Food Packaging Safety: 3 Categories of Testing — Migration/Microorganisms/Heavy Metals. What Print Shops Need to Verify Before Submission

In November 2025, a print shop producing milk tea cups submitted 12 testing items for a lab report. All passed, and the client accepted the batch. Three months later, the client was spot-checked by the market regulator and found the total migration of these cups exceeded the limit by 2.3x. On retesting, it turned out: the cups the print shop submitted were blank laminated paper cups, while the actual cups the client used had an additional pearlescent coating on the inner wall — and the migration of that coating was never tested separately.

This is the most common blind spot in food packaging testing: print shops assume "testing 12 items is enough," but only 3 categories truly determine compliance — migration, microorganisms, and heavy metals. Each category has specific sub-items and submission strategies. Here's a full breakdown of all three.

Category 1: Migration — The Decisive Indicator, 3 Sub-Items Must Be Distinguished

Migration refers to the amount of chemical substances in food contact materials that transfer into food upon contact. It is the "core indicator" of food packaging safety; all other indicators are supplementary.

Migration is divided into 3 sub-items:

1. Total Migration

The total amount of all non-volatile substances that migrate into food. The GB 4806 series typically sets the total migration limit at 10 mg/dm² (contact area) or 60 mg/kg (food).

Testing method: soak the packaging in food simulant liquid (typically 10% ethanol, 3% acetic acid, olive oil, etc.) at a specified temperature for a specified time, then evaporate the simulant and weigh the residue.

The most common failure point for print shops: total migration exceeding limits is often not a material issue but the wrong simulant being chosen. For example, acidic food (juice, yogurt) requires 3% acetic acid; alcoholic food requires 10% ethanol; fatty food requires olive oil. If the print shop only tests one simulant during submission, exceeding limits may occur when other types of food are actually used.

2. Specific Migration Limit (SML)

Migration limits for a specific substance (such as formaldehyde, heavy metals, aromatic amines, plasticizers, etc.). Different substances have different limits, typically expressed in mg/kg or mg/dm².

Common SML items that fail:

• Formaldehyde (may be present in plastics/paper/coatings)
• Heavy metals (lead, cadmium, arsenic, mercury, chromium, etc.)
• Aromatic amines (decomposition products of azo dyes)
• Plasticizers (phthalates)
• Free phenols, free formaldehyde (coatings)

The most common failure point for print shops: SML items are missed. For example, the ink used by the print shop contains aromatic amines, but only total migration was tested — the specific migration of aromatic amines was never tested.

3. Conditional Migration Testing

For certain special scenarios, conditional testing is required: high-temperature use (microwave heating), low-temperature freezing, long-term contact, etc. Migration results can differ several-fold under different conditions.

The most common failure point for print shops: the print shop submits samples at room temperature (e.g., 20°C for 10 days), but the client's actual scenario is microwave heating (100°C for 2 hours). Under these two conditions, migration can differ by 5-10x.

Category 2: Microorganisms — The Hidden Minefield for Paper Packaging

Microbiological indicators mainly apply to paper packaging. GB 4806.8-2016 requires the following microbiological limits for food contact paper:

• Total bacterial colony count ≤ 100 CFU/g
• Coliforms must not be detected
• Pathogenic bacteria (Salmonella, Shigella, Staphylococcus aureus, etc.) must not be detected

There are 3 common reasons for microbiological exceedance:

Reason 1: Substandard production environment. If the print shop's paper warehouse has excessive humidity and paper rolls are stored in a humid environment for over 3 months, bacteria can easily proliferate.

Reason 2: Raw material contamination. Recycled pulp and recycled cellulose raw materials themselves may carry large amounts of microorganisms.

Reason 3: Post-process contamination. During laminating, die-cutting, and forming, operators' hand oils and sweat directly contact the inner wall of the packaging, causing secondary contamination.

The most common failure point for print shops: the print shop picks the cleanest batch of samples for testing, while what the client actually receives is a batch that has been sitting in the warehouse for several weeks. It is recommended that the samples submitted by the print shop should be tested after simulating actual storage conditions (e.g., stored at 25°C and 65% humidity for 4 weeks before testing).

Category 3: Heavy Metals — No Escape for Paper/Metal/Plastic

Heavy metal indicators cover lead, cadmium, arsenic, mercury, chromium, etc. that may leach from packaging. Limits vary slightly across different material standards:

There are 3 common sources of heavy metal migration:

Source 1: Lead chrome yellow in ink. Although GB 4806.1 has banned it, some small ink manufacturers still use it. When sourcing ink, print shops should request the heavy metal testing report from the ink supplier.

Source 2: Lead and arsenic in pulp. Recycled pulp has complex sources; if the recycled paper contains heavy metals (cosmetic boxes, pesticide boxes), the regenerated pulp will carry heavy metals.

Source 3: Alloy composition of metal packaging itself. The lead and cadmium in aluminum alloy cans mainly come from the alloy formula, and heavy metal content varies significantly across different aluminum alloy grades. When sourcing tinplate and aluminum cans, print shops should request material certification from the supplier.

The most common failure point for print shops: assuming heavy metals are only "a metal packaging issue," but in fact paper and plastic packaging must also be tested. If the print shop only tests the paper substrate and not the heavy metals in ink and adhesive, once lead chrome yellow in the ink exceeds limits, the entire batch will fail.

Compliance Thresholds for the 3 Categories: A Table to Understand at a Glance

3 Self-Check Lists Before Print Shop Submission

List 1: Confirm the simulant matches the actual food. When submitting samples, the print shop must tell the testing lab: what food is the packaging for (acidic/alcoholic/fatty/neutral)? What are the contact temperature and time? Don't cut corners by using "general simulant."

List 2: Coating/ink/adhesive must be tested separately. Substrate compliance does not equal finished product compliance. If the packaging has coating, ink printing, or adhesive bonding, each of these requires separate migration testing.

List 3: Test after storage simulation. Microbiological indicators change over storage time. It is recommended that print shops simulate actual storage conditions (25°C, 65% humidity for 4 weeks) before submission, so the test data better reflects the state the client actually receives.

The Compliance Logic Chain for the 3 Testing Categories

The compliance logic for food packaging safety is chain-based:

1. Substrate compliance: The finished product passes GB 4806.7/8/9 testing
2. Coating compliance: The inner wall coating passes GB 4806.11 testing
3. Raw material compliance: Ink/adhesive/coating have GB 4806.1 declarations
4. Specific migration compliance: Specific substance migration qualified for the actual food
5. Microbiological compliance: Microorganisms qualified under actual storage conditions

All 5 links are indispensable. Print shops often only look at link 1 and assume everything is fine, but in reality links 2-5 are the truly decisive ones.

FAQ

Common questions have been compiled in the FAQ section.

Further Reading

• Food Contact Packaging GB 4806 Testing in Practice: 5 Common Failure Items + 3 Remediation Methods
• Food Contact Materials GB Standards: 3 Core Standards Explained — How GB 4806.1/7/8/9/11 Map to Your Products
• 5 Core Standards for Food Packaging: GB 4806.1/7/8/9/11