Effect of composition and pore structure on binding energy and effective diffusivity of moisture in porous food

Xiong, Xiao-Bing; Narsimhan, Ganesan; Okos, Martin R.

doi:10.1016/0260-8774(92)90050-g

Cited by 83 publications

(44 citation statements)

References 8 publications

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“…The mobility of water in solid food is also strongly dependent on porosity and pore structure. Information on the relationship between food composition, structure and the water mobility is useful not only for the understanding of the influences of food composition and structure on moisture removal but also in the development of an energy-efficient method of drying [15].…”

Section: Resultsmentioning

confidence: 99%

Hot air drying of cooked and uncooked tarhana dough, a wheat flour-yoghurt mixture

Maskan

İbanoğlu

2002

European Food Research and Technology

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Drying behaviour of cooked (CTD) and uncooked tarhana dough (UTD) slabs (1, 3 and 6 mm) were determined at constant air temperature (80°C) and velocity (1.86 m/s). Both samples dried in the falling rate period. An analysis of variance (ANOVA) revealed that slab thickness and cooking process significantly affected the drying rate. The effective moisture diffusivity values of CTD and UTD samples were determined from drying experiments using Fick's diffusion model. Effective diffusivity was higher in cooked sample than in uncooked one (1.3-23.5×10 -10 and 0.99-10.0×10 -10 m 2 /s, respectively). This was attributed to the development of channels and pore structure during starch gelatinisation in the cooked sample.

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Section: Resultsmentioning

confidence: 99%

Hot air drying of cooked and uncooked tarhana dough, a wheat flour-yoghurt mixture

Maskan

İbanoğlu

2002

European Food Research and Technology

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“…1 -3 It can be assumed that the observed decrease of the drying rate is mainly caused by the decreasing availability of free water molecules. 1,4 This assumption is based on the existence of two classes of water: the bound and free water. The bound moisture corresponds to water molecules connected strongly to the material molecules.…”

Section: Introductionmentioning

confidence: 99%

“…The free moisture corresponds to the water molecules connected loosely to the material molecules. 1,4 The portion of free moisture content is initially very large. As drying reaches its last stages, the bound moisture molecules form the majority of the water molecules, and then the conversion between the bound and free water controls the overall mass transfer phenomenon.…”

Section: Introductionmentioning

confidence: 99%

“…As drying reaches its last stages, the bound moisture molecules form the majority of the water molecules, and then the conversion between the bound and free water controls the overall mass transfer phenomenon. 1,4 This forms the basis of the newly developed diffusion-sorption drying model, which is presented by Quirijns et al 5 In this model, the moisture transfer during the drying process is described by three basic transfer phenomena: free water diffusion, conversion between bound and free water inside the material, and external convection at the boundary of the material. The model for the conversion between bound and free water makes the diffusion-sorption model original.…”

Section: Introductionmentioning

confidence: 99%

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Sorption isotherms, GAB parameters and isosteric heat of sorption

et al. 2005

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The diffusion-sorption drying model has been developed as a physics-based way to model the decreasing drying rate at low moisture contents. This new model is founded on the existence of different classes of water: free and bound water. The transition between these classes and the corresponding thermodynamics form distinct components of the drying model. This paper shows that the characteristics of the different classes of water and of the transition between them can be deduced from the GAB sorption isotherm. The parameters in the GAB sorption isotherm support the theory of localised sorption, establishing the existence of different classes of water. Moreover, the sorption mechanism retrieved from the GAB parameters is in accordance with the sorption mechanism, which is obtained from the moisture dependence of the net isosteric heat of sorption. This holds for experimental sorption data of corn and starch as well as for literature data on five vegetables and four fortified cassava products. An extremum in the net isosteric heat of sorption coincides with the transition between bound and free water, and the partition moisture content corresponds with the monolayer value derived from the GAB equation. This confirms that the GAB monolayer value can be chosen as model boundary between bound and free water. Moreover, it reveals that this method can be developed into a technique to estimate the bound water content in foods.

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“…It has been noted that diffusion coefficient is related to inverse absolute temperature by Arrhenius type of equation (Islam, 1980 andHeldman, 1974) and the diffusion coefficient is also related with sample thickness (Rahman& Kumar, 2007). Xiong et al (1991), 5.25 Kcal/g-mole for Stevia leaves by Syduzzaman and Sharmin (2009) and the difference in activation energy (E a ) might result from differences in product characteristics (such as water activity, moisture content, solid concentration, pH and others), temperature employed for drying and structure of the fresh material undergoing drying as reported by Islam(1980), Iqbal & Islam (2005), Karel (1975), Villota and Hawkes (1992). The differences in activation energy values (7.656 and 8.252) of the current study including mechanical and solar systems might be attributed to among others, difference of the temperature ranges used.…”

Section: Diffusion Co-efficient and Activation Energymentioning

confidence: 99%

The Construction and Testing of a Combined Solar and Mechanical

Bhuiyan

Alam

Islam

2012

J. Environ. Sci. & Natural Resources

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The combined solar and mechanical dryer was constructed to use solar energy and electrical energy either separately or in combination to conduct air drying. There was various arrangement of drying condition for mechanical drying system such as using either 1KH-1F or 1KH-2F or 2KH-1F or 2KH-2F. While for solar drying either no fan or one fan or two fans were used. Different drying conditions were applied by changing the heating source and flow of air. The highest temperature was obtained in 2KH-1F condition for mechanical drying and convection gives highest temperature among different solar drying alternatives. The temperature in upper shelf for different solar operational condition ranged from 1.53 to 1.67 times of ambient temperature (25 0 C-31 0 C) at peak time and 1.28 to 1.36 for lower shelf. The air velocity was 0.35 m/sec and 0.70 m/sec for 1-fan and 2-fan respectively. The performance of dryer was evaluated by drying potato slices having thickness 3, 5 and 7 mm. In both methods, drying rate increases with the increasing temperature and decreases with the increasing slice thickness following the power law equation. The values for the index 'n' of the power law equation are less than 2 (range from 0.53 to 1.42) for all the conditions, this indicating that external resistance to mass transfer was significant and internal resistance to mass transfer did not control the drying process under the given conditions. The effect of temperature on Diffusion co-efficient (D e ) follows Arrhenius type relationship. While analyzing the effect of temperature, the maximum activation energy for diffusion of water from Potato (7 mm thick slices, at upper shelf) was found to be 7.656 Kcal/g-mole and 8.252Kcal/g-mole for mechanical and solar conditions respectively.

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Effect of composition and pore structure on binding energy and effective diffusivity of moisture in porous food

Cited by 83 publications

References 8 publications

Hot air drying of cooked and uncooked tarhana dough, a wheat flour-yoghurt mixture

Hot air drying of cooked and uncooked tarhana dough, a wheat flour-yoghurt mixture

Sorption isotherms, GAB parameters and isosteric heat of sorption

The Construction and Testing of a Combined Solar and Mechanical

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