[Insight] What is canned food sterilization?
For the production of canned food -vegetables or animals- to be generated under good safety conditions and also these can be preserved at room temperature, they need to be sterilized. In addition, in the majority of regulatory bodies in all countries, the sterilization of food by autoclaving is a legal requirement to produce and market canned food.
Canned food sterilization, also known as commercial sterilization, is a physical technique of preserving food that is hermetically packaged in a container and subjected to high temperatures for a time to completely destroy its microorganisms, pathogens or not, and spores.
We say that it is a physical method because it does not use gases or reagents (chemical sterilization).
Thanks to this complete eradication of any bacteria or fungus, the life of sterilized products significantly lengthens, which can be more than four months and, in addition, they do not require cold storage.
Unlike pasteurization, sterilization removes all types of microorganisms and spores. Pasteurization only removes most microorganisms and does not remove spores. There is confusion between both techniques when we talk about microorganisms or temperature.
Sterilization without altering the product
However, the use of high temperatures in sterilization can affect the quality of the product, reducing its nutritional value by destroying some vitamins and aromas. It can also produce some organoleptic change such as color and flavor alterations.
In order to minimize these possible losses as much as possible, it is essential to play correctly with the parameters of exposure time and temperature. And for that, you must take into account:
Characteristics of the food
Although all the particularities of an ingredient: shape, length, width and composition count when sterilizing. The level of acidity, the pH, is the most important element, since it determines the viability in the product.
Foods with a neutral pH (> 4.5) are usually sterilized at temperatures above 100º, because in products with an acidic pH, microorganisms cannot grow or are more sensitive to heat treatment and, therefore, lower temperatures are used. at 100ºC.
The type of packaging
The container also plays an important role when it comes to preserving food. The material with which it is made, its porosity, shape and morphology of the closure are decisive to guarantee the quality and useful life of the product, avoiding its possible subsequent oxidation.
All kinds of meat, fish, vegetables and fruits are usually sterilized. In jams, syrups, pickles, creams, soups, sauces and stews among others.
The method most used in the sterilization of canned foods is humid heat, which uses steam to transfer thermal energy and eliminate microorganisms. This is a system with a short cycle due to the great heat transfer capacity of water vapor.
The sterilization process
Sterilization of food by autoclaving is structured in three phases:
- Warm-up phase : in which the temperature of the water and the product increases from room temperature until the food reaches the preprogrammed sterilization temperature.
- Sterilization phase : The sterilization temperature is maintained steadily for the preprogrammed sterilization time.
- Cooling phase : At the end of the sterilization phase, by means of a cold water shower, the chamber of the autoclave is filled with water to cool the product and stop the cooking process.