What is Required to Establish a Functional Barrier?
With all the recent announcements of potential chemicals migrating from inks and adhesives into foods through various barrier films (ITX, BPA, benzophenone, etc.), what is being done to clarify the concept of functional barriers? For example, does an FDA acceptable overprint over standard water-based inks printed on BOPP represent a sufficient functional barrier? From what I understand, it is still the responsibility of the packaging stakeholders to prove that the functional barrier is in fact an adequate barrier. Are there any recent updates from FDA on functional barriers?
The functional barrier doctrine that you refer to dictates that, if a substance is not part of the food-contact surface of a package and is separated from the food by a barrier that prevents migration of the substance to food, then the substance is not reasonably expected to become a component of food, and, thus, is not a food additive according to the Food, Drug, and Cosmetic Act (FD&C Act). You are correct that it is the responsibility of the food packaging stakeholder to determine whether a true functional barrier exists. This can be accomplished by considering the package structure and the exposure conditions anticipated for the package based on the intended conditions of use or, in some instances, through diffusion modeling or migration testing.
There has not been a lot of explicit guidance from FDA on this point. Although not from FDA's Center for Food Safety and Applied Nutrition (CFSAN), "CMC Reviews of Type III DMFs for Packaging Materials" (March 22, 2010), a manual published by FDA's Office of Pharmaceutical Science, points out that no formal definition for a functional barrier exists in the FD&C Act or in FDA regulations. However, the Agency's guidances on the use of recycled plastics in food packaging (published in 2006) and on chemistry recommendations for premarket submissions for food-contact substances (published in 2007) address functional barriers. For example, FDA defines a 1 mil (25 micron) thick PET layer intended for use under room temperature conditions and below as a functional barrier in its Recycled Plastics Guidance.