Effect of different types of nanocellulose on the structure and properties of gelatin films*

The use of nanocellulose to enhance the performance of biopolymer films is a recent trend in food packaging. This current study aims to investigate the impact of incorporating different morphologies of nanocellulose, namely cellulose nanofibrils (CNFs), cellulose nanospheres (CNSs), and cellulose nanocrystals (CNCs), on the structures and properties of gelatin film. The FTIR confirmed the formation of triple helix structures among CNF and CNC groups due to more hydrogen bonds generated between cellulose and gelatin molecules compared to CNSs. SEM analysis revealed a uniform distribution of CNCs in gelatin but aggregated with an increase in CNC contents, while CNF and CNS groups exhibited aggregation of cellulose upon the surface of gelatin because the vast surface area of nanospheres along with the nanofibrils structure led to irregular dispersion of cellulose (especially CNSs). In comparison to the CNF5% and CNS groups, CNC and CNF2% (w/w) groups greatly improved the mechanical characteristics of the gelatin films to 131.27% EAB and 20.71 MPa TS due to strong hydrogen bond interaction, more triple helix structures, and the relatively thorough dispersion of cellulose in the gelatin film. The incorporation of nanocellulose reduced the solubility and transparency of the gelatin films. Of all the films, CNC2% film exhibited a significant reduction of water vapor permeability due to the facile and even dispersion of CNCs in the gelatin network structure. Adding nanocellulose had little impact on the gelatin films' heat stability. Therefore, the current work may be a new viable strategy for the construction of a novel molecular network system for enhancing the effectiveness of gelatin film containing lower content of CNCs.