Micellar-type aggregates of HP-ß-CD/GML inclusion complex: Increased water-solubility and effective antibacterial capabilities.

The inclusion complex (IC) was successfully obtained by encapsulating glycerol monolaurate (GML) into the cavity of hydroxypropyl-ß-cyclodextrin (HP-ß-CD). Compared with solubility of pure GML <80 µg/mL in water, and the water-solubility of encapsulated GML was significantly improved and reached to 270,000 µg/mL. IC can form nanoparticles by self-assembly, probably assigned to its strong capability to form micellar-type aggregates. A Higuchi's AL-type phase-solubility diagram indicated the strong interaction between host and guest molecules with the formation of 1:1 GML/HP-ß-CD complex and the stability constant at 6248 L/mol. Compared with pure GML, encapsulated GML at the same concentration can also show good antibacterial capabilities against S. aureus and E. coli in sterile water, and the effective preservative capabilities towards beef meatballs. The boosted enhancement in water-solubility of GML and the effective antibacterial capabilities endowed IC with potential in the application of food decontamination.

Cellulose laurate films containing curcumin as photoinduced antibacterial agent for meat preservation.

Hydrophobic cellulose laurate (CL) with high degree of substitution has been successfully synthesized. The mechanical property, water-resistance, antimicrobial activity, barrier properties and food decontamination of cellulose-laurate-curcumin films (CL-Cux, x = 0.1, 0.5, and 1) were investigated. The results showed that the mechanical properties of CL-Cux hardly change after soaking in water for 24 h, probably due to the strong hydrophobicity of cellulose laurate. CL-Cu1 represented a good photoinduced antibacterial effect against S. aureus. After irradiation of white light at 60 mW·cm-2 for 20 min, the inhibition efficiency reached to 95 ± 2.02%, probably owing to the generated active 1O2. In comparison with CL-Cu1 stored in natural light, the bacteriostatic effect of CL-Cu1 in dark storage was better, and the inhibition rate of CL-Cu1 remained 80 ± 1.22 at 60th day. The stabler excited state of curcumin in hydrophobic cellulose laurate was probably assigned to inhibition of tautomerism or conformational transition, which was beneficial to the generation of singlet oxygen. CL-Cu1 can significantly inhibit the growth of TVBN and TVC values of chilled meat upon white light irradiation, indicating the potential application of cellulose-laurate-curcumin films in food decontamination.

Cellulosic films reinforced by chitosan-citric complex for meat preservation: Influence of nonenzymatic browning.

The methods to obtain cellulose-chitosan composite films exhibiting excellent water-resisting and antibacterial abilities have been widely explored. Cellulose-chitosan-citric films (C-Chx-F) were successfully obtained by a facile coating of chitosan-citric complex on the surface of cellulose. The occurrence of nonenzymatic browning at 80 °C improved the thermal stability, water-resistance, mechanical property and oxygen-barrier ability of C-Chx-F membranes. C-Ch3-F hydrogel showed excellent breaking stress of 6.03 ± 0.25 MPa, and elastic module of 27.09 ± 1.21 MPa, probably assigned to nonenzymatic browning. Under different test temperatures, the nonenzymatic browning and the content of chitosan-citric complex will significantly improve the oxygen barrier property of membranes (P < 0.05), and C-Ch3-F membrane represented the value of oxygen permeation below the detection level. Excellent antibacterial capability of C-Chx-F hydrogels demonstrated that polycationic chitosan-citric complex immobilized in films still retained excellent antibacterial ability. The excellent decontamination in meat preservation endowed C-Chx-F films with potential application in food packaging.

Photoinduced Antimicrobial Activity of Curcumin-Containing Coatings: Molecular Interaction, Stability and Potential Application in Food Decontamination.

Polyvinyl acetate (PVAc) and curcumin (Cu) were utilized for preparing new protecting PVAc-Cu x (x = 1, 5 and 10) coatings exerting antimicrobial photodynamic activity upon white light irradiation. Toward Salmonella typhimurium or Staphylococcus aureus, the killing efficiency represented the dependence on the Cu concentration and irradiation intensity. Toward S. aureus, the killing efficiency of PVAc-Cu 10 coating reached 93% at an energy density of 72 J/cm2. With the change in storage time of coating, the results implied significant stability of photosterilization efficiency within 60 days. Compared with the control experiment, lower total viable counts (TVCs) and total volatile basic nitrogen (TVB-N) values in fresh meat packaged by PVDC films with PVAc-Cu 10 coatings during storage at 4 °C demonstrated the practicability of the PVAc-Cu x coatings in decontaminating fresh pork. PVAc packed curcumin tightly within polymer chains, thus preventing tautomerization or, more probably, conformational transition, which is advantageous for improving photostability and emission lifetime.

Preparation of Elastic and Antibacterial Chitosan-Citric Membranes with High Oxygen Barrier Ability by in Situ Cross-Linking.

Chitosan-citric biomembranes Ch-CA-Gx (x = 0-3) were prepared by a simple cross-linking. The dependence of mechanical property, water-resisting capacity, microstructural characteristic, oxygen barrier ability, and thermal properties of membranes on the content of glycerin was investigated. The results revealed that vacuum drying at 80 °C can lead to low-yield amidation and the Maillard reaction, thus affecting the thermal stability and water resistance of biomembranes. Owing to the ionic cross-linking and amidation, the chitosan-citrate complex showed weaker compatibility when the glycerin content increased, thereby leading to discontinuity of microstructure in the Ch-CA-Gx (x = 1-3) membranes, which was in line with the weaker mechanical properties and water-resisting abilities of membranes, compared to Ch-CA-G0. Chitosan membranes showed interestingly high oxygen barrier capabilities under 40 and 80% relative humidity (RH) conditions, probably attributed to the increased diffusion length arising from the hydrogen-bonding, ionic, and covalent cross-linking. The oxygen transmission rates of Ch-CA-Gx were below 0.1 cm3 m-2 day-1 at 40% RH. The Ch-CA-Gx membranes showed a good elasticity assigned to the reversibly cross-linked structure. The membranes presented strong antibacterial activities against Staphylococcus aureus and Escherichia coli bacteria, probably owing to the citric acids. The results demonstrated that these materials have potential applications as membranes or protecting coatings for food packaging and successful cross-linking by means of amidation, and the Maillard reaction under the condition of vacuum drying can be probably applied as a green and alternative method for the fabrication of mechanically tough and antibacterial membranes, fibers, and gels.