Effect of phenolic acids on the properties of films from Poly (vinyl alcohol) of different molecular characteristics

Cinnamic and ferulic acid were incorporated into highly hydrolysed and partially acetylated poly (vinyl alcohol) (PVA) for the purpose of obtaining active films. The microstructure, crystallinity, tensile and barrier properties and thermal behaviour were analysed in order to ascertain the changes provoked by phenolic acids in the film properties, depending on the kind of PVA. Phenolic acids were more compatible with the partially hydrolysed PVA. Ferulic acid led to greater changes in PVA films than cinnamic acid, promoting the crystallinity, stiffness and barrier capacity to water vapour and oxygen, although in no case the thermal stability of the polymers was affected. Films of partially hydrolysed PVA, with lower melting (170 degrees C) and higher thermodegradation (onset: 220 degrees C) temperature, could be thermoprocessed by means of the technology commonly used in the plastics industry. Therefore, the incorporation of ferulic or cinnamic acid into this matrix could be of great potential in the development of active packaging for food preservation, on the basis of the antioxidant and antimicrobial activity of phenolic acids.