One of the types of packaging that is used in the industry is metal cans, including cans, which have found many different uses today and are used to pack all kinds of food, from fish to beans.
The science used in the packaging industry is to store food in packages that have the ability to store food for a long time without changing its taste and color, or harm and disease to humans.
These metal cans are covered with a layer of polymer material so that no chemical combination is created with the food inside the can, because the food has a high acid strength and accelerates the development of corrosion with the metal body of the can. Corrosion of the metal leads to the leakage of the contents inside the can and finally the spoilage of the food inside the can. The polymer coating that covers these cans prevents chemical reactions between the food and the metal body of the can.
Features of metal cans
Cans are a type of food packaging that can preserve food for a long time. One of the most important advantages of metal cans is its high impact resistance. Also, these cans prevent oxygen and moisture from reaching food and do not spoil in hot weather. The most important feature of these cans is that it prevents the migration of polymers; For this reason, cans are widely used in the packaging industry today.
Cans can prevent tin from entering the contents of the can. Of course, the amount of tin in food depends on the following:
Lacquered cans containing tin
The presence of oxidizing agents or corrosion accelerators such as nitrates
Filled product acidity
Of course, in addition to tin, other heavy metals that are present in aluminum cans may have the possibility of entering the food, so the cans should be carefully examined.
A research has been done on 40 samples of canned cans, during which the quality of the internal coating of the samples has been examined to determine whether these coatings are in accordance with national standards or not. that during this research, the coverage of 4 of these samples was not of the required quality and was not approved by the standards.
Since the use of these cans in the food packaging industry, which is supposed to have a long shelf life, has become very widespread, so it is necessary to ensure that they are healthy in terms of not being contaminated and heavy metals not entering into the can, especially tin. The basis of the ingredients of canned food should always be taken into account and be able to comply with national standards.
Tin can rust
Many things should be taken into account in making these cans. Among other things, you should pay attention to the suitability of the body of the can with the food it contains; Because there may be reactions between them that eventually cause the inner body of the can to rust. It is also possible that when filling these cans with food, oxygen has entered inside them, which eventually causes rusting of its inner surface and causes microbial and chemical interactions of food, and finally the smell and taste of the food inside. change that these items appear immediately after opening the can.
How to detect the air inside the can
In the process of producing cans, there is a device that is related to some kind of pressure and is called a baroquiometer. This device has a relatively thick needle with a hole in the middle and a special rubber washer is placed in the place where it is connected to the body of the can. During the test, the needle is inserted into the head or the bottom of the can with great pressure.
At this time, if there is any type of gas or oxygen inside the can, the needle is inserted into the pressure gauge through the hole, and the hands that are installed there show its amount. In this case, if the material inside the can has a vacuum, the amount of vacuum can be measured by pulling the air inside the tool into the can. Canned cans, if they are healthy, should not have any pressure and the amount of vacuum varies according to the type of product and the size of the can.
Changing the color of the contents of the can
There are many factors that can lead to a change in the color of a metal can, the most important of which is the presence of metal ions such as iron and copper, which, due to the high temperature of sterilization, leads to a change in the color of the material inside the can. Heat causes the release of sulfur from sulfur proteins, and then this sulfur is combined with copper or iron and leads to the production of iron or copper sulfur. Iron sulfur in some canned goods such as corn is not desirable at all. And in some protein products such as meat, chicken, fish, etc., the ion acts in the opposite way and causes these materials to become colorless.
Another reason for the change in the color of the contents of the can can be due to the activity of microorganisms, which in materials such as peas and green beans, corn and fish, turn their color back to black.
Chemical tests of cans
It is possible that in the process of producing canned goods, Bacillus and Clostridium species, yeasts and molds have not been destroyed and then grow and reproduce and decompose the materials inside the can and finally lead to adverse changes in the product that can be measured by measurement. identified the metabolite of these bacteria. These bacteria can exist in the raw materials of the contents of cans or can be created during the canning process. For whatever reason they have arisen, they must be detected during tests, before the end of the production process and before it reaches the consumer.