Characterisation of Hydrophilic Bioactive Extracts of Fruits from Mexico: Phenolic Content, Thermal and Kinetic and Thermodynamic Analysis.

Abstract

The total soluble phenolic content (TSPC), decomposition profiles and kinetic and thermodynamic parameters of hydrophilic bioactive extracts from Randia monantha (RME), Coccoloba uvifera (CUE) and Vaccinium corymbosum (VCE) fruits were investigated. The TSPC was determined using the Folin-Ciocalteu method. The decomposition profiles of the extracts were obtained via thermogravimetric analysis (TGA). Then, the kinetic parameters (preexponential factor, A, and activation energy, E_a) and thermodynamic parameters (enthalpy, ΔH; entropy, ΔS; and free Gibbs energy, ΔG) of each stage of decomposition were obtained via the Coats-Redfern method. The highest TSPC was shown for RME extract, followed by VCE and CUE extracts due to the plant material. The thermal analyses showed that RME and VCE extracts had three mass loss events, and the CUE extract had only two. Moreover, RME exhibits higher decomposition temperatures. These differences in the thermal profile were attributed to the TSPC concentration in the extracts. Compared with the RME and VCE extracts, the CUE extract presented the lowest values of E_a, A, ΔH, and ΔS due to the low TSPC. On the contrary, all extracts presented high ΔG values in the final stage of the thermal process. Notably, the RME extract demonstrated the highest values, followed by the VCE and CUE extracts. The kinetic and thermodynamic parameters revealed that the thermal decomposition of the extracts was an endothermic process. This would allow for adaptation processing conditions or the implementation of encapsulation technologies that avoid the degradation of the extracts.