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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]

[Display omitted] • Double emulsion prior to complex coacervation was effective for co-encapsulation. • Mononuclear ellipse-like shape was obtained at 2% total biopolymer concentration. • Structural similarity of conjugated linoleic acid and PGPR damaged co-encapsulation. • The capsules made by conjugated linoleic acid has worst encapsulation of vitamin C. • Quercetin carried by conjugated linoleic acid and fish oil got better encapsulation. A two-step emulsification prior to complex coacervation was employed to develop a co-encapsulation technology of hydrophilic and hydrophobic components for nutrition enhancement. Processing parameters of mononuclear ellipse-like microcapsules using gelatin and sodium carboxymethyl cellulose as wall materials were evaluated. The particle size and morphology of microcapsules and the encapsulation efficiency of L-ascorbic acid were significantly affected by the water–oil phase ratio and total biopolymer concentration. The L-ascorbic acid and quercetin co-encapsulated microcapsules with an average size of 65.26 µm showed good physical and chemical stability. The encapsulation efficiencies of L-ascorbic acid and quercetin were 69.91% and 88.21%, respectively. To predict the potential of functional lipids as hydrophobic carriers, microcapsules using soybean oil, olive oil, fish oil, and conjugated linoleic acid as interlayer oils were developed. The encapsulation efficiencies of hydrophobic compounds carried by different oils were similarly high (88.21–93.08%), whereas, hydrophilic ones carried by conjugated linoleic acid had the lowest encapsulation efficiency (32.54%). The interface tension results indicated that the interfacial stability was impaired by a competitive relation between conjugated linoleic acid and hydrophobic emulsifier at the interface, due to their structural similarity. These results provided the guidance for improving the quality of interlayer oils from microcapsules. [ABSTRACT FROM AUTHOR]