Moisture Sorption Isotherm (moisture + sorption_isotherm)

Distribution by Scientific Domains


Selected Abstracts


MOISTURE SORPTION ISOTHERM, PROPERTIES OF SORBED WATER AND HEAT OF SORPTION OF SANDESH, AN INDIAN MILK PRODUCT

JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 1 2010
J.K. SAHU
ABSTRACT Moisture sorption isotherm of sandesh, one of the most popular milk products in India, was determined in terms of its moisture adsorption isotherms by gravimetrical method at 20 and 30C using various saturated salt solutions in the range of 11.2 to 97.2%. The isotherms obtained were of sigmoid shape and of the Brunauer,Emmett,Teller type. Out of three sorption models fitted to the experimental data, Caurie's model was found superior in interpreting the moisture adsorption characteristics of sandesh. The monolayer moisture content as calculated from the Caurie's model at 20 and 30C were 5.89% (dry basis [d.b.]) and 5.21% (d.b.), respectively. The values of isosteric heat of sorption as calculated from Clausius,Clapeyron equation was found to increase with decreasing moisture content at lower moisture content and approached the value of heat of vaporization of free water above 17.25% (d.b.). PRACTICAL APPLICATIONS The present paper describes basically the storage stability of sandesh. The sandesh is a heat,acid coagulated product of milk in Indian subcontinent and forms the part and parcel of social life, ceremonies and festivals. It has an excellent market potential and higher profit margin compared with other milk products like table butter, cheese and milk powder. Although Indian dairy industry has made rapid strides in the last few decades, there is no proper packaging system, developed so far, for storage of sandesh. Keeping pace with the growing consumers' demand for fresh, convenient and microbiologically free foods, design of proper packaging system is the need of the hour. The data presented in the paper will be very much essential for the researchers and research and development institutions for proper designing of packaging system for sandesh. [source]


Moisture sorption isotherm and xerophilic moulds associated with dried cocoyam chips in storage in Nigeria

INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 5 2008
J. Obeta Ugwuanyi
Summary Extended storage of cocoyams (Colocasia antiquorum and Colocasia esculenta) is achieved in parts of Nigeria by processing them into smoked and dried chips. In this study, cocoyam chips were collected from parts of Nigeria at the end of drying, at various periods of storage and from markets, and analysed for moisture content, moisture sorption characteristics and xerophilic moulds. Moisture content of chips ranged from 7.07 ± 1.1% for freshly dried samples to 16 ± 2.2% for samples stored up to 8 months. Six mould species from four groups of the genus Aspergillus (including five xerophiles) identified as Aspergillus fumigatus, Eurotium repens, Eurotium amstelodami, Eurotium chevalieri and Aspergillus flavus and Aspergillus niger and Mucor sp. were isolated. The variety of moulds increased with storage and moisture content of samples. Moisture sorption in dried chips showed type II sigmoidal behaviour. Wood smoke significantly protected chips from mould colonization, but in cooperation with reduced water activity. Simple and inexpensive storage of freshly dried samples in airtight bags led to prolonged storage of up to 14 months without deterioration. [source]


MOISTURE SORPTION ISOTHERM, PROPERTIES OF SORBED WATER AND HEAT OF SORPTION OF SANDESH, AN INDIAN MILK PRODUCT

JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 1 2010
J.K. SAHU
ABSTRACT Moisture sorption isotherm of sandesh, one of the most popular milk products in India, was determined in terms of its moisture adsorption isotherms by gravimetrical method at 20 and 30C using various saturated salt solutions in the range of 11.2 to 97.2%. The isotherms obtained were of sigmoid shape and of the Brunauer,Emmett,Teller type. Out of three sorption models fitted to the experimental data, Caurie's model was found superior in interpreting the moisture adsorption characteristics of sandesh. The monolayer moisture content as calculated from the Caurie's model at 20 and 30C were 5.89% (dry basis [d.b.]) and 5.21% (d.b.), respectively. The values of isosteric heat of sorption as calculated from Clausius,Clapeyron equation was found to increase with decreasing moisture content at lower moisture content and approached the value of heat of vaporization of free water above 17.25% (d.b.). PRACTICAL APPLICATIONS The present paper describes basically the storage stability of sandesh. The sandesh is a heat,acid coagulated product of milk in Indian subcontinent and forms the part and parcel of social life, ceremonies and festivals. It has an excellent market potential and higher profit margin compared with other milk products like table butter, cheese and milk powder. Although Indian dairy industry has made rapid strides in the last few decades, there is no proper packaging system, developed so far, for storage of sandesh. Keeping pace with the growing consumers' demand for fresh, convenient and microbiologically free foods, design of proper packaging system is the need of the hour. The data presented in the paper will be very much essential for the researchers and research and development institutions for proper designing of packaging system for sandesh. [source]


Moisture sorption isotherms and thermodynamic properties of apple Fuji and garlic

INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 10 2008
Mariana A. Moraes
Summary The moisture equilibrium isotherms of garlic and apple were determined at 50, 60 and 70 °C using the gravimetric static method. The experimental data were analysed using GAB, BET, Henderson,Thompson and Oswin equations. The isosteric heat and the differential entropy of desorption were determined by applying Clausius,Clapeyron and Gibbs,Helmholtz equations, respectively. The GAB equation showed the best fitting to the experimental data (R2 > 99% and E% < 10%). The monolayer moisture content values for apple were higher than those for garlic at the studied temperatures; the values varied from 0.050 to 0.056 and from 0.107 to 0.168 for garlic and apple, respectively. The isosteric heat and the differential entropy of desorption were estimated in function of the moisture content. The values of these thermodynamic properties were higher for apple (in range 48,100 kJ mol,1 and 14,150 J mol,1 K,1) than for garlic (in range 43,68 kJ mol,1 and 0,66 J mol,1 K,1). The water surface area values decreased with increasing temperature. The Kelvin and the Halsey equations were used to calculate the pore size distribution. [source]


Effects of Water-Glycerol and Water-Sorbitol Interactions on the Physical Properties of Konjac Glucomannan Films

JOURNAL OF FOOD SCIENCE, Issue 2 2006
Lai Hoong Cheng
ABSTRACT Konjac glucomannan (KGM)-edible films were prepared with different amounts of glycerol or sorbitol as a plasticizer. Films were characterized by moisture sorption isotherm, and following conditioning at different relative humidities, by differential scanning calorimetry and tensile tests. Moisture and polyols (sorbitol and glycerol) were found to plasticize KGM-based films with respect to their tensile properties. However, thermal properties and water sorption capacity (WSC) of polyolplasticized KGM films were found to vary with water activity (aw), namely at low aw (< 0.6), WSC and melting enthalpy were decreased with increasing in polyol content and the opposite was true at higher aw (>0.6). This was attributed to extensive interactions between plasticizer and KGM that reduced the available active site (-OH groups) for water adsorption. The presence of polyols at low aw appeared to suppress crystalline structures due probably to restricted molecular mobility. These effects were diminished when the moisture content was >20%. [source]


Mathematical modelling of moisture sorption isotherms and determination of isosteric heat of blueberry variety O,Neil

INTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 10 2009
Antonio Vega-Gálvez
Summary The sorption isotherms of blueberry variety O'Neil were determined at 20, 40 and 60 °C, for a range of water activity of 0.10,0.95. The isotherms showed that the equilibrium moisture content increased when temperature decreased at constant water activity. The BET, GAB, Halsey, Henderson, Caurie, Smith, Oswin and Iglesias-Chirife equations were tested for modelling the sorption isotherms. The results showed that GAB, BET and Halsey models gave the best fit quality for the experimental desorption data, and BET, Oswin and Henderson for adsorption data as suggested by the statistical tests employed. The net sorption heat was calculated using the Clausius,Clapeyron equation giving 38.62 kJ mol,1 (desorption) and 30.88 kJ mol,1 (adsorption) at a moisture content of 0.01 g water (g d.m.,1). Tsami equation was applied to estimate the net isosteric heat of sorption as function of equilibrium moisture content with satisfactory results. [source]


Moisture sorption in moulded fibre trays and effect on static compression strength

PACKAGING TECHNOLOGY AND SCIENCE, Issue 4 2003
Gitte Sřrensen
Abstract This study provides a basic understanding of moisture sorption in moulded fibre packaging for food at varying environmental temperatures and humidities, and the resultant effects on static compression strength. The Guggenheim,Anderson,de Boer (GAB) model is used successfully to construct moisture sorption isotherms in the range 2,25°C and 33,98% relative humidity (% r.h.) (R2 = 0.949,0.999), in which moisture content varies from 5.4 to 28.3,g/100,g dry fibre. Static compression strength (SCS) is substantially affected by changes in moisture content of moulded fibre and decreases exponentially with increasing moisture content. The results indicate a minor hysteresis effect on static compression strength. For adsorption of moisture, a relative strength measure, % SCS (experimental SCS in kg divided by a standard SCS in kg), is given by % SCS = 13.83 + 166.50,·,e,0.0978,m (m is moisture content). The temperature dependence of moisture adsorption is incorporated in the GAB model by relating GAB coefficients, m0 and C, exponentially to temperature, T. By combining this with the exponential model for % SCS, static compression strength can be predicted directly from the surrounding temperature and humidity. Illustrated in a response surface plot the effects of changes in the surroundings are simple and readily accessible, e.g. for packaging designers and sales people. It is noted that an increase in humidity from 50% r.h. to 95% r.h. at constant temperature results in a drastic reduction in % SCS from 100% to 40%, whereas the temperature effect is typically less than 10% SCS when reducing temperature from 25°C to 2°C. Copyright © 2003 John Wiley & Sons, Ltd. [source]