Arrhenius activation energy for water diffusion during drying of tomato leathers: the concept of characteristic product temperature

FIORENTINI, CECILIA; DEMARCHI, M. SILVANA; QUINTERO RUIZ, N. ANDREA; TORREZ IRIGOYEN, RICARDO MARTÍN; GINER, SERGIO ADRIÁN

BIOSYSTEMS ENGINEERING

ACADEMIC PRESS INC ELSEVIER SCIENCE

Lugar: Amsterdam; Año: 2015 vol. 132 p. 39 - 46

1537-5110

The drying kinetics of tomato leathers was studied between 40 and 80ºC to compare the Arrhenius activation energy (Ea) obtained by correlating the diffusion coefficient (D) with (a) the air temperature and (b) the mean product temperature. Drying curves comprised a wet zone, where moisture content fell almost linearly with time, and a subsequent dry zone. In the first zone, the Arrhenius relationship with the air temperature yielded an Ea of 18.5 kJ/ mol whereas, when utilizing the mean product temperature the activation energy was of 46.9 kJ/ mol, comparable to the heat of desorption of water. In the second zone, activation energies were 21.5 and 31.9 kJ/ mol, respectively. The molecular mobility theory suggests a stronger temperature dependence of diffusion-limited phenomena in higher moisture content matrices and thus would forecast a higher Ea in the wet zone. Therefore, use of the average product temperature appears more meaningful.