One of the critical requirements of barrier packaging is to maintain package integrity without compromise to product quality and safety. In order to achieve this, along with the packaging and processing method, ensuring an effective seal is achieved between the rigid barrier substrate and the flexible lidding film is critical. This is no easy task when you consider a number of key factors, such as flange contamination, can directly impact the quality of the seal in addition to understanding the performance requirements of the seal itself. This presents additional challenges when you consider the bond required to maintain the seal through the distribution chain while balancing the peelability of the lidding film from the container itself by the consumer.
Regardless of the material or method used to produce the package, distribution of the final shelf-stable food product will require the package to be sealed with a lidding film.
There are a number of key factors that need to be considered for barrier packaging driven by the target shelf-life of the product based on the OTR (Oxygen Transmission Rate) and MVTR (Moisture Vapor Transmission Rate) of both the barrier rigid structure and lidding film. It is important to choose the right lidding film considering sealing integrity, barrier characteristics, and processing technique necessary to protect the products’ quality for the targeted shelf-life. Barrier properties of a lidding film must be matched to the barrier demands of the overall package.
A wide variety of lidding solutions exist today for both barrier and non-barrier form-fill-seal and thermoformed container applications that range from die-cut foil lidstock to multi-layer and metalized films. Considerations need to be given to the sealant layer of the rigid barrier rollstock structure and the compatibility of the sealant on the lidding film depending of the target performance criteria. Sealing systems can be custom engineered on the food contact sealant layer for both the rigid and lidding film structures to accommodate various materials such as PP, PS and PE.
In extended shelf-life form-fill-seal food packaging, bond of the lidding film to the substrate, as well as the ease of peel-ability of the lidding film from the package at time of consumption are key requirements. Using polypropylene as the food contact layer there are many excellent sealant options to improve the peel characteristics of FFS lidding systems. In order to draw a comparison all you need to do is peel the lid-stock from various single-serve polypropylene container applications such as shelf-stable applesauce or pet food containers to feel the difference.
Some options include easy peal and weld seal (or lock tight) peeling characteristics. When the product is designed to be consumed within a short period of time or a ready-to-use concept that requires quick and easy access, the outer material is generally formulated such that the lidding film creates an easy peel upon sealing. Weld seal, in comparison, is a permanent seal that acts similar to tamper evident packaging in that it can only opened once and cannot be re-sealed.
In addition, there are a broad range of physical characteristics designed into lidding films, including clarity, thickness, color, composition, food compatibility, heat resistance, chemical resistance, and sustainability. Properties such as dwell time, temperature and pressure play an important role in the seal integrity of a package. The substrate material and lidding material combined with above processing variables plays the most vital role in a packages seal effectiveness.
For more information download a copy of our Barrier Food Packaging Materials and Processes Whitepaper: