Fat Migration in PFAS-Free Paper Packaging: What 2022–2026 Research Shows for Hot, Oily Foods

Introduction

As food manufacturers move away from fluorinated grease barriers, reliable oil resistance in paper packaging remains a technical challenge. A material that performs well in an ambient laboratory test may behave differently against hot, fatty food. This review examines 2022–2026 research on fat migration in PFAS-free paper packaging: how fat moves through paper, how it is measured, how fluorine-free barriers perform, and what this means for food product development and pack design. For the regulatory side of the switch, read Part 1: PFAS-free paper packaging rules in the GCC.

Why Fat Migration Is the Key Test for PFAS-Free Paper

What fat migration is and why heat makes it worse

“Oil migration” in food packaging has two meanings. This article uses it for strike-through: fat wicking into and through the paper. The second meaning, substances moving from the packaging into the food, is the subject of migration testing and, for PFAS, of Part 1. Liquid penetration into porous paper is commonly modelled with the Lucas–Washburn equation, in which penetration slows as viscosity rises.^[1] Warmer, thinner fat should therefore move faster, and longer holds give it more time. That is an inference from the model, not a measured hot-food result.

The oil-rich, heat-served food challenge

GCC food-service formats combine these variables: free oil on fried items and shawarma, steam and oil in biryani, hot juices from grilled meats, and long delivery holds. Published tests cover only parts of this: dyed canola oil at 60 °C for 4 h on recycled copy paper,^[2] and an edible oil of unstated type at 95 ± 5 °C for 30 min on moulded-pulp meal boxes.^[3] No reviewed study followed a real GCC dish through a PFAS-free pack, so conclusions for these formats are inferences from laboratory data.

What 2022–2026 Research Shows

Performance of fluorine-free barrier coatings

Fluorine-free coatings now reach high kit ratings in laboratory tests. Polyvinyl alcohol blended with bamboo-derived cellulose nanofibres (PVA/CNF) on a 110 g/m² base paper raised the kit rating from 0 (uncoated) to 9 at 2.0 g/m² and 12 at 4.0 g/m² (TAPPI T559).^[4] TEMPO-oxidised cellulose nanofibril (TOCN) coatings of about 10 g/m² on recycled copy paper averaged kit 11.7 of 12, and 2–3 g/m² of TOCN reduced dyed canola-oil penetration (60 °C, 4 h) on uncreased sheets to essentially zero. Papers coated with as-received cellulose nanocrystals (CNC) reached a highest average of only about kit 1.^[2] For comparison, a 2024 review lists perfluoropolyether-coated paper at kit 10–11 and other fluorinated coatings at kit 3–9.^[5]

Chitosan, starch and wax alternatives

Highly deacetylated chitosan (>95% degree of deacetylation (DD), 4% w/v solution, about 3.7 g/m² coating load) sprayed on moulded-pulp meal boxes reached kit 12/12 and held edible oil at 95 ± 5 °C for 30 min without leakage in three replicates. The 80–95% DD grade let hot oil infiltrate, and uncoated boxes leaked hot oil in about five minutes.^[3] A 2025 review reports microcrystalline wax at 10 g/m² on cationic-starch-precoated paper at kit 12/12; the wax is petroleum-derived, so it is fluorine-free but not biobased. The same review notes the water sensitivity of alginate and cationic starch coatings.^[6] These figures come from peer-reviewed studies. Commercial dispersion or cellulose coatings offered by converters remain supplier claims until they are tested on your pack, a point that also applies when reformulating for compostable packaging.

Where barriers still fail under hot, oily conditions

Reported weak points fall into three groups.

• Creases: after a double fold, dyed oil stained more than 20% of the receiving blotter under CNC-coated papers even above 12 g/m², while creased TOCN-coated papers stayed below 5% at high coat weights.^[2]
• Coverage: the uncoated edge of a chitosan-coated meal box showed noticeable oil leakage while the coated interior held.^[3]
• Coat weight: kit rose from 9 at 2.0 g/m² to 12 at 4.0 g/m² in one PVA/CNF study,^[4] and a follow-up PVA/CNF composite study cites earlier work finding at least 10 g/m² desirable for nanofibril barriers.^[7]

Hot-oil tests often leave the oil type unstated,^[3] so a pass temperature cannot be generalised across fats. Kit ratings therefore only partly predict how a pack performs in service.

Table 1. Literature-based fat-resistance results (no FRL laboratory data; n/s = not stated)

Takeaway: every high kit rating comes from a flat or uncreased sample; the only heated tests used 60 °C and 95 °C, and creasing raised penetration.

Test fat migration on your product and pack

A supplier’s kit rating describes a flat sheet at room temperature. FRL can plan hot-oil and hold-time tests around your recipe, filling temperature and finished pack.

Request a packaging compatibility assessment

How Fat Migration Is Measured

Kit test, Cobb and grease-penetration methods

Grease resistance in paper is measured by repellency, penetration and permeability methods, and each answers a different question. The kit test (TAPPI T559) rates surface repellency with 12 numbered solutions of castor oil, toluene and n-heptane.^[2] ISO 16532-2:2007 is the ISO surface-repellency test and is not intended to measure grease permeability.^[8] ISO 16532-1:2008 covers permeability, timing how long palm kernel oil takes to penetrate creased or uncreased paper and board.^[9] The Cobb test measures water absorption, not fat: PVA/CNF at 4.0 g/m² reached kit 12 while its Cobb value (21.80 g/m²) was higher than the base paper’s 17.75 g/m².^[4] A sound programme pairs a repellency method with a penetration or permeability method before any oil- and grease-resistance (OGR) claim is made.

Realistic time–temperature testing

A realistic protocol fixes the oil type, temperature, contact time, creases and seams, and coat weight. Published conditions range from 60 °C for 4 h^[2] to 95 ± 5 °C for 30 min under GB/T 36787-2018.^[3] A kit rating measured without heat says nothing direct about hot service. For substance migration, simulant choice also matters: PFAS migration into 50% ethanol was significantly higher than into real food, and fluorotelomer alcohols did not migrate into 20% ethanol at all.^[10] Align every test with the serving temperature and hold time.

Table 2. Fat-migration test methods compared

Takeaway: only the last two heated methods approach service conditions, and neither uses a real food.

Implications for Formulators and Packaging Developers

FRL PFAS-Free Compatibility Matrix

Table 3 maps the tested barriers to the nearest GCC food format so formulation and packaging choices can be reviewed together. It is a literature-based screening judgement, not FRL laboratory data.

Table 3. Literature-based compatibility matrix (screening judgement)

Takeaway: no GCC format has a direct PFAS-free test on a real dish; the closest evidence is a proxy oil on a flat or moulded sample.

Reformulation levers: surface oil, fat and structure

What the evidence suggests formulators can change (inference, not tested on PFAS-free packs):

• Surface oil: less free fat at filling leaves less liquid to wick.
• Fat system: oil contact angles vary by about 20° depending on the oil used,^[5] and lower-viscosity liquids penetrate faster,^[1] so fat type and filling temperature belong in the test plan.
• Food matrix: PFAS transfer into real foods differed from transfer into ethanol simulants,^[10] so the food itself matters for substance migration as well as strike-through risk.

Treat these as hypotheses for pilot trials in food product development, not validated fixes. Container softening from oil and moisture is covered in our review of biodegradable packaging shelf life.

Worked example (proposed test plan): a paper fried-rice box

Brief: A paper-based fried-rice box carries a PFAS-free declaration, and the concern is oil appearing at the base seam after a long delivery hold. The declaration addresses PFAS content, not grease holdout, so it does not show how the box performs with hot oil over time.

Approach: Record the dish’s oil load, filling temperature and delivery hold time. Identify the exact paper grade and any barrier layer, since a PFAS-free board may be uncoated, dispersion-coated or laminated. Test the finished, folded box at filling temperature, and assess fat moving through the board (strike-through) separately from substance transfer into the food.

• Specification: oil load, filling temperature and hold time, so test conditions match real use.
• Surface repellency: the kit test (TAPPI T559; ISO 16532-2) shows surface repellency only, not whether oil passes through the board.
• Permeability: ISO 16532-1 on creased as well as uncreased samples, since creasing can damage the barrier layer.
• Hot-oil hold test: fill the folded box, hold it at filling temperature for the delivery time, and check the base seam and corner folds for stain or strike-through. Published hot-oil methods such as GB/T 36787-2018 (95 ± 5 °C, 30 min) can serve as a reference.
• Reformulate and retest: if oil breaks through, reduce free surface oil within food-safety limits and repeat the same test.

What it delivers: a test plan matched to real use, with a defined route from a failed test to a reformulation step. This is a proposed framework, not a report of completed FRL testing; suitability is decided only after the results are reviewed.

Request a fat migration and compatibility assessment

FRL can scope tests on your recipe, filling temperature and finished pack before launch.

Talk to our packaging team

Research Gaps and What to Watch Next

No oil has been adopted as a standard for oil contact-angle measurement, and reported values vary by about 20° between oils.^[5] Studies use different units, coat weights and conditions, and biopolymers cost about USD 4,000–15,000 per tonne against about USD 1,500 for synthetic polymers.^[6] Oil types are often unstated,^[3] and replicate numbers vary between studies. Creasing remains a challenge for nanocellulose coatings.^[2] No reviewed study compared fluorinated and PFAS-free coatings in the same hot-oil test. Watch for head-to-head trials and standardised hot-oil methods.

Formulator’s note: report the whole test, not the rating

Quote the exact paper, barrier, coat weight, oil, temperature and hold time with every result. A kit 12 at room temperature is not a hot-oil pass. Test your own fat, at your filling temperature, on the finished, folded pack.

Conclusion

Research on fat migration in PFAS-free paper packaging shows real progress: several fluorine-free coatings reach kit 11–12 in the laboratory, and one chitosan coating held 95 °C oil for 30 minutes on a moulded-pulp box. High kit ratings still do not guarantee resistance to hot, oily food in a folded, creased pack held through a delivery run. Testing the finished pack with your own food before launch finds failures early and supports better product decisions. For the regulatory requirements, read Part 1: PFAS-free paper packaging rules in the GCC.

For Brands & Formulators: Testing PFAS-Free Packs for Hot, Oily Foods

If you are moving a hot, oily product into PFAS-free paper packaging for the UAE or wider GCC, FRL can plan a compatibility study built around your own food and finished pack, not a flat-sheet rating.

• Define the challenge: oil load, filling temperature and delivery hold time.
• Match the methods: surface repellency (kit), permeability on creased and uncreased board, and a hot-oil hold test on the folded pack.
• Close the loop: if oil breaks through, adjust free surface oil or the pack specification and retest under the same conditions.

Start with FRL’s packaging testing services, pair them with a shelf-life study of the finished product, or contact the team to scope the work.

1. Waldner, C., & Hirn, U. (2023). Modeling liquid penetration into porous materials based on substrate and liquid surface energies. Journal of Colloid and Interface Science, 640, 445–455. https://doi.org/10.1016/j.jcis.2023.02.116
2. Sabo, R., Schilling, C., Clemons, C., Franke, D., Gribbins, N. R., Landry, M., Hoxie, K., & Kitin, P. (2024). Grease, oxygen, and air barrier properties of cellulose-coated copy paper. Polysaccharides, 5(4), 783–806. https://doi.org/10.3390/polysaccharides5040049
3. Shen, Z., Yang, Y., Hu, S., & Kong, W. (2025). Sustainable water- and oil-repellent coating for disposable meal boxes based on highly deacetylated chitosan. Materials, 18(12), Article 2741. https://doi.org/10.3390/ma18122741
4. Huang, S., Wang, X., Zhang, Y., Meng, Y., Hua, F., & Xia, X. (2022). Cellulose nanofibers/polyvinyl alcohol blends as an efficient coating to improve the hydrophobic and oleophobic properties of paper. Scientific Reports, 12, Article 16148. https://doi.org/10.1038/s41598-022-20499-8
5. Guzman-Puyol, S. (2024). Fluorinated compounds in paper and paperboard based food packaging materials. npj Science of Food, 8, Article 82. https://doi.org/10.1038/s41538-024-00326-2
6. Rozas, B., Bruna, J. E., Guarda, A., Galotto, M. J., Reyes, C., Valenzuela, X., Rodríguez-Mercado, F., & Torres, A. (2025). Bio-based coatings on cellulosic materials resistant to humidity and fats. Polymers, 17(20), Article 2755. https://doi.org/10.3390/polym17202755
7. Huang, S., Wang, X., Zhang, Y., Meng, Y., Hua, F., & Xia, X. (2023). Water and oil-grease barrier properties of PVA/CNF/MBP/AKD composite coating on paper. Scientific Reports, 13, Article 12292. https://doi.org/10.1038/s41598-023-38941-w
8. International Organization for Standardization. (2007). Paper and board: Determination of grease resistance: Part 2: Surface repellency test (ISO Standard No. 16532-2:2007). https://www.iso.org/standard/40042.html
9. International Organization for Standardization. (2008). Paper and board: Determination of grease resistance: Part 1: Permeability test (ISO Standard No. 16532-1:2008). https://www.iso.org/standard/37980.html
10. Lerch, M., Nguyen, K. H., & Granby, K. (2022). Is the use of paper food contact materials treated with per- and polyfluorinated alkyl substances safe for high-temperature applications? Migration study in real food and food simulants. Food Chemistry, 393, Article 133375. https://doi.org/10.1016/j.foodchem.2022.133375