Effect and mechanism of cellulose nanofibrils on the active functions of biopolymer-based nanocomposite films.

Cellulose nanofibrils (CNFs) are superfine cellulose fibrils with a nanoscale diameter and have gained increasing attention due to their great potential in the food industry. However, the applications of CNFs in active food packaging are still limited. The objectives of this study were to develop biopolymer-based edible nanocomposite films using CNFs, corn starch, and chitosan, and to investigate the effect and mechanisms of CNFs on the active functions and properties of the nanocomposite films. Important functional properties of the films were measured and the films were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Zetasizer. The results demonstrate that CNFs increased the rigidity of the films due to more hydrogen bonds being induced by CNFs (≥60%). Incorporating a high content of CNFs (≥60%) in the film resulted in enhanced filling effect on the structure of the biopolymer films, which significantly improved the light barrier, oxygen barrier and water vapor barrier capacities. As CNF content increased to 100%, the film opacity increased by 59%, while the peroxide value of corn oil protected with edible films was reduced by 23%. Furthermore, the antimicrobial properties of the edible films with 80% and 100% CNFs were increased by up to 2logCFU/g on day 8 in a beef model, due to more positive charges in the films and improved blocking effects on oxygen. These results demonstrate that CNFs can effectively enhance the antimicrobial effect and barrier properties of biopolymer-based nanocomposite films and have great potential in applications of active packaging for food products.

Cellulose nanofibers coated with silver nanoparticles as a SERS platform for detection of pesticides in apples.

A nanocomposite based on cellulose nanofibers (CNFs) coated with silver nanoparticles (AgNPs) was developed in this study as a flexible and effective substrate for use in surface-enhanced Raman spectroscopy (SERS) analysis. An effective Raman indicator molecule, 4-aminothiophenol (pATP), was used to characterize AgNPs impregnated on CNFs. The CNF-AgNP films were used in SERS analysis to detect thiabendazole (TBZ) pesticides in apples. The influence of pH on the SERS spectra of TBZ was investigated because TBZ is a neutral molecule that has a low affinity for AgNPs. The pH of TBZ solution was decreased to below the TBZ's pKa, thus enabling the electrostatic attraction between TBZ and AgNPs. CNFs can prevent the uncontrolled aggregation of AgNPs in low pH environment and serve as an effective AgNP/nanocellulose platform for SERS analysis. Results of this study demonstrate that CNF-AgNP nanocomposites can be used to rapidly detect TBZ pesticides in various food products.