What "food grade" really means

No plastic is food-grade in the abstract. A resin qualifies for food contact only as a combination of three things: the polymer and its additives appear in the FDA's food-additive regulations for food-contact substances (the 21 CFR chapters), the specific grade you are buying is documented as compliant, and that compliance is stated for defined conditions of use — temperature, food type, contact duration, and whether the part is single-use or repeatedly reused. A material can be perfectly compliant for cold water contact and non-compliant for prolonged contact with hot, fatty food. Define your use case first; ask for compliance second.

That distinction is what surprises founders. The part in your hand is not the deliverable — the paper trail behind it is. Retail buyers, importers, and customs brokers will ask for documentation, and if you skipped the question during design, you usually discover it after the injection mold already exists.

The resins that actually get used

  • Polypropylene (PP) — the workhorse default. Inexpensive, good heat resistance, survives dishwashers and microwaves, molds easily. Most food containers, closures, and utensils start here.
  • HDPE and LDPE — excellent for bottles, jugs, closures, and flexible parts in cold contact. Very well characterized for food use.
  • PET and clear copolyester — when you need transparency, clarity retention, and stain resistance. Watch the upper temperature limit closely.
  • Liquid silicone rubber (LSR) — seals, gaskets, bakeware, and soft parts that see high temperature. The go-to elastomer for hot food contact.
  • Food-grade TPE — soft grips and flexible components, but only in a grade documented for food contact; the industrial grade that looks and feels identical is not interchangeable.
  • Polycarbonate and nylon — possible in the right grades, but they need deeper scrutiny of additives and behavior under repeated hot washing.

Within every one of those families there are dozens of grades, and the only difference between a compliant grade and a visually identical industrial grade may be the additive package and the documentation. Choose the material from your mechanical and thermal spec first, then filter for food contact — that ordering is explained in how to choose the right plastic for your product, and if you are deciding between two common engineering resins, ABS vs polycarbonate covers that tradeoff.

The part that fails projects: everything else that touches the part

Compliance is a whole-path property, not a resin property. All of the following have to be food-contact appropriate:

  • Colorant and masterbatch. A standard pigment disqualifies an otherwise compliant part. Colorants need their own food-contact documentation.
  • Mold release. Common industrial release sprays are not food-contact rated. The better answer is a tool designed so release agents are unnecessary.
  • Regrind. Grinding rejected shots back into the feed needs a written policy. For food-contact parts it is usually prohibited outright.
  • Adhesives, printing inks, and gaskets. Every secondary material in the contact path is judged by the same standard.
  • Line hygiene. A machine that just ran a non-compliant industrial resin needs a documented purge before your run.

Migration testing: the test that decides it

The central laboratory test is migration — how much substance transfers from the plastic into the food. Labs run overall migration and specific migration of individual components against food simulants (water, dilute acid, alcohol, and an oil or fat surrogate) at temperatures and durations chosen to represent your real use case, including repeat-use cycles where applicable.

Two practical notes. First, testing is performed on parts from actual production, not on raw pellets, because molding conditions themselves affect the result — residence time, melt temperature, and cycle time all matter. Second, budget both money and calendar time for it before your first production run. Costs land in the low-to-mid four figures for a straightforward part and climb with the number of simulants, conditions, and specific analytes. Plan it alongside your other product safety testing requirements.

Documentation you should be collecting

  1. A letter or declaration of compliance from the resin supplier, naming the exact grade and the conditions of use it covers.
  2. The same for every colorant, additive, and secondary material.
  3. Certificates of analysis or batch traceability tying delivered material to the documented grade.
  4. Your migration test report on production parts.
  5. A written statement of intended use — food types, temperatures, contact time, reuse cycles — that everything above is measured against.

Keep these as a package. When a retailer's compliance team, a distributor, or a customs broker asks, you want one folder, not a scramble. If you are manufacturing overseas, make the document set an explicit deliverable in the manufacturing agreement, and verify parts against it during AQL inspection before you pay the factory.

Design decisions that make compliance easier

  • Reduce the contact surface. If only one component touches food, you only have to qualify one component.
  • Avoid crevices and blind pockets. Cleanability is part of safety, and it is a geometry decision.
  • Uncolored where possible. Natural resin sidesteps the pigment question entirely.
  • Design for the real thermal cycle. Dishwasher exposure is more aggressive than most founders assume, and repeated hot washing is where cheap grades fail visibly.
  • Lock the material in the drawing. Name the grade, not the family, so a substitution cannot happen quietly at the factory.

Tooling amortization and per-part economics still apply, of course — see injection molding costs — and if you are selecting a production partner, working with a contract manufacturer covers what to put in the agreement.

Get the material decision right before the tool is cut

Projects House designs food-contact products and takes them to production, which means the resin, the colorant, the tool design, and the test plan get decided together rather than in sequence. If you are developing a product that touches food or drink, describe it through our contact form and we will map out the material and documentation path. More background on process selection sits in our manufacturing technologies section.