Proteolytic potential of psychrotrophic microorganisms isolated from fresh cheese

Abstract

Given the economic importance of the dairy industry, product quality should be a constant concern. Some sensorial and technological properties of milk and dairy products are related to the spoilage contaminant microbiota, which is mainly represented by psychrotrophic proteolytic bacteria producing thermoresistant enzymes. Fresh artisanal cheeses are generally produced with raw milk, so it is of great importance to know the microbiota of these products. Therefore, the objective of this work was to count and isolate the psychrotrophic proteolytic bacteria and to evaluate the spoilage potential of these microorganisms isolated from fresh cheeses handcrafted and commercialized in Salinas, MG, Brazil. After the isolation of psychrotrophic proteolytic bacteria present in fresh cheese, the isolates were characterized in terms of Gram staining, shape, and oxidase activity. The proteolytic activity of the isolates was confirmed by a spot halo test using specific agar. The results highlighted the predominance of Gram-positive psychrotrophic proteolytic bacteria when the spoilage microbiota of the fresh cheese samples was evaluated. Considering the proteolytic potential, 34% of the isolates were considered highly proteolytic. The results showed that the initial contamination of fresh cheeses may interfere with the microbiological quality of these products.

Keywords

• proteolysis
• spoilage
• quality
• raw milk.