Accordingly, there can be numerous combinations of time and temperatures for heat treatment to preserve the nutritional value of milk, different types of low-temperature pasteurization are commonly used onsite, such as vat pasteurization or low temperature, long time pasteurization (63°C for 30 min), HTST pasteurization (72°C for 15 s), and higher heat, shorter time pasteurization.
The long hold or vat pasteurization is a batch type method where the pasteurization is carried out at 63°C for 30 min.
The vat pasteurizer jacket is a double-walled covering. In the space between the walls, circulating water which heat the product in the vat. This unit is made up of the following sub-component parts, milk tank, water jacket, coil heater milk inlet and outlet valve, water inlet and outlet valve and insulation case.
Types of vat pasteurizers (Classification based on flow of heating medium)
1. Spray type – (A film of water is sprayed from a perforated pipe over the surface of the tank)
2. Flooded type
3. High velocity flooded type
Study demonstrated that vat pasteurization was an efficient and mild means of milk preservation resulting in only minor changes to the metabolites (J. Dairy Sci. 103).
In vat pasteurizers, an electric or air operated control can be connected with a timing clock so that the heat is shut off when the proper milk temperature has been reached and a bell rings when the proper length of holding time has elapsed.
Vat pasteurized milk tastes fresher, thus providing a taste similar to raw milk without the health concerns. It is reported that vat-pasteurized milk has become popular again as more small dairy processors are using it to appeal to customers seeking a more “farm-fresh” milk.
Milk vat pasteurization
