ISOTHERMS AND ISOSTERIC HEAT OF JATROPHA SEEDS - DOI: 10.13083/1414-3984/reveng.v23n1p9-18

Abstract

This study was conducted at the Postharvest Laboratory of Vegetable Products of the Instituto Federal de Ciência, Educação e Tecnologia Goiano - Câmpus Rio Verde, seeking to obtain the desorption isotherms and the values of isosteric heat of desorption of jatropha seeds. The fruits were harvested and then preceded to processing of the seeds which presented an initial moisture content of 20.9 % (d.b.). They were then dried in an oven with forced air ventilation at 40 °C until the moisture content of 13.6, 11.1, 8.7, 6.4 % (d.b.). The desorption isotherms of jatropha seeds were obtained by the indirect static method, and the water activity (aw) determined using the Hygropalm Aw Model 1 device. For temperature control a B.O.D was used, set at 10, 20, 30 and 40 °C. Experimental data was fitted to mathematical models often used to represent the hygroscopicity of agricultural products. The Sigma Copace model is that which best represents the hygroscopicity of jatropha seeds. The integral isosteric heat of desorption increased with decreasing moisture content, and the values for the jatropha seed in the moisture content range from 5.6 to 13.4 % (d.b.) varied from 3035.61 to 2631.89 kJ kg-1.