DEVELOPMENT AND EVALUATION OF ANTIMICROBIAL BIODEGRADABLE PBAT FILMS INCORPORATED WITH OREGANO ESSENTIAL OIL (THYMOL AND CARVACROL)

The food industry has been looking for new ways to conserve their products. The use of antimicrobial packaging films incorporated with essential oils accomplishes all the functions of a conventional packaging in addition inhibits the growth of microorganisms extend shelf life of foods. Furthermore, eco-friendly polymer materials like butyl adipate-co-terephthalate (PBAT) stand out as alternatives to reduce environmental impacts. The objective of this work was to evaluate the effectiveness of active PBAT films incorporated with oregano essential oil to reduce the growth of E. Coli (gram-positive), S. aureus (gram negative) and Aspergillus Nigger (fungus) and evaluate if the essential oil addition altered the film properties. The PBAT films were prepared using a solvent-casting method (containing 0, 10, 20, 30, 40 wt% oregano essential oil) and the films thickness and grammage were mesured. The microbial activity was evaluate by measuring the growth-inhibition halo, and the mechanical properties was tested by the tensile strength at break (TB), elongation at break (EB) and maximum load (ML). It was observed there was no significant growth-inhibition up to 20% essential oil in the polymer and there was a significant difference between 30% and 40%. The films containing 40% showed the highest inhibition diameter halo (14.98 ± 0.80 mm for E. coli, 14.12 ± 0.13 mm for S. aureus and 12.77 ± 0.55 mm for A. niger). Thymol and carvacrol, presents in oregano essential oil, sensitizes the phospholipids bilayer of the microbial cytoplasmatic membrane and damage the bacterial enzymatic system. However, it is possible that to sensitize this layer requires at least 30% of oregano oil in the polymer, probably because below this concentration the attraction between then is greater, preventing the releasing of terpene compounds into the medium. The films grammage and thickness did not differ by Tukey's test (p = 0.80). The average thickness obtained was 0.076 ± 0.006 mm and the average grammage was 67.78 ± 2.25 g/m2. About the mechanical properties, the control film (0%) presented the higher ML value (14.11N) and the film with 40% the least one (9.17N). The film with 40% showed the lowest EB (287.30%) and the film with 10% presented the greatest EB value (376.13%) possibly because the little presence of the oil in the polymer matrix increase the forces, but when we rising the oil concentration this phenomenon is reversed. There were not significantly difference between the TB values by the tukey test (p=1), indicating a rupture value of 5.21MPa. These results prove the efficiency of the antimicrobial PBAT films with oregano oil for the tested microorganisms. However, the mechanical properties decrease with the increase of oil concentration in the film, so the better use will depend on the application of the polymer. This active antimicrobial polymer is a very attractive alternative for packed in the food industry.