Advantages of UHT

High quality:

The D and Z valves are higher for quality factors than microorganisms. The reduction in process time due to higher temperature (UHTST) and the minimal come-up and cool-down time leads to a higher quality product.

Long shelf life:

Greater than 6 months, without refrigeration, can be expected.

Packaging size:

Processing conditions are independent of container size, thus allowing for the filling of large containers for food-service or sale to food manufacturers (aseptic fruit purees in stainless steel totes).

Cheaper packaging:

Both cost of package and storage and transportation costs; laminated packaging allows for use of extensive graphics.

Difficulties with UHT

Sterility:

Complexity of equipment and plant are needed to maintain sterile atmosphere between processing and packaging (packaging materials, pipework, tanks, pumps); higher skilled operators; sterility must be maintained through aseptic packaging

Particle Size:

With larger particulates there is a danger of overcooking of surfaces and need to transport material - both limits particle size.

Equipment:

There is a lack of equipment for particulate sterilization, due especially to settling of solids and thus overprocessing

Keeping Quality:

Heat stable lipases or proteases can lead to flavour deterioration, age gelation of the milk over time - nothing lasts forever! There is also a more pronounced cooked flavour to UHT milk.