Moisture sorption characteristics of mango–soy-fortified yogurt powder

Moisture adsorption isotherms of plain yogurt, mango–soy-fortified yogurt (MSFY) and MSFY containing 0.4% gelatin stabilizer (MSFYG) powder were determined at 20, 30, 40 and 50°C. A gravimetric static method was used under 0.11–0.81 water activity ranges for the determination of sorption isotherms that were found to be typical type II sigmoid. Experimental data were fitted to five mathematical models viz. modified Henderson, modified Chung–Pfost, Oswin, Smith and Guggenheim–Anderson–de Boer (GAB). It was found that both Oswin and GAB models were acceptable in describing equilibrium moisture content–equilibrium relative humidity (EMC–ERH) relationships for yogurt powder samples over the entire range of temperatures.     

Modelling moisture sorption isotherms for maize flour

The sorption isotherm of food material is pertinent in the processing and storage of food products. Adsorption and desorption isotherms for maize flour were investigated using the static gravimetric method over the range of temperature (27–40 °C) and water activity (a_w) (0.10–0.80) commonly 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 (MGAB), modified Oswin (MOE), modified Henderson (MHDE), and modified Chung–Pfost (MCE)). The GAB, MGAB, and MOE models were found to be acceptable in predicting the moisture sorption isotherms for maize flour. Overall, the MGAB appears to be most suitable for fitting the adsorption and desorption moisture isotherms data for the maize flour.     

Moisture sorption characteristics of curd (Indian yogurt) powder

The moisture sorption behaviour of curd (Indian yogurt) powder was studied at 20, 30, 40 and 50°C for water activity ranging from 0.07 to 0.85. GAB, BET, Henderson, Halsey, Chung & Pfost, Smith, Oswin and Peleg models were applied to analyse the data. Estimated parameters and fitting ability for sorption models were evaluated. The GAB model showed the best fit to the sorption data of curd powder at 20, 30 and 40°C, and the Peleg model fitted well at 50°C.     

Moisture sorption study on Nigerian foods: Kuka

Kuka is an important vegetable in the Nigerian food chain. The moisture sorption characteristics of the vegetable studied at 34, 37 and 45°C between a_w 0.10–0.96, revealed a BET type II behaviour. The Kuka exhibited hysteresis and an increase in EMC with increase in a_w and decrease in temperature. Four sorption models (Oswin, Halsey, Kuhn, and GAB) were studied and the Oswin model was the most suitable. The constants in the Oswin model and GAB monolayer moisture contents were obtained and found to be temperature-dependent. Heats of sorption were greater for desorption than adsorption and in either mode, they reduced with an increase in moisture content. An exponential equation was obtained to relate heat of sorption with moisture content.     

Water sorption isotherms of fresh and partially osmotic dehydrated pumpkin parenchyma and seeds at several temperatures

Experiments were conducted to determine the equilibrium moisture content of pumpkin (cv Cucurbita Pepo L.) at different temperatures (278.1 K, 298.1 K and 318.1 K) and relative humidities (8–91%). Fresh and partially osmotically dehydrated (using sucrose solutions) samples of pumpkin parenchyma were employed. The desorption isotherm of pumpkin seeds at 298.1 K was determined as well and was found to be similar to other sorption isotherms of other seeds with similar fat and protein compositions. No significant dependence of the equilibrium experimental data on the temperature or osmotic pre-treatment was found. Several common mathematical models were used to fit the experimental data. For the parenchyma tissue, statistical analysis proved that those of Halsey, Oswin, Chirife and GAB were the best, while for the seeds, the Henderson, GAB and Peleg models are preferable.     

Moisture adsorption isotherms of guar (Cyamposis tetragonoloba) grain and guar gum splits

Moisture adsorption isotherms of guar grain and guar gum splits were determined at 10, 20, 30 and 40 °C and 23-96% relative humidities using gravimetric method. The sorption data were fitted to six well-known sorption isotherm models (modified Chung-Pfost, modified Halsey, modified Henderson, modified Oswin, Chen-Clayton, and GAB models) using non-linear least square method. The GAB model was found the most satisfactory for representation of the equilibrium moisture content data for guar grain and guar gum splits. The equilibrium moisture content of guar gum splits was found to be significantly higher (p < 0.05) than that of guar grain. The isosteric heat of sorption was determined from the equilibrium moisture adsorption data using Clausius-Clapeyron type equation. Exponential relationship described well the dependence of isosteric heat of sorption on the equilibrium moisture content. The enthalpy-entropy compensation theory applied to sorption isotherms indicated enthalpy controlled sorption process.     

Equilibrium moisture content and heat of desorption of saffron

The equilibrium moisture contents of saffron (Crocus sativus L.) stigmas were determined experimentally using the standard gravimetric method at temperatures 30, 45 and 60 °C and water activity ranging from 11% to 83%. The sorption isotherm curves of saffron were sigmoidal in shape and decreased with increased temperature at constant relative humidity. Five selected isotherm models GAB, modified Henderson, modified Chung‐Pfost, modified Halsaey and modified Oswin were tested to fit the experimental isotherm data. Modified Oswin and modified Henderson models were found acceptable for predicting desorption moisture isotherms and fitting to the experimental data, respectively. The isosteric heats of desorption, determined from equilibrium data using the Clausius‐Clapeyron equation, were found to be a function of moisture content. The net isosteric heat of desorption of saffron varied between 1.38 and 5.38 kJ mol^?1 at moisture content varying between 2% and 20% (d.b).     

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

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.     

Moisture sorption isotherms of sorghum malt at 40 and 50 °C

The desorption and adsorption equilibrium moisture isotherms of sorghum malt at the temperatures of 40 and 50 °C, over the water activity range of 0.1-0.9, were determined using the static gravimetric method. A non-linear regression programme was used to fit five moisture sorption isotherm models [Modified Henderson, Modified Chung-Pfost, Modified Guggenheim-Anderson-de Boer (GAB), Modified Halsey and Modified Oswin] to the experimental data. The models were compared using the standard error of estimate, mean relative percentage deviation, fraction explained variation and residual plots.The Modified Chung-Pfost model was found to be the best for predicting the desorption equilibrium moisture content, while the adsorption equilibrium moisture content was best predicted by the Modified Oswin model. The desorption and adsorption water activities were found to be best fitted by the Modified Oswin model.The moisture sorption isotherms were sigmoidal in shape and showed a marked effect of temperature. The span of the moisture sorption hysteresis loop formed, decreased with increase in temperature, while the size increased with increase in temperature.     

Moisture sorption isotherms of grape pestil and foamed grape pestil

Moisture sorption isotherms of grape pestil and foamed grape pestil were determined using the static gravimetric method at 10, 20 and 30 degrees C. The overall shape of the curves was typical of sugar-rich materials. The effect of temperature on moisture content in the lower aw range was not significant (P > 0.05). Four models, namely the Brunauer, Emmet and Teller (BET), the Guggenheim, Anderson and DeBoer (GAB) the Halsey and the Oswin, were evaluated to determine the best fit for the experimental data. The BET and GAB models fitted well the data of the samples in the temperature and water activity range studied. The Clausius-Clapeyron equation was used to evaluate the isosteric heats of sorption.     

Desorption isotherms and isosteric heat of desorption of previously frozen raw pork meat

Some meat products involve drying previously frozen pork meat, which makes the knowledge of sorption characteristics very important for the design and management of meat dehydration processes. The sorption isotherms of raw pork meat from the Biceps femoris and Semimembranosus muscles were determined at four temperatures: 25, 30, 35 and 40 °C. The experimental results were modelled using the GAB (Guggenheim, Anderson and De Boer) model. The effect of temperature was also taken into account to model the experimental sorption isotherms using four models (GAB, Oswin, Halsey and Henderson). The best results were provided by the GAB model. From the experimental sorption isotherms the isosteric heats of sorption were determined. For a moisture content higher than 0.15 kg water/kg dm, the isosteric heat of meat was similar to the latent heat of vaporization for pure water. For a lower moisture content, an increase in the isosteric heat was observed when the moisture content decreased.     

Water sorption isotherms for lemon peel at different temperatures and isosteric heats

Lemon peel constitutes a potential source of dietary fiber to formulate new and healthier products, as well as a source of essential oils. The relationship between moisture content and water activity provides useful information for lemon peel processing, especially for drying and storage. Water sorption isotherms of lemon peel were obtained using a standardized conductivity hygrometer at four different temperatures (20, 30, 40 and 50 °C) and wide ranges of moisture content (5.381-0.002 kg water/kg dry solid) and water activity (0.984-0.106). One theoretical (GAB) and four empirical equations (Oswin, Henderson, Halsey and Ratti) were used for modelling sorption isotherms. After evaluating the models according to several criteria, the GAB model appeared as the best option. Isosteric heats of sorption were assessed from experimental sorption isotherm data using different methods.     

MOISTURE SORPTION CHARACTERISTICS of STARCH GELS. PART 1: MATHEMATICAL DESCRIPTION of EXPERIMENTAL DATA

The moisture sorption isotherms of potato starch, starch‐sugar and starch‐salt gels were determined using a gravimetric static method at 30, 45 and 60C, and over a range of relative humidities from 0.10 to 0.84. the starch gels exhibited Type II behavior, with incorporation of sugar or salt into the samples resulting in Type III form. the sorption capacity decreased with increasing temperature. the experimental data were analyzed using seven models; two‐parameter relationships (Halsey, Henderson, Smith), three‐parameter equations (Ferro‐Fontan, Guggenheim‐Anderson‐de Boer, modified‐Oswin) and four‐parameter equation (Peleg). the empirical Peleg equation and kinetic GAB model (parameters have physical significance) were found to be the most suitable for describing the sorption characteristics within the temperature range 30–60C and water activity range 0.05–0.95.     

Moisture sorption characteristics of dudh churpi,a traditional milk product in India

The sorption isotherms of dudh churpi, a shelf-stable traditional milk product in India, determined at 15, 25, 35 and 45 degrees C, were typical type II sigmoidal according to the BDDT (Brunauer-Deming-Deming-Teller) classification. Nine equations, namely Bradley, Henderson, Iglesias and Chirife, Khun, Mizrahi, GAB (Guggenheim-Anderson-de Boer), modified Mizrahi, Oswin and Caurie were fitted to the sorption data. Caurie's equation was found to be suited best to predict equilibrium moisture content of dudh churpi. Monolayer value, density of sorbed water, number of monolayers and area of adsorbent decreased with the increase in temperature.     

Moisture Sorption Isotherms of Oolong Tea

The sorption isotherms of Oolong tea were determined at temperatures ranging from 5 to 50 °C. Estimated parameters and fitting ability for nine equilibrium relative humidity (ERH) models were evaluated. The modified Oswin equations were found to be an adequate model of three parameters to describe the sorption data. The Andrieu model was the only adequate model of four parameters. In comparing the results of this study with previously published data, it was found that the sorption properties were affected by species and manufacture techniques. The Guggenheim–Anderson–de Boer (GAB) model was not an adequate model as indicated by checking residual plots. The monolayer moisture content calculated from the Brunauer–Emmett–Teller (BET) model was lesser than that calculated from the GAB model. The errors of moisture content determined by measuring the ERH and temperature of samples was within 0.35%.     

Comparison of five three-parameter equations for the description of moisture sorption data of mustard seeds

Equilibrium moisture contents (EMC) of seeds of yellow, brown, and oriental mustards were determined at five different temperatures (2, 10, 25, 40, and 55°C) by equilibrating about 10-g samples at relative humidities in the range of 11–96%, obtained using saturated salt solutions. the EMCs of all three types of mustard decreased with an increase in temperature at constant relative humidity. At most temperatures and at the relative humidities tested, oriental mustard seeds had the lowest, yellow mustard the highest, and brown mustard intermediate EMC values. Differences in the moisture adsorption characteristics of the three mustards were attributed to differences in mucilaginous material, oil and protein contents of the seed. the modified GAB equation together with four other commonly used three-parameter equations (modified Henderson, Chung-Pfost, Halsey, and Oswin equations) were evaluated for their ability to fit the experimental data for the three types of mustard. the modified GAB equation gave the best fit to the experimental data and the modified Oswin equation was the second best model for describing the EMC data of mustard seeds. the predicted safe storage moisture contents of oriental, brown and yellow mustard seeds at 25°C were 10.0, 10.6 and 10.7% (db), respectively.     

Effect of temperature and initial moisture content on sorption isotherms of banana dried by tunnel drier

Sorption isotherms of intermediate moisture content (IMC) products are essential to predict shelf-life of packaged moisture-sensitive product by modelling moisture uptake during storage and distribution. The effect of temperature and initial moisture content (MC) of IMC banana on the relationship between MC and water activity were investigated. Raw bananas were dried in a tunnel dryer at 2% relative humidity (RH), 70 °C, and a 3.2 ± 0.2 m s^–1 air velocity. Drying procedure was carried out a number of times until various IMC levels were obtained (5%, 14%, 22% and 33% db for banana). Sorption isotherms of bananas were determined at 10, 20, 30 and 40 °C. The initial MC of IMC banana had no significant effect on the relationship between MC and water activity according to statistical analysis. All the sorption curves were found to be Type II. BET, GAB, modified GAB, Oswin, Halsey and modified Freundlich models were fitted to the data and it was found that the best results were obtained with a modified Freundlich equation. A secondary modified Freundlich model was built accounting for the effect of a _w and temperature on the sample MC.     

Moisture sorption isotherms and isosteric heat of sorption of leaves and stems of lemon balm (Melissa officinalis L.) established by dynamic vapor sorption

The equilibrium moisture contents (MC) of leaves and stems of lemon balm (Melissa officinalis L.) were determined separately at temperatures of 25, 35 and 45 °C over a stepwise increase of relative humidity (RH) ranging from 3 to 90% by an automatic, gravimetric analyzer (DVS system). Equilibrium was achieved within 6 h for most of the target values of relative humidity. The equilibrium moisture content of leaves was significantly higher than that of stems (p < 0.05). Differences in moisture sorption capacity between the leaves and stems can be attributed to chemical composition and structure of the tissues. Five three-parameter moisture sorption models (modifications of Chung–Pfost, GAB, Halsey, Henderson and Oswin) were tested for their effectiveness to fit the experimental sorption data. The modified Oswin equation was found to be the best model to describe the adsorption isotherms of both leaves and stems of lemon balm. The recommended MC values of leaves and stems for microbial safe storage at 25 °C were 0.124 and 0.113 kg water per kg dry solids, respectively. The net isosteric heat of sorption was computed from the predicted sorption data by applying the integrated form of the Clausius–Clapeyron equation.     

Moisture sorption characteristics of dudh churpi,a traditional milk product in India

The sorption isotherms of dudh churpi, a shelf‐stable traditional milk product in India, determined at 15, 25, 35 and 45°C, were typical type II sigmoidal according to the BDDT (Brunauer‐Deming‐Deming‐Teller) classification. Nine equations, namely Bradley, Henderson, Iglesias and Chirife, Khun, Mizrahi, GAB (Guggenheim‐Anderson‐de Boer( modified Mizrahi, Oswin and Caurie were fitted to the sorption data. Caurie's equation was found to be suited best to predict equilibrium moisture content of dudh churpi. Monolayer value, density of sorbed water, number of monolayers and area of adsorbent decreased with the increase in temperature.     

MOISTURE ADSORPTION ISOTHERMS AND ISOSTERIC ENERGY FOR ALMOND

The equilibrium moisture contents of almond were determined using the gravimetric‐static method at 15, 30, 55 and 75C for powder and 15, 55 and 75C for nut state of almond for water activity (a_w) ranging from 0.11 to 0.87. At a given a_w, the results show that the moisture content decreases with increasing temperature. The experimental sorption curves are then described by the BET, GAB, Henderson, Oswin, Smith and Halsey models. A nonlinear regression‐analysis method was used to evaluate the constants of equations. The GAB model was found to be the most suitable for describing the sorption curves; the monolayer‐content values for the sorption at different temperatures are calculated. Also, the isosteric heats of adsorption of water were determined as a function of moisture content from the equilibrium data at different temperatures using the Clasius‐Clapeyron equation.