Effect of Brazilian green propolis on microorganism contaminants of surface of Gorgonzola-type cheese.

Blue cheeses are susceptible to yeast and bacterial growth on their surface, which causes spoilage during ripening process and the formation of slime. The dairy industry frequently control the proliferation of undesirable microorganisms with natamycin and high salt concentration. The green propolis is a complex of substances that presents antimicrobial properties with great potential as preservative in the food industry. The aims of the present study were to identify the mesophilic aerobic microorganisms present on the surface of Gorgonzola-type cheese, evaluate the antifungal and antibacterial effects of the ethanol extract of green propolis (EEP) on the development of those microorganisms and verify the effects of EEP on the sensory quality of cheese. Ten yeast species belonging to genera Yarrowia, Candida, Debaryomyces and Saccharomyces were identified, as well as seven species of bacteria belonging to genera Staphylococcus, Bacillus, Enterococcus, Corynebacterium and Proteus. The EEP showed minimum biocide concentration (MBC), between 0.3% (weight/weight) and 5% for Bacillus cereus and Proteus vulgaris, respectively. Saccharomyces cerevisiae was the most sensitive species (MBC of 0.63%) and Candida parapsilosis the most resistant one (MBC of 5%). In the sensory analysis, the cheeses involved with EEP at 5% concentration did not differ from the control, while at 10%, there was a slight decrease in acceptance. The EEP has potential and feasibility to be used in Gorgonzola-type cheese, inhibiting the main bacteria and yeasts without affecting largely the sensory characteristics of the product.