Desorption isotherms of flaxseeds (Linum usitatissimum L.) and thermodynamic parameters of the process

Maria da Conceição da Costa Valente, Rafael Alves do Nascimentro, Elza Brandão Santana, Lênio José Guerreiro de Faria, Cristiane Maria Leal Costa


Sorption isotherms of flaxseeds were determined by static gravimetric method at temperatures 40, 60, and 80 ºC, over a relative moisture range of 10-95%. Six mathematical models were applied to analyze the experimental data. The modified GAB model showed the best fitting to the experimental data. The isosteric heat and differential entropy were determined by applying the Clausius-Clapeyron and Gibbs-Helmholtz equations, respectively. The isosteric heat and the entropy of desorption isotherm presented similar behavior, with a sharp change of 10% in the equilibrium moisture content. The enthalpy–entropy compensation theory was applied to the isotherms, indicating that they are enthalpy-controlled.



Equilibrium moisture content; Drying; Isosteric heat

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ALPIZAR-REYES, E. et al. Thermodynamic sorption properties and glass transition temperature of tamarind seed mucilage (Tamarindus indica L.). Food and Bioproducts Processing, v. 101, p. 166-176, 2017.

ALVES, T. P.; FÓZ, H. D; NICOLETI, J. F. Isotermas de dessorção de pimentão verde e energia envolvida no processo. Brazilian Journal of Food Technology, v. 18, n. 2, p. 137-145, 2015.

ANDRADE, P. R. D.; LEMUS, M. R.; PEREZ, C. C. E. Models of sorption isotherms for food: uses and limitations. Vitae, v. 18, n. 3, p. 325-334, 2011.

BELGHITH, A.; AZZOUZ, S.; ELCAFSI, A. Desorption isotherms and mathematical modeling of thin layer drying kinetics of tomato. Heat Mass Transfer, v. 52, p. 407-419, 2016.

BOTHEJU, W. S.; AMARATHUNGE, K. S. P.; ZIYAD MOHAMED, M. T. Modeling moisture desorption isotherms and thermodynamic properties of fermented tea dhool (Camellia sinensis var. assamica). Drying Technology, v. 26, n. 10, p. 1294-1299, 2008.

CABEZA, L. F.; SOLÉ, A.; BARRENECHE, C. Review on sorption materials and technologies for heat pumps and thermal energy storage. Renewable Energy, v. 110, p. 3-39, 2017.

CHISTÉ, R. C. et al. Hygroscopic behaviour of cassava flour from dry and water groups. Ciência Rural, v. 45, n. 8, p. 1515-1521, 2015.

CHOO, W. S.; BIRCH, J.; DUFOUR, J. P. Physicochemical and quality characteristics of cold-press flaxseed oils. Journal of Food composition and Analysis, v. 20, n. 3, p. 202-211, 2007.

CLADERA-OLIVERA, F. et al. Thermodynamic properties of moisture desorption of raw pinhão (Araucaria angustifólia seeds). International Journal of Food Science and Technology, v. 43, n. 5, p. 900-907, 2008.

CORRÊA, P. C. et al. Moisture desorption isotherms of cucumber seeds: modeling and thermodynamic properties. Journal of Seed Science, v. 37, n. 3, p. 218-225, 2015.

FREITAS, M. L. F. et al. Sorption isotherms and thermodynamic properties of grated Parmesan cheese. International Journal of Food Science & Technology, v. 51, n. 1, p. 250-259, 2016.

GONELI, A. L. et al. Moisture sorption isotherms of castor beans. Part 2: Thermodynamic properties. Revista Brasileira de Engenharia Agrícola e Ambiental, v. 20, n. 8, p. 757-762, 2016.

GREENSPAN, L. Humidity fixed points of binary saturated aqueous solutions. Journal of Research of the National Bureau of Standards - A. Physics and Chemistry, v. 18, n. 1, p. 89-96, 1977.

HORWITZ, W. (ed.). Official Methods of Analysis of the AOAC International. 18 th ed. Gaithersburg: Association of Official Analytical Chemists, 2005. 771 p.

KAJLA, P.; SHARMA, A.; SOOD, D. R. Flaxseed: a potential functional food source. Journal of Food Science and Technology, v. 52, n. 4, p. 1857-1871, 2015.

LABUZA T. P. Standard procedure for isotherm determination. Cereal Foods World (USA), v. 28, n. 4, p. 258, 1983.

MADAMBA, P. S.; DRISCOLL, R. H.; BUCKLE, K. A. Enthalpy-entropy compensation models for sorption and browning of garlic. Journal of Food Engineering, v. 28, n. 2, p. 109-119, 1996.

MAZZA, G.; JAYAS, D. S.; WHITE, N. D. G. Moisture sorption isotherms of flax seed. Transactions of the ASAE, v. 33, n. 4, p. 1313-1318, 1990.

MENKOV, N. D. Moisture sorption isotherms of chickpea seeds at several temperatures. Journal of Food Engineering, v. 45, n. 4, p. 189-194, 2000.

MIANOWSKI, A.; URBAŃCZYK, W. Enthalpy-entropy compensation for isosteric state adsorption at near ambient temperatures. Adsorption, v. 23, n. 6, p. 831-846, 2017.

MOREIRA, R. et al. Thermodynamic analysis of experimental sorption isotherms of loquat and quince fruits. Journal of Food Engineering, v. 88, n. 4, p. 514-521, 2008.

OLIVEIRA, D. E. C. de et al. Hygroscopicity of ‘sucupira-branca’(Pterodon emarginatus Vogel) fruits. Revista Brasileira de Engenharia Agrícola e Ambiental, v. 21, n. 4, p. 285-289, 2017.

RIZVI, S. S. H. Thermodynamics properties of foods in dehydratation. In: RAO, M. A.; RIZVI, S. S. H.; DATTA, A. K. Engineering Properties of Foods. 3. ed. New York: Academic Press, 2005. p. 239-326.

SINGH, A. K.; KUMARI, N. Moisture sorption isotherm characteristics of ground flaxseed. Journal of Food Processing & Technology, v. 5, n. 4, 2014.

SIQUEIRA, V. C.; RESENDE, O.; CHAVES, T. H. Mathematical modelling of the drying of jatropha fruit: an empirical comparison. Revista Ciência Agronômica, v. 44, n. 2, p. 278-285, 2013.

SORMOLI, M. E.; LANGRISH, T. A. G. Moisture sorption isotherms and net isosteric heat of sorption for spray-dried pure orange juice powder. LWT- Food Science and Technology, v. 62, p. 875-882, 2015.

SPIESS, W. E. L.; WOLF, W. F. The results of the COST 90 project on water activity. In: JOWITT, R. (ed.). Physical properties of foods. London: Applied Science Publishers, p. 65-91, 1983.

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