According to the EU regulations, thermization is a sub-pasteurization treatment, performed under mild conditions (i.e., 57–68 °C for no less than 15 s in a heat exchanger), so as to guarantee the preservation of phosphatase activity and, consequently, part of the indigenous microbiota.
Thermization targets pathogenic bacteria while leaving the good bacteria in the product. The low temperatures do not alter the structure and taste of the product. It is used as a pre-pasteurization treatment of raw milk to safeguard milk quality during prolonged storage in insulated silos.
The process is also used as a post-pasteurization treatment of dairy products. The treatment always causes the elimination of psychrotrophic bacteria and the reduction of total bacterial count, enabling thermized milk to be stored for up to 3 days longer at 8 °C.
Psychrotrophic bacteria grow at less than 7°C. Common species in cold stored milk, which is the storage norm in most jurisdictions, are Micrococcus, Bacillus, Staphylococcus, Pseudomonas, Flavobacterium, and coliforms.
Thermization process
