The packaging of food is an essential medium for preserving food quality, decreasing the wastage of food and also reducing preservatives used in food. And printing inks play a critical role in food safety as it may come into contact with food due to ink migration or the nature of packaging. In this article we will discuss factors that need to be taken into consideration before deciding upon the type of ink for printing on the packaging.
Food packaging must be manufactured such that it does not transfer its constituents to the packed foodstuffs in quantities which could endanger human health, cause an acceptable change in the composition of the food or inadvertently affect foodstuffs in terms of odour and taste. Depending on the type of food being packaged, the food packaging is of mainly two types:
- ASEPTIC PACKAGING
Aseptic packaging is a specialized manufacturing process in which food, pharmaceutical, or other contents are sterilized separately from packaging. The contents are then inserted into the container in a sterile environment. This method uses extremely high temperatures to maintain the freshness of the contents while also ensuring that it’s not contaminated with microorganisms. It is mainly used for packaging foods such as:
Drinkable products containing milk
Processed foods that require long periods of preservation time
- FLEXIBLE PACKAGING
Flexible packaging is a non-rigid package that can take on any shape. Like bags, it protects the contents from the environment and extends their shelf life. The examples of flexible packaging are bagged salad varieties, wrappers for candy or bars etc.
Printing on packaging
The food industries are interrelated with all components like food production, packaging and marketing. Although packaging does play a major role in sales, an appealing design, color scheme and labelling on packaging are as significant when it comes to drawing customer attention to product. Printed food packaging does provide the consumer with related and legally required information of the product such as weight, manufacturer details, ingredients, nutritional details to name a few. And here printing inks come into play for making packaging more decorative as well as informative without adding much to the total cost of packaging- around 5% approximately.
Printing inks or packaging inks, including varnishes are formulated from colourants, binders, solvents and additives. There are different solvent-based, waterborne, oleo-resinous or energy-curing (UV or electron beam) systems. They are applied by printing or varnishing processes such as offset, flexography, gravure printing and roller varnishing. However, when it comes to selecting the appropriate ink for printing on a package, it all comes down to whether the ink will be used for direct or indirect food contact.
Direct Food Contact
When packaging has printed areas that are in direct contact with the food or there is a significant risk of migration, it can be reasonably assumed that ink constituents will transfer to the food under both normal condition or foreseeable conditions of use. In these cases, DFC (Direct Food Contact) inks come to the rescue as they are specifically formulated to function under wide range of food contact and usage conditions. They adhere excellently to paper or film and are scratch resistance as well as moisture and grease resistance. That makes them suitable for dry as well as fatty and greasy foods. However, it’s only the exceptional instances that require printing inks to be applied to the inner side of food packaging. Mainly, printing ink application is restricted to the non-food contact surface of food packaging.
Characteristics and Properties of Printing Inks for indirect food contact
The requirements related to the proper imparting of color and gloss are only met with the perfect pigment dispersion, optimal pigment particle size, and long-time stabilization of the dispersed particles in the formulation. And the quality of the dispersion process is directly linked to the components used.
There is requirement for a continuous improvement in ink formulation to meet the ever-changing needs of faster press printing, use of new substrates, etc. The inks need to be subjected to different testings and controllings to adapt to the different types of substrates and fulfill the diverse requirements of printers in packaging industry.
With the focus on food safety increasingly encompassing all aspects of food packaging process, what type of printing ink should be used and the choice of substrate have become central concerns. And that has made it a prerequisite for printing inks to have low migration property among others to allay the concerns regarding food safety when used for printing in both indirect or direct food contact. For that reason, low migration inks are specially formulated using selected components that ensure that migration will stay within the accepted limits.
However, it must be noted that the choice of ink is also influenced by the packaging processes employed such as heat sealing, speed of packaging machines, necessary slip, packing at low temperatures, etc.
Barrier function of Packaging Material
The barrier properties of food packaging material ensure that the taste of the food is maintained, while protect against any external contamination as well. So, it is important to ascertain the barrier property of a packaging material before deciding upon the type of printing ink or coating to be used. For instance, containers such as metal cans and glass bottles provide an absolute barrier, and therefore, printers do not have to pay special attention to the choice of printing ink before applied to the outer surface of them. At the same time, when it comes to plastic packaging or flexible substrates like films, aluminium foils etc., there is still some apprehensions regarding their ability to serve as an absolute barrier material. This is primarily due to the infinite number of combinations of food type, packaging material and printing inks/coatings that are possible where the packaging layer might show different barrier functionality.
The solution lies in carrying out the comprehensive migration tests in order to carry out as much as substrate/food combinations possible. It helps in mitigating the migration and ensure that packaging materials acts as a functional barrier if not absolute barrier. These migration tests include Organoleptic testing- for taste and odour; practical migration tests on the printed packaging material both when empty and filled. Lastly, a calculation of all possible worst-case scenarios needs to be carried out to comprehensively evaluate whole packaging construction and decide on the inks that will best meet its needs.
Considering the growing focus on food safety practices in food packaging, it seems a good practice to opt for the ‘Food Packaging Compliant’ inks often termed as low migration inks as well. Basically, these inks under normal or foreseeable use of conditions do not migrate into the food or at least do not exceed the accepted levels. However, it must be paid heed to as well that when it comes to safe packaging of food, only assuming that all the compliances on the part of a printer will ensure safety of food against any contamination will be a false sense of safety. All components of the packaging like substrate, adhesive, coatings and other parts of production must adhere to compliances as well to achieve a true safety in food packaging.