Drying Characteristics of Toona sinensis and Thermal Degradation Kinetics of Its Characteristic Aroma Compounds
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Abstract:
The moisture transfer pattern during the drying process of Toona sinensis was studied, and the effects of different heat treatment conditions on the stability of the characteristic aroma compound of Toona sinensis, 2-mercapto-3,4-dimethyl-2,3-dihydrothiophene (MDD), were investigated. The kinetics and thermodynamics of MDD thermal degradation were analyzed. The results showed that the higher the temperature for heat treatment, the higher the drying rate for Toona sinensis, which was in accordance with the rate changing trend for traditional drying. The MDD degradation process accorded with the first-order kinetics and Arrhenius model. The reactionrate constants ranged from 0.015 5 to 0.034 5 min-1 and increased with an elevated heat treatment temperature. The half-life values (t1/2) at different temperatures were 44.719, 32.239 and 20.091 min, respectively, and decreased with an increase of thermal treatment temperature. The activation energy (Ea) value of the reaction was 39.052 kJ/mol. The positive activation enthalpy (ΔH) value indicated that the thermal degradation of MDD was an endothermic reaction, and the positive Gibbs free energy (ΔG) value indicated that MDD thermal degradation was a non-spontaneous process. The results provide a theoretical basis for effective control of the degradation of characteristic flavor substances in Toona sinensis processing process.
