Emerging challenges and trends in UHT processing of milk and other dairy products
In order to obtain safe dairy products with a long shelf-life, heating processes have been designed to ensure the necessary inactivation of the indigenous microbial flora. One of the methods is the ultra-high temperature (UHT) processing of milk which has become widespread since the implementation of aseptic packaging processes1. Nowadays, this method is not only used for milk, but it is also applied to a whole range of dairy products with different microbial, physical and chemical properties. Therefore, new challenges for the manufacturers arise as these products require a different treatment to guarantee the safety and quality. UHT processing in general as well as emerging trends and challenges in processing of milk and milk products will be discussed in this article.
UHT processing of milk generally refers to processes that are conducted at 135 to 150°C for 10 to one seconds1,2. In production plants working with direct steam injection, even higher temperatures of 150 to 152°C are used for up to 13 seconds3. In contrast to this, sterilisation of milk is realised at temperatures varying from 109 to 120°C for 40 to 20 minutes2. These two processes are designed in such a way that the destruction of microorganisms of importance (bacterial spores) is the same in both cases as this is essential for the sterility of the final product. However, the effects on vitamins and other substances (e.g., lactose, amino acids) can differ greatly3. Nowadays, with the emerging application of UHT treatments to dairy products other than milk, such as products containing functional ingredients (e.g., infant food), new processing conditions have to be defined.