Preparation, Structural, Morphological, Thermal, Mechanical Properties Antibacterial Activity of Polyvinyl Alcohol/Cellulose Nanocrystal/Eryngium planum Extract/Barberry Anthocyanin Smart Film

Abstract

Indicator nanocomposite films were prepared by 1% anthocyanin, nanocellulose, and aqueous extract of Eryngium planum with 1%, 2%, and 3% concentrations. According to the results of FTIR, new interactions were observed between the components of the film. SEM showed that anthocyanin and Eryngium planum extract were well dispersed in cellulose nanocrystals and polyvinyl alcohol–based film. DSC test showed an increase in the melting temperature of the film. The combination of anthocyanins and Eryngium planum extract also improved the mechanical properties of the films. The tensile strength increased from 0.05 ± 0.02 (N/cm²) to 0.09 ± 0.02 (N/cm²). The addition of the extract significantly increased to 0.12 ± 0.01 (N/cm²). The elongation also increased from 30.004 ± 1.90% in the control sample to 33.06 ± 0.86% and 44.41 ± 3.91% in the anthocyanin extract samples, respectively. Investigation of the color changes of the film at different pH showed that the addition of anthocyanin reduced the transparency of the films. At acidic pH, the films’ redness reduced; at alkaline pH, the greenness increased. Investigations showed good antibacterial properties of the films against Escherichia coli and Listeria monocytogenes. Increasing the concentration of the Eryngium planum extract in the polymer matrix significantly affected the films’ inhibitory properties. The inhibition zone against E. coli increased from 9.66 ± 0.57 mm to 18.66 ± 0.57 mm by increasing extract from 1% to 3% in biopolymers. For Listeria monocytogenes, it was equal to 7.33 ± 0.71 and 88.66 ± 3.91 mm, respectively. A comparison of the inhibitory percentage of films against the two bacteria indicated that E. coli was more sensitive to Eryngium planum extract. This smart, active, degradable biopolymer is recommended as a food-appropriate film.