Antimicrobial, antioxidant, and pH-sensitive polyvinyl alcohol/chitosan-based composite films with aronia extract, cellulose nanocrystals, and grapefruit seed extract.

Aronia or black chokeberry (Aronia melanocarpa), cellulose nanocrystals (CNCs), and grapefruit seed extract (GSE) were used for the preparation of multifunctional polyvinyl alcohol/chitosan (PVA/CS) composite films with pH-sensitivity, antimicrobial, antioxidant, and UV-barrier properties. Aronia extract showed total phenolic content of 297 ± 0.5 µg GAE/mg aronia extract, potent antioxidant activity, and high color-response efficiency. Isolated CNCs showed a needle-like structure with a length of 470 nm and a width of 35 nm. The tensile strength of the PVA/CS composite film increased by 74% after the incorporation of CNCs, whereas the film flexibility was enhanced by 75% after adding GSE. The PVA/CS-A (aronia extract) composite film showed a significant color change at different pHs and potent antioxidant activity. At the same time, the PVA/CS-G (GSE) showed the highest antimicrobial activity against Escherichia coli (Gram-negative) and Listeria monocytogenes (Gram-positive) bacteria. The PVA/CS-CGA composite film, reinforced with CNCs/GSE/Aronia extract, showed the highest UV-barrier (95.5%), highest antioxidant activity (95%), potent antimicrobial activity, pH-sensitivity, lowest water vapor permeability (WVP), and desirable mechanical properties. The multifunctional properties of the produced composite films encourage their use as active and intelligent food packaging films to extend shelf life and monitor food quality.

Multifunctional poly(vinyl alcohol) films using cellulose nanocrystals/oregano and cellulose nanocrystals/cinnamon Pickering emulsions: Effect of oil type and concentration.

Poly (vinyl alcohol) (PVA) films with high transparency, UV-barrier, antioxidant, and antimicrobial properties were prepared using oregano essential oil (OEO) and cinnamon essential oil (CEO) Pickering emulsions. The effect of Pickering emulsion type and concentration on the PVA film properties was studied. Cellulose nanocrystals (CNCs) were used as a natural stabilizer to prepare OEO and CEO Pickering emulsions. Both emulsions showed spherical droplets with diameters of 155-291 nm, zeta potential of -36.2 to -49.6 mV, minimum inhibition concentration of 6.25-12.5 µL/mL, and inhibition zone of 40-65 mm, depending on oil type. Morphology and FTIR analysis showed that OEO and CEO Pickering emulsions were compatible with the PVA matrix. The UV-transmittance of PVA films decreased from 77.3% to 30.4% and 2.0% without sacrificing the transparency after adding OEO and CEO Pickering emulsions, respectively. Antimicrobial results showed that E. coli was more sensitive to CEO, while S. aureus was sensitive to OEO Pickering emulsion. PVA/CEO film displayed higher properties than PVA/OEO film.