Analysis of 10 Types of Retort Pouch Structures and Features

As people’s demand for food safety, convenient storage and long shelf life continues to increase, retort pouches, as an important material in modern food packaging, are playing an increasingly critical role. Retort pouches can not only withstand high-temperature sterilization, but also have good sealing, barrier and mechanical strength. They are widely used in the packaging of cooked food, prepared food, meat products, seafood, soups and other foods.

This article will analyze 10 common retort pouch structures and their respective characteristics in detail to help food manufacturers and packaging purchasers choose the most suitable material structure combination more scientifically.

PET/Glue/CPP Structure

This is a typical transparent retort pouch structure with good visual display effects. PET provides good stiffness and printability, and CPP has heat sealing performance and high temperature resistance. This structure can be changed to PA/glue/PE, and PE can be changed to HDPE, LLDPE, and MPE.

Due to the temperature resistance of PE, it is generally used for sterilization bags at around 100~110℃. Ordinary polyurethane glue and boiling glue can be used for glue. It is not suitable for meat packaging. The barrier property is poor. The bag will wrinkle after steaming, and sometimes the inner film sticks to each other. In essence, this structure is just a boiling bag or pasteurized bag.

PET/Glue/CPP Structure

This structure is a typical transparent retort pouch structure, which can package most steaming products. Its characteristics are strong visibility of the product, and the contents can be seen directly, but it cannot package products that need to be protected from light. The product feels hard and often needs to be rounded.

This structure product is generally sterilized at 121℃, ordinary high-temperature steaming glue, and ordinary-grade steaming CPP. However, the glue should be selected with a small shrinkage rate, otherwise the shrinkage of the glue layer will drive the ink to move, and there is a possibility of stratification after steaming.

BOPA/Glue/CPP Structure

This is a common retort pouch product, used for 121℃ steaming sterilization, with good transparency, soft feel, and good puncture resistance. This product cannot be used for packaging products that need to be protected from light.

Due to the high moisture permeability of BOPA, color penetration is easy to occur when printed products are steamed, especially when red series inks penetrate the surface. During production, curing agents are often added to the ink to prevent this. In addition, due to the low adhesion of inks in BOPA, it is also easy to produce anti-sticking, especially in high humidity environments. Semi-finished products and finished bags in processing must be sealed and packaged.

KPET/Glue/CPP, KBOPA/Glue/CPP Structure

This structure is not commonly used. The pouch has good transparency and high barrier properties, but it can only be used for steaming and sterilization below 115°C. The temperature resistance is slightly poor, and there are doubts about its hygienic safety.

PET/Glue/BOPA/Glue/CPP Structure

The retort pouch of this structure has high strength, good transparency, and good puncture resistance. Due to the large difference in shrinkage between PET and BOPA, it is generally used for product packaging at 121°C and below.

When the contents of the package are acidic or alkaline, this structure product is selected instead of the aluminum-containing structure. The outer layer of glue can be made of boiled glue, and the cost can be appropriately reduced.

PET/glue/AL/glue/CPP structure

This is the most typical non-transparent retort pouch structure. Depending on the ink, glue, and CPP, this structure can be used for cooking temperatures ranging from 121 to 135°C.

• The structure of PET/single-component ink/high-temperature glue/AL7μm/high-temperature glue/CPP60μm can meet the cooking requirements of 121°C.
• The structure of PET/two-component ink/high-temperature glue/AL9μm/high-temperature glue/high-temperature CPP70μm can be higher than the cooking temperature of 121°C, and the barrier property is increased, and the shelf life is extended to more than one year.

BOPA/Glue/AL/Glue/CPP Structure

This structure is similar to the previous structure, but due to the high water absorption and shrinkage of BOPA, it is not suitable for high-temperature cooking above 121°C, but it has good puncture resistance and can meet the cooking requirements of 121°C.

PET/Glue/PVDC/Glue/CPP, BOPA/Glue/PVDC/Glue/CPP Structure

This retort pouch structure has excellent barrier properties and is suitable for steam sterilization at 121℃ and below, and products with high barrier requirements for oxygen.

The PVDC in the above structure can be replaced by EVOH, which also has high barrier properties, but its barrier properties are significantly reduced during high-temperature sterilization, and BOPA cannot be used as the surface layer, otherwise the barrier properties will also drop sharply with the increase of temperature.

PET/Glue/AL/Glue/BOPA/Glue/CPP Structure

This structure of retort pouch is a high-performance structure that can package almost all steam-cooking products and can also withstand steaming at 121~135℃.

• Structure 1: PET12μm/high temperature glue/AL7μm/high temperature glue/BOPA15μm/high temperature glue/CPP60μm. This structure has good barrier properties, good puncture resistance, and good light-proof strength. It is an excellent 121℃ steam-cooking bag.
• Structure 2: PET12μm/high temperature glue/AL9μm/high temperature glue/B0PA15μm/high temperature glue/high temperature CPP70μm. In addition to the performance characteristics of structure 1, this structure has the characteristics of resistance to high temperature cooking at 121℃ and above.
• Structure 3: PET/glue A/AL/glue B/BOPA/glue C/CPP, the glue amount of glue A is 4g/m, the glue amount of glue B is 3g/m’, and the glue amount of glue C is 5~6g/㎡, which can meet the requirements, reduce the glue amount of glue A and glue B, and appropriately save costs. Another situation is that glue A and glue B use better boiling grade glue, and glue C uses glue with high temperature resistance, which can also meet the 121℃ cooking requirements and reduce costs.
• Structure 4: PET/glue/BOPA/glue/AL/glue/CPP. This structure is a change of position of BOPA. The overall performance of the product has not changed significantly, but the advantages of BOPA such as toughness, puncture resistance, and high composite strength have not been fully utilized. Therefore, this structure is relatively less used.

PET/Glue/Co-extruded CPP Structure

The co-extruded CPP in this structure generally refers to 5-layer and 7-layer CPP with high barrier properties, such as:

• PP/adhesive layer/EVOH/adhesive layer/PP
• PP/adhesive layer/PA/adhesive layer/PP
• PP/adhesive layer/PA/EVOH/PA/adhesive layer/PP

Therefore, the application of co-extruded CPP increases the toughness of the product, reduces the breakage of the package during vacuum, high pressure, and pressure fluctuation, and prolongs the shelf life due to the improvement of barrier properties.

Recommendations for Selecting the Structure of Retort Pouches

When selecting the structure of retort pouches, the following factors should be considered comprehensively:

• Product attributes: whether it contains bones, oil, soup, or is easy to oxidize
• Sterilization method: pasteurization, high-temperature retort at 121℃, high-pressure sterilization at 135℃
• Storage requirements: room temperature, refrigeration, light-proof, moisture-proof
• Cost budget: the balance between performance and price
• Appearance requirements: whether transparent display and high-definition printing are required

Stanley Package: Your Trusted Partner for Retort Pouches

As a professional flexible packaging manufacturer, Пакет Stanley has rich experience in retort pouch structure design and can provide customers with:

• Multiple functional film material options
• Customized printing, customized thickness, customized number of layers
• Composite structure solutions suitable for various sterilization conditions
• Application solutions of food-grade inks and high-temperature composite glues
• Fast proofing and stable large-volume delivery capabilities

Please contact us to customize the most suitable retort pouch packaging solution for your product.