Modeling of textural changes during drying of potato slices

The objective of this research was to study the kinetics of textural changes during convection drying of potato slices by using different mathematical models. The following four models were proposed to validate texture experimental data: (i) two irreversible serial chemical reactions; (ii) two irreversible serial chemical reactions with k2 = 0, which means that only the tissue softening stage is considered; (iii) fractional conversion; (iv) first-order kinetics. These models link the dimensionless textural parameter, maximum force FMAX∗ with drying time. Experimental textural changes were followed during drying of potato slices at different air temperatures (50, 60, 70 and 80 °C). Regardless of the different drying temperatures, the trend of FMAX∗ with drying time was almost the same, showing a progressive and significant decrease in its value as the exposure time increased. However, FMAX∗ of potato slices during drying decreases as the moisture content and temperature decreases, reflecting a clear softening of the potato tissue. A satisfactory agreement between experimental and predicted values was observed for two irreversible serial chemical reactions, with k2 ≠ 0 and k2 = 0, and fractional conversion models, with root mean square error values (RMS’s) in the range of 4.0–9.1%, 3.0–7.4% and 2.0–7.3%, respectively. These RMS’s values are much better than 5.6–23.4% obtained with the traditional first order kinetics. The temperature dependence of model parameters was described by Arrhenius-type relationship and the activation energy for tissue softening ranged between −6565 and 3562 J/mol.