Microbial safety of raw milk cheeses traditionally made at a pH below 4.7 and with other hurdles limiting pathogens growth

Raw milk acid cheeses are manufactured and consumed in some tropical regions in America, North Africa and in the East Mediterranean countries. For tropical cheeses, little information is available on its microbial safety. This review give some insights of the microbiological safety of some raw milk acid cheeses around the world which are traditionally made at a pH below 4.7 and which contain other hurdles which are generally known as limiting factors for pathogens growth. It is described the occurrence of microbial pathogens in acid cheeses; the intrinsic and extrinsic conditions favoring its survival and growth, including pH, moisture, the presence of lactic acid bacteria and temperature. It is reviewed the published information on outbreaks of human illness linked to consumption of the raw milk cheeses made with acid curds. This information is important at epidemiological level because raw milk cheeses with higher pH values are generally known as vehicles of infection. Cheeses with lower pH values might be considered as a low microbial risk group where pathogen might be at a low level of concern. Microbial safety of these cheeses is due to the bacteriostatic properties given by its manufacture peculiarities. Microbial safety of these cheeses may be enhanced by the usage of good quality raw milk and by following good manufacturing practices in the whole process of cheese making to prevent cross-contamination of the product. Some other strategies used to improve the safety level of this kind of cheeses are mentioned.