Have you ever wondered why UHT products have a shelf life of only three months even though it's completely sterile (free from microbes and its spore) ??
The shelf life of UHT products is not only limited to microbial spoilage. The spoilage of UHT products also happens in physical means.
These spoilage includes
- development of rancid/bitter flavour,
- sediment and separation of ingredients,
- proteolytic and lipolytic activity facilitated by the bacterial enzymes (basically from psychotrops) and native enzymes Ex.plasmin (native proteolytic enzyme in milk)
- colour changes
- gelation caused by enzymes.
- destruction of vitamins over time.
Figure. Sedimentation of UHT milk in the package.
Ocassionly, the survival of thermoduric spores during UHT processing also germinate over time and also spoils the UHT product. Clearly, this issue comes with quality of UHT processing equipment and raw milk quality.
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