I. Material Selection
How to select materials? According to industry food-grade standards, the selection process is as follows: Definition of “food-grade”—food-grade stainless steel is a regulatory classification rather than a specific material specification (referring to materials evaluated and approved for food contact by authorities such as the US FDA, EU EFSA, and China CFDA);
grades like 304 and 316 are merely material designations and do not automatically guarantee compliance with food-contact requirements. Stainless steel—Grade 304 is generally sufficient for standard food contact; Grade 316L is recommended for contact with acidic foods (citrus, tomatoes, vinegar-based products) or environments involving chlorine-based disinfectants (316L contains 2%–3% molybdenum, providing superior corrosion resistance). To verify food-grade 304 stainless steel, check three things: the grade designation, the applicable standard, and the test report (compliance with GB 4806.9-2023 and a corresponding test report). Plastics—PP, PE, PET, PC (US 21 CFR 177), PTFE. Silicone and rubber—Silicone (platinum-cured for minimal extractables), EPDM (peroxide-cured; sulfur-cured is unsuitable for food), NBR (non-fatty foods only), FKM (high-temperature food processing). Ceramics and glass—Lead and cadmium leaching tests (using 4% acetic acid immersion). Core principle of material selection: The grade designation is just the starting point; the GB 4806.9 test report and heavy metal migration test results constitute the actual proof of food-grade status.
II.
Standards and Certification
How to evaluate standards and certifications.
Regarding industry compliance requirements, here is how to approach standard certifications: China Standards—GB 4806 series for food-contact materials and articles (including GB 4806.9 for metal materials/articles, GB 4806.16-2025 for silicone rubber materials/articles—effective Sept 2, 2026, and GB 4806.10-2025 for paints and coatings), GB 16798-2023 (safety requirements for food machinery), testing for overall migration, specific migration, and additives, and CQC safety certification for food-contact products (involving factory inspections and surveillance sampling); USA—FDA 21 CFR Parts 170–189 (e.g., 21 CFR 177 for plastics, 21 CFR 177.2600 for silicone rubber, 21 CFR 175.300 for stainless steel regarding heavy metal migration—Cr, Ni, Mn—in acidic food simulants, and ceramics tested for lead/cadmium leaching via 4% acetic acid immersion), requiring test reports plus a Declaration of Compliance (DoC) or Food Contact Notification (FCN); EU—EU 10/2011 and Regulation (EC) No 1935/2004, Germany’s LFGB, and France’s DGCCRF; Export Principles—Select the corresponding standard based on the destination country (the schemes for China’s GB 4806, US FDA, and EU 10/2011 are mutually independent; reports cannot be substituted for one another)—certification standards must align with the target market; a common pitfall is submitting an FDA report for silicone rubber when seeking approval for a plastic product.
III.
Hygienic Design
How to implement hygienic design.
In accordance with industry sanitary design standards, sanitary design is implemented as follows: Surface Roughness—Ra ≤ 0.8 µm for food-contact areas (corresponding to a No.4 finish, where microscopic valleys are too shallow for bacteria to hide) and Ra ≤ 0.4 µm for valve seats and plugs (achieved via precision grinding and lapping), with even lower values for high-risk points like aseptic filling zones; Radii—a minimum radius of 3.2 mm (1/8 inch) for all corners to facilitate cleaning; Dead Zones—elimination of dead legs, threads, crevices, grooves (where organic matter accumulates), and blind cavities; Drainage—equipment designed for self-drainage to prevent liquid retention (no pooling on product-contact surfaces); Welding—smooth, cleanable welds in product zones (orbital welding followed by repolishing; full penetration with Ra ≤ 0.8 µm); CIP/SIP—integrated Clean-in-Place and Sterilize-in-Place capabilities (spray balls covering all internal surfaces; nozzles reaching corners; turbulent flow with a Reynolds number > 10,000; cleaning efficacy verified by ATP testing < 100 RLU). The five core concepts of sanitary design are: smooth surfaces, rounded corners, no dead zones, self-drainage, and cleanability.
IV.
Process Cleanliness
Implementation of process and cleanliness requirements.
In accordance with industry standards for food-grade processing, “process cleanliness” is achieved as follows: Surface treatment—electropolishing, passivation, and mirror finishing of stainless steel to prevent contamination (Ra 0.4 to 0.8 μm), with mechanical polishing combined with electropolishing to meet contact surface standards; Welding—full-penetration orbital welding for internal seams followed by refinishing (EHEDG Doc 9), ensuring weld seam roughness (Ra) of ≤0.8 μm; Molds—use of 304 stainless steel (free of harmful substances) for export-grade food molds, cavity polishing for a smooth finish and tactile feel, use of food-grade coolant during machining to prevent contamination, and handling with sterile gloves during installation to avoid touching the cavity; Contamination control—prevention of cross-contamination in the workshop and use of dedicated tooling/fixtures; Lubrication—use of food-grade lubricants (NSF H1 rated) at equipment contact points and platinum-cured silicone seals with low extractables; Surface treatment—electropolishing to remove surface impurities and reduce bacterial adhesion. In short, “process cleanliness” means that food-contact surfaces come into contact only with food-grade materials—coolants, lubricants, and gloves are all food-grade.
V.
Acceptance and Traceability
Procedures for acceptance and traceability.
Industry-standard food-grade acceptance and traceability verification involve the following steps: **Testing Reports**—provision of reports for each batch regarding food-contact materials (GB 4806.9 standards for heavy metal migration, overall migration, and specific migration) and a Declaration of Conformity (DoC); **Documentation**—material certification (stainless steel grade and heat/batch number) and food-grade certification (CQC safety certification for food-contact products, FDA test reports, and EU 10/2011 compliance); **Labeling**—product labeling in accordance with GB 4806.1 (general safety requirements for food-contact materials) and clear indication of material type; **Verification**—actual measurement of surface roughness (Ra) using a roughness tester, inspection of corner radii, visual and endoscopic checks for “dead zones” (areas where residue can accumulate), self-draining verification, and inspection of ground welds; **Factory Audit**—CQC factory inspections and ongoing assurance through random sampling; **On-site Inquiry**—asking three key questions: “Are material test reports available?”, “What is the Ra value of the contact surface?”, and “How is cleaning validation performed?”; and **Data-based Acceptance**—confirming that Ra is ≤ 0.8 μm, there are no dead zones, and test reports accompany the shipment;
compliance with all three criteria is required to qualify as food-grade.
Conclusion
How should food-grade customization for automation equipment components be approached? The conclusion is to ensure food-grade standards across five key areas: materials, certification, design, manufacturing processes, and acceptance verification.
Materials—”Food-grade” is a regulatory classification rather than a specific alloy grade (subject to FDA, EU, and Chinese approvals). 304 is for general contact; 316L is for contact with acidic foods and chlorine-based disinfectants (containing 2%–3% molybdenum). Plastics include PP, PE, PET, and PC; elastomers include platinum-cured silicone, peroxide-cured EPDM, and NBR (restricted to non-fatty foods); ceramics and glass are tested for lead and cadmium leaching. Certifications—China GB 4806 series (4806.9 for metals, 4806.16-2025 for silicone rubber, 4806.10-2025 for coatings) plus GB 16798-2023 (safety requirements for food machinery); US FDA 21 CFR 170–189 (177 for plastics, 177.2600 for silicone, 175.300 for stainless steel); EU 10/2011; and Germany’s LFGB. Standards must be selected based on the destination country; reports are not mutually interchangeable. Design—Surface roughness (Ra) ≤ 0.8 μm (contact surfaces) and 0.4 μm for valve seats; corner radii ≥ 3.2 mm; elimination of dead ends, threaded gaps, and blind cavities; self-draining capability; orbital welding with re-polishing of weld seams; CIP/SIP integration (full spray ball coverage, Reynolds number > 10,000, ATP < 100 RLU). Manufacturing Processes—Electropolishing and passivation to a mirror finish; full-penetration orbital welding followed by re-polishing; mold polishing (304 grade); use of food-grade coolants and sterile gloves; food-grade lubricants (NSF H1). Acceptance—Batch-specific test reports (heavy metal migration, overall migration, specific migration); CQC certification; material certificates; actual Ra measurements; endoscopic inspection of dead zones;
self-drainage verification; factory inspections and random sampling.
In summary, regarding custom food-grade components: the alloy grade is the starting point, test reports serve as proof, a "dead-zone-free" layout is the design requirement, and food-grade compliance is the baseline—all four criteria must be met for components to enter a food processing line.
