Decolorization testing is a critical safety evaluation that determines whether colorants and pigments in health supplement bottles can migrate into the product or into food-contact simulants under realistic conditions of use. As a mandatory requirement under food contact material regulations such as GB 4806.7-2016 in China, this test helps packaging manufacturers, brand owners, and supplement producers verify product safety, protect formulation integrity, and secure regulatory market access worldwide.
Technical Overview
Health supplement bottles—including HDPE, PP, and PET containers—are frequently colored with pigments and masterbatches to provide light protection, brand differentiation, or content masking. The decolorization test evaluates whether these colorants remain immobilized within the polymer matrix or whether they can transfer to the product under intended and foreseeable conditions of use.
The test is primarily governed by food contact material frameworks. In China, GB 4806.7-2016 (National Food Safety Standard for Food Contact Plastic Materials and Articles) explicitly requires that plastic materials and articles shall not transfer color to food. Similar safety principles are enforced in the EU through Regulation (EU) No 10/2011 and Resolution AP(89)1 on colorants, and in the United States through FDA 21 CFR 178.3297 governing colorants for polymers. Test preparation and preconditioning follow GB 5009.156-2016, which defines how food simulants, contact temperatures, and contact times are selected to represent actual use scenarios.
The underlying principle is straightforward: the food-contact surface of the bottle is exposed to selected simulants using either a rubbing (wipe) technique or full immersion, after which the simulant and the wiping medium are examined for visible color transfer. Any discernible staining constitutes a failure, indicating that non-polymer-bound colorants, poorly dispersed pigments, or unsuitable dye chemistries are present in the material.
Testing Samples
Plastic Bottle Bodies
Colored or opaque bottle bodies made from HDPE, PP, PET, or PETG represent the most common test articles. Both the exterior and interior surfaces may be evaluated, but regulatory emphasis is placed on surfaces intended to contact the supplement product directly, including tablets, capsules, powders, and liquids.
Closures, Caps, and Liners
Screw caps, flip-top closures, induction seals, foam liners, and shrink bands are frequently molded from different resin and colorant systems than the bottle body. Because closures are in direct or indirect contact with the product, they must be evaluated independently for color migration risk.
Multi-Component Assemblies
Desiccant cap assemblies, measuring spoons, dosing cups, silica gel canisters, and tamper-evident rings are composite systems that combine multiple polymers, adhesives, and pigments. Decolorization testing should cover each component that contacts or resides in close proximity to the supplement formulation.
Testing Items
A comprehensive decolorization assessment for health supplement packaging typically includes the following evaluations:
- Color migration into aqueous food simulants (e.g., deionized water or 10% ethanol)
- Color migration into acidic simulants (e.g., 4% acetic acid solution)
- Color migration into alcoholic simulants (e.g., 20% or 50% ethanol, relevant for herbal tinctures and liquid extracts)
- Color migration into fatty food simulants (e.g., olive oil, 95% ethanol, or isooctane as substitute simulants, relevant for softgel capsules and oil-based formulations)
- Surface color fastness determined by rubbing the contact surface with simulant-soaked cotton gauze
- Visual examination of simulant staining, turbidity, and surface bleaching after exposure
- Optional spectrophotometric quantification of extracted color and migration screening of regulated colorant species
Testing Methods
Testing is performed by accredited third-party laboratories or in-house quality laboratories using controlled procedures. Sample preparation follows GB 5009.156-2016, which specifies cleaning, conditioning, and the selection of simulants and exposure conditions based on the intended food type, contact temperature, and contact duration.
The two principal techniques are applied as follows:
- Rubbing (Wipe) Method: A piece of absorbent cotton gauze is saturated with the selected food simulant and rubbed repeatedly against the food-contact surface of the bottle or closure under standardized pressure. The gauze is then examined for visible color pickup. This method detects surface contamination, blooming pigments, and poorly bonded surface colorants.
- Immersion Method: The sample is fully immersed in the food simulant and held at a temperature and time reflecting worst-case intended use (for example, reflux conditions or extended room-temperature storage). After exposure, the simulant is inspected for coloration, and the sample surface is checked for fading, mottling, or pigment bleed.
Evaluation is conducted against a pass criterion of no visible color transfer to the simulant, the gauze, or a white contrast background. For borderline results, instrumental color measurement using a spectrophotometer can provide objective delta-E values to support the visual judgment. When failures occur, root causes commonly include the use of solvent dyes in polar simulants, excessive colorant loading, inadequate pigment dispersion, or contamination during injection molding and blow molding processes.
Applications
Decolorization testing serves multiple commercial and regulatory purposes across the supplement industry supply chain:
- Regulatory compliance demonstration for market entry in China under GB 4806.7-2016, including product registration and filing dossiers
- Export certification support for EU Regulation (EU) No 10/2011 and FDA 21 CFR requirements in the United States
- Incoming material quality control for bottle and closure suppliers to supplement manufacturers
- Qualification of new resin grades, masterbatches, or colorant systems before production release
- Verification of packaging compatibility with specific formulations, such as oily softgel products, alcohol-based extracts, and acidic liquid supplements
- Failure analysis and corrective action support when color staining or product contamination is observed in the field
FAQ
How many bottles are required for testing? Typically, laboratories request 20 to 50 complete bottles or closures per simulant condition to ensure representative sampling across production variation. Additional units are recommended if both rubbing and immersion methods are required.
What is the typical turnaround time? Standard decolorization testing usually completes within 5 to 10 working days, depending on the exposure conditions selected. Extended migration conditions simulating long-term storage may require additional time for preconditioning and evaluation.
Do all colored supplement bottles need this test? In jurisdictions applying GB 4806.7-2016, the no-color-transfer requirement applies to all plastic food contact materials, including natural and colored bottles. Colored and heavily pigmented containers carry higher inherent risk and warrant priority testing.
Which simulant applies to oil-based softgel products? Fatty food simulants such as olive oil, or substitute simulants such as 95% ethanol or isooctane, are selected because lipid-contact conditions maximize the extraction of many organic pigments and solvent dyes.
How can a failing bottle be corrected? Common remedies include switching to polymer-bound pigments or pre-approved colorant lists, reducing masterbatch loading, improving dispersion during compounding, and implementing stricter incoming inspection of color concentrates with the support of accredited third-party laboratories.