Physical stability, microstructure and antimicrobial properties of konjac glucomannan coatings enriched with Litsea cubeba essential oil nanoemulsion and its effect on citruses preservation.

This study purposed to develop konjac glucomannan (KGM) based antimicrobial coatings containing Litsea cubeba essential oil nanoemulsion (LNE) for citruses preservation. Physical stability, rheological, structural and antimicrobial properties of the coating solutions were investigated, along with the release characteristics of Litsea cubeba essential oil (LCO). Results showed that the coating solutions displayed shear thinning behavior. The oil droplets were distributed homogeneously in KGM phase with good stability. The coating structure became loose with increasing LNE content due to LNE interfering with molecular interactions and entanglement of KGM. The coating solutions showed stronger antibacterial activity against Escherichia coli than against Staphylococcus aureus and were effective in inhibiting the growth of Penicillium italicum on citrus surfaces. KGM-LNE 10 negatively affected citruses due to phytotoxicity caused by high levels of LCO. LCO was released slowly and continuously from the coatings, and its release was faster in deionized water than in an ethanol-water solution. KGM-LNE 2.5 coated citruses had the least weight loss, the greatest hardness, and kept the minimum changes in total soluble solids, total acid and vitamin C content, implying that KGM-LNE 2.5 best maintained the quality of citruses. The findings suggest that KGM-based coatings containing LNE have high potential for citruses preservation.

Influence of interfacial properties/structure on oxygen diffusion in oil-in-water emulsions.

Oxygen diffusion played an important role in the lipid oxidation of food emulsions. In this study, a simple method was developed to quantitatively observe the oxygen diffusion in the oil-water biphasic system, and it was further applied to investigate the relationship between the oxygen diffusion and lipid oxidation in O/W emulsions. Various factors that related to the emulsion oxidation were considered, from their influence on the oxygen diffusion and lipid oxidation in the emulsions. Results showed that there was obvious correlation between the oxygen diffusion and lipid oxidation in O/W emulsions, which reveals the inhibition of oxygen diffusion could apparently slow down the lipid oxidation. Moreover, the changes of oil phase, water phase and interfacial layer of the emulsions, which were related to the oxygen diffusion, could improve the oxidative stability of the emulsions effectively. Our findings are helpful for deep understanding the mechanisms of the lipid oxidation in food emulsions.

pH-Sensitive drug delivery system based on hydrophobic modified konjac glucomannan.

Amphiphilic aliphatic amines grafted konjac glucomannan (KGM-g-AH8, KGM-g-AH12 and KGM-g-AH18) micelles were prepared via a simple two-step synthesis with Schiff's base as the "switch" to achieve intracellular acid-triggered curcumin release. The KGM-g-AH8 self-assembled into spherical nano-micelles (107.6±11.6nm) in an aqueous medium, and presented high curcumin loading capacity as well as good physical stability in 28 days. The in vitro curcumin release behaviors proved the controlled release property and the endosomal/lysosomal pH response of KGM-g-AH8 micelles. The cytotoxicity and cellular uptake studies were also investigated to exhibit the intracellular pH-sensitivity, safety and biocompatibility of KGM-g-AH8 micelles. This research focuses on the feasibility of KGM-based micelles to be extrapolated as promising strategies for cancer therapy and offers new potential options for intracellular drug delivery.