Micropartículas de eugenol por gelificação iônica: ação antimicrobiana

Abstract

Microbiological contamination can make food susceptible to deterioration and be a vehicle for disease, which can be circumvented by the application of antimicrobials. The use of synthetic antimicrobials in foods warns of the negative health effects of the population, indicating the need for alternatives to replace them with natural ones, such as eugenol. However, its application in food is limited due to its odor and sensitivity to environmental conditions. Thus, the microencapsulation process, in addition to controlling the odor, promotes greater protection to the compound. The combination of this technique with the protein coating process allows obtaining microparticles with better protective characteristics. Thus, the present study aimed to evaluate the antibacterial potential of microencapsulated eugenol, using the technique of ionic gelation using sodium alginate as a wall material, in association with the emulsifier Tween 80, and coating with isolated whey protein. Protein coating was evaluated qualitatively and quantitatively to determine its efficiency. The quantification of phenolic compounds was performed to evaluate the efficiency of eugenol encapsulation. The microparticles were characterized by the techniques of optical microscopy (OM), scanning electron microscopy (SEM) and dynamic light scattering (DLS) that determined the average size, polydispersity index and zeta potential. The in vitro antimicrobial activity of eugenol was determined in concentrations equivalent to its free and microencapsulated form using the techniques of minimum inhibitory concentration and minimum bactericidal concentration against contaminating food species: Escherichia coli, Salmonella typhimurium, Staphylococcus aureus and Listeria monocytogenes. The qualitative efficiency of the protein coating obtained a satisfactory result due to the blue color of the microparticles when the specific protein dye (Coomassie Brillante Blue) was used. The percentage of 16% protein adsorption allowed a low quantitative efficiency. The OM allowed to observe uniform microparticles with spherical shape, as well as through SEM it was possible to perceive the decrease of the microparticles' roughness after the protein coating process. The size obtained was 1.33 ± 0.5 μm, favorable to food applications, and its polydispersity index (0.32) shows the uniformity of this size. The zeta potential remained negative after protein adsorption. The in vitro antimicrobial activity against the tested microorganisms proved to be effective according to the smallest microbial growths found. In this way, it was possible to develop a microparticle system with coverage with an antibacterial effect.