Raw milk is the essential element of a cheese's character and good quality milk provides the fundamental basis of a good cheese.
Raw milk produce is made at the milk-producing farm or at village level and, for reasons evidently linked to access and collection, is more common in mountain regions than in lowland areas. The milk must be processed within 12 hours of milking. Using raw milk is the only way to capture the genuine essence of the terroir since it expresses the full richness, character and flavour of the pastures which it conveys faithfully in the cheese.
Pasteurised milk is used extensively today for reasons of cost-effectiveness. Milk is collected across entire regions and stored in refrigerated vats at approximately 4°C. Even at this stage, this cooling alters the balance of the flora naturally present in the milk, to the detriment of the lactic flora The milk is then heated to approximately 72°C for 15 seconds which is enough to destroy all of the active microbial flora as well as other special flora which give a cheese the flavour of its terroir. Pasteurisation is thus used in industrial cheesemaking to extend the shelf-life of products. The art of industrial cheesemaking is therefore to artificially revive "dead" milk.
Micro-filtered milk is purified. The cream is separated and then pasteurised while the milk is filtered through extremely fine membranes which capture bacteria. These components are then mixed together again in varying proportions according to the required result. This process enables some of the milk's flavour to be conserved, however its physico-chemical structure is modified.
Thermised milk is heated to between 40°C and 72°C for 15 seconds in order to destroy certain bacteria which can be pathogenic. The dairy industry uses this method on milk collected across relatively large geographical areas. Variations in flavour and quality are significantly reduced, however, despite the method being less harsh than pasteurisation, the product's character is still partially lost.