacuum desiccators, which contained saturated salt solutions in the range of 11-93% RHs. The mono-layer moisture content calculated by the Brunauer–Emmett–Teller (BET) model (6.76 g/100 g solid) was lesser than that calculated by the Guggenheim–Anderson–De Boer (GAB) model (10.53 g/100 g solid). The energy constants were 10.45 and 4.64 as per BET and GAB equation, respectively. Both models gave suitable fits for corn. The activation energy (Ea) for diffusion of water was found to be 11.09 kcal/gm-mole for corn. Furthermore, it was noticed that, with the increase of corn layer, the drying rate decreased in case of both sun and mechanical drying. However, higher loading density resulted in efficient drying, at least up to 10.7 kg/m2. It was shown that the drying time to obtain stability was the lowest for moisture content (12.08 %) corresponding to aw of 0.65 in case of BET or GAB monolayer moisture content. This finding could be helpful in predicting the storage life of corn.J. Bangladesh Agril. Univ. 15(2): 309-317, December 2017

scholarly journals Study on the Effects of Physical Properties of Tenera Palm Kernel during Drying and Its Moisture Sorption Isotherms

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1658
Author(s):  
Mina Habibiasr ◽  
Mohd Noriznan Mokhtar ◽  
Mohd Nordin Ibrahim ◽  
Khairul Faezah Md Yunos ◽  
Nuzul Amri Ibrahim
Keyword(s):  
Moisture Content ◽  
Physical Properties ◽  
Surface Area ◽  
Palm Kernel ◽  
Gravimetric Method ◽  
Sorption Isotherms ◽  
Moisture Sorption ◽  
Kernel Length ◽  
Moisture Sorption Isotherms ◽  
Ground Kernel

A study on the effect of the physical properties and moisture sorption isotherm of palm kernels constitutes the critical criteria in evaluating the drying performance. The drying was evaluated as a function of moisture content (MC) in the range of 0.31–0.02 kg/kg (d.b.). Whereas, the equilibrium moisture content (EMC) of palm kernels (whole kernel and ground kernel) was determined experimentally using the standard gravimetric method at different temperatures (50 °C to 80 °C), over a range of relative humidity (RH) from 10% to 81%. Palm kernel length, width, and thickness decrease from 16.08 ± 2.09 mm to 14.17 ± 2.30 mm, 12.06 ± 1.40 mm to 11.24 ± 1.08 mm, and 10.01 ± 1.27 mm to 9.18 ± 1.04 mm, respectively, when MC decreased. Bulk density, surface area, and specific surface area decreased as the MC decreased, while porosity and true density were increased. EMC of palm kernels (whole kernel and ground kernel) decreased with an increase in temperature at constant RH. Modified Oswin and modified Halsey models were found to be the best for predicting desorption moisture isotherms for whole and ground palm kernel, respectively. Therefore, the study of the effect of drying on physical aspects as well as moisture sorption isotherms is important to further analyze the drying performance of Tenera palm kernel (e.g., equipment design and energy requirement).

Moisture Sorption Isotherms and Net Isosteric Heats of Sorption of Green Soybean

2012 ◽  
Vol 8 (3) ◽  
Author(s):  
Zhao Yang ◽  
Enlong Zhu ◽  
Zongsheng Zhu
Keyword(s):  
Moisture Content ◽  
Equilibrium Moisture Content ◽  
Sorption Capacity ◽  
Water Activity ◽  
Sorption Isotherms ◽  
Moisture Sorption ◽  
Isosteric Heat ◽  
Model Parameters ◽  
Desorption Process ◽  
Moisture Sorption Isotherms

Abstract Moisture sorption isotherms of green soybean seeds were determined by static gravimetric method and water activity ranging from 0.11to 0.94 at 20, 30 and 40°C. The optimal sorption model of green soybean was determined by using nonlinear regression method. Modified BET multilayer sorption theory model parameters at different temperatures were calculated, isosteric sorption heat was derived by the water activity sorption isosteric model. Results indicated that sorption isotherms were belong to type III behaviour, a notable hysteresis effect was observed, Green soybean monolayer saturated sorption capacity was greater in desorption process than that of adsorption. The monolayer saturated sorption capacity decreased with increasing temperature, while the number of multilayer had a reverse trend with the monolayer saturated sorption capacity, the optimal sorption isotherm model for green soybean is Halsey model, The thermodynamic parameters including net isosteric heat of adsorption and desorption calculated at 40°C were 105.2-1865.4 kJ/kg and 111.62-1939.0 kJ/kg with equilibrium moisture content between 5% and 32% (d.b.), respectively. The net isosteric heat of sorption decreased with increasing equilibrium moisture content.

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