Application of Gab Model for Water Sorption Isotherms of Food Products

Singh, Pawan; Singh, Raghuraj

doi:10.1111/j.1745-4549.1996.tb00743.x

Cited by 46 publications

(27 citation statements)

References 29 publications

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“…These results concur with the observations of other authors for other species of wood (Themelin et al 1997;Fernandez et al 2014). The values are always positive because of the strong exothermic interaction between the water vapour and the sorption sites (Singh and Singh 1996;Kouhila et al 2002;Quirijns et al 2005a, b). Maskan and Gogus (1997) determined that a negative C g value is physically impossible.…”

Section: Resultssupporting

confidence: 92%

Juvenile and mature wood of Abies pinsapo Boissier: sorption and thermodynamic properties

et al. 2015

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For industrial processes, it is important to study the hygroscopicity and thermodynamic properties of juvenile and mature wood. Samples of Abies pinsapo Boiss. collected in the natural areas of the species in Spain were used to study these properties in both types of wood. The equilibrium moisture contents were obtained, and the 15, 35 and 50°C isotherms were plotted following the Guggenheim-Anderson-Boer-Dent model. The thermodynamic parameters were calculated using the integration method of the Clausius-Clapeyron equation. Chemical analyses, infrared spectra and X-ray diffractograms were applied to assess chemical modifications and possible changes in the cell wall structure. The chemical composition of the mature wood shows a decrease in the lignin and hemicelluloses content and an increase in the extracts and a-cellulose. The sorption isotherms for the three temperatures studied are higher in the mature wood than in the juvenile wood. Causes of this include the higher content of a-cellulose, the higher crystallinity index and the shorter crystallite length in the mature wood. No difference was found between the juvenile and mature wood in relation to the point of inflexion where the multilayer starts to predominate over the monolayer (approximately 30 %). In terms of the thermodynamic properties, the heat involved is greater in desorption than in adsorption, and more heat is involved in the mature wood than in the juvenile wood.

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Section: Resultssupporting

confidence: 92%

Juvenile and mature wood of Abies pinsapo Boissier: sorption and thermodynamic properties

et al. 2015

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“…The C g value is positive due to the strong exothermic interaction between the water molecules and the sorption sites [56][57][58]. The K constant cannot be greater than one because sorption becomes infinite for water activities lower than 1 [59,60] ( Table 2).…”

Section: Discussionmentioning

confidence: 99%

Thermodynamic analysis of water vapour sorption behaviour of juvenile and mature wood of Abies alba Mill.

et al. 2015

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The hygroscopicity and thermodynamic properties of juvenile and mature wood of Abies alba Mill. were studied through the 15, 35 and 50°C sorption isotherms. The Guggenheim, Anderson and de Boer-Dent model was used to fit the isotherms. The thermodynamic parameters were obtained from the sorption isotherms by applying the integration method of the Clausius-Clapeyron equation. The chemical composition of both types of wood (extractives, lignin and carbohydrate polymer-cellulose and hemicellulose-content) was determined, and infrared spectroscopy and X-ray diffractograms were used to identify any chemical modifications and changes in the crystal structure of the cell wall. The mature wood has more cellulose and hemicellulose content and less extractives content than the juvenile wood. The shorter crystallite length in the mature wood creates a higher amount of amorphous zones and, as a consequence, a higher number of access areas to the -OH groups. The combination of these phenomena explains the different hygroscopic behaviour between the juvenile and the mature wood, as the latter has higher moisture content in the three isotherms. As regards the thermodynamic properties, the amount of energy involved in the sorption process is greater in the mature wood than in the juvenile wood.

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“…The four isotherms show appropriate fits for a type II (C > 2) curve [21,34]. They also have regression coefficients higher than 0.990, and the RMS is lower than 4% (Fig.…”

Section: H Emc a Emc D ---------------=mentioning

confidence: 99%

Comparison of the hygroscopic behaviour of 205-year-old and recently cut juvenile wood fromPinus sylvestrisL.

et al. 2006

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-The hygroscopic response of the juvenile wood of Pinus sylvestris L. from recently cut trees from the Valsaín Forest in Segovia, Spain (new wood) was compared to that of the juvenile wood of the same species used in roof rafters installed at the end of the eighteenth century (old wood), which came from the same forest. The 35 ºC isotherms were plotted using the saturated salts method, and the mathematical fit used was the GAB model. The infrared spectrums and the X-ray diffractograms were used in order to study the possible chemical variations and crystallinity indices of the cell wall. The adsorption-desorption loop of the old wood is above the loop of the new wood, although the hysteresis coefficient is higher in the old wood. The peaks corresponding to the -OH groups are similar, although the degree of crystallinity is significantly lower in the old wood. While cellulose crystallinity differs between the old and new wood, and has a major influence on wood hygroscopicity, other modifications in the amorphous components of the cell wall may have contributed to the changes in hygroscopicity between the old and new wood. hygroscopicity / sorption isotherm / juvenile wood / Fourier transform infrared spectroscopy (FTIR) / X-ray diffraction (XRD)Résumé -Comparaison du comportement hygroscopique d'un bois juvénile de Pinus sylvestris L. âgé de 205 ans avec celui d'un bois juvénile récemment coupé. La réponse hygroscopique du bois juvénile de Pinus sylvestris L. provenant d'arbres récemment coupés de la forêt de Valsaín en Segovia, Espagne (bois récent) a été comparée à celle de bois juvénile de la même espèce utilisé comme bois de charpente à la fin du XIII e siècle (vieux bois), originaire de la même forêt. Les isothermes de sorption à 35 ºC ont été obtenus par la méthode des sels saturés, et l'ajustement mathématique utilisé était le modèle GAB. La spectrographie infrarouge et la diffractométrie par rayons X-ont été utilisées pour étudier d'éventuelles différences de composition chimique et d'indices de cristallinité de la paroi cellulaire. La boucle d'adsorption-désorption du vieux bois est au-dessus de celle du bois récent, tandis que le coefficient d'hystérésis est plus élevé dans le vieux bois. Les pics correspondant aux groupes -OH sont similaires, bien que le degré de cristallinité soit significativement plus bas dans le vieux bois. Bien que ces différences de cristallinité puissent expliquer pour une bonne part le contraste hygroscopique entre bois vieux et actuel, des modifications au niveau des composés amorphes de la paroi peuvent également être invoquées. hygroscopicité / isotherme de sorption / bois juvénile / spectroscopie infrarouge par transformée de Fourier / diffraction par rayons X

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Application of Gab Model for Water Sorption Isotherms of Food Products

Cited by 46 publications

References 29 publications

Juvenile and mature wood of Abies pinsapo Boissier: sorption and thermodynamic properties

Juvenile and mature wood of Abies pinsapo Boissier: sorption and thermodynamic properties

Thermodynamic analysis of water vapour sorption behaviour of juvenile and mature wood of Abies alba Mill.

Comparison of the hygroscopic behaviour of 205-year-old and recently cut juvenile wood fromPinus sylvestrisL.

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