Kinetic Models of -Carotene Degradation During Air Drying of Carrots

The objective of this study was to determine the kinetic parameters of models that describe the joint influence of temperature and moisture content on the thermal degradation of -carotene in a drying process of carrots. Two models were used: a first-order decay model with an Arrhenius and a polynomial dependency on temperature and water content, respectively, and a decay model with a WLF dependency of the decimal reduction time on glass transition temperature (Tg), with the Gordon and Taylor equation describing the influence of moisture content on Tg. Carrots were dehydrated in a cabinet air dryer at 50, 60, 70, and 80 degrees C. Carrot samples were drawn at 20-min intervals and analyzed for moisture and -carotene content. The parameters of the two models were estimated by nonlinear regression. In addition, the models were evaluated by comparing their predictions and experimental data during drying at 80 degrees C of carrot slices with thickness of 3, 6, and 9mm. Both models were found suitable for modeling the -carotene degradation, though the lower sum of squares of residuals (SSQ) of the Tg approach model and the similar WLF parameters calculated at different drying air temperatures demonstrated the higher predictive ability of the Tg model over the more common empirical dependence model.