Populations, types and biochemical activities of aerobic bacteria and lactic acid bacteria from the air of cheese factories

Abstract

This investigation was carried out in order to identify the airborne bacteria in the processing rooms of two creameries that make, mainly, feta cheese and study some of their biochemical activities. Our results suggest that the numbers of airborne micro‐organisms may differ between plants, and the same was observed with the predominant types. The bacteria isolated were primarily Gram‐positive, catalase‐negative cocci, micrococci and bacilli. The predominant lactic microflora were lactococci and mesophilic lactobacilli, commonly found in feta and other traditional Greek cheeses. A significant number of aerobic bacteria could grow at 4°C and in 6.5% NaCl. In addition, both aerobic and lactic acid bacteria (LAB) exhibited acidifying and proteolytic activities. Slow‐ and medium‐acidification ability of LAB strains were found. There was also a tendency of the strains to preferentially degrade αs‐casein. The amounts of amino acids accumulated in the milk were strain dependent. Therefore, there is a possibility that airborne bacteria contaminating cheese milk in the open vats may multiply and contribute to the ripening changes in the cheese.