Downdraft heating
Downdraft heating , also known more generally as downdraft process, is a special steam injection process for the production of milk with an extended shelf life (so-called ESL milk ). It is closely related to pasteurization and is viewed by some as a further development of it. A striking distinguishing feature is the use of higher processing temperatures, which is why one speaks here of milk that has been pasteurized by high heating.
The downdraft heating owes its name to the way the material is processed. The milk is fed through a distributor (from above) into an overpressure chamber, where it is heated to a temperature of 125 to 135 ° C by steam for about 2 seconds. In the lower part of the chamber, the milk is again separated from the steam and then cooled to 5 ° C.
The aim of the process is a longer shelf life milk whose organoleptic and nutritive properties (the properties of taste and nutritional value) correspond to those of conventionally pasteurized fresh milk. For this purpose, at least equivalent and sometimes even higher quality requirements are placed during the entire processing and storage process. One problem with this process, however, is that the milk must be thoroughly "degassed" after it has been heated. H. freed from the oxygen that was absorbed by the milk through the steam injection and which greatly contributes to the vitamin breakdown during prolonged storage.
From a sensory point of view , the "longer fresh " milk can be classified between pasteurized fresh milk and long -life milk (UHT milk).
However, it is controversial in the EU whether milk treated by downdraft heating is to be equated with pasteurized fresh milk under food law. Some countries such as B. Austria or Italy stipulate a use-by date of no more than five days after the filling date for pasteurized fresh milk. Otherwise the milk should not be marketed under the label "fresh". Germany, on the other hand, makes an explicit distinction between pasteurized fresh milk and milk that has been pasteurized through high heating. The latter can also carry the imprint “fresh” on the label, but is characterized by a shelf life of 15 to 20 days.
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- ↑ Archive link ( Memento of the original from March 6, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Eberhard, P .; Bütikofer, U .; Sieber, R. Vitamins in Stored Superheated Milk. Publication by the Agroscope Liebefeld-Posieux ALP research institute (Swiss federal authorities)
