“Food grade” is the most loosely used phrase in seal purchasing. It appears on quotations, in catalog descriptions and on invoices, and it carries no legal definition on its own. What it means in practice is that a specific compound, in a specific finished form, satisfies a specific regulation for a specific food type — and the differences between those three specifics are where recalls come from.
This guide covers what the two main regulatory systems actually require, then ranks seven materials by where they genuinely fit rather than by reputation.
What the Law Actually Requires
United States: 21 CFR 177.2600
Rubber articles for repeated food contact fall under 21 CFR 177.2600. The regulation works in two layers. First, the compound may contain only the polymers and additives listed in the section — nitrile, EPDM, HNBR, silicone, FKM and others — and no substance beyond what good manufacturing practice requires. Second, the finished article has to pass an extraction test matched to the food type.
| Food type | Simulant | Conditions | Limit, first 7 h | Limit, next 2 h |
|---|---|---|---|---|
| Aqueous | Distilled water | Reflux, 9 h total | 20 mg/in² | 1 mg/in² |
| Fatty | n-Hexane | Reflux, 9 h total | 175 mg/in² | 4 mg/in² |
| Dry food | None required | GMP only | — | — |
Three consequences follow, and buyers miss all three. A compound that passed in water has not been tested for fatty food, and the fatty limit is nearly nine times the aqueous limit for a reason. Dry-food service requires no extraction test at all, so a “food grade” claim for a dry application may rest on GMP alone. And 177.2600 covers only the rubber — metal inserts, PTFE faces and plastic cages are assessed substance by substance under 21 CFR 174-179, most of them under 177.1550 for PTFE.
Europe: 1935/2004, GMP, and a gap worth knowing
Regulation (EC) 1935/2004 sets the general rule: a material may not transfer constituents to food in quantities that endanger health or change the food’s composition, taste or smell. Regulation (EC) 2023/2006 requires documented GMP at every stage.
What surprises North American buyers is that the EU has no specific harmonized measure for rubber. Regulation (EU) 10/2011 — the one most often quoted on seal certificates — covers plastics, including PTFE, and states explicitly that it does not apply to rubber or silicones. A declaration of compliance that cites 10/2011 for an EPDM O-ring is citing a regulation that does not cover the part.
For plastics under 10/2011, the overall migration limit is 10 mg/dm² of food-contact surface, with individual specific migration limits for listed substances, and a written declaration of compliance is mandatory. For rubber, the practical route in Europe runs through national provisions — Germany’s LFGB with BfR Recommendation XXI is the most widely referenced — plus customer-specific specifications.
Hygienic design: 3-A and EHEDG
Material compliance and cleanability are separate questions. A compound can be fully compliant and still create a bacteria trap in a groove. 3-A 18-03 sets rubber classes by maximum exposure temperature: Class I at 149 °C, Class II at 121 °C, Class III at 49 °C for product contact only, Class IV at 38 °C for product contact only. All four are tested against cleaning and sanitizing solutions up to 82 °C. EHEDG’s mechanical seal guideline covers arrangement and design rules that 3-A does not.
The Seven Materials, Ranked by Fit
| 材質 | Service range | Hardness | Hot water / CIP | Fat and oil | Relative compound cost | Where it wins |
|---|---|---|---|---|---|---|
| Platinum-cured silicone (VMQ) | −60 to +200 °C | 40-80 Shore A | Fair below 130 °C | 不良 | 1.2-1.8× | Dry heat, closures, sight-glass seals |
| Peroxide-cured EPDM | −50 to +150 °C | 50-90 Shore A | 優れている | 不良 | 1.0× | CIP circuits, steam, dairy and brewery |
| FKM (food grade) | −20～+200 °C | 60-90 Shore A | 不良 | 優れている | 3-5× | Fatty foods, frying oil, oily sauces |
| FFKM | −20 to +300 °C | 70-90 Shore A | 良好 | 優れている | 15-25× | Aggressive CIP chemicals, solvent-laden product |
| NBR (food grade) | −30～+100 °C | 50-90 Shore A | Fair | 良好 | 0.6-0.8× | Ambient oily product, dry goods, water lines |
| バージンPTFE | −200～+260 °C | Non-elastomeric | 優れている | 優れている | 1.5-3× | Gaskets, valve seats, chemical resistance |
| UHMWPE | −80 to +80 °C | Non-elastomeric | Good below 80 °C | 優れている | 0.8-1.2× | Wear strips, guide rails, scraper edges |
1. Platinum-cured silicone (VMQ)
The default for anything that touches dry food, and the one material most often chosen for the wrong reason. Silicone handles −60 to +200 °C continuously, stays flexible at freezer temperatures, and is odorless and tasteless, which is why it dominates baking equipment, closures and dispensing heads. Platinum-cure matters: peroxide-cured silicone leaves volatile byproducts that require a post-cure bake, and an under-post-cured part can taint product for weeks.
What silicone does not do is fat. It swells in frying oil and in fatty dairy, and its tear strength is the lowest of the group, so it is a poor choice for any seal that gets pried out with a screwdriver during cleaning. Specify 60-70 Shore A and plan on replacing it, not on it surviving a knife.
2. Peroxide-cured EPDM
The workhorse of wet food processing. EPDM resists hot water, steam, caustic CIP solutions and hypochlorite better than any elastomer at its price, and peroxide curing keeps compression set low enough to hold a sanitary clamp joint through repeated CIP cycles. Dairy, brewery, beverage filling and CIP pump seals are EPDM work.
Two limits: it swells badly in mineral oil and moderately in animal fat, and it is attacked by aromatic and chlorinated solvents. A line that runs both a fatty product and a caustic clean cannot be sealed with one compound, and pretending otherwise produces the classic failure of a swollen, nibbled gasket after six weeks.
3. FKM, food grade
Fat and temperature together is where FKM earns three to five times the compound cost. A food-grade FKM handles continuous 200 °C, resists animal and vegetable fats, and holds up against the acidic and oily products that destroy EPDM. Fryer applications, oily sauce lines, chocolate and confectionery equipment with hot oil all belong here.
FKM is the wrong answer for steam and hot water — it degrades in steam above roughly 150 °C and in hot water generally, which is exactly the environment many food plants clean with. Check whether the part sees steam before selecting on product compatibility alone.
4. FFKM
Perfluoroelastomer is what you buy when the CIP chemistry includes solvents, strong oxidizers or amines that break FKM, and when the temperature sits above 200 °C. It behaves like PTFE with elastic recovery. It also costs 15-25 times an EPDM compound, has lower tensile strength, and is usually a special order.
The honest use case: a valve or pump in a pharmaceutical or specialty chemical food line where a seal change means a validated shutdown. Everywhere else, the money is better spent on a correct gland.
5. Food-grade NBR
Cheap, oil-resistant, and adequate for ambient fatty product and for water lines that never see CIP. Food-grade NBR uses non-staining antioxidants and no nitrosamine-generating accelerators, which is the only thing that separates it from a general-purpose nitrile. Above 100 °C, or in repeated caustic cleaning, it hardens and takes set faster than EPDM, and the difference is not visible until the joint weeps.
6. Virgin PTFE
Not an elastomer, and should not be specified as one. PTFE gaskets and valve seats cover the widest chemical range and the widest temperature range of anything on this list, −200 to +260 °C, and they do not extract into food. They also cold-flow under load, which means a PTFE gasket in a clamp joint relaxes and needs re-torquing, and a PTFE seal in a dynamic application wears quickly unless it is filled.
Use virgin PTFE where chemical inertness is the requirement and the joint is bolted. Use filled PTFE or a spring-energized PTFE jacket where the seal has to move. Under 10/2011, PTFE parts need a declaration of compliance with migration data, not a 177.2600 letter.
7. UHMWPE
The material for wear parts rather than seals: guide rails, star wheel inserts, scraper edges, conveyor wear strips. It is FDA-compliant in the right grade, has the lowest friction of any unfilled polymer at its price, and resists abrasion better than PTFE. Its limits are temperature — 80 °C continuous — and creep under sustained load. In a plant that steam-cleans at 90 °C, a UHMWPE guide will deform and the line will track badly within a month.
Three Documents, and What Each One Proves
| Document | Issued by | What it covers | What it does not cover |
|---|---|---|---|
| FDA letter of guaranty | The manufacturer | Compound acceptable under 177.2600 for a named food type | FDA does not certify seals; the letter is the supplier’s own statement |
| EU declaration of compliance | Material or part supplier | 1935/2004 plus, for plastics, 10/2011 with migration data | Rubber and silicone, which 10/2011 excludes |
| 3-A 18-03 certificate | Rubber manufacturer, backed by lab test | Compound, rubber class, part number | Design hygiene, which is assessed separately |
| Migration test report | Accredited laboratory | Actual extraction results for named simulants and conditions | Any food type or temperature not tested |
Ask for the document that names the compound, not the material family. A 177.2600 letter for “silicone” is worth nothing; a letter naming the compound number, its durometer and the food type is the one an auditor will accept. Compound numbers change when formulation changes, so check that the number on the certificate matches the parts in the box — this is the single most common finding in a supplier audit.
Where These Programs Fail
Five failure points account for most non-conformances we see:
- Colorants. A white compound with a non-compliant pigment is not a food-grade compound. Color is part of the formulation and has to be listed in the compliance documentation.
- Release agents and mold sprays. Applied at the press, not in the compound, and almost never on the certificate. Silicone mold release on a food-contact surface is a contaminant.
- Post-cure. Silicone and some fluoroelastomers need a bake to drive off volatiles. Skipping it saves a day and produces taste complaints that take months to trace.
- Assembly lubricants. A food-grade seal installed with a general-purpose grease is no longer a food-grade assembly. Specify the lubricant or require a dry install.
- Silent compound substitution. A supplier short of a pigment or an accelerator substitutes an equivalent, and the part looks identical. Only batch-level compound traceability catches this.
主なポイント
- “Food grade” has no standalone legal meaning. Match the claim to the regulation, the food type and the finished form.
- 21 CFR 177.2600 limits total extractives at 20 mg/in² in water and 175 mg/in² in hexane for the first 7 hours. A water test does not qualify a part for fatty food.
- EU 10/2011 covers plastics, including PTFE. It does not cover rubber or silicone, whatever the certificate says.
- Choose by cleaning regime as much as by product: EPDM for steam and caustic CIP, FKM for hot fat, silicone for dry heat, FFKM only when nothing else survives.
- Platinum-cure and post-cure are process requirements, not marketing terms. Ask for both in writing.
- The certificate must name the compound number and match the parts delivered. Family-level claims are not evidence.
Our food-contact O-ring range is quoted with compound-level documentation on request, and カプセルシール are the practical answer where a chemical-resistant jacket has to sit on a compliant core. For CIP and steam service, the high-temperature seal range covers the EPDM and FKM grades used in most sanitary plants, and custom molded parts can be produced against a named regulation rather than a generic claim.
The regulatory text is short and worth reading directly: 21 CFR 177.2600 on eCFR. For the European side, EFSA’s food contact materials material explains how substances are evaluated, and EHEDG publishes the hygienic design guidelines that decide whether a compliant seal can actually be cleaned. Counter-level guidance on stocking food-grade compounds is at Seal Sales, 、および Darcoid maintains compound comparisons that help when two suppliers both claim compliance and the certificates look identical.