What You Need To Know About Chemical Migration In Food Packaging 

While it’s always important to consider how your barriers, adhesives and inks will work together to deliver high performance in food packaging, it’s also critical to understand how these three main components could impact chemical migration into food. 
 
Barriers:

With flexible packaging, the barrier is often a film; however, this does not mean it can sufficiently stop chemical migration. This is because film barriers aren’t truly complete barriers.  Chemicals in adhesives can move through these “barriers” to achieve equilibrium with food side of the package; they have a tendency to move from high concentration to low concentration until chemical diffusion between the package and the food is the same. 
 
Materials such as stainless steel and glass can resist movement to prevent chemical migration from the outside; however, these materials do not provide lightweight solutions or lower transportation costs like flexible packaging.  
 
Adhesives:

An adhesive’s chances of migrating chemicals into food often depend on the size of its molecules and chemical reactivity. If the molecules are small, the risks for chemical migration increase because they have higher diffusion rates compared to large molecules. If the chemicals don’t react, they are free to migrate.  This is common when adhesive formulations include the following: 
 

• Plasticizers allow an adhesive formulation to offer flexibility by allowing molecules to move more freely. However, plasticizers tend to be small, unreactive molecules which migrate more easily through packaging and into food, similar to other molecules like deformers, surfactants and thickeners.  

Additionally, environmental factors such as humidity or UV light can also cause chemical changes in an adhesive formulation and result in a reaction that increases chemical migration. For example, an adhesive may contain isocyanates to provide bonding strength, but a package with excessive moisture may allow the formation of aromatic amines, which are carcinogens and can migrate into food. 
 
Inks:

It is recommended to avoid using inks in food packaging, as it is common for residual on the seal side of the film to touch food and cause chemical migration. For example, if the film is rolled up and has a coating such as ink on the outside for a logo or branding message, it’s possible for that ink to offset on to the side of the barrier film.  This can happen if the ink isn’t sufficiently dried, or the coating and varnishes used with the ink aren’t completely cured. This will eventually touch food, increasing chances for chemical migration. This can also occur with paper to-go cups that have a coating or printed logo on the outside getting stacked on top of each other.  
 
Additionally, it’s important to keep in mind that chemicals within these components tend to be more likely to migrate into fatty foods compared to aqueous (water) foods. This is because  chemicals, like fat, are non-polar and are more likely to migrate into a fatty food than an aqueous food. Understanding this can help you gain a full understanding of why these packaging components may be susceptible to chemical food migration. 

Water-based adhesive technology is FDA-compliant for produce and low temperature packaging applications. They have low to no VOC emissions, which can benefit the environment.  Water-based does, however, tend to have a higher number of unreacted components than other technologies, which could increase migration.   To maintain low migration, it is better to use water-based technology in packaging that will not be exposed to high humidity or water for a long time, such as a barrier film for dry pantry food; otherwise, the adhesive could potentially degrade and allow migration to occur. 
 
Solvent-based adhesive technology meets FDA compliance and can be used in all types of food packaging applications, from frozen to retort. Solvent-based technology has a low-water water solubility, which reduces the chances of chemical migration, especially when blushing occurs in high-moisture products. This technology can offer chemical resistance both inside or outside the packaging to protect the food. It also provides a strong bond to reduce migration through potential gaps and can be formulated with additives to enhance the migration through barriers. The solvent, however, does result in volatile organic compound (VOC) emissions. Solvents are also flammable, so it’s crucial the packaging is stored in a safe place.  
   
Solvent-free adhesive technology can also meet FDA requirements for all food types and conditions, including retort and ovenable packaging. Since this technology is formulated with 100% solids, it reduces chemical migration by minimizing the risks of VOCs which could otherwise migrate into food and pose health dangers. It also has reactive chemistry that depends on the adhesive’s curing time to be completed before the food is packed. This technology is designed for durability and chemical resistance, providing the bond strength to stop chemicals from moving to the food. 
 
UV, LED and electron beam (eBeam) technologieshave been evaluated for chemical migration, and some have met FDA requirements for migration. However, these chemistries are often composed of reactive, small molecules that can migrate easily to food if not fully reacted. This is especially true for unreacted photoinitiators. Additionally, the majority of components used in these chemistries do not have FDA pre-market clearance.  Therefore, it is crucial that the potential migration of these chemistries is understood prior to using them in food packaging.These products also have zero VOCs and use lower energy compared to water-based and solvent-based technologies, which benefits the environment. 
 
How Adhesive Processing Can Reduce Chemical Migration 
 
There are a several recommendations that can help you ensure the adhesive processing will not contribute to additional chemical migration to food packaging: 
 

• Wait to roll coated films: By allowing a printed ink to fully dry, you can decrease the chances of offset-migration occurring on the side of the film that will eventually contact the food once it is rolled and sent to the brand owner.  
• Allow adhesive to fully cure: The more time an adhesive is allotted fully cure, the more likely it will provide increased protection against chemical migration, because it has had time to form a strong bond.  

Communicate with brand owners: Sharing tactics your brand owners can use to lower chemical migration with food packaging can help you become a trustful resource within their value chain. For example, if a different ink is used for their logo or messaging, they may not be aware of how this could impact migration levels to the barrier and adhesive. Encouraging them to share these details with you can further decrease chances of migration occurring.