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The major objective of this work was to develop a green and facile process to prepare gallic acid-chitosan conjugate and comprehensively evaluate the physicochemical properties and biological activities of an as-prepared water-soluble chitosan derivative. A free-radical-induced grafting approach using an ascorbic acid-hydrogen peroxide redox pair was adopted. The obtained conjugate was characterized by Fourier transform infrared spectroscopy, UV-vis, X-ray diffraction, and pKa analysis. The antioxidant activities were evaluated by 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azino-bis(3-ethylbenzothiazoline-6)-sulphonic acid (ABTS), reducing power, and oxygen-radical antioxidant-capacity assays. The results showed that the mass ratio of gallic acid to chitosan played a vital role in determining the grafting degree and ζ potential of the conjugates, with the ratio of 0.5:1 being the optimal ratio that resulted in the highest grafting degree. The antioxidant assays demonstrated that conjugation significantly improved the antioxidant activities, being dramatically higher than that of free chitosan. It was notable that the DPPH- and ABTS-scavenging activities of conjugate at 0.4 mg/mL reached the same level as the free gallic acid at the equivalent concentration. Our study demonstrated a green and facile synthesis approach to preparing a novel water-soluble chitosan derivative that may have promising potentials in the food industry.

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16Development of delivery systems from natural protein/polysaccharide complexes is of 17 particularly interests for applications in food, pharmaceutics and biomedicine. In this study, 18 novel nanogels smaller than 60 nm were prepared from egg yolk low density lipoprotein (LDL) 19 and pectin complexation via a pH-and heat-induced facile process. The nanostructure of egg 20 yolk LDL was elucidated for the first time under different pH conditions and its complexation 21 with pectin was comprehensively investigated. Under optimized condition, the prepared nanogels 22 had a diameter of 58 nm and zeta potential of -41 mV, with spherical shape, smooth surface, and 23 homogeneous size distribution, as evidenced by dynamic light scattering, scanning and 24 transmission electron microscopes. The Fourier transform infra-red spectrum revealed that 25 hydrophobic and electrostatic interactions were the driving forces to form nanogels. The 26 innovative Nano Spray Drying technology was studied and optimized to obtain nano-size powder 27 of nanogels which exhibited excellent re-dispersibility in water, overcoming the drying challenge 28 (irreversible gelation) of egg yolk LDL and greatly expanding its practical applications. 29Curcumin was adopted as model compound to investigate the drug delivery potential of 30 LDL/pectin nanogels. The mass ratio of curcumin/LDL played an essential role in determining 31 the particle size and encapsulation efficiency. The LDL/pectin nanogels had excellent stability 32 under simulated gastrointestinal conditions with the presence of digestive enzymes and enabled 33 controlled release of curcumin. The novel LDL/pectin nanogels have promising features for oral 34 delivery of nutrients and drugs.35