Óleos essenciais encapsulados em matrizes coacervadas e potencial antimicrobiano para aplicação em alimentos

Abstract

Essential oils have antimicrobial activity on various pathogenic and spoilage microorganisms, however, current research indicates several factors that limit their application. Therefore, the use of protective barriers on these volatile substances is necessary. In this work, an encapsulating system based on proteins (whey, soybean and pea) in combination with gum arabic was developed for encapsulating a blend of essential oils (thyme, oregano and clove) using the complex coacervation technique. Coacervates were produced varying their proportions (1:1, 1:2, 1:3, 2:1, 3:1) and pH between 3.0 and 6.0. Essential oils were characterized by gas chromatography in order to identify their major components (thymol, carvacrol and eugenol, respectively). Analyzes of the minimum bactericidal concentration (CMB) of each essential oil were performed and its mixture analyzed at different concentrations in order to assess synergism. For Listeria monocytogenes, the CMB of essential oils was 0.3125% oregano and clove and for thyme oil was 0.6250%. For Weissella viridescens, the CMB of essential oils were 0.0780% oregano, 0.15625% clove and 0.625% thyme. When mixing the oils the CMB decreased by 50%. The microparticles containing essential oils showed antimicrobial action, showing inhibition halos of up to 22.34 mm. The size of the microcapsules ranged from 0.2 to 1.8 μm. The influence of release in culture medium of Listeria monocytogenes and Weissella viridescens was evaluated and significant release of compounds from the microcapsules was identified from 180 min. There was an encapsulation efficiency of up to 83.5% for Soy protein/gum arabic, 73.97% for Whey isolate/gum arabic and a lower efficiency of 56% for Pea protein/gum arabic. In a second step, 1:1 Soy Protein/Gum Arabic microcapsules with a 1:1 blend of essential oils of oregano (Origanum vulgare), thyme (Thymus vulgaris) and clove (Syzygium aromaticum) (1:1:2) were applied to fresh sausage composed of pork and bacon and inoculated with Listeria monocytogenes. The samples were vacuum packed and stored for 15 days at 7°C, with measurements taken every 3 days. The growth of Listeria monocytogenes was evaluated. From day 6 onwards, a decrease in microbial growth is observed in T1 and T2 and continued growth in T3 and the control. This profile remained until the 15th day with no growth in T2 from the 9th day onwards, indicating elimination of the microorganism and inhibition of microbial growth in T1. Color analysis of L*, a* and b* parameters was performed. Over time, with the release of oils from the microcapsules, there were interactions between the meat and the blend of oils, causing an increase in the red color. In the pH analysis over days T1 and T2, a smaller variation in pH was observed, which gives us evidence of greater stability in storage compared to the other treatments. In general, microcapsules (T2) were effective in inhibiting the evaluated microorganisms and the study contributes to a better understanding of the mechanisms of microencapsulation by complex coacervation applied to food matrices.