What Is Ultra High Temperature (UHT) Processing Of Milk_
                     What Is Ultra High Temperature 
(UHT) Processing Of Milk?
Ultra high temperature, also known as UHT, in which milk is ultra-pasteurized and 
packaged in sterilized containers. It’s natural milk, just like you purchase at the dairy 
store; however, the unique packaging and pasteurization process makes it have a 
shelf-life of some months.
While most milk goes through a standard pasteurization process, UHT milk goes 
through ultra high temperature pasteurization, which safely heats the milk to a 
higher-than-usual temperature and kills the milk’s harmful bacteria. It is then packed 
in sterilized containers, also called aseptic packaging, which keeps the milk fresher 
for longer.
UHT milk may be kept in the fridge for three months, but it depends on the brand. 
When the container is opened, the milk must be refrigerated and have the same 
shelf-life as any other kind of milk (7 to 10 days).
The UHT Process
The most critical steps of the UHT process are as follows: 
● Heating, with or without waiting the time
● Homogenization (for indirect systems)
● Heating to the temperature of sterilization
● Sterile temperature is maintained.
● Initial cooling
● Homogenization (alternative for direct or indirect methods)
● Final cooling
● Aseptic packaging
The preheating phase increases temperatures from ~ 5°C to ~90°C using the hot milk post-
sterilization process. In certain plants, the milk is held for a certain period in a holding tube 
following preheating, e.g., for 60 seconds at 95°C. The primary purpose behind this is to 
minimize the risk of fouling or deposit creation in the subsequent heat exchangers. However, 
it could also significantly affect the overall quality due to the inactivation of a natural milk 
enzyme.
The last heating step required to reach the necessary sterilization temperature can be 
accomplished through one of two main kinds of heating methods referred to as indirect and 
direct systems. Direct methods heat the milk via direct contact with superheated culinary 
steam. At the same time, indirect systems utilize heat exchangers where superheated steam 
heats milk indirectly via the stainless steel barrier in the form of an elongated tube or a plate. 
Once the temperature for sterilization is achieved, the milk goes into an insulated tube. 
The temperature of the milk and the length of time needed to pass through the hold tube 
is the normative condition that is typically cited in the UHT procedure, e.g., 140°C for 5 
minutes. 
In natural systems, the initial coolant of the milk happens exceptionally quickly when it is 
pumped through a vacuum chamber, which, in turn, reduces to the original temperature 
generally around 75°C. In the last cooling step, directly-based systems, and both cooling 
stages for indirect methods, the heat generated by heated milk gets transferred into cold 
milk during the preheating or heat regeneration processes.
A homogenization process is also included in the ultra-high temperature pasteurization if 
fat is present within the product. The process is completed at 60-70°C, either before and 
after the sterilization stage. It puts enormous pressure on plant operators to ensure that 
the homogenizer is sterile. That is why, if feasible, homogenization must be done before 
the sterilization process. It is known that milk produced by directly heating processes 
needs to be homogenized downstream to break down the aggregates of protein that 
form in the healing process, causing an unpleasant taste in the milk.
The process of packaging aseptically is an essential step. The product must be moved 
from the cooling point to the packaging and then sealed in the packaging. Different 
packaging types are readily available, but the most commonly used are multilayered 
plastic and paperboard. The packaging is sterilized before filling.
Contact Details
MicroThermics, Inc. 3216-102 Wellington Ct.
Raleigh, NC 27615, USA
Phone: +1 919 878 8045
Fax: +1 919 878 8032
Email: [email protected] 
Website : https://microthermics.com