Metal Packaging: From Farm to Fork, Risk Assessment and Management of Food Coatings

Enzo Orellana
Global Market Strategy Manager

In this article, I will explore risk assessment and risk management of food coatings used in the manufacturing of single-use metal packaging. These coatings prepared mainly from organic materials, form a layer/film on the substrate in such a way to create a protective layer essential for the long-term performance of any can.

Coatings serve these main key functions:

  • Chemical protection – prevents interaction between the metal and the pack contents
  • Mechanical protection – protects against temperature and humidity, as well as physical properties of the can.
  • Decoration & functionality – contribute to easy removal of can contents, adhesion of end sealants and improved can appearance         

Importance of Mitigating Migration

Liquid metal packaging coatings are formulated with resins, cross-linkers, solvents and additives. They are applied directly by a roller or spay on the metal surface. These coatings are then heat-cured to form a solid film. When cured, the coatings original ingredients are cross-linked forming the uniform film that lines the can. As many chemical reactions occur during the film polymerization, in any given formula “non-intentionally added substances” (or NIAS) may be formed as molecules bond with each other.  After cans are filled, and coatings are in direct contact with food, new chemical reactions may occur, and some of the known non-linked monomers as well as these NIAS may migrate from the solid film onto the food stuff.  

The different food safety agencies of the world have determined safe levels at which this migration may occur without causing harm to human health. Thus, migration from the can linings to food must be constantly tested to ensure it is below safe levels. 

Migration evaluations are conducted to measure actual migration into food simulants according to guidelines. These tests target mostly the know substances in the coating, and are designed to measure both the thermal processing (sterilization and/or pasteurization) and the long-term storage of food.

Regulatory Landscape

There are four main food safety references often requested around the world regulating food contact legislation. 

These food contact regulations vary from region to region, and are constantly evolving, but common principles are consistently applied to coatings:

  1. Under normal foreseeable conditions for use they do not transfer their constituents to food in quantities that could endanger human life, bring unacceptable change to the food composition, or bring about a deterioration in the organoleptic characteristics.
  2. Coatings should be manufactured in compliance to GMP
  3. Coatings shall be accompanied by a written declaration stating that they comply with the rules applicable to them 

Bisphenol-A. An inflexion point in the industry

As described in my previous blog, in the late 2000s the concerns about migration of BPA (bisphenol-A), a monomer used in epoxy-based coatings to ensure the transition from liquid to solid state of metal packaging coatings, have revolutionized the metal packaging industry.

BPA, a tiny particle that mimics estrogen in its physical molecular composition, was a known endocrine disruptor if ingested and process by the human body; yet considered safe for use in direct food contact based on the principle that any reasonable migration of unbonded BPA molecules into the food stuff would be way below the threshold of regulation, or the quantity considered concerning due to its potential effects to human health.  

Despite the reassurances of food safety agencies around the world about the use of BPA based on the known migration and safety levels, public opinion thought otherwise.  Consumers prefer avoiding “any risk” if alternatives are available, especially when it comes to food safety. 

Today, the North America market of cans is 95% BPA-free; and the rest of the world is slowing moving in the same direction.

The industry has learned an important lesson.  Guidance based in sound science may not be sufficient in a world of increasing distrust in government and industry.  And as marketing 101 would suggest, the consumer is “always right”.

Brand owners are paying increasing attention to the subject of migration and monitoring consumer chatter in the blogosphere with the aim of being proactive in light of any other potential “BPA” lurking in the horizon.

Moving forward: Industry led initiatives to improve food safety

Despite the ongoing success of BPA-free technologies, companies that manufacture can coatings must remain vigilant, always scouting for new safety concerns.

The question keeping awake many brand owner food & packaging specialists is “what is the next BPA”?

Given the fact that non-intentionally added substances can be generated in the process of curing a coating, the answer is not simple.  A regulatory assessment of the known ingredients of a coating may be enough to comply with food safety regulation, however, not enough to ensure peace of mind for brand owners.

As analytical technology advances and techniques can identify substances at the part per trillion level, our risk assessment also must evolve to apply a ‘finer mesh’ in the quest to prevent that no toxic nor endocrine disruptive non-intentionally added substances may be present in the can lining.

Henkel answer to these concerns materialized in the form of our Triple Safety process,  which is conducted for every new BPA-free can coating formula.

Triple Safety extends beyond regulations to analyze ‘peaks and valleys’ of non-intentionally added substances (NIAS) within the coating formulation.  The program incorporates in addition to the traditional regulatory assessment two key steps:

  • Toxicological Assessment
  • Analytical Assessment

Regulatory Assessment
Step one involves a traditional regulatory assessment, which involves an independent review of the chemical composition in the can linings. This includes additives, expected contaminants, degradation products and oligomers. It also looks at the current FDA/EU listing of these chemical compositions.

Toxicological Assessment
The next step is a toxicological assessment. This includes an analysis of the parts of the can coating that will migrate to the food, to ensure there are no toxicological or endocrinological concerns.

Analytical Assessment
An analytical assessment then provides an overall evaluation of the can coating migrates, including overall and specific migration limits (OML/SML) testing, organoleptic properties, and NIAS screening.

Triple Safety Statement
A triple safety statement is then produced, encompassing the following:

  • Compositional overview
  • Regulatory assessment
  • Analytical assessment – Migration
  • Analytical assessment – NIAS
  • Toxicological Assessment
  • Overall Summary

The Triple Safety check ensures can manufacturers & brand owners remain frontrunners in the quest for the ultimate food safe container, relying on Henkel’s global team of recognized experts in the market.

To learn more we invite you to view our web seminar broadcast: link on “Risk Assessment and Management for Internal Food Coatings”.

About the Author

Enzo Orellana

As the Global Market Strategy Manager for the Coatings and Sealants segments of the Metals business, Enzo is responsible for developing global business and product development strategies based on trends and innovations in the industry, such as the drive for more recyclable, sustainable and safe products as well as more efficient production processes.

With a background in business & marketing and almost 15 years of experience in the industry, he offers a wealth of product expertise to both internal stakeholders and external customers.

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