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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 × 10 7  ± 1.62 × 10 7  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. [ABSTRACT FROM AUTHOR]

The complexation mechanism of gelatin (G) and carboxymethyl cellulose (CMC) and their coacervates formation process were studied as a function of pH and protein (Pr) to polysaccharide (Ps) mixing ratio (Pr:Ps). Three different CMCs were chosen (FL9, FH9 and FVH6) and five mixing ratio of 1:1, 6:1, 7:1, 8:1 and 9:1 (w/w), were studied to disclose their individual coacervates transition pattern for zeta potential, turbidity, morphology, size distribution and coacervates yield. The coacervates formation mechanism and stability of formed coacervates were examined using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR), Circular Dichroism (CD), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Coacervates with better morphology, good size distribution and highest yield were observed with G-FL9 at mixing ratio of 7:1 and pH 4.40. The evaluation of coacervates formation mechanism showed that G molecules experienced a conformational change in its secondary structure from a flexible pattern to an ordered poly-proline II (PPII) helix. The vibrations of O H and N H bonds spectra at 3437 and 3449 cm −1 , respectively for G/CMC coacervates, shifted to lower wave numbers due to the conformational changes of gelatin and CMC, during the coacervates formation. G/CMC complex coacervates were more thermally stable than individual gelatin. Therefore, these complex coacervates will be able to protect and deliver heat sensitive bioactives and food ingredients. [ABSTRACT FROM AUTHOR]