Synergistic stabilization of high internal phase Pickering emulsions by peanut isolate proteins and cellulose nanocrystals for ß-carotene encapsulation.

In this study, high internal phase Pickering emulsions (HIPPEs) were stabilized by the complexes of peanut protein isolate (PPI) and cellulose nanocrystals (CNCs) for encapsulation ß-carotene to retard its degradation during processing and storage. CNCs were prepared by H2SO4 hydrolysis (HCNCs), APS oxidation (ACNCs) and TEMPO oxidation (TCNCs), exhibiting needle-like or rod-like structures with nanoscale size and uniformly distributed around the spherical PPI particle, which enhanced the emulsifying capability of PPI. Results of optical micrographs and droplet size measurement showed that Pickering emulsions stabilized by PPI/ACNCs complexes exhibited the most excellent stability after 30 days of storage, which indicated that ACNCs had the most obvious effect to improve emulsifying capability of PPI. HIPPEs encapsulated ß-carotene (ßc-HIPPEs) were stabilized by PPI/ACNCs complexes and showed excellent inverted storage stability. Moreover, ßc-HIPPEs exhibited typical shear thinning behavior investigated by rheological properties analysis. During thermal treatment, ultraviolet radiation and oxidation, the retentions of ß-carotene encapsulated in HIPPEs were improved significantly. This research holds promise in expanding Pickering emulsions stabilized by proteins-polysaccharide particles to delivery systems for hydrophobic bioactive compounds.

Properties of Pickering emulsions stabilized by cellulose nanocrystals extracted from litchi peels.

The development of Pickering emulsions which are applicable to the food industry still remains challenges due to the limited availability for biocompatible, edible and natural emulsifiers. The purpose of this study was to extract cellulose nanocrystals from litchi peels (LP-CNCs), and evaluate their emulsifying properties. The results showed that the LP-CNCs were needle-like and they possessed high crystallinity (72.34 %) and aspect ratio. When the concentrations of LP-CNCs were >0.7 wt% or the contents of oil were no >0.5, stable Pickering emulsions were obtained. The microstructures of emulsions confirmed that LP-CNCs formed dense interfacial layers on the surface of oil droplets, which functioned as barriers to prevent aggregation and flocculation among droplets. Rheological results showed that the emulsions exhibited typical shear thinning behavior. The elastic of emulsions was dominant, and their gel strength could be enhanced by regulating the contents of emulsifiers or oil. Additionally, the Pickering emulsions stabilized by LP-CNCs showed extremely high pH, ionic strength, and temperature tolerance. This strategy provides an innovative alternative to tackle the dilemma of preparing highly stable Pickering emulsions using natural particles in food products.

Impact of interactions between peanut protein isolate and cellulose nanocrystals on the properties of Pickering emulsions: Rheological properties and physical stabilities.

The interactions between cellulose nanocrystals and proteins can regulate the interfacial properties of Pickering emulsions, which plays a leading role in the stabilities of Pickering emulsions. In this work, oil-in-water (O/W) Pickering emulsions with different oil-water ratios were prepared using peanut protein isolate modified by cellulose nanocrystals (PPI/CL-CNCs). The distributions of PPI/CL-CNCs at the oil-water interfaces and the microstructures of Pickering emulsions were observed by CLSM and cryo-SEM. The results showed that stable complexes PPI/CL-CNCs formed thick and dense interface layers on the surface of oil droplets. The results of rheological tests clarified that the Pickering emulsions showed an elastic and gel texture, and their gel strength could be enhanced by regulating the oil-water ratios from 3:7 to 7:3. In addition, after one month of storage, the EI of all emulsions remained above 92 % with no obvious phase separation or demulsification. These results suggested that the PPI/CL-CNCs-stabilized Pickering emulsions showed good physical stabilities. The study on the rheological properties and physical stabilities of PPI/CL-CNCs-based Pickering emulsions provided novel insights on developing highly stable Pickering emulsions.

Characterization and antibacterial properties of epsilon-poly- l-lysine grafted multi-functional cellulose beads.

In recent years, harmful microorganisms in water pose great harm to ecological environment and human health. To solve this problem, epsilon-poly-l-lysine (EPL) grafted cellulose beads were prepared via 2, 2, 6, 6-tetramethylpiperidine-1-oxyl (TEMPO) mediated oxidation and carbodiimide mediated cross-linking reaction. Hydroxyl groups on C6 of cellulose were oxidized to carboxyl groups by TEMPO and grafting reaction was achieved between newly formed carboxyl groups of cellulose and amino of EPL. The beads were characterized by FTIR, SEM, XRD and TGA. The crystalline form of cellulose transformed from cellulose I to cellulose II after being dissolved and regenerated. The grafted cellulose beads showed good antibacterial activities against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus and Alicyclobacillus acidoterrestris with 10 h. The beads could be biodegraded in soil after 28 days. It is expected that the bio-based composite beads could have potential applications in water purification and food treatment fields.

Fabrication and characterization of antibacterial epsilon-poly-L-lysine anchored dicarboxyl cellulose beads.

Pathogens in the food and environment pose a great threat to human health. To solve this problem, we described a novel route to synthesize antibacterial epsilon-poly-L-lysine (EPL) anchored dicarboxyl cellulose beads. Cellulose beads were prepared via a sol-gel transition method and oxidized by sodium periodate and sodium chlorite to form carboxyl groups. EPL was anchored on the beads using carbodiimide mediated amidation. The structure and morphology of beads were characterized by FTIR, XPS, XRD, SEM, and TGA. After dissolution and regeneration, the crystalline form of cellulose is transformed from cellulose I to cellulose II. The thermal degradation temperature of the beads is 200∼300 °C.The samples displayed excellent antimicrobial activity against Staphylococcus aureus, Alicyclobacillus acidoterrestris and Escherichia coli within 12 h. The beads could be biodegraded in soil after 20 days. The biodegradable beads exhibited great potential in food and environmental applications.