Canned foods’ long shelf life is due to a method of canning known as appertization. It is one of the most widely used methods for food preservation.
Heated and stored in anaerobic conditions, the appertization process is sufficient to destroy pathogens as well as any potential spoilage organisms that may be able to grow in the can's contents during storage. This is often referred to as “commercially sterile” since the process is not designed to completely sterilize the food but only to render it safe and microbiologically stable. However, the present appertization processes may have a serious effect on the nutritional content and sensory characteristics of some food. This is particularly relevant for heat sensitive food ingredients that may be severely damaged under these conditions and results in reduced product quality.
A solution to this problem is the use of an ultra-high temperature (UHT) process where food is heated quickly to temperatures in the range of 135 to 150 degrees Celsius for a few seconds and then cooled rapidly to ambient temperature. This has the same effect on the microbial population as a conventional canning process but with less effect on the sensory and nutritional qualities of the food, which are much more sensitive to the duration of the process than to increases in temperature.
The commercial sterility of the finished UHT processed product depends on excluding microbial contamination from two sources:
In today’s advanced UHT food manufacturing plants, sterility is achieved by a robust process design and by HACCP-based controls instead of routine microbiological testing of finished products. Commercial sterility testing continues to play an important role as a verification tool to demonstrate that the process and its controls are effective.
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