Microbiological characterization of Fruhe cheese

“Fruhe” is the name of a fresh cheese traditionally manufactured in Sardinia (Italy) from sheep or goat milk. When the cheese is stored for long time in brine it is called “Merca”. The Fruhe is a fermented curd characterized by a compact coagulum, a white shining paste and a soft texture. The taste is slightly sour and aromatic. The Fruhe is manufactured from whole milk, raw or heat-treated, deriving from Sardinian farms. It is produced using the following general manufacturing process: - the milk, brought at 36-38 °C, is inoculated with autochthonous lactic acid bacterial (LAB) cultures and coagulated with calf or lamb liquid rennet; - this milk is now distributed in plastic containers that can have a variable volume; - the cheese ripening takes place in 12-24 hours; - the coagulum within the container can be cut in cubes of approximately 4 cm and the whey is usually partially discarded; - the cheese is stored at 4 °C. In the present study we investigated the microbial populations associated with this traditional product. For this aim twenty samples of Fruhe, manufactured from sheep and goat milk by using different cheesemaking technologies, have been investigated. Microbiological analyses showed that total mesophilic bacteria counts of Fruhe samples were between 1.00E+06 and 2.70E+09 CFU/g. Lactobacilli and lactic streptococci were constantly present in a 1:1 ratio and in a few samples they reached significant numbers (around 1.00E+09 CFU/g) while in general the size of these populations was more limited (around 1.00E+06 CFU/g). This was attributed to an excessive acidification and post-acidification of the cheese. It is important to mention that the presence of a suitable number of LAB (at least 1.00E+07 CFU/g) is crucial for the nutritional quality of fresh dairy products. The presence of total coliforms and coagulasenegative staphylococci was limited and related to some extent to the reduced number of LAB in most of the samples. Heterofermenting LAB, faecal coliforms and coagulase-positive staphylococci were always absent while yeasts were isolated only from three Fruhe samples. The study showed that lactic microflora associated to Fruhe cheese was substantially homogeneous in all the samples analyzed. However, the number of LAB was globally low in the majority of samples and quite different from other fresh cheeses