Extração e caracterização dos óleos das pimentas Biquinho e da cultivar Maria Bonita: nanoencapsulamento com quitosana e ensaios de atividade antimicrobiana

Abstract

The growing environmental and sanitary concerns associated with the indiscriminate use of synthetic antimicrobials and sanitizers have driven the search for effective and sustainable natural alternatives for microbial control. In this context, this study aimed to extract, characterize, and nanoencapsulate oils from Biquinho and Maria Bonita peppers (Capsicum chinense), using chitosan as a polymeric matrix for the evaluation of antimicrobial activity.The selected microorganism, Limosilactobacillus fermentum, is a Gram-positive heterofermentative bacterium associated with fermentation processes and microbiological imbalances, potentially compromising product stability and quality by competing with desirable microorganisms. The oils were obtained by Soxhlet extraction using hexane and characterized by Fourier Transform Infrared Spectroscopy (FTIR), which revealed the presence of C–H bands from lipophilic groups, C=C bands from phenolic groups, and C=O bands from esters, as well as by Proton Nuclear Magnetic Resonance (^1H NMR), which confirmed the presence of capsaicin and dihydrocapsaicin. To enhance the stability of the active compounds, the oils were nanoencapsulated in chitosan obtained from shrimp waste through fermentative bioextraction followed by alkaline deacetylation, adding value to agro-industrial byproducts. The selection of chitosan is based on its biocompatibility, biodegradability, low toxicity, intrinsic antimicrobial activity, and its ability to form nanoparticles through ionic gelation. FTIR characterization confirmed the structural integrity of chitosan and the incorporation of the oils, evidenced by band shifts and reduction of C–H signals (3000–2800 cm⁻¹), indicating protection of lipophilic fractions. Field emission scanning electron microscopy (FEG-SEM) micrographs showed that pure chitosan exhibited an irregular and rough surface, whereas the encapsulated systems evolved into more spherical, homogeneous, and stable morphologies. Nanoparticles without oil showed an average diameter of 689 nm and a zeta potential of +32.40 mV, indicating colloidal stability. Oil incorporation promoted distinct structural changes: a 48.8% increase in diameter for the Biquinho oil system (1025.35 nm) and a 39.4% reduction for the Maria Bonita system (417.27 nm), highlighting different interactions with the polymeric matrix. Assays against Limosilactobacillus fermentum demonstrated high antimicrobial activity of the free oils (82.4% for Biquinho and 78.6% for Maria Bonita). After nanoencapsulation, modulation of activity was observed (54.3% and 49.8%, respectively). The results suggest that nanoencapsulation in chitosan not only protects bioactive compounds but also enables modulation of their biological action, expanding the possibilities for biotechnological applications, particularly in the development of natural and sustainable antimicrobial systems.