Efeito da nanoemulsão de óleo essencial de Lippia origanoides nas propriedades antioxidantes e antimicrobianas de filmes biodegradáveis com proteção UV

Abstract

This thesis centers on the development, characterization, and application of a nanoemulsion containing Lippia origanoides essential oil (NE-OELO) within biodegradable active films composed of carboxymethylcellulose (CMC). The objective is to create functional materials suitable for potential use in food packaging. The study is structured into two complementary phases, culminating in two scientific articles. Chapter 1 explores the antimicrobial properties of both Lippia origanoides essential oil and its nanoemulsion, and analyzes their chemical composition and physicochemical characteristics. The essential oil was extracted by hydrodistillation and characterized by gas chromatography, which revealed carvacrol as the major compound, accounting for 41.56% of the composition. The nanoemulsion of the essential oil (NE-OELO) was obtained through ultrasound-assisted emulsification and was characterized in terms of droplet size, polydispersity index (PDI), and zeta potential. It demonstrated good physicochemical stability, with an average droplet size of 30.00 ± 1.70 nm, a PDI of 0.25 ± 0.03, and a zeta potential of −23.96 ± 3.61 mV. The antimicrobial activity of NE-OELO was assessed by measuring the minimum inhibitory concentration (MIC) against foodrelated microorganisms. The evaluation indicated that NE-OELO exhibited significantly greater antimicrobial activity than the free essential oil, with lower MIC values against Staphylococcus aureus (ATCC 00039), E. coli ETEC (ATCC 11105) and Salmonella typhimurium (ATCC 14028). In Chapter 2, the developed nanoemulsion was incorporated into biodegradable carboxymethylcellulose films using the casting method, at various concentrations of NE-OELO (10%, 15%, and 20%). The films were characterized for mechanical, optical, thermal, structural, and barrier properties, as well as antioxidant and antimicrobial activities. The inclusion of NE-OELO brought about significant structural and functional enhancements in the polymeric films. The films exhibited uniform thickness and a homogeneous surface, along with favorable optical properties, retaining high transparency and a low color variation index, qualities desirable for food packaging applications. Although an increase in opacity was observed, it did not detract from the films' overall visual appeal. With respect to functionality, the films containing NE-OELO demonstrated antioxidant activity, which increased with nanoemulsion concentration, a phenomenon linked to the presence of phenolic compounds. In vitro antimicrobial activity studies revealed that the volatile compounds released by the films were effective in inhibiting the growth of Staphylococcus aureus, with inhibition zones directly correlated with NE-OELO concentration. These findings suggest that NE-OELO not only enhances antimicrobial activity but also facilitates its incorporation into biodegradable polymeric matrices. The integration of the nanoemulsion into CMC films yielded active materials with physicochemical and functional properties that meet the technological requirements for food packaging. This underscores the potential of these systems as a natural and sustainable alternative for enhancing food safety and preservation.