Antimicrobial and food barrier properties of polyvinyl alcohol–lactic acid food packaging films

Abstract

Microbial contamination and the need for sustainable food production are driving the shift toward biodegradable food packaging materials. There is an urgent need to develop smart food packaging materials that can prevent contamination and prolong the shelf life of meat. To achieve this, the physical-chemical characteristics of polyvinyl alcohol (PVA)-based packaging films were enhanced through incorporation of lactic acid and anthocyanins to act as a pH indicator. The mechanical, hydrophilic, barrier, and antibacterial properties of the composite films were then evaluated to test the ability of the film to act as a packaging material. In addition, the surface morphology was studied by scanning electron microscopy (SEM), the functional groups by Fourier transform infrared (FTIR) spectroscopy, optical transparency using ultraviolet-visible (UV-vis) spectrophotometer, crystallinity by powder diffraction, and their thermal properties by thermal gravimetric analysis (TGA). The films had a swelling degree (SD) of 222.60 ± 21.19%, dry content (DC) of 70.56 ± 2.54%, moisture content (MC) of 29.44 ± 2%, ALRO moisture (AM) content of 41.85 ± 5.06, and total soluble matter (TSM) of 8.05 ± 1.05%. Moreover, incorporation of lactic acid enhanced the mechanical and the thermal properties of the films but it reduced their optical transparency. The water vapor permeability (WVP) was found to be 14.32 × 10^-3 g^-1 s^-1 Pa^-1 and it inhibited the growth of <i>Escherichia coli</i> (EC) (10.67 ± 0.58 cm), <i>Staphylococcus aureus</i> (SA) (10.50 ± 0.40 cm), <i>Pseudomonas aeruginosa</i> (PA) (10.33 ± 0.58 cm), and <i>Staphylococcus epidermidis</i> (11 ± 1 cm) but not <i>Bacillus subtilis</i> (BS). The film's hue changed from red to green over time when used as a packaging material for meat under ambient condition indicating a deterioration in freshness. In conclusion, the developed packaging film exhibited enhanced mechanical, antimicrobial, and hydrophilic properties and it can be used to store and relay information when stored meat begins to decompose through a visible color change of the films.