EFFECT OF DRYING METHODS ON MOISTURE SORPTION ISOTHERMS OF FUFU AT THREE TEMPERATURES

Moisture sorption characteristics for dried fufu using three drying methods at 25°C, 32°C and 45°C were determined experimentally for water activity ranging from 0.11 to 0.96. At a given temperature and water activity, the rotary dried fufu had the highest equilibrium moisture content while the sun dried had the lowest.

Four linear and four nonlinear sorption models were used to analyze the data. The linear GAB model showed the best fit while the nonlinear Bradley model was the best over the whole range of water activity in their respective groups. Also estimates of the net isosteric heats of sorption and their dependence on moisture content were presented for each product.     

EQUILIBRIUM MOISTURE CONTENT OF DRIED BLOOD FLOUR FN THE TEMPERATURE RANGE OF 20 - 50°C

ABSTRACT

The paper presents results of water sorption tests of dried blood flour carried out tinder laboratory conditions and mathematical analyses of sorption isotherms obtained. Moisture equilibrium data were investigated at air temperatures in the range of 20–50°C and water activity ranging from 0 4 to 0 99. The experimental procedure used was a gravimetric dynamic method with continuous registration of sample weight changes. Sorption capacity decreases as temperature increases. Rehydration of the dried material results in hysteresis but this phenomenon was small. Four models of equilibrium moisture content/equilibrium relative air humidity (Chung—Pfost. Halsey. Henderson, and Oswin) were evaluated for their ability to fit data for the samples of dried blood. The modified Henderson equation was a good model for moisture adsorption and desorption of dried blood flour     

THE MOISTURE SORPTION ISOTHERMS OF CEFOTAXIME SODIUM SALT

ABSTRACT

The water sorption isotherms of the cefotaxime sodium salt were determined at 30 and 40° C. Cefotaxime sodium salt was maintained at equilibrium relative humidities ranging from 40 to 80 %. Equilibrium moisture content was determined by the Karl Fischer method. The moisture sorption isotherms showed that the equilibrium moisture decrease while the temperature increase. The experimental curves of equilibrium humidity were fitted by different models (Bradley, Halsey, Henderson, Kuhn, Smith and Iglesias and Chirife and GAB). Parameters of each equations were determined by non-linear regression analysis. The best fit was obtained by Iglesias and Chirife model. The isosteric heat of moisture sorption calculated by Claussius Clapeyron equation varied from 64·45 to 48·03 kJ/mol when moisture content changed from 7 to 9·5 %.     

DESORPTION ISOTHERMS OF WATER IN TRIFOLIATE YAM )Dioscorea dumetorum Pax.(

Abstract

Desorption isotherms of water in trifoliate yam (Dioscorea dumetorum Pax) were determined using a dynamic gravimetric method at temperatures of 20°, 34°, 46° and 62°C, in the relative humidity range from 11 to 86% A nonlinear least squares regression program was used to fit the measured data to the Modified Henderson, the Modified Halsey, the Chung-Pfost, and the GAB sorption models. The GAB model gave the best fit. The net isosteric heat of sorption, estimated using the Clasius-Clapeyron equation, ranged from 1412 kJ/kg at a moisture content of 0.05 kg/kg, dry basis, to 325 kJ/kg at 0.20 kg/kg. Results obtained in this study should be important in controlling the water content of yam during processing, handling, packaging and storage.     

Letter to the Editor

Abstract

The water sorption isotherms of the Erythrina fusca Lour bark at 30 and 40°C were determined over relative humidity ranging from 55 to 85%. The equilibrium moisture content was determined gravimetrically. The moisture sorption isotherms showed that the equilibrium moisture decreases with increase of temperature. Six models were used for to fit the experimental curves of equilibrium humidity. Parameters of each equation were determined by nonlinear regression analysis. The isosteric heat of moisture sorption was calculated using the Claussius-Clapeyron equation.     

Sorption Isotherms of Vaccum-Fried Carrot Chips

Abstract

The moisture sorption isotherms for carrot chips after vacuum frying were determined using a gravimetric technique at 10, 25, and 40°C and fitted with BET, GAB, Smith, Halsey, Henderson, and Peleg models. A nonlinear least-squares regression program was used to determine the models constants. The Peleg, Halsey, and GAB models were found to best represent the experimental data throughout the entire water activity range.     

THERMODYNAMIC BEHAVIOR OF FISH MEAL DURING ADSORPTION

ABSTRACT

Anchovy fish meal with an approximate uniform moisture content of 10% was used for this study. Vapor adsorption isotherms were determined at 25 ° C, 35 ° C and 45 ° C. The differential and integral thermodynamic properties were estimated using the Othmer method. The isosteric heat or differential enthalpy, as a function of moisture content, showed a maximum value around 4.5 g of water/100 g d. s. The heat of sorption increased gradually with an increase in sorbed water until reaching its maximum value near the monolayer, and at a given moisture content, decreasing with temperature. The molar entropy values obtained were high at low water contents and fell to a minimum near the monolayer value.     

PREDICTING THE SORPTION BEHAVIOUR OF GARLIC SLICES

ABSTRACT

Moisture desorption properties of fresh garlic (cv. Early Californian) were investigated at 20 °C to 70°C and relative humidities ranging from 11% to 85% using the gravimetric static method. The slices were allowed to equilibrate in a constant humidity environment (hygrostats) maintained by salt solutions. The effect of temperature and relative humidity on the equilibrium moisture content was highly significant (P<0.0001). Four models available in the literature, namely the Chung-Pfost, modified Halsey, modified Henderson and the Guggenheim-Anderson-de Boer (GAB) were evaluated (the correlation coefficient, F-ratio and plots of residuals) to determine the best fit for the experimental data. On the basis of the F-test, The modified Henderson model was found adequate and the GAB model superior for characterising the sorption behaviour of garlic slices in the temperature and water activity range investigated.     

MODELLING OF SORPTION ISOTHERMS OF DRIED VEGETABLE WASTES FROM WHOLESALE MARKET

ABSTRACT

The moisture sorption isotherms of dried vegetable wastes (based on green leaves and fruits) from wholesale market were determined at 25, 40, 60 and 90°C by the static gravimetric method. Experimental data were fit by using several mathematical models. The G.A.B. and the Halsey model gave the minimum mean square error. G.A.B. parameters were related with temperature by Arrhenius expressions.     

PREDICTING THE SORPTION BEHAVIOUR OF GARLIC SLICES

ABSTRACT

Moisture desorption properties of fresh garlic (cv. Early Californian) were investigated at 20 °C to 7O° C and relative humidities ranging from 11% to 85% using the gravimetric static method. The slices were allowed to equilibrate in a constant humidity environment (hygrostats) maintained by salt solutions. The effect of temperature and relative humidity on thc equilibrium moisture content was highly significant (P < 0.0001). Four models available in the literature, namely the Chung-Pfost, modified Halsey, modified Henderson and the Guggenheim-Anderson-de Boer (GAB) were evaluated (the correlation coefficient, F-ratio and plots of residuals) to deterinhe the best fit for the experimental data. On the basis of the F-test, The modifled Henderson model was found adequate and the GAB model superior for characterising the sorption behaviour of garlic slices in the temperature and water activity range investigated.     

EFFECT OF DRYING METHODS ON PHYSICOCHEMICAL AND SENSORY QUALITIES OF FUFU

ABSTRACT

Fufu was dried using rotary drier, cabinet drier and sun drying methods. The effects on the physical, chemical and sensory properties of fufu by the different drying methods were evaluated. The drying methods did not appreciably affect the yield, proximate composition or acidity of fufu, but affected pasting properties. Panellists (P < 0.05) rated the rotary dried fufu best.     

Moisture Adsorption Isotherms and Glass Transition Temperature of Xanthan Gum

The moisture adsorption isotherms of the xanthan gum were determined at 30–70°C over water activity ranging from 0.11 to 0.94. The moisture adsorption isotherms revealed that the equilibrium moisture content increased with water activity. Increased temperature, in general, resulted in decreased equilibrium moisture content. However, in some cases equilibrium moisture content values increased with temperature. Selected sorption models were tested to describe the adsorption isotherms. Parameters of each sorption model were determined by nonlinear regression analysis. The modified Oswin model gave the best fit for xanthan gum. The isosteric heat of sorption decreased with increase in moisture content and varied between 1.66 and 7.61 kJ/mol. The glass transition temperature decreased with increase in moisture content for xanthan gum.     

DRYING KINETICS FOR SOME FRUITS: PREDICTING OF POROSITY AND COLOR DURING DEHYDRATION.

ABSTRACT

Drying kinetics of four fruits (prune, quince, fig and strawberry) were studied by using a simple mass transfer mathematical model involving a characteristic parameter (K) as a function of process variables. The model was tested with data produced in a laboratory air dryer, using non-linear regression analysis. The investigation involved three values of sample thickness (5, 10, 15mm) and three different air temperatures (50, 60, 70?°C).

The parameters of the model were found to be greatly affected by sample thickness and air temperature. The effect of moisture content on the porosity of three fruits (namely avocado, prune and strawberry) was also investigated. A simple mathematical model was used to correlate porosity with moisture content. It was found that porosity increased with decreasing moisture content.

Samples of three fruits (avocado, prune and strawberry) were investigated to estimate color changes during conventional drying at 70?°C. A first order kinetic model was fitted to experimental data with great success. It is found that the color of avocado and strawberry change while the color of prune remains the same.

Furthermore, the water sorption isotherms of three fruits (avocado, prune and strawberry) at 25° temperature were determined experimentally and the parameters at the GAB equation were evaluated by means of non-linear regression analysis. The use of the above equation produced a very good fit.     

Optimization of Drum Drying Parameters for Low Amylose Rice (KDML105) Starch and Flour

Abstract

An attempt was made to study and model the effects of drum drying process variables on the physico–chemical properties of low amylose rice (KDML105) flour and starch. Drum surface temperature, holding time and solid content of the slurry were varied at three levels: 115–135°C, 14–84 s and 20–40%, w/w, respectively. The dependent variables were moisture content (MC), degree of gelatinization (DG), water absorption index (WAI), water solubility index (WSI) and pasting property. High solid content led to a decrease in DG, WAI and initial peak viscosity (IPV) and increase in WSI of dried samples. Longer holding time resulted in increased DG while surface temperature had no significant effect on all characteristics. Predictive correlations were developed using stepwise multiple linear regression to predict MC, DG, WAI, WSI, and IPV of dried products from drum drying variables.     

DETERMINATION OF MOISTURE DIFFUSIVITY AND BEHAVIOR OF TOMATO CONCENTRATE DROPLETS DURING DRYING IN AIR

ABSTRACT

The drying mechanism and diffusion coefficient of water in spherical droplets (1.73 – 2.08 mm diameter) of tomato concentrates were successfully interpreted and modelled by using Fick's law. Solids content of the initial concentrate (5–15% w/w), and drying temperature (60^° – 100^° C) were varied but the drying air was kept at constant velocity and humidity.

The effective moisture diffusivity was estimated from the drying rate curves and expressed by an Arrhenius relation. Further, it was observed that case hardening has a large effect on the diffusion process causing the effective diffusional distance and the rate of moisture accumulation in the hardened crust to vary with the moisture content, according to a sorption controlled mechanism.     

Sorption Characteristics of Whole Pistachio Nuts (Pistacia Vera L.)

ABSTRACT

Moisture sorption characteristics of whole pistachio nuts were investigated at 10, 20, and 30°C using the static method. The sorption isotherms exhibited hysteresis over the range of 0.10-0.80 water activity which was succesfully interpreted using BET, GAB, Oswin, Smith, Henderson, Chung-Pfost and Halsey mathematical models and from which the BET, GAB and Oswin models were found to give the best fit. Monolayer moisture content of pistachio nuts was determined from BET and GAB equations and the isosteric heat of sorption data were derived using Clausius-Clapeyron equation and presented in graphical form. The information generated can be utilized to optimize the packaging parameters for long term storage of pistachio nuts.     

A CALCULATION METHOD OF OBTAINING DESORPTION ISOTHERMS OF BEECH (FAGUSMOESL4CA) WOOD

ABSTRACT

This paper presents the specific methods to obtain sorption isotherms. Sorption isotherms were first obtained experimentally for 20°C and 100°C and then, by using the presented method, isotherms were also obtained for 50°C and 80°C. The same treatment can be applied in finding any isotherm sorption in the temperature range between 20°Cand 100°C.

The experiments were carried out on beech (Fagus moesiaca) and sample dimensions were 3×3×3cm. Based on the results of the experiment, by regression analysis, the most suitable analytic formula was proposed. It relsites temperature and air humidity with the equilibrium moisture content in wood. Experimental results were compared with psychrometric tables and Bramhall's formula for desorption curves with good agreement. This proves that the method presented in this paper is precise and efficient to decrease the lime needed to obtain sorption isotherms experimentally.     

EFFECT OF OSMOTIC DEHYDRATION ON COLOR AND SORPTION CHARACTERISTICS OF APPLE AND BANANA

ABSTRACT

Color and sorption characteristics of osmotically treated and air dried apple and banana were studied during air drying at 70^°C. The color parameters: Lightness (L), Redness (a) and Yellowness (b) were studied, using a Hunter Lab chromatometer. A first order kinetic model was fitted to the experimental data adequately for color parameters, while sorption data for treated and air dried products were fitted to the GAB model. Untreated fruits showed an extensive browning which was monitored by a significant drop of the lightness (L) and an increase of redness (a) and yellowness (b). Osmotically pretreated samples did not brown as much as the untreated samples and the lightness L decreased only slightly while a, b increased slightly. Osmotic pretreatment resulted in a shift in sorption isotherm for both fruits. Osmotic dehydration prevented color damages and decreased the sorption capacity of dehydrated products.     

Effect of process variables of spray drying employing heat pump and nitrogen on aromatic compound yield in powders obtained from vanilla (Vanilla planifolia Andrews) ethanolic extract

Abstract

Spray drying process design for vanilla extract with a given aromatic compound retention requires process analysis and elucidation of empirical relations of the retentions as functions of process variables. Therefore, vanilla ethanolic extracts were spray dried under N₂ at different inlet (170–180?°C) and outlet (80–90?°C) temperatures and carrier material (modified potato starch, DE-10 maltodextrin, β-cyclodextrin, and precipitated silica) concentrations. The moisture content, water activity, aromatic compound (vanillin, vanillic acid, p-hydroxybenzaldehyde and p-hydroxybenzoic acid) retention, and color were empirically modeled as functions of process variables. The significance of the process variables was evaluated with linear statistics.     

THERMODYNAMIC MODELS FOR WATER SORPTION BY GRAPE SKIN AND PULP

ABSTRACT

The enthalpy-entropy compensation theory was applied to water sorption for grapes of Italy variety. The moisture sorption isotherms were analyzed using the static gravimetric method at 35, 40, 50, 60, 70 and 75° C. For isotherms construction, the skin and pulp of the grape were used separately and it was possible to observe significant differences. The GAB equation was fitted to the experimental data, using direct nonlinear regression analysis; the agreement between experimental and calculated values was satisfactory. The net isosteric heat or enthalpy of water sorption, determined from the equilibrium sorption data, showed a different behavior when compared with other works, as it was obtained for skin and pulp separately. Plots of Ah vs AS for skin and pulp provided the isokinetic temperatures T_BS = 423.2 ± 27.6 K and T_BP = 424.5 ± 25.3 K, respectively, indicating an enthalpy-controlled desorption process over the whole range of moisture content considered.