Question 

FDA does not provide specific criteria for what constitutes a functional barrier. We would like to test a material that would coat a cup made of bagasse to see if it creates a functional barrier and prevents any migration of the bagasse components. What types of materials are acceptable to use as test standards as universal materials that would allow approval of the coating for a functional barrier? If there is not a set of materials to test for migration, how can a new material be tested to be a functional barrier?

Answer 

In the United States, if a substance is not part of the food-contact surface of a package and is separated from the food by a barrier that does not permit migration of the substance to food, the substance may not be expected to become a component of food and does not fall within the definition of a food additive subject to FDA review. 

FDA has not provided a lot of explicit guidance concerning functional barriers, although the Agency has stated that aluminum foil and 1 mil (25 micron) thick PET layer intended for use under room temperature conditions constitute functional barriers (see 21 C.F.R. Section 177.1390(a) and FDA’s Recycled Plastics Guidance, respectively). Beyond these examples, it is the responsibility of the food packaging stakeholder to determine whether a true functional barrier exists. Determination of a functional barrier 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. See FDA’s Chemistry Guidance for Premarket Submissions for Food Contact Substances (2007) for testing recommendations, such as food simulating solvents that can be used. Also, see the Plastics Regulation, (EU) No 10/2011, Annex III, for food simulating solvents that the European Food Safety Authority (EFSA) would find acceptable in Europe.

Before doing any testing, though, it will be important to determine what, if any, components of the Bagasse would require regulation. You may wish to retain counsel or a consultant to assist in this work as assessing the status of the bagasse and designing an appropriate test protocol could be complicated.