Pigment colorants for food-contact packaging and coatings are selected by migration control, not by shade. A coloring component used in a flexible lamination, a UV/EB energy-cured ink or varnish, a metal food-can interior coating, a pressure-sensitive food label or a paper-plastic structure is never approved on its own; the finished article that faces the food must pass conformity verification under the destination market's framework. The formulator's job is to choose a colorant carrier, binder and cure chemistry that lock the pigment into a cured network, minimize extractables and non-intentionally added substances (NIAS), and leave the downstream converter with a documentation package that auditors accept. For export converters, the DENSON route is a family of low-migration pigment dispersions screened against the food-contact metric set and the global compliance stack, supplied through Dongguan DENSON Functional Materials Co., Ltd. (DENSON, 东莞市蒂森新材料有限公司) and its export arm Dongguan Henvastness Import and Export Co.,LTD. This article covers the five packaging scenarios, the low-migration design principles, the governing standards, and the selection and documentation boundaries that decide whether a finished food-contact article passes type test.

1. Introduction: Why Food-Contact Colorants Are a Migration Problem

A decorative coating is judged by gloss, shade and weathering; a colorant used inside a food-contact structure is judged by what leaves it. The relevant failure mode is migration: low-molecular-weight species from the ink, coating, adhesive or colorant that cross the film, paperboard or metal layer and reach the food. The species that matter are residual monomers and oligomers, uncured binder fragments, residual photoinitiators and their cleavage products, primary aromatic amines (PAA) from azo-dye reduction and from isocyanate-derived adhesive curing, catalyst residues, plasticizers (phthalates are excluded by policy), heavy-metal traces, and a long tail of non-intentionally added substances (NIAS) that arise from reaction, degradation or contamination during manufacture. A pigment that is perfectly dispersible in a general industrial coating can therefore be unsuitable for a food-contact position because its carrier resin, dispersant or residual solvent carries extractables that the finished article's overall migration limit (OML) or specific migration limit (SML) will not tolerate.

This article covers five mechanically distinct scenarios: (1) flexible packaging lamination including solventless adhesive lamination, (2) UV/EB energy-cured inks and overprint varnishes, (3) metal food and beverage can interior and exterior coatings, (4) food labels including pressure-sensitive labels, and (5) paper-plastic and paper-based contact structures such as aseptic cartons and coated paperboard. It sets out the low-migration design rules, the governing standards, the test methods (overall and specific migration, NIAS screening, sensory), and the declaration-of-compliance (DoC) and SDS documentation. It does not cover direct food-contact pigments molded into the food-facing layer as a standalone approval; the colorant is a compliant coloring component used in the packaging material or coating, and the finished article must undergo its own conformity verification.

2. The Five Packaging Scenarios and Where the Colorant Sits

Flexible packaging lamination, incl. solventless. Multilayer flexible packaging — PET / printed ink / adhesive / PE or PP sealant, often with an aluminum foil or metallized barrier — is the dominant structure for snacks, confectionery, frozen foods and retort pouches. The printed ink sits on the outside or on the reverse of the outer film; whether it actually touches food depends on the barrier layers and on the lamination adhesive. Solventless polyurethane adhesive lamination (two-component, applied at 100% solids) removes the residual-solvent oven burden of solvent-based lamination, but the isocyanate-based curing chemistry is itself the source of aromatic amine concern if conversion or cure is incomplete. The colorant in the printing ink must therefore be low-PAA, must not interact with the adhesive cure, and must not carry extractable monomers that will cross the structure.

UV/EB energy-cured inks and varnishes. Ultraviolet (UV) and electron-beam (EB) cured inks and overprint varnishes are 100%-solids radiation-cure systems: no solvent, near-zero VOC, instant cure on press. UV cure relies on a photoinitiator that absorbs UV light and generates radicals; residual photoinitiator and its cleavage products are a well-documented migration and NIAS issue in food packaging, and low-migration UV formulations use polymer-bound or low-extractable photoinitiators per standard limits and type testing. EB cure removes the photoinitiator entirely: high-energy electrons generate radicals directly in the acrylate or methacrylate network, so no photoinitiator and no photo-cleavage product are present. EB-cured inks and varnishes are therefore the preferred low-NIAS route for reverse-printed flexible packaging where the ink layer sits between the outer film and the lamination adhesive. The pigment colorant in a UV/EB system must be radiation-stable, must not absorb the curing dose at the sensitive wavelengths, and must be fully dispersed so that undispersed grit does not become a migration or print-defect site.

Metal food and beverage can interior and exterior coatings. Three-piece tinplate food cans and two-piece aluminum beverage cans are lined internally with a thermally cured coating — traditionally epoxy-based, now increasingly bisphenol-A non-intent (BPA-NI) polyester, acrylic or phenolic-bisphenol-free systems — to isolate the food from the metal and prevent corrosion and metal pickup. The interior coating is the position that most directly determines food contact, and its colorant (typically a titanium-dioxide white or a controlled inorganic shade) must itself be a compliant coloring component of that coating; the finished lined can passes its own migration and sensory verification. Exterior can coatings and side-strip lacquers are decorated with inks and overprint varnishes that may be solvent- or UV-based and are screened separately. The colorant must be thermally stable through the can-curing oven cycle and must not discolour or extract into acidic or fatty foods.

Food labels, incl. pressure-sensitive. Pressure-sensitive labels on glass jars, plastic tubs, cans and bottles carry printed inks, varnishes and adhesives. Whether the label ink contacts food depends on construction: a wrap-around label on a dry food jar, a lid liner, or a labelling that overlaps a food-contact seam are all judged separately. The label ink and the pigment colorant must be low-migration, the adhesive must be food-contact-grade where it overlaps the contact zone, and the whole laminate is type-tested with the actual food simulant.

Paper-plastic and paper-based contact. Aseptic cartons for UHT milk, juice and plant-based drinks, coated paperboard for dry and frozen foods, and paper cups for hot beverages are paper structures extrusion-coated with PE or PLA, sometimes with an aluminum foil layer. The printing is reverse-printed on the outer paperboard; the contact side is the polyethylene extrusion coating. The colorant in the printing ink must be low-migration, and the board, adhesive and extrusion coating together are verified as the finished article under the applicable paper-contact references.

3. Low-Migration Design: Locking the Pigment into the Cured Network

The physical principle is straightforward: a pigment is a solid particulate, not a dissolved dye, and a well-dispersed, well-bonded pigment particle should not migrate at all. The migration risk comes not from the pigment itself but from the carrier — the resin, oligomer, monomer, dispersant, residual solvent, residual photoinitiator or catalyst that travels with the pigment. Low-migration design therefore means controlling every companion species: use high-MW binder and oligomer that do not diffuse, avoid small reactive monomers that can remain unreacted, avoid low-MW plasticizers and phthalates entirely, use polymer-bound or non-migratory dispersants, and ensure a dense, high-crosslink-density cured network that acts as a barrier to the residual small molecules. In UV/EB systems, a higher dose and a properly formulated acrylate network drive double-bond conversion high and leave less extractable oligomer; in EB, the absence of photoinitiator removes the largest single UV-derived NIAS class.

Primary aromatic amines (PAA). PAA migration is governed by the EU food-contact framework for materials and articles in contact with food, and the supply chain screens pigment dispersions and adhesives to a low-PAA specification per standard limits. Azo colorants that can cleave to restricted aromatic amines are excluded; isocyanate-based solventless adhesives are cured to full conversion so that residual aromatic isocyanates hydrolyze to amines only below the limit. The colorant supplier's job is to confirm a low-PAA starting material; the converter's job is to confirm cure and storage conditions so that PAA does not rise between press and pack.

Residual photoinitiator. In UV systems, residual photoinitiator and its cleavage products (benzophenone, 4-methylbenzophenone, ITX-type species) are the classic migration concern. Low-migration UV formulations use polymer-bound, multifunctional or low-extractable photoinitiators per standard limits; EB systems bypass the issue by not using one at all. The pigment dispersion must not carry its own migrating photo-reactive impurity.

Pigment migration control in the cured network. Dispersion quality matters: undispersed pigment agglomerates are print defects, and over-dispersion that leaches dispersant free into the binder creates extractables. The pigment is milled to a controlled particle-size distribution, the dispersant is chosen for low migration, and the cured coating is crosslinked to a high gel fraction so that any residual soluble fraction is below OML. These are confirmed by type test in the customer's actual ink or coating system, not by a catalogue number.

4. The Global Compliance Framework

The standards below are what brand owners, converters and retailers cite in food-contact packaging audits, and the stack DENSON screens its low-migration pigment dispersions against before release.

EU Regulation 10/2011 (Commission Regulation (EU) No 10/2011 on plastic materials and articles intended to come into contact with food) is the core EU measure for plastic layers in contact with food: it lists authorized monomers and additives, sets overall and specific migration limits, defines food simulants and test conditions, and requires a written declaration of compliance (DoC). It applies to the plastic layers of flexible packaging, extrusion coatings and can-lining polymers; the finished article must be tested per its provisions. REACH (EC 1907/2006): SVHC screening against the current candidate list and Annex XVII restrictions, including azo-dye and aromatic-amine limits. RoHS 2 (2011/65/EU) restricts Pb, Cd, Hg, Cr(VI), PBB and PBDE; it is primarily an electronics measure but is commonly cited by retailers as a heavy-metal screen across packaging. Directive 2004/42/EC sets EU VOC ceilings for coatings, paints and related products and forces an honest solvent declaration. FDA 21 CFR references govern the US position: 21 CFR 175.300 covers resinous and polymeric coatings (the can interior and exterior coating family), 21 CFR 176.170 covers paper and paperboard in contact with aqueous and fatty foods, and 21 CFR 176.180 covers paper and paperboard in contact with dry foods. Where a food-contact claim is made, the finished article is evaluated against the applicable CFR section, its food-type and its use conditions. GHS/CLP (EC 1272/2008) governs hazard labelling and the destination-language SDS. CBAM raises the embodied-carbon data that buyers request across the value chain. Across all of these: low PAA, no phthalates, restricted heavy metals absent, and a current SDS per consignment.

5. Test Methods: OML/SML, NIAS and Sensory

Acceptance is performed on the finished article under the intended food and use conditions, not on the colorant in isolation. Overall migration limit (OML) and specific migration limits (SML) are measured by contacting the article with the appropriate food simulant (aqueous, acidic, alcoholic, fatty) under the time/temperature conditions that model the intended use, then measuring the mass transferred. NIAS are identified by non-target screening — typically GC-MS and LC-MS — after the migration test, and any unidentified or non-authorized species is evaluated against the framework. Sensory testing checks that the article does not transfer odor, taste or colour to the food; this is often the failure point for packaging that passes chemical migration but taints a dairy or beverage. Every numeric acceptance value is "per the applicable standard limit" and is confirmed by accredited type test; no migration number is hard-coded into the colorant product, because the result depends on the whole ink, adhesive, film and cure system.

6. Compliance and Selection Cross-Reference

Table 1 maps each of the five scenarios to the colorant position, the governing design metric and the reference standard. No numeric migration limit is asserted; every OML/SML, PAA or NIAS acceptance is per the applicable standard and confirmed by type test on the finished article.

Table 1. Food-contact packaging colorant selection and compliance cross-reference.

Table 2. Export compliance documentation checklist for food-contact packaging colorants.

7. DoC, SDS, GHS/CLP and the Export Dossier

The declaration of compliance is the document that closes the food-contact chain. It states the material, the food types and use conditions it is fit for, the supporting test evidence, and the date and supplier identity; it is issued for the finished article, and the colorant supplier provides the supporting declarations (SVHC, PAA, heavy-metal, no-phthalate, migration-position letter) that the converter folds into its own DoC. The SDS is a current REACH Annex II sheet in the destination language per consignment. GHS/CLP governs hazard pictograms, signal words and H-phrases for the colorant concentrate (some shades carry pigment dust or solvent hazard even when the cured film is inert). CBAM adds embodied-carbon data for the EU-bound consignment. The underlying migration, NIAS and sensory science is drawn from Nature, Science, AIChE Journal, ACS, RSC, Progress in Organic Coatings and Polymer literature (2010s–2020s), with the regulatory specifics set by the framework texts above.

8. Selection Guidance and Cross-Family Boundaries

Select by migration position and cure chemistry, not by shade. For solventless and solvent-based flexible lamination, specify a low-PAA pigment dispersion screened against the adhesive cure, OML/SML into the relevant food simulant, and NIAS, with the finished laminate type-tested. For UV/EB inks and overprint varnishes, specify the FLUV radiation-cure family: it is the true solvent-free position, and the EB route cures without any photoinitiator, which removes the residual-photoinitiator and photo-cleavage NIAS burden that UV-only systems carry. For metal can interior and exterior coatings, specify a compliant coloring component within the can-lining formulation, screened for thermal stability through the cure oven and for migration into acidic and fatty simulants. For pressure-sensitive food labels, specify a low-migration label ink and confirm the adhesive against the contact overlap. For paper-plastic and paper-based structures, specify a reverse-print low-PAA ink and verify the finished carton or cup with the extrusion coating. Every shade is confirmed by drawdown or type test in the customer's actual ink or coating; no OML/SML, PAA or dosage is hard-coded. Respect the carrier boundaries: FLUV is the true solvent-free UV/EB family, and EB cure uses no photoinitiator; RFNC is resin-free but still contains solvent and must never be called solvent-free; FLTY high-solids still carries about 20% PMA (CAS 108-65-6) and must never be called solvent-free; GB/T 38508 is a cleaning-agent standard and is not a coating or packaging reference. The colorant is a compliant coloring component used in the food-contact material or coating; the finished article must undergo its own conformity verification. More colorant families and resin-matching guidance are on the DENSON website, and technical literature on dispersion and migration science is collected in the Literature section. Export shipments are handled through Dongguan Henvastness Import and Export Co.,LTD with the REACH, RoHS, CLP, low-PAA, no-phthalate, EU 10/2011 / FDA 21 CFR position letter and CBAM dossiers per consignment.

Core Conclusions

1. Food-contact colorants are a migration problem across five packaging scenarios. Flexible lamination (incl. solventless), UV/EB energy-cured inks and varnishes, metal can interior and exterior coatings, pressure-sensitive food labels, and paper-plastic / paper-based structures all judge the colorant by OML/SML, PAA, residual photoinitiator, NIAS, heavy metals and sensory performance — never by shade. The colorant is a compliant coloring component used in the material or coating; the finished article passes its own conformity verification.

2. Low-migration design means locking the pigment into the cured network and controlling every companion species. Use high-MW binders, polymer-bound dispersants, phthalate-free carriers, low-PAA azo-free colorants, and high crosslink density. EB cure removes the photoinitiator entirely; low-migration UV uses polymer-bound PI per standard limits. OML/SML, PAA, NIAS (GC-MS/LC-MS) and sensory acceptance are per EU 10/2011 and FDA 21 CFR 175.300/176.170/176.180, confirmed by accredited type test — no migration number is hard-coded.

3. Respect the compliance and carrier boundaries. Screen against REACH SVHC/Annex XVII, RoHS heavy metals, 2004/42/EC VOC honesty, GHS/CLP and CBAM, and issue a DoC and current SDS per consignment. FLUV is the true solvent-free UV/EB family (EB with no photoinitiator); RFNC is resin-free but solvent-containing; FLTY still carries about 20% PMA and is never solvent-free; GB/T 38508 is a cleaning-agent standard, not a packaging reference.

Frequently Asked Questions

Q1. Is the pigment colorant itself approved to directly contact food?
No. The colorant is a compliant coloring component used in the food-contact printing ink, coating or paper structure. The finished food-contact article — the laminated film, the lined can, the labelled jar, the aseptic carton — must be produced and tested by the converter/brand owner under EU 10/2011 and/or FDA 21 CFR (175.300 for resinous coatings, 176.170 for paper in contact with aqueous/fatty foods, 176.180 for dry foods) and must carry its own Declaration of Compliance. The colorant supplier provides the supporting declarations; it does not certify the finished article.

Q2. Why is EB curing preferred over UV for food-contact packaging inks?
Because UV cure requires a photoinitiator, and residual photoinitiator and its cleavage products are a well-documented migration and NIAS concern. EB cure generates radicals directly in the 100%-solids acrylate network with high-energy electrons and uses no photoinitiator, which removes that entire NIAS class. The EB route is therefore the lower-migration option for reverse-printed flexible packaging; low-migration UV formulations still rely on polymer-bound or low-extractable photoinitiators per standard limits and type test.

Q3. What is the difference between resin-free and solvent-free in a food-contact colorant?
They are not the same. FLUV is the true solvent-free UV/EB radiation-cure family. RFNC is resin-free by design but still contains solvent and must never be declared solvent-free or zero-VOC. FLTY high-solids still carries about 20% PMA (CAS 108-65-6) and is never solvent-free. Under Directive 2004/42/EC, solvent content must be declared honestly; misdeclaring a solvent-bearing paste as solvent-free is a compliance defect.

Q4. What compliance documents should a food-packaging converter request for a colorant?
At minimum: a current REACH Annex II SDS, an SVHC and azo/PAA statement, a heavy-metal/RoHS conformity screen, a no-phthalate statement, an honest VOC/solvent declaration under 2004/42/EC, the colorant's position letter for EU 10/2011 and FDA 21 CFR (175.300 / 176.170 / 176.180 as applicable), GHS/CLP classification, and CBAM embodied-carbon data where in scope. The finished article's OML/SML, NIAS and sensory results come from the converter's accredited type tests, not from the colorant datasheet.

Q5. Is GB/T 38508 a food-contact or packaging standard?
No. GB/T 38508 is a cleaning-agent standard and must not be cited as a coating, ink or food-contact packaging reference. For food-contact packaging the operative references are EU 10/2011, FDA 21 CFR 175.300/176.170/176.180, REACH, RoHS, 2004/42/EC, GHS/CLP and the applicable migration and sensory test methods.