Physical and active properties of poly (vinyl alcohol) films with phenolic acids as affected by the processing method

Abstract

Poly (vinyl alcohol) (PVA) films containing cinnamic acid (C) and ferulic acid (F) at 1% w/w and 2% w/w were successfully produced by solvent-casting the polymeric solution and melt blending and compression moulding. The effect of the processing method and the phenolic acid content on the microstructure, crystallinity and the optical, thermal, barrier and mechanical properties of partially hydrolysed PVA based films have been analysed, as well as the antioxidant and antimicrobial properties of the films. The processing method influenced the microstructural arrangement of the matrix, leading to differences in the degree of crystallinity and in the tensile and barrier properties of the films. Cast films were more stretchable and more resistant to break, while thermoprocessed films exhibited values of oxygen and water vapour permeability significantly higher than those obtained by casting. The incorporation of phenolic acids, especially ferulic acid, enhanced the barrier properties of the materials without affecting their thermal stability. The presence of phenolic acids in the films clearly induced the inhibition of Listeria innocua growth and had a positive antioxidant response, thus suggesting the great potential of these active materials for food packaging applications.