Thermization

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Some cheeses, including varieties of blue cheese, are made from thermized milk.

Thermization, also spelled thermisation, is a method of sterilizing raw milk with heat. The process is not used on other food products,[1] and is similar to pasteurization but uses lower temperatures, allowing the milk product to retain more of its original taste.[2] In Europe, there is a distinction between cheeses made of thermized milk and raw-milk cheeses. However, the United States' Food and Drug Administration (FDA) places the same regulations on all unpasteurized cheeses. As a result, cheeses from thermized milk must be aged for 60 days or more before being sold in the United States, the same restriction placed on raw-milk cheeses by the FDA.[3]

Thermization involves heating milk at temperatures of around 145–149 °F (63–65 °C) for 15 seconds, while pasteurization involves heating milk at 160 °F (71 °C) for 15 seconds or at 145 °F (63 °C) for 30 minutes.[2] Thermization is used to extend the keeping quality of raw milk (the length of time that milk is suitable for consumption)[4] when it cannot be immediately used in other products, such as cheese. Thermization can also be used to extend the storage life of fermented milk products by inactivating microorganisms in the product.[5]

Thermization inactivates psychrotrophic bacteria in milk, preventing the growth of heat-resistant enzymes[5] and allowing the milk to be stored below 8 °C (46 °F) for three days,[1] or stored at 0–1 °C (32–34 °F) for seven days.[6] Later, the milk may be given stronger heat treatment to be preserved longer.[1] Cooling thermized milk before reheating is necessary for the destruction of bacterial spores. When the milk is first heated, spores begin to germinate, but their growth is halted when the milk is refrigerated. The resulting vegetative bacteria are easier to kill with another heat treatment than the original spores.[6]

References[edit]

  1. ^ a b c Brennan, James G., ed. (2006). Food Processing Handbook. Wiley-VCH. p. 48. ISBN 978-3-527-30719-7. 
  2. ^ a b Rich, Robert (September 5, 2003). "Keeping it raw". The Mountain View Voice (Embarcadero Publishing Company). Retrieved October 23, 2010. 
  3. ^ Fletcher, Janet (July 13, 2006). "Wisconsin's Buttermilk Blue adds pizazz to summer salads". San Francisco Chronicle (Hearst Communications Inc). Retrieved October 23, 2010. 
  4. ^ Baker, John C.; Van Slyke, Lucius L. (December 1, 1919). "A method for the determination of the keeping quality of milk". The Journal of Biological Chemistry (American Society for Biochemistry and Molecular Biology) 40 (2): 373. 
  5. ^ a b Sun, Da-Wen (2006). Thermal Food Processing: New Technologies and Quality Issues. CRC Press. p. 274. ISBN 978-1-57444-628-9. 
  6. ^ a b Early, Ralph (1998). The Technology of Dairy Products (2 ed.). Springer. pp. 13–14. ISBN 978-0-7514-0344-2.