Ilyasoglu, Huri; Nadzieja, Marcin; Guo, Zheng

The aim of this study was to develop a novel dual-functional stabilizer for food-grade Pickering emulsions by grafting caffeic acid onto chitosan via a free radical mediated method. The grafting of caffeic acid onto chitosan was confirmed by UV-vis absorption spectra, FTIR spectra and H-1 NMR spectra and DSC thermogram. The antioxidant properties of the caffeic acid grafted chitosan (CA-g-Ch) were measured by three in vitro assays. Caffeic acid-grafted chitosan displayed much better Fe2+ chelating property than both chitosan and caffeic acid, and retained comparable DPPH radical scavenging activity as caffeic acid. Moreover, the formation of the CA-g-Ch based emulsion was monitored by the turbidity, zeta potential, and particle size measurements. The CA-g-Ch polymers were found to be pH-responsive. The oil (linoleic acid) in water emulsions with the CA-g-Ch (as emulsifier/Pickering stabilizer) was prepared to examine its potential to stabilize Pickering emulsions, as well as its additive antioxidant properties. The results (zeta potential, mean droplet size, creaming index and TBARS values etc) demonstrated that the CA-g-Ch could act as a dual-functional stabilizer for Pickering emulsions. The emulsions made with the CA-g-Ch were found to be stable at a broad pH range of 3-6. Our findings proved that CA-g-Ch as novel dual-functional polymeric surfactant, may have great potential to find applications in food and pharmaceutical industries.

İlyasoğlu, Huri; Guo, Zheng

A water soluble chitosan-caffeic acid conjugate (C-CAC) was prepared by chemical modification of chitosan using activated caffeoyl with dimethyl aminopyridine as a catalyst. The C-CAC was characterized using UV–visible spectrometry, Fourier transform infrared, nuclear magnetic resonance spectroscopies and differential scanning calorimetry. The caffeoyl content in the C-CAC was 65 mg/g. To study the introduction of a new function into chitosan, the antioxidant activities of the synthesized C-CAC was determined using three in vitro assays: DPPH (2,2-diphenyl-1-picrylhydrazyl), ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), and ferric reducing antioxidant power. The half inhibition concentration values for DPPH and ABTS radicals were 370 and 172 μg/ml, respectively; showing its good radical scavenging activity. The emulsifying properties of the C-CAC were investigated by preparing 10% fish oil-in-water emulsions. C-CAC not only showed a good ability to stabilize oil-in-water emulsions, but also was more effective in retarding lipid oxidation compared to chitosan; implying that the synthesized C-CAC was functioning in an oil-in-water emulsion system as both emulsifier and antioxidant. Chitosan-phenolic conjugates, as a biopolymer-based surfactant, may represent a promising ingredient for enabling stable oxidation-sensitive oil-in-water emulsions.

İlyasoğlu, Huri; Anankanbil, Sampson; Nadzieja, Marcin; Guo, Zheng

To develop novel polymeric emulsifiers/stabilizers for improved functionalities, an array of chitin fatty acid esters (chitin octanoate, laurate, palmitate, and stearate) were synthesized using a trifluoroacetic anhydride (TFAA)/methanesulfonic acid (MSA) catalytic system. The synthesized products were characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC); successful lipophilization of chitin was confirmed by analysis results of FTIR, NMR, and DSC, with the degree of substitution (DS) of the products that ranged from 0.89 to 1.05. Ten percent fish oil-in-water emulsions were prepared using the synthesized chitin fatty acid esters, and characteristic properties (droplet size, zeta potential, and creaming stability) were determined. It turned out that chitin octanoate and chitin laurate were capable to solely enable homogeneous nanoemulsion (200–240 nm, polydispersity index 0.22–0.26), with excellent stability (no creaming after 14-day storage), which may find great potential applications in food, biomedical, and cosmetics sectors.