The material used in a metal container is selected so that it is compatible with the product it will contain. The characteristics of the different products packaged in metal boats are very varied, and each of them has its own peculiarities. Hence, the choice of raw materials for the manufacture of packaging, must aim to give the recipient the best qualities of resistance to the product. Conversely, the container can also have a negative effect on the product, if the materials are not suitable to prevent interactions between product and container.
RELATIVE ACIDITY (pH)
One of the first factors to take into account the product is the “pH”, or the relative acidity of the same. The product may be too acidic, such as orange or lemon, or very alkaline, such as lyes and cleaners, or have an intermediate pH between these extreme values. Depending on the degree of acidity or alkalinity, the container may require different types of interior coatings of varnish, to avoid a chemical attack of the container.
The color of the product can be an important factor to consider. For example, if the color is a red or a deep blue, a varnish that acts as a curtain or barrier will be required to prevent the Tin Tin from discoloring the natural color of the pigment of the packaged product. Fruits of a lighter color such as apples, pears, etc. they retain their tonality, even when the body of the container is not varnished inside. Certain products included in the category of low acidity, such as vegetables, meat and fish, which are subjected to a heat treatment to preserve and sterilize them commercially, require a special interior coating called the “C” type, to prevent the appearance of dark spots of sulfur in the container and in the same product.
The products that are packed in metal cans are classified when defining the container in two large groups: food – or food – and non-food. Food products are classified as processed and unprocessed. The process involves subjecting the product to a thermal treatment immediately after filling and closing the container, to destroy the microorganisms that cause the decomposition. Processed packaged foods can be closed under an atmospheric, vapor or vacuum environment. Unprocessed foods can be closed under atmospheric, vacuum, or gas conditions.
Non-food products are inedible products that are packed without heat process, and can be closed under any of the above conditions, depending on their characteristics.
Processed foods not only require the container to be perfectly hermetic, to keep the product sterile and intact after the heat treatment, but it also requires that the container is strong and rigid enough to withstand the internal pressure generated during the sterilization process .
The operation of “packaging” a perishable food product involves applying a heat sterilization treatment to it. The containers used for this are mostly cylindrical and receive the generic name of “sanitary containers”. The most common examples of products packaged as processed foods are fruits, vegetables, legumes, meats, fish, dairy products, etc.
They do not require a heat process to sterilize them and “keep them”, although they may be subject to some deterioration due to factors such as time, temperature … These foods are relatively stable, and can be resistant to deterioration caused by microorganisms and enzymes. To differentiate them with processed products, they are usually designated as “packaged” and not “packaged” products. The containers they use do not need to withstand high internal pressures, and are commonly classified as “general line” packages, which cover a variety of very different shapes and sizes. Examples of unprocessed foods are: nuts, coffee, edible oils, pasta and biscuits, butter, etc.
Non-food products are generally products for the home, automotive, agriculture, and industrial, usually packaged in non-hermetic containers that do not require sterilization. For its conservation, containers of general lines are used that have different forms, measures and characteristics. They are differentiated according to their destination, by the manner of opening, emptying, transport, possibility of being closed again when their use is partial, etc.
Examples of non-food products packaged in many different forms are, among others: paints, adhesives, automotive products, cosmetics, insecticides, medicines, chemical products, greases, inks and varnishes.
STANDARD AND FORMULATED PRODUCTS
Another way to classify the products is to divide them into three large groups: standard, standard formulated and formulated.
Standard products are consistent or uniform in their form and content universally, and therefore are fairly stable in the requirements of the container that must contain them. Natural foods can be considered standard products.
The formulated products are mixtures or mixtures such as sauces, which may have different ingredients in varying proportions in each case and according to a particular formula.
The formulated standard products are a combination of a standard product and another formulated such as “tuna in sauce”. The formulated products are a concern for the packaging supplier, since small differences in the formulation of the contents or a change of supplier of any of the ingredients, can be the cause of alteration of the required specifications of the container for a given product.
The containers are designed not only to take into account the characteristics of the product, but also the regulations and governmental dispositions of each country, the different methods of sterilization, the conditions of storage and handling and the high production speeds.
The ideal container is one that is strong enough to protect its contents in its useful life, in addition to light and resistant, as simple as possible to manufacture in desired shapes and measures, air and water tight, pleasant in appearance, easy to open, economical … The sanitary containers must also be able to withstand the pressures and temperatures of the process. As a rule of thumb the container must always meet the needs of the product to be contained.
The manufacturers of containers usually have lists of where they relate, depending on the product to contain, the characteristics of the suitable container: metal thickness, minimum tin coating, interior varnishes, compound … It also influences the cover / fund profile employed and the type of corded body. To which you can add a series of supplements depending on their use, such as opening, handle, neck, key … These lists are fruits of experimental packaging in the laboratory corroborated by the experience during years of activity.
All the materials are subject to a certain degree of deterioration and attack during the service they perform over a period of time, the basic idea is to build a container of reasonable duration through the correct selection of materials, which should comfortably cover the legal provisions on the shelf life of preserves.