Effect of active phenolic acids on properties of PLA-PHBV blend films

Phenolic acids (ferulic, p-coumaric, and protocatechuic) have been incorporated into polylactic (PLA): Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) (75:25) blend films that were obtained by melt-blending and compression moulding, using PEG1000 as a plasticizer. Film microstructure, thermal behavior, functional properties, and release kinetics of phenolic acids in different food simulants were analyzed, and the film antimicrobial activity against Listeria innocua. Phenolic acids led to an increase in the glass transition temperature of PLA while PHBV supercooling occurred in the films containing protocatechuic acid, which affected their thermal degradation behavior. Polymer matrices with phenolic acids were stiffer and more resistant to break than the polyester blend, but with similar extensibility, while oxygen and water vapor barrier capacity were also improved, especially in films containing protocatechuic acid. The release rate and ratio of phenolic acids increased when the polarity of the food simulant decreased, although very slow delivery was observed in all cases. The limited release of active compounds in aqueous media provoked that films did not significantly inhibit the growth of Listeria innocua in inoculated culture medium.