There are five critical standards for food machinery materials: ① Food-contact metals must be 304/316 stainless steel (non-toxic, odorless, corrosion-resistant, and resistant to flaking); ② Surface roughness Ra ≤ 0.8μm (prevents bacterial harboring); ③ Plastics must be food-grade PP/PE; ④ Certifications (FDA/NSF ANSI 51/GB 4806); ⑤ Hygienic design (no dead zones, easy to clean, and passivated welds)—true food-grade status requires the combination of material, surface finish, and design.
I. How to Choose Stainless Steel (Key Factor)
304 Stainless Steel: 18% chromium + 8% nickel (18/8);
meets food-grade standards; covers over 80% of applications (baking, dry goods, neutral foods); 316/316L: Contains an additional 2–3% molybdenum; resistant to chlorides, acids, brine, and coastal environments (seafood, pickled products, high-humidity areas; 30–40% more expensive); 430: Suitable for low-corrosion environments; Acidic foods (pH < 4.5), brine, and strong cleaning agents require 316L (304 is prone to pitting corrosion, which harbors bacteria)—choose 304 for dry applications and 316L for acidic, salty, or wet conditions (select based on operating conditions; the most expensive option isn't always the best).
II. Surface Finish (More Important Than Material Grade)
Ra ≤ 0.8μm: International standard for food-contact surfaces (Alibaba guidelines / 3-A Sanitary Standards); Internal Polishing: Internal surface Ra ≤ 0.8μm for sanitary piping (Φ19–63); Welding: Smooth welds with no dead zones (welds are hotspots for bacterial accumulation); Passivation: Pickling and passivation to restore the corrosion-resistant layer (mandatory before equipment leaves the factory); Hollow Parts: Avoid hollow structures where water can pool (breeding ground for bacteria)—smoother surfaces are easier to clean (surface finish determines whether sanitary audits are passed).
III.
Non-Metallic Materials
Plastics: Food-grade PP/PE (engineering plastics permissible for non-food-contact parts); Seals: Silicone/EPDM/Fluoroelastomer (food-grade gaskets/seals); Lubricants: Food-grade lubricants (NSF H1 certified); Coatings: Teflon/Ceramic coatings (non-stick + corrosion resistance); Hoses: Food-grade hoses (phthalate-free)—non-metallic components are equally critical (seals and lubricants are the most frequently overlooked items).
IV.
Certification Requirements
China: GB 4806 standards for food-contact materials (metal/plastic/coatings); USA: FDA 21 CFR (food-contact compliance); EU: EU 1935/2004 (framework for food-contact materials); North America: NSF/ANSI 51 (sanitary certification for food equipment); International: 3-A Sanitary Standards (dairy/fluid processing equipment); Procurement: Require suppliers to provide type-test reports and material certificates (Shenzhen Market Supervision guidelines)—configure food machinery for export according to the target country’s certifications (FDA/NSF/CE food-contact standards).
V. Recommendations for Procurement and Acceptance
1. Specify materials clearly (contracts must list grades—e.g., 304/316L—and the specific components); 2. Require test reports (material certification, type testing, and surface finish/roughness reports); 3. Verify hygienic design (no dead zones, detachable/washable, and CIP-compatible); 4. Inspect welding (smooth welds + pickling and passivation); 5. Check certifications (FDA, NSF, or GB 4806, depending on the destination country)—Food machinery materials: 304 for general use / 316L for acidic/wet environments; Ra ≤ 0.8 μm; PP/PE plastics;
certifications + test reports (acceptance based on the “three-piece set”: material list, test reports, and design documentation).
