Mechanical, barrier, and antimicrobial properties of anchote (Coccinia abyssinica) starch films containing cellulose nanocrystals and rosemary essential oil

In this research, the mechanical, barrier, and antimicrobial properties of anchote (Coccinia abyssinica) starch films containing different concentrations of anchote cellulose nanocrystals (AnchCNC) (1, 3, and 5%) and rosemary essential oil (REO) (2, 4, and 6%) were investigated. The thickness, moisture content, water solubility, water vapor permeability, mechanical properties, and antimicrobial properties of films were analyzed. Films containing 3% AnchCNC, 2% REO, and 5% AnchCNC, 2% REO, were chosen based on improved tensile strength and water vapor permeability. In addition, the Fourier transform infrared spectroscopic analysis, thermal characteristics, and morphological characteristics were determined. Films were prepared by the solution casting method, using water as a solvent and glycerol as a plasticizer. The tensile strength and water vapor permeability of anchote starch films were both dramatically improved by increasing the amount of AnchCNC. A significant reduction in the water vapor permeability of films was seen when the amount of rosemary essential oil was increased. The tensile strength of the films was found to decrease as the concentration of rosemary essential oil was increased. The tensile strength of the anchote starch (control) film was 9.42 MPa. Films containing 3% AnchCNC, 2% REO, and 5% AnchCNC, 2% REO, had shown the highest tensile strength of 23.41 MPa and 23.44 MPa, respectively. With the addition of 5% AnchCNC and 6% REO, the water vapor permeability of anchote starch film was decreased from 8.72 to 3.11 x 10(-11) g H2O/Pa.m.s. The films showed satisfactory antimicrobial efficiency against E. coli, Staphylococcus aureus, and Listeria monocytogenes. Both REO and AnchCNC contributed to the film's antibacterial effectiveness, but REO's contribution was higher. A sample containing the highest percentage, 5% AnchCNC and 6% REO, recorded the highest antibacterial efficiency. TGA results showed films containing 3% AnchCNC, 2% REO, and 5% AnchCNC, 2% REO, had better thermal properties than the control (anchote starch) film. The findings implied that the film would have significant potential for active packaging to increase food products' shelf lives with good mechanical and barrier capabilities.