Ação antimicrobiana da própolis verde em microrganismos isolados e identificados na superfície de queijo tipo gorgonzola

Abstract

The objective of this work was to isolate and identify aerobic mesophilic microorganism contaminants of surface of Gorgonzola cheese, to evaluate the effect of the ethanolic extract of green propolis on bacteria and yeasts isolated from the surface of Gorgonzola cheese and to evaluate sensorially cheeses with the application of ethanolic extract of green propolis on the surface. Adequate dilutions of the samples were inoculated in media DRBC (Dichloran Rose-Bengal Chloramphenicol) and agar nutrient, for yeast and bacteria respectively. The identification was performed by MALDI-TOF (Matrix Assisted Laser Desorption Ionization – Time of flight) technique. In order to evaluate the inhibition of the green propolis extract, the test of MBC (minimum biocide concentration) was carried out in all species of the microorganisms isolated from the Gorgonzola cheese surface. The characterization of the propolis extract was performed by physical-chemical analysis and for crude propolis, gas chromatography to identify volatile compounds. For sensory evaluation, a multiple comparison test and acceptance test were performed at the concentrations 5 and 10% of the ethanolic extract on the cheeses surface plus control treatment. It were identified 10 species of yeasts belonging to four genera (Yarrowia, Candida, Debaryomyces and Saccharomyces) and seven bacterial species belonging to five genera (Staphylococcus, Bacillus, Enterococcus, Corynebacterium and Proteus). The ethanolic extract of green propolis presented an inhibitory effect in bacteria, being Bacillus cereus the most sensitive (0.31% MBC) and the most resistant Proteus vulgaris (MBC of 5%). The yeasts showed more resistance to the action of the propolis extract, being the species most sensitive Saccharomyces cerevisiae (MBC of 0.63%) and Candida parapsilosis the most resistant (MBC of 5%). The propolis extract showed high biocide activity on the microorganism inoculated on the surface of cheese. The multiple comparison test presented significant differences of the cheeses smeared with extract of propolis on the surface in relation to the control treatment. The acceptance test showed that the application of extract of propolis in 5% (g/g) did not differ to control, while the 10% (g/g) concentration brings a little worsening in acceptation. The green propolis extract has potential and viability for use in Gorgonzola type cheese, inhibiting the main bacteria and yeasts with no disadvantage the sensorial characteristics of the cheese.