The main shortcoming of poly(lactic acid) (PLA) for food packaging applications is its brittleness. The aim of this work was to evaluate the potential use of Origanum vulgare L. essential oil (OEO) in PLA-based matrices to obtain developed bio-based films with enhanced mechanical properties as well as antimicrobial performance. The PLA-essential oil composite films were more flexible than neat PLA films; so that up to 6-fold increase in the elongation-atbreak values (2.82-16.78%) were acquired when 0.5% (w/w) oil was added to the polymer matrix. The addition of essential oil decreased the PLA glass transition temperature (Tg), as the result of the polymer plasticization, and led to modification of the tensile behavior. AFM results confirmed that the PLA surface microstructure was drastically influenced in terms of roughness parameters (Ra and Rq) when OEO was added. The films' antimicrobial activities were induced by incorporating essential oil, which were more effective against the bacteria in direct contact method than a vapor phase. However, in both of test methods, Staphylococcus aureus was the most sensitive bacterium to OEO-containing films, while Escherichia coli was the most resistant. Then, efficacy of bioactive film included with 1.5% (w/w) essential oil to reduce microbial growth of rainbow trout during chilled storage was evaluated; the results indicated that antimicrobial PLA film was effective against all the microorganisms tested in this study. These results suggest that the developed PLA films with active substance could be used in designing antimicrobial packaging materials.
Multi-layer film structures of poly(lactic acid) (PLA) and fish gelatin (FG), prepared using the solvent casting technique, were studied in an effort to produce bio-based films with low oxygen (OP) and water vapor permeability (WVP). The scanning electron microscopy (SEM) images of triple-layer film showed that the outer PLA layers are being closely attached to the inner FG layer to make continuous film. The OP of multi-layer film (5.02cm/mdaybar) decreased more than 8-fold compared with that of the PLA film, and the WVP of multi-layer film (0.125gmm/kPah m) also decreased 11-fold compared with that of the FG film. Lamination with PLA profoundly increased the water resistance of the bare gelatin film. Meanwhile, the tensile strength of the triple-layer film (25±2.13MPa) was greater than that of FG film (7.48±1.70MPa). At the same time, the resulting film maintains high optical clarity. Differential scanning calorimetry (DSC) analysis also revealed that the materials were compatible showing only one T which decreased with FG deposition. This material exhibits an environmental-friendliness potential and a high versatility in food packaging.
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