10. Safety issues in the production of cheeses from raw milk and natural starters

Raw milk cheeses are widely produced in Europe, particularly in France, Italy and Switzerland and in many regions of the USA. These cheeses are artisanal products, linked to specific geographical areas, and are characterised by unique textural and sensory qualities. The use of raw milk and natural starters requires careful attention to the cheesemaking process to ensure a good quality product. Cheeses can be contaminated with pathogenic microorganisms if these organisms are present in the raw milk used in the manufacturing of cheeses and are able to survive the cheesemaking process. The unique characteristics of each specific cheese variety can affect the growth and survival of microbial pathogens. However, a combination of parameters, including the use of lactic acid bacteria starters, pH, water activity, salt content and temperature, interact to produce cheeses that are microbiologically safe. The content of this chapter provides some insights into the microbiological safety of raw milk and raw milk cheeses. It describes the occurrence of microbial pathogens in raw milk and cheeses made of raw milk and the intrinsic and extrinsic conditions that favour their survival and growth. The microbial safety of these cheeses may be enhanced by the use of high microbiological quality raw milk and by following good manufacturing practices throughout the whole cheesemaking process to prevent the crosscontamination of the product.