Plasticized films based on PLA and PHB: from the choice of plasticizer to the study of packaging perspective

PLA- and PHB-based films were plasticized with triacetin (TA), triethyl citrate (TEC), tributyl-o-acetyl citrate (TBAC) in concentrations ranging from 1 to 10 wt.%. We found that introduction of TA and TEC affected the surface of PLA films, leading to the formation of closed pores and cavities, whereas TBAC did not noticeably affect the surface. Upon plasticization, the elongation at break of PLA films increased up to 30-fold. The introduction of plasticizers caused less than a two-fold change in the values for PHB films. The plasticized PLA and PHB films were characterized by lower melting points (around 143–144 °C and 166–167 °C, respectively) compared to the non-plasticized films (147 °C and 168 °C). Following incubation in aqueous model solutions (5% sodium chloride, 2% citric acid, 0.3% lactic acid), the plasticizers gradually migrated from the films into the environment, reaching 0.0034 mg∙mg–1. This migration led to a reduction in the films' mechanical properties: at pH 6.0, the tensile strength and elongation at break decreased by a factor of 1.3–1.5, while at pH 2.6, a fivefold decrease was observed. The shelf life of chicken fillets was extended up to one week without any obvious change in sensory characteristics. The plasticizer was detected in chicken fillets at a very low concentration (approximately 2.1 µg/g) on day 3 but was no longer detectable by day 7 of the experiment.