A broad range of substrates comprise the list of approved food contact (direct and indirect) packaging materials

FDA considers, controls and regulates direct contact packaging materials in the same manner as food ingredients

Assumptions are that packaging substrates and all contacting substances can and may be consumed along with the food

Manufacturers of packaging raw materials and finished, converted packages alike are expected to understand, apply and validate their processes for consistency, quality, safety and adherence to required methods and protocols

Contact Material Regulations

Direct and indirect contact packaging materials, substances, processing aids, coatings, adhesives and adjunct substances controlled and conditionally approved for use are described and referenced in 21CFR sections 173-182.

Additional information, directives, procedures and controls may be found in sections of 21CFR dedicated to the specific food type (i.e., package fill level control for certain food categories) Additional sections of 21CFR control and direct GMP (110-111), while others control the packaging of specific food categories and systems (e.g., 113, thermally-processed low acid foods and 129, bottled water)

21CFR may categorize foods, ingredients and materials by type, processing method, packaging methods and other qualifiers. Manufacturers and suppliers are strongly advised to consult 21CFR or experts to verify that materials and adjunct substances are approved for each and every intended use.

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Source: http://www.ehagroup.com/food-packaging-safety/