**7.3 Canned food products**

The practice of preservation of vegetables and fruits by drying or salting can be traced to prehistory. Today, major processes for food preservations are cooling, freezing, dehydration, candying and canning. The main concern is for food quality, conservation and the prevention of spoilage. For cans fabrication is used tin one of the oldest available metals with a non toxic nature. The cans have been made from tin since 80 years ago when refrigeration of food was not easily available. According to their convenience the use of cans has been focused on food and beverages dispensers creating an intense competition between manufacturers not only for tinplate cans but also other materials, notably chromized steel, aluminum alloys and polymers.

Modern tinplate for cans is getting by continuous electrodeposition on steel strips, chemical conversion coating and finish polymeric coating. The manufacturing is made following three different types classified according to the methods of fabrication: a) The three piece can, b) The two piece draw/redraw (DRD), and c) The draw/wall ironed (DRW). In all of them the tinplate process is customized to economize and fulfill the requirements for corrosion resistance, filling and mechanical properties.

Aluminum cans are also widely used as containers for pressured beverages which are designed to have a minimum of material at the strength required for operation. The walls acquire rigidity by effect of the internal gas pressure from the content, but the bottom base support and the top are made from thicker metal and formed into an internal dome.

The processed fruits and vegetables are hermetically sealed and sterilized by heat and stored in glass jars and aluminum or coated steel cans. Sterilized canned food, include all types of vegetables under acidic or salty conditions and fruits in acidic, sweet syrup. The canning process consists of several stages: vegetable and fruit cleaning, filling the containers, closing and sealing, sterilizing the canned product, labeling and warehousing the finished goods. All these operation, carried out under excessive, humid conditions; require corrosion resistant equipment and machinery, currently fabricated from SS such as S30400 and S31600.
