Today, more and more traditional grocery stores, including most organic milk, are over-pasteurized. The official definition of ultra-pasteurized dairy products stipulates that “such products should be heat treated at 280°F or above for at least 2 seconds before or after packaging in the Milk Production Line to produce a longer shelf life under refrigeration conditions. The product.” Confusingly, ultra-pasteurized milk is often referred to or marked as ultra-high temperature. It is high temperature processing that extends the shelf life of milk (ESL).
Why does the processor accept ultra-high temperature milk? Because today’s milk is no longer a local product; it is processed in large processing plants and shipped to all parts of the country. When packaged in a sterile container, the ultra-high temperature milk remains stable for up to six months at room temperature. It has a shelf life of up to 50 days in standard packaging (eg plastic bottles) – enough to be transported nationally or internationally and sold to customers away from the milk producing area.
In the commercial processing of ultra-high temperature milk, the raw milk is first preheated to 176-194 degrees Fahrenheit through a UHT Milk Machine, and then one of two heating methods is used: direct heating or indirect heating. In the direct method, milk is injected into superheated steam, or milk is sprayed into the steam. This immediately increased the temperature of the milk, but also slightly diluted the milk. When the milk is subsequently cooled in the vacuum chamber, excess water is removed. Indirect heating is achieved by contacting the milk with a superheated metal plate heated by steam – thus, the steam „indirectly” heats the milk. Some new systems combine these two processes.