Materials in Contact With Food: Stainless Steel, Food-Grade Plastics, Rubber

Three Principles for Choosing Materials

Taiwan's regulations don't provide an "approved list" of materials for food machinery contact surfaces; instead they regulate by performance. Article 7 of the Standards for Food Factory Buildings and Equipment (食品工廠建築及設備設廠標準) is clear: equipment and utensils in contact with food must be made of materials that don't produce or leach toxins, are free of odors or off-flavors, non-absorbent, corrosion resistant, and able to withstand repeated cleaning and sanitizing, and materials prone to contact corrosion must be avoided. Together with the material and migration tests in the Sanitation Standard for Food Utensils, Containers and Packaging (食品器具容器包裝衛生標準, current version amended January 11, 2023), these form the basis for choosing materials.

The EU's Regulation (EC) No 1935/2004 follows the same spirit: under normal use, food contact materials must not transfer their constituents to food in ways that endanger health, bring about an unacceptable change in food composition, or deteriorate taste and texture.

Stainless Steel

Stainless steel is the most common material for food machinery contact surfaces because it resists corrosion, can be polished very smooth, and withstands hot water and cleaning agents. Common grades are 304 and 316. 316 contains molybdenum and has better resistance to salt and chloride ions, so it's often used for savory fillings, pickled products, or environments where chlorine sanitizers are used frequently; the actual choice depends on the machine design.

Table 1 of the sanitation standard places metal contact surfaces under "metal alloys": lead 0.1% or less and antimony 5% or less in the material, and they must pass migration tests.

Stainless steel can rust too: soaking for long periods in chlorinated sanitizer, scratching the surface with wire brushes, or picking up iron particles from carbon steel tools can all cause rust spots. GHP Annex 2 requires contact surfaces to be kept smooth and free of dents or cracks, so cleaning methods matter as much as the material.

Can Aluminum Contact Food?

The sanitation standard doesn't prohibit aluminum; it falls under "metal alloys" in Table 1 and must likewise meet the material and migration requirements. What to consider on the floor is performance: aluminum is softer than stainless steel and scratches easily, and it corrodes easily with strongly acidic or alkaline foods and cleaning agents. Article 7 of the factory standards requires corrosion resistance and the ability to withstand repeated cleaning and sanitizing, so if aluminum parts are used on contact surfaces, pay special attention to the pH of cleaning agents and the surface condition. Table 1 also specifies that electrodes passing current directly through food are limited to iron, aluminum, platinum, and titanium (stainless steel may also be used if the current is very small).

Copper and copper alloys need care: Table 1 requires utensils to be constructed so there's no risk of copper, lead, or their alloys being scraped off; except for copper utensils with an inherent luster that don't rust, contact surfaces must be fully tin-plated, silver-plated, or suitably treated.

Requirements for Plastic Parts

Scrapers, hopper lids, conveyor belts, and forming molds are often made of plastic. Table 1 requires lead and cadmium of 100 ppm or less each in plastic materials and restricts 8 phthalate plasticizers; Table 2 sets further requirements by material. The current Table 2 lists migration tests for polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyethylene (PE), polypropylene (PP), polystyrene (PS), polyethylene terephthalate (PET), plastics made with formaldehyde as a raw material, polymethyl methacrylate (PMMA), polyamide (nylon), polymethylpentene (PMP), polycarbonate (PC), polylactic acid (PLA), polyethersulfone (PES), and others.

Three things to check when choosing plastic parts:

1. Material name: You need to know whether it's PE, PP, nylon, or POM to match it to the migration requirements.
2. Operating temperature: For the same plastic, contact with food at 100°C or above has stricter migration conditions (95°C, 30 minutes).
3. Test reports: Migration test reports according to the sanitation standard.

Rubber, Silicone, and Seals

Seal rings, gaskets, and roller surfaces are often made of rubber or silicone. The current Tables 1 and 2 don't have separate entries for rubber and silicone, so businesses usually ask suppliers for test data according to the general provisions of Table 1, or, for exports, documents meeting the importing country's rules (such as EU or US food contact material regulations). Seals are consumables; replace them when they harden, crack, or chip, or fragments may become foreign matter.

Materials Used in Dong-Yih Machines

The website doesn't list the materials used in each model item by item; if you need material information, please call 06-257-4644 or visit our contact information page. For the regulatory division of responsibilities and documents, see Are Machine Contact Parts Food Utensils?

FAQ

Q: Which materials can contact food?
A: Taiwan has no approved list; instead it requires materials that don't leach toxins, have no off-odors, are non-absorbent, corrosion resistant, and withstand repeated cleaning and sanitizing (Article 7 of the factory standards), and that meet the material and migration requirements of the Sanitation Standard for Food Utensils, Containers and Packaging. Stainless steel, certain food-grade plastics, and compliant rubber and silicone are all common.

Q: Can aluminum be used on food machinery?
A: The sanitation standard doesn't prohibit it; aluminum is a metal alloy and must meet Table 1. But aluminum is soft and doesn't tolerate strong acids or alkalis, so when used on contact surfaces, watch for scratches and cleaning agents.

Q: What are the requirements for plastic parts?
A: Table 1 requires lead and cadmium of 100 ppm or less each and restricts 8 plasticizers; Table 2 sets separate migration tests for PE, PP, PC, nylon, and other materials. When buying, you need to know the material name and operating temperature.

Q: What's the difference between 304 and 316 stainless steel?
A: 316 contains molybdenum and has better resistance to salt and chloride ions; 304 is the grade commonly used in general food machinery. Which one is used depends on the design and operating environment.