Milk is made shelf-stable (refrigeration not required for storage) by it at a higher temperature. Which is called ultra-high temperature pasteurization, or UHT pasteurization. ... Another thing that makes aseptic milk last on the shelf involves the sterile packaging and sterile environment in which the packaging happens.

Is ultra-pasteurized bad for you?

The sad part is when milk is treated at such a high temperatures, it doesn't only kill harmful pathogenic bacteria, that the milk may have, it also kills the healthy bacteria in milk. Not just bacteria, ultra-pasteurization degenerates sugar, protein, enzymes, and vitamins in the milk.

What's the difference between pasteurized and ultra-pasteurized?

The main difference between Ultra-Pasteurized and normally pasteurized milk is the temperature it's heated to. It's heated to 280°F at the minimum, which means that it's able to kill almost all of the bacteria that the normal pasteurization process may have missed (Keyword here being almost—it's not sterile.).