TL;DR: Choosing between PVA, pullulan, and starch-based formats is a material science decision first — the dissolution profile, seal geometry, and food-contact compliance path all branch differently from that single choice.
TL;DR: In our qualification trials, PVA film at 25µm dissolves in cold water (10–15°C) within 90 seconds, but the same grade fails seal integrity below 130°C sealing jaw temperature — a parameter most incoming briefs omit entirely.
Dissolution Rate vs. Seal Integrity — The Specification Conflict That Drives Most Sample Failures #
The parameter buyers most often specify is dissolution time. The parameter that actually determines whether a pouch survives shipping is seal strength — and these two properties pull in opposite directions.
Thinner PVA film (15–20µm) dissolves faster but produces weaker seals. The ASTM F88 seal strength test measures peel force in N/15mm; for cold-water-soluble PVA pouches in unit-dose detergent applications, we target ≥4.5 N/15mm minimum seal strength while keeping cold-water dissolution under 120 seconds at 10°C. Getting both in the same structure requires film grade selection at the polymer level — hydrolysis degree and molecular weight both matter. A film with 87–89% hydrolysis degree dissolves readily in cold water; a film at 98%+ hydrolysis needs hot water (≥60°C) to fully disperse. Brands specifying “water-soluble” without defining water temperature have created an ambiguous brief.
For pullulan-based edible film (used primarily in oral-strip supplements and breath strips), the specification axis shifts entirely. Dissolution in saliva at 37°C within 30 seconds is the functional target, but tensile strength at ≥30 MPa (per ASTM D882) is what keeps the strip intact through production handling and blister-pack loading. Pullulan strips we produce run at 20–30µm finished thickness with ±2µm caliper tolerance on our slot-die coating line.
Starch-based formats — cassava, corn, or potato starch blends — occupy a different quadrant. They are typically 40–80µm, compostable under EN 13432 conditions, but their water sensitivity makes them unsuitable for high-humidity environments without a secondary overwrap. We track incoming moisture content on starch film lots using our MI-04 intake protocol — lots arriving above 14% moisture content are quarantined pending retest, because above that threshold, the film becomes tacky and blocks on the roll.
Supplier Qualification — What to Request and What the Response Tells You #
Ask any candidate supplier for a Certificate of Conformance that explicitly references FDA 21 CFR §177.1670 (for PVA in food-contact applications) or EU Regulation No. 10/2011 for plastic materials and articles intended to contact food. A supplier who responds with a general “food-grade” declaration and no regulation number should be treated as unqualified for regulated markets.
Request the specific hydrolysis degree and degree of polymerisation (DP) for PVA film. Suppliers who decline to share these values are protecting formulation IP, which is legitimate — but insist they at minimum confirm whether the film is cold-water or hot-water soluble grade, and at what temperature threshold. The distinction between 88% and 98% hydrolysis is not academic; it changes the end-user experience completely.
For pullulan or starch-based materials, request migration test data per EN 13130-1 for specific migrants relevant to the application. If the packaging will contact lipid-rich food (nut bars, chocolate centres), ask specifically for fat simulant (olive oil or isooctane) migration results. A supplier who has never run fat simulant migration testing should not be supplying direct-contact edible packaging for those applications — their material may be compliant for aqueous food but untested for fat contact.
Turnaround time on these data requests is diagnostic. Qualified suppliers in our approved vendor list (AVL) return full TDS and compliance documents within 72 hours. A response time of over five business days usually indicates the data does not exist in ready form.
Cost-Performance Trade-offs Across Edible and Water-Soluble Formats #
PVA unit-dose film for laundry or dishwasher pods is the highest-volume format and benefits from scale. At 50,000+ pouches per run, material cost per unit is manageable. Pullulan oral strips cost significantly more per square metre of substrate — pharma-grade pullulan film runs at a noticeable premium over commodity PVA, which is why the oral supplement market defaults to pullulan only where the tactile melt and flavour-carrier properties are genuinely required.
Starch-based formats offer the most competitive sustainability story for compostable claims, but their moisture sensitivity adds downstream cost: storage must be climate-controlled at ≤55% RH, and shelf-life for unfilled starch pouches is typically 12–18 months versus 24+ months for PVA. For brands entering a market where compostable packaging is a regulatory requirement (several EU member states are moving in this direction under the PPWR framework), the cost premium on starch formats is a compliance cost, not a discretionary upgrade.
The counterargument worth stating: for single-use agricultural pods (fertiliser, pesticide concentrate) intended to dissolve in large-volume outdoor water, cold-water PVA is often the wrong choice. Hot-water-soluble PVA at 76–78µm with a minimum seal strength of 8 N/15mm is the specification we recommend for agricultural applications — cold-water grades risk premature dissolution during rain exposure before the product is deployed.
Technical Deep-Dive — Seal Geometry and Its Effect on Dose Accuracy in Unit-Dose Pouches #
This is the specification area where briefs are most consistently incomplete, and where sample iteration cycles are longest.
A unit-dose pouch — whether laundry gel, dishwasher detergent, or nutraceutical powder — has four seals: two longitudinal (side seals) and two transverse (top and bottom, or one of each in pillow format). The seal width on each affects both structural integrity and fill volume accuracy. Our standard unit-dose pouch tooling produces 8mm seal width on all four sides. Narrowing to 5mm seal width gains approximately 12% more fill volume in the same footprint, but the burst pressure drops measurably under the ASTM D4169 distribution simulation protocol — we’ve measured burst pressure reductions of 18–25% when moving from 8mm to 5mm seals in 25µm PVA film.
| Pouch Format | Film Thickness | Seal Width | Cold-Water Dissolution | Seal Strength (N/15mm) | Primary Application |
|---|---|---|---|---|---|
| Cold-water PVA unit-dose | 25µm | 8mm | <90 sec at 10°C | ≥4.5 | Laundry/dishwasher pods |
| Hot-water PVA agricultural | 76–78µm | 10mm | <60 sec at 60°C | ≥8.0 | Fertiliser/pesticide pods |
| Pullulan oral strip | 20–30µm | N/A (cut sheet) | <30 sec at 37°C | N/A (strip, not pouch) | Supplement/pharma strips |
| Starch-blend compostable pouch | 40–60µm | 8–10mm | Degrades in 12 weeks (EN 13432) | ≥3.5 | Food portioning, EU compostable |
Dissolution and seal strength values are format-typical targets from our qualification trials. Final specifications are set per product brief.
Jaw temperature during heat-seal is the variable that causes the most rework in our production runs. PVA is unforgiving: below 125°C, seals are weak and peel-prone; above 155°C on a 25µm film, you get burn-through or deformation at the seal edge. Our production sealing window is 130–150°C at 0.3 MPa jaw pressure and 1.0–1.5 second dwell time. Outside that window, 100% of pouches go through our leak-and-seal integrity check (offline hydrostatic pressure test at 35 kPa) before release — and we expect a higher rejection rate.
One variable we’re still tracking: the interaction between fill liquid viscosity and seal contamination in liquid-fill PVA pouches. Gel detergents above 8,000 cP have shown a higher incidence of seal-area contamination in our 2024 production data across 14 runs, leading to incomplete seals that pass visual inspection but fail the hydrostatic test. We’ve tightened our fill-head purge cycle to address it, but the dataset across gel viscosity ranges is still building.
Specification Notes for Brand Partners #
When you brief us on an edible or water-soluble packaging project, the information that unblocks the most work fastest is: dissolution trigger (temperature of water, saliva, or ambient humidity), fill type (dry powder, liquid gel, solid tablet, strip substrate), and the regulatory market (US FDA, EU, AU TGA, or unregulated agricultural). Without those three inputs, we cannot confirm film grade, seal specification, or compliance pathway — and first samples will almost certainly require iteration.
The brief gap that causes the most sample cycles is fill viscosity for liquid-fill pouches. If your product is a gel rather than a low-viscosity liquid, state the cP range in your brief. We set fill-head parameters, purge cycles, and dwell time based on viscosity — briefs that say “liquid detergent” without a viscosity figure default to our low-viscosity setup, which produces contaminated seals on high-viscosity gels and requires a full retooling between sample rounds.
Our standard sampling timeline for a new unit-dose PVA pouch format is 15–18 working days from confirmed specification. Pullulan oral strip samples run 20–25 working days due to coating lead time. Starch-blend compostable formats add approximately 5 working days if we need to source a new starch grade outside our current three approved suppliers.
What dissolution temperature should I specify for my water-soluble pouch?
It depends on your application water temperature. Cold-water-soluble PVA (87–89% hydrolysis) is correct for household laundry machines running at 10–30°C. Hot-water grades (98%+ hydrolysis) are more appropriate for dishwasher applications where water reaches 60–65°C, or agricultural pods that need resistance to rain before use. If your end-use water temperature is variable, we test dissolution at both 10°C and 60°C before releasing a film grade.
Can PVA pouches be printed directly?
Yes, with constraints. Water-based flexo inks are compatible with PVA film surface energy (typically 38–42 mN/m after corona treatment). Solvent-based inks and UV-cure inks require migration testing before use in food-contact or direct skin-contact applications — we run ink migration screening per EN 13130-1 on any non-validated ink system before production approval.
What’s the minimum order quantity for custom unit-dose PVA pouches?
Our minimum production run for custom-format PVA unit-dose pouches is 50,000 units. Below that threshold, tooling amortisation makes unit economics unfavourable for most buyers. Pullulan oral strips carry a higher setup cost and our minimum run is 100,000 strips for a custom-dimension format.
Is compostable starch packaging suitable for liquid fills?
Not in most current starch-blend films without modification. Uncoated starch pouches absorb moisture from liquid contents and lose structural integrity within hours. For liquid-fill compostable applications, a thin PVOH coating on the inner surface is the current technical solution, though this adds cost and requires re-evaluation of the compostability claim under EN 13432, since the full structure must meet the standard — not just the substrate.
How do you verify seal integrity at production scale?
Every production lot of unit-dose pouches goes through AQL Level II sampling per ANSI/ASQ Z1.4, with a 100% visual seal inspection inline and offline hydrostatic pressure testing at 35 kPa on the sampled units. For pharmaceutical or nutraceutical strip applications, we apply tighter AQL Level I sampling with an expanded defect classification that includes pinhole detection via methylene blue dye penetration testing.
Planning a packaging project? Contact our team to request a complimentary specification review and sample quote.
