Effect of ferulic and cinnamic acids on the functional and antimicrobial properties in thermo-processed PLA films

Abstract

The incorporation of ferulic or cinnamic acids as antimicrobial agents into PLA matrices to produce films with active properties for food packaging applications is evaluated in this study. The acids were incorporated by thermal processing at 1 and 2 wt% presenting good stability with 84–98% retentions. The addition of acids provoked about a 5% reduction of elastic modulus and up to 20% reduction in the resistance to break in the PLA films, slightly decreasing their extensibility. Oxygen and water vapor barrier capacities were enhanced by about 6% and 45% respectively for the highest acid concentrations. The acids did not change the glass transition of the polymer but increased the thermal resistance. No significant antimicrobial activity was detected, despite the proven activity of the acids, due to their limited release into the aqueous culture media. Release kinetic studies revealed that significant release was only achieved in intermediate polarity simulant (50% aqueous ethanol), where the final percentages of the active released increased along with the total amount in the films (15% and 31%, respectively, for 2% of ferulic and cinnamic acids). Further studies are necessary to improve the compound release into food matrices and antimicrobial effectiveness.