Chlorogenic acid-chitosan copolymers: Synthesis, characterization and application in O/W emulsions for enhanced ß-carotene stability.

In this study, chlorogenic acid-chitosan (CA-CS) copolymers were prepared with varying Chitosan (CS): chlorogenic acid (CA)ratios and characterized for their water solubility, antioxidant capacity, and emulsions stability. Results showed that CA-CS samples exhibited up to 90.5 % increase in DPPH scavenging efficiency and 20 % increase in hydroxyl radical scavenging efficiency compared to CS alone. CA-CS copolymers used to stabilize oil in water (O/W) emulsions, which were evaluated for their potential in encapsulating and protecting ß-carotene. Microscopic observations revealed homogeneous spherical droplets in stable emulsions, suggesting effective interfacial structures. The selected CA-CS-stabilized O/W emulsions demonstrated encapsulation efficiencies of 74.8 % and 75.26 % for ß-carotene. The CA-CS stabilized O/W emulsions provided the most effective protection against ß-carotene degradation under UV exposure, retaining over 80 % of ß-carotene content after 12 h of testing. These findings indicate that CA-CS-based O/W emulsions show promise as carriers and protectors for bioactive compounds, due to their improved antioxidant capacity, emulsions stability, and protection against degradation.

Preparation of amphoteric double network hydrogels based on low methoxy pectin: Adsorption kinetics and removal of anionic and cationic dyes.

The objective of this research was to devise a functional hydrogel was synthesized using pectin (PE), acrylic acid (AA), dimethyldiallyl ammonium chloride (DC), and polyvinyl alcohol (PVA), designed to adsorb both cationic and anionic dyes concurrently. The low methoxy pectin formed double network hydrogel through chemical and physical crosslinking with AA and PVA respectively. DC is combined into the hydrogel system through copolymerization reaction. Analysis of hydrogel's physicochemical properties was conducted using techniques such as infrared spectroscopy, texture analysis, thermogravimetry, and scanning electron microscopy. Dyes adsorption studies showed that the LP/AA/DC/PVA-2 hydrogel, prepared at the molar ratio of AA to DC of 1:2, exhibited higher adsorption efficiency for methylene blue (MB) and Congo red (CR). Kinetics and isotherms studies indicated that the adsorption behavior conformed to the pseudo-second-order kinetic model and Langmuir isotherm model. By the Langmuir isotherm fitting, the maximum adsorption capacities of MB and CR by LP/AA/DC/PVA-2 were recorded to be 222.65 mg/g and 316.46 mg/g, respectively. The adsorption mechanism is dominated by the hydrogen bonding and electrostatic interactions. Further, the adsorption and desorption experiments demonstrated that LP/AA/DC/PVA-2 hydrogel have excellent reusability.

Novel Pickering emulsion gels stabilized solely by phenylalanine amidated pectin: Characterization, stability and curcumin bioaccessibility.

Pickering emulsion gels represent a novel class of non-toxic and biocompatible emulsions, offering extensive applications in the pharmaceutical and food additive sectors. This study delineates the synthesis of Pickering emulsion gels utilizing native and amidated pectin samples. Phenylalanine amidated pectin (AP) was procured via an ultra-low temperature enzyme method, while the control group (LP) adhered to an identical procedure without papain catalysis. Experimental outcomes revealed that the AP Pickering emulsion gel manifested superior stability compared to pectin emulsion samples (PE and LP). The Pickering emulsion gel from 5 % amidated pectin (5AP) retained stability throughout a 14-day emulsion stability assessment. Furthermore, all emulsion samples were evaluated for their capacity to deliver and sustain curcumin within an in vitro digestion simulation. Rheological properties and oil droplet size results indicated that the 5AP Pickering emulsion gel exhibited optimal cream index and emulsion stability, effectively inhibiting premature water-oil stratification within the emulsion and augmenting curcumin bioaccessibility. Within the in vitro digestion simulation, the 5AP Pickering emulsion gel demonstrated the highest curcumin bioaccessibility, measured at 17.96 %.

Construction of double-network hydrogel based on low methoxy pectin/polyvinyl alcohol and its structure and properties.

In this study, an interpenetrating double-network hydrogel (LMP/AA/PVAH) was prepared based on low methoxy pectin (LMP), acrylic acid (AA) and polyvinyl alcohol (PVA). The first rigid network of chemical crosslinking was constructed via free radical polymerization of LMP and AA, and the second of ductile physical crosslinking network was constructed via cyclic freeze-thaw of PVA. The first cycle hardness and elasticity of the LMP/AA/PVAH significantly increased from 13.08 N and 0 to 24.28 N and 0.79, respectively, when the second network structure was constructed in the hydrogel by PVA. Besides, the PVA network might enhance the ductile and limit the swelling of hydrogel. In addition, the adsorption properties of LMP/AA/PVAH were evaluated by adsorption of methylene blue (MB). The adsorption behavior of MB by LMP/AA/PVAH conformed to the pseudo-second-order kinetic model. Besides, after 4 cycles of adsorption, there was no significant difference in adsorption capacity of LMP/AA/PVAH. The results showed that LMP/AA/PVAH had good reusability.

Preparation of hydrogels based on pectin with different esterification degrees and evaluation of their structure and adsorption properties.

In this study, pectin (Pe) with different esterification degrees was used as raw materials to prepared hydrogel adsorbents via free radical polymerization. The effect of Pe esterification degree on hydrogel structure and adsorption performance was studied by FTIR, SEM and XPS characterization and copper ion adsorption experiment. The results demonstrated that the carboxyl group in the hydrogels was bonded to Cu2+ through electrostatic force and coordination, which was an important factor in its adsorption capacity. The hydrogels prepared from Pe with low esterification degree had finer pores and higher carboxyl content, so the adsorption capacity on both water and Cu2+ was stronger. The preparation of hydrogels from low-ester Pe was more conducive to the adsorption of copper ions. Besides, the adsorption behavior of the hydrogels on Cu2+ was investigated through the adsorption thermodynamics and kinetics. The results indicated that the adsorption kinetics of the hydrogels was in accordance with the quasi-second-order model. The adsorption of Cu2+ by hydrogels was the result of physical and chemical adsorption, which was endothermic under natural condition, and a higher temperature will result in more favorable spontaneous adsorption.