Mono-PP Retort Pouches: What Modern Recyclable Sterilisation Packaging Can Deliver

Yes, retortable stand-up pouches made of mono-PP are already working today, and in series production. That is the short answer from the INNO-Talk “Retortable mono-material laminates – Barrier is key” on September 18, 2026, moderated by Julian Thielen (Innoform Coaching GmbH). The longer answer is more interesting for flexible packaging converters, food packers, and brand owners: Whether a mono-PP structure is suitable for a specific product is not decided by the barrier of the raw film. It is decided by what remains of it after lamination, pouch conversion, and autoclaving.

Two speakers contextualized the topic: Marc Heyer from KIN GmbH in Neumünster, a specialist in thermal preservation, spoke about sustainable food packaging and its thermal resistance. Sebastian Ritter, New Business & Sustainability Manager at Toppan Packaging Czech s.r.o., a manufacturer of SiOx-coated BOPP high-barrier films for hot filling and retort, presented “Monomaterial High Barrier Pouches – Innovation, Collaboration & Commercial Reality”.

Three levels of thermal treatment, and only one is the supreme discipline

Marc Heyer began with a classification that should stand at the beginning of every material decision: What thermal treatment does the packaging actually need to withstand?

• Hot filling and aseptic filling: around 75 to 85 °C, short holding time of a maximum of about five minutes.
• Pasteurization: 85 to 100 °C, non-pressurized, typically 30 to 60 minutes.
• Sterilization (retort): over 100 °C, in practice 105 to 130 °C at approx. 1.5 to 3 bar, with a specific pressure and temperature profile.

In sterilization, temperature, pressure, and time always work in tandem. The packaging must ensure two things during this process: barrier and seal integrity. Heyer compared four common systems. The liquid packaging board (beverage carton) with aluminum is suitable for hot filling and aseptic filling, but not for humid environments under pressure. The plastic-laminated paperboard tray with a 100 µm PP inliner is microwaveable, but cannot withstand autoclaving due to open edges. For PET trays, only C-PET, not A-PET, is suitable for sterilization. Finally, the PP pouch offers the best thermal and retort performance, but was previously limited in recyclability.

Striking was Heyer’s answer to the question of why liquid packaging cartons score well in his evaluation despite low recyclability: The system provider not only developed packaging, but also built up its own take-back and recycling stream with paper mills as early as the 1990s. There is a lesson in this for flexible packaging converters. A package is only as sustainable as the waste stream that receives it after use. Flexible PP packaging in Europe is currently collected in good quality by only a few sorting plants. Although new sorting lines are increasingly equipped with PP flex fractions, the infrastructure is still developing.

Why retort is a stress test for the entire laminate

Sebastian Ritter emphasized that temperature is only part of the stress. In addition, there are pressure, steam or hot water, long exposure times, mechanical stress, and pressure and temperature cycles. And there is no single retort process: steam, water immersion, and water spray autoclaves, HTST processes, and systems with rotation or agitation each stress the package differently.

After the process, everything must still be right: heat seal intact, bond strength preserved, barrier effective, product safe, shelf life achieved. Therefore, a universal retort structure does not exist. The right solution depends on the filling goods, process, required shelf life, and packaging requirements. How strongly autoclaving can change material properties and food contact suitability can be specifically tested in the laboratory.

From four-layer laminate to mono-PP: SiOx instead of aluminum

Conventional retort laminates like PET/Alu/CPP or PET/Alu/PA/CPP offer very good barrier properties, high bond strength, and reliable retort resistance. However, they combine different polymer families and usually aluminum, making them virtually unrecyclable. Under the PPWR, this becomes a major problem.

Toppan’s approach replaces the aluminum layer with a SiOx-coated BOPP film. The presented structure:

• Outer layer: BOPP 20 µm
• Middle (barrier): BOPP-SiOx 20 µm (“GL-RP”), consisting of BOPP base film, SiOx vacuum deposition, and an additional barrier top coat
• Sealing layer: CPP 80 µm

Vapor deposition and top coat add virtually no thickness; the laminate remains predominantly PP-based. The top coat serves three purposes: It protects the brittle inorganic layer from stretching during printing and lamination, improves adhesion to adjacent layers, and ensures stable printability. The principle stems from Toppan’s PET films with AlOx and SiOx coatings. For those wanting to understand the differences: Organic and inorganic barrier layers behave fundamentally differently. For a broader overview of materials and mechanisms, see our article Understanding barrier films.

The stated values: OTR around 0.8 cm³/(m²·d) and WVTR around 0.5 g/(m²·d), currently around 0.5/0.5 and partially lower according to Ritter. Testing was conducted up to 131 °C for 30 minutes. Validation at 130 °C for half an hour has so far been achieved for smaller three-side seal pouches with 85 to 100 g filling weight. Toppan considers same-sized stand-up pouches with bottom gussets to be feasible. With high-barrier values of this magnitude, measuring technology also becomes demanding, see More precise OTR analysis for high-barrier packaging.

Barrier before retorting does not count: the five-step test

For converters and packers, this part is the most critical. A film can have outstanding values in the laboratory. If the barrier is damaged during pouch conversion or in the autoclave, the structure will still fail. Toppan therefore tests in five steps:

1. Measure barrier of single film
2. Laminate
3. Convert pouch
4. Pass through retort process
5. Measure barrier again

After retorting, OTR and WVTR alone are not enough. In addition, heat seal strength, delamination, flex-crack resistance, appearance and deformation, as well as the actual storage test belong in the test program. Toppan’s customers typically carry out drop tests from a height of one meter. For small pouches this is uncritical, for 400 g stand-up pouches it is demanding, but feasible.

Practical example: Stand-up pouches for soups and ready meals

Ritter demonstrated that this is not just a lab concept using a commercial project with Australian brand Flavour Makers, running for about two years and awarded a Gold Award. A stand-up pouch for soups and ready meals switched from PET/Alu/PA/CPP to OPP 20 µm / BOPP-SiOx 20 µm / CPP 80 µm. The results:

• good seal integrity at 140 °C sealing temperature
• unaltered line speed of 22 packs per minute
• 18-month shelf life after sterilization at 121 °C for 45 minutes
• thinner laminate, less material complexity, designed for recycling according to Australian standards

Line speed in particular is often the decisive factor for brands and retailers: No one wants to sacrifice packaging output for recyclability. According to Ritter, 100 g three-side seal pouches made of mono-PP are also running on the market without speed losses, and further applications are commercialized in the UK.

What does the barrier gap compared to aluminum mean for shelf life?

Aluminum is an absolute barrier. SiOx comes close, but does not achieve it completely. This affects shelf life, but the degree depends on the product. Wet pet food usually requires 24 months, while food for human consumption often calls for 12 to 18 months. According to Ritter, a customer recently achieved 24 months with a tuna product. Severe retort conditions deteriorate the barrier and thus the shelf life. Ritter considers 12 to 18 months realistic, and 24 months possible in some cases.

Marc Heyer added an important distinction. Microbiologically, a sufficiently sterilized product, such as wet pet food with high F-values, is virtually stable indefinitely. The limiting factor is sensory shelf life—meaning oxidation, loss of flavor, and color changes. This is precisely where the oxygen barrier comes into play. For specifications, this means: Derive OTR requirements from the sensory shelf life goal, rather than requesting ‘like aluminum’ as a rule of thumb.

Sealing: Ultrasonic uncritical, thermal contact more demanding

A question from the audience will sound familiar to many packers: “We made similar pouches, but sealing was an issue.” Ritter’s assessment: Ultrasonic sealing works well; heat contact sealing can be more difficult. The reason lies in the mono-material itself. In conventional laminates, each layer serves a distinct function, and outer layer and sealing layer differ significantly in melting behavior. With mono-PP, the sealing window is narrower. Toppan therefore offers on-site technical support to align the laminate and machine settings. Read more on the interaction of film, machine, and packaged goods in Safe packaging: Interaction of film, machine, and filling goods.

Where mono-PP retort fits today, and where it does not yet

Ritter cited wet pet food, ready meals, rice and grains, beans and pulses, seafood, stews, sauces, and soups as suitable application fields. The poll at the start of the INNO-Talk matched this: Over 40 percent of participants believe mono-retort pouches can replace multi-material laminates, but only for selected applications. Limits are set by particularly large pouches, very long or hot sterilization profiles, and demands for very long shelf lives.

A side note addressed high-pressure processing (HPP): around 6,000 bar for about three minutes, applicable only with flexible packaging and within the cold chain. In Germany, it is rarely used due to high investment costs, slow batch processes, and former novel food classification. Heyer contributed a detail: Around 95 to 98 percent of global guacamole production uses HPP.

Costs, PPWR, and timing: What brands must decide now

87 percent of participants see a significant impact of the PPWR on the selection of heat-treatable packaging, 11 percent a moderate impact, and only 2 percent none. Brand owners and retailers cited technical issues and costs as the biggest hurdles to switching with about equal frequency. Ritter estimated the cost gap of a mono-PP structure compared to a conventional laminate at roughly 30 percent, depending on supplier and converter. On the other hand, there are lower material weight, elimination of the aluminum layer, and future eco-modulated EPR fees favoring recyclable packaging. What the PPWR since August 2026 specifically means for flexible packaging manufacturers, we have summarized separately, as well as the question of recyclability by 2030.

The time factor is crucial. Material validation and approval take 12 to 36 months for wet pet food. Ritter’s advice to brand owners: start now, SKU by SKU, instead of waiting until 2029 and then having to transition the entire product range at once.

Conclusion: Technically feasible, now the value chain is called upon

The question is no longer whether mono-material retort is possible, but when the market will make the shift. Mono-material does not mean simply replacing a PET or aluminum layer with PP. It requires enhanced barrier technology, matched adhesive and ink systems, and careful process adaptation. No single company can achieve this alone. Raw material suppliers, film manufacturers, adhesive and printing ink providers, machine builders, recyclers, brands, and retail must collaborate.

What this means for the individual roles:

• Flexible packaging converters: Lamination and pouch making are critical steps for barrier properties. The barrier after retorting is the metric that counts. Adhesive systems and sealing windows must be specifically designed for mono-PP.
• Food packers: Share retort type (steam, immersion, water spray, rotation), F-value, and profile early with the supplier. Re-qualify sealing parameters. Include drop tests and storage testing in the release process.
• Brands and retail: Justify shelf-life targets sensorially, plan for a validation time of up to three years, start with products having moderate requirements, and roll out the transition step by step.

The topic will be explored live at INNO-Pouch 2026 on October 8 and 9, 2026, at HP in Barcelona. There, Sebastian Ritter will showcase further practical examples from collaborations along the value chain, including retort applications with water-based printing inks and adapted adhesive systems.

Frequently Asked Questions about Mono-PP Retort Pouches