There are systems for processing canned foods at high temperature for short times. These are referred to as HTST or High Temperature Short Time processes. In such system, commercial sterilization is achieved at temperatures of 280 – 300 F. Large discrete particles cannot be processed by High Temperature Short Time methods because they require some time for heat to penetrate their centers. HTST methods are applied only to liquids, and to foods that have been pureed (mashed bananas, concentrated pea soup, etc). There are five main ways to preserve foods and remove microorganisms:
Chemicals
Drying
Refrigeration
Canning
Radiation
The History of HTST
The process of pasteurization was named after Louis Pasteur who discovered that spoilage organisms could be inactivated in wine by applying heart at temperatures below its boiling point. The process was later applied to milk and remains the most important operation in the processing of milk.There are various methods of pasteurization. In early 1900’s a batch method as used where a tank of milk was held at 145 degrees for 30 minutes. Pasteurization did not sterilize the milk and it still needed to be refrigerated afterwards. It did greatly reduce the number of bacteria in the milk so the chance of bacterial illness was minimized and the shelf life of the milk was increased. High Temperature Short Time continuous processes were developed between 1920 and 1927 and for some time the ability of the HTST process to produce safe milk was questioned.
There is also a UHT (ultra High temperature) method where the milk is heated well above boiling under pressure for just a few second. This product is essentially sterile and does not have to be refrigerated until it is opened. For most continuous processing, a high temperature short time pasteurizer is used. The heat treatment is accomplished using a plate heat exchanger. High Temperature Short Time Process
