Determination of desorption isotherms, latent heat and isosteric heat of pequi diaspore

• Main Authors: Kelly A. de Sousa, Osvaldo Resende, Bruno de S. Carvalho
• Format: Article
• Language: English
• Published: Universidade Federal de Campina Grande 2016-05-01
• Series: Revista Brasileira de Engenharia Agrícola e Ambiental - Agriambi
• Subjects: equilíbrio higroscópico; atividade de água; propriedades termodinâmicas
• Online Access: http://www.scielo.br/scielo.php?script=sci_arttext&pid=S1415-43662016000500493&lng=en&tlng=en

ABSTRACT The objective was to determine water sorption isotherms of diaspores of pequi fruits in order to obtain information on the amount of water that this product desorbs at the temperatures of 10, 20, 30 and 40 °C and water activities from 0.20 to 0.89, adjusting different mathematical models to experimental data, and to determine its latent heat and isosteric heat. The equilibrium moisture content was obtained through the indirect static method, using the device Hygropalm Model Aw 1. The Modified Henderson model was the one that best fitted the data and was selected to predict the equilibrium moisture content of pequi diaspore. It was observed that the higher the temperature for the same equilibrium moisture content (% d.b.), the higher the water activity values. As temperature values increased, there was a reduction in the vaporization latent heat of the product. Isosteric heat values of diaspores of pequi fruits in the moisture content range of 4.02 to 16.63 (% d.b.) varied from 2,776.49 to 2,558.39 kJ kg-1.