Resumo

PUMACAHUA-RAMOS, AUGUSTO; LIMAYLLA-GUERRERO, KATHERINE MILUSCA; TELIS-ROMERO, JAVIER  e  LOPES-FILHO, JOSÉ FRANSCISO. WATER ADSORPTION ISOTHERMS AND ISOSTERIC HEAT OF QUINOA STARCH. Rev.Bio.Agro [online]. 2017, vol.15, n.1, pp.95-104. ISSN 1692-3561.  https://doi.org/10.18684/BSAA(15)95-104.

The objective of this study was to evaluate adsorption isotherms and isosteric heats of quinoa's starch at five temperatures (20, 30, 40, 50 and 60°C) and ten water activities (0,036 to 0,907). The experimental values were fitted to mathematical models of GAB, Oswin, Henderson, Peleg and Ferro-Foltan. Activation energies for water adsorption were determined by the constants of GAB model and the isosteric heat by Peleg model. The isotherms exhibited type II in the classification of Brunauer. Monolayer moisture contents (Xm) obtained by GAB model ranged from 10,38 to 7,90% in dry basis (d.b.) at temperatures of 20 to 60°C, respectively. Activation energies determined using constants Xm, C and K of GAB model were 300, 160 and 6 kJ/kg, respectively. The isosteric heat of adsorption was 3732 kJ/kg at moisture equilibrium of 0,5% d.b. The value decreased next to latent heat of vaporization of pure water as moisture increased up to 36% d.b. The results obtained are characteristic of starches with high amylopectin content.

Palavras-chave : Chenopodium quinoa Willd; Quinoa starch; Isoterms sorption; Sorption isosteric heat.

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