Thermodynamic characterization of Gelatin–Sodium carboxymethyl cellulose complex coacervation encapsulating Conjugated Linoleic Acid (CLA)

The interactions of gelatin (G) with sodium carboxymethyl cellulose (CMC) were investigated at different pHs. Isothermal titration calorimetry (ITC) was used to determine the type and magnitude of the energies involved in the G-CMC complexation process and evaluated the thermodynamic behavior of their complexation. Moreover, dynamic light scattering (DLS), Zeta potential, optical microscopy and thermogravimetric analysis (TGA) were applied to better understand the sum of complex phenomena at the origin of G-CMC coacervates formation. Also, coacervated G-CMC was further used for CLA encapsulation at different core/wall ratios (1:1, 2:1 and 3:1). Results revealed that coacervates size ranged between 5 and 200 μm and increased with decreasing pH. Similar trend was observed with G-CMC complex coacervates morphological evolution. Additionally, the structuring stages were characterized by exothermic signals and were mainly controlled by favorable enthalpy changes due to electrostatic interactions between both biopolymers. ITC further confirmed that G and CMC electrostatically interacted with high affinity (K = 4.12 × 107 ± 1.62 × 107 M−1) at pH 4.40, and revealed that this binding was mainly driven by enthalpy. In addition, the microencapsulated CLA (CLA:GCMC, 2:1) capsules were multinuclear rod like and showed high encapsulation efficiency, yield and payload of 93.50%, 96.50% and 64.34%, respectively, confirming the potential of G-CMC complex coacervates for bioactive molecules encapsulation. The present study provided useful information about G-CMC complexation and binding processes, which could facilitate their application in functional ingredients encapsulation for food, nutraceutical and pharmaceutical industries.