Retail outlets, from large supermarket chains to small corner shops, are becoming more and more like walk in/walk out restaurants, with convenience foods, sandwiches and snacks providing a high proportion of turnover. Here, Joe Barenberg, chief operating officer of Octal, discusses the materials available for the plastic containers used in food packaging, the performance characteristics of each and how maximum performance can be realized.

Each plastics material available to the food packaging industry -- PP, PVC, OPS, and APET -- brings its own benefits and characteristics. Many people influence the selection of packaging material and the final design, and it is important that each is committed to matching the proper material and design to the application. It takes more than dedication to the optimal solution; it takes a sound understanding of the duty the package is likely to see and the strengths of each candidate material.

In food processing, processors require ease of filling and sealing or closing, depending on whether the end product is to be sealed or have a snap closure. In these cases APET delivers several options to address the various scenarios. In the case of clamshell packages, APET’s mechanical traits ensure a package with clarity and the mechanical toughness protects products in transit. This is unique with APET as, while OPS has very good clarity, it has limits in terms of shock and vibration protection and is more prone to cracking.

APET is available with PE lamination, which allows for effective adhesion of lidding stock in applications like yoghurt cups, and sandwich wedges for example.  It can also have a multi-layer structure that has a thin layer of PETG (a heat sealable form of PET) on at least one side. This allows for many of the same applications as the PE/APET laminate, and is especially suitable for consumer product clamshells, where extensive welding is the norm.

For food products that are to be microwaved or heated conventionally in the original package, or for hot liquids, polypropylene (PP) is still the best choice because of its ability to withstand most cooking temperatures. PP dominates this application and performs very well, enabling a wide array of take out foods, including whole precooked chicken and prepared dishes. Often a PP bottom tray serves as the primary heat tolerant container with an APET dome as a clear lid that preserves the food’s freshness but allows the consumer easily to see the product inside. The lid is generally coated with an antifog agent and is removed prior to reheating at home.

While PP is an excellent heat resistant food packaging plastic, it does not have the rigidity of OPS or APET, which makes it less suitable for stacking heavier items on table displays or in transit. While considered a clear rigid packaging plastic, it has substantially inferior clarity compared to OPS or APET, though there have been recent efforts to improve clarity.

To maximize the amount of saleable inventory on display, retailers often prefer to stack food products on the store shelves or on display tables. In this case, a non-brittle, but tough plastic is needed along with rigidity in design.

APET and PVC both provide the necessary mechanical strength here, but clarity is very important for visual appeal, which makes APET the material best suited for this application overall. Additionally, its oxygen barrier properties help to extend shelf life, making it well suited for fresh foods, including dairy products. However, it is important to remember that in cold display applications, a fog resistant coating on the inside of the package -- no matter what the material - is essential.

In all cases, clarity is key. It is important to consumers to be able to see a food product inside the packaging, so if the need is to combine clarity with toughness, then APET will deliver high performance. Labelling and direct printing may also be a consideration for in-store merchandising. Most polymers are suitable for this.
Packagers and retailers also need to consider waste recovery implications when making a choice of packaging materials. PVC, OPS and PP do not have a well-developed and readily available re-use stream. APET, however, has the advantage of being able to piggyback on the already well-established PET bottle recovery infrastructure.

With product protection and clarity being critical needs for food merchandising and point of sale impact, APET is a good choice when it comes to retail food packaging. However, an historic lack of sufficiently dedicated capacity and inefficiencies in the manufacturing and logistics of delivering the finished package, have held back its growth well below potential.

Nevertheless, APET is now the fastest-growing material in the clear rigid packaging segment because it combines clarity, gloss and mechanical toughness -- all key factors when it comes to the packaging of food -- and it has real potential to deliver greater efficiency.

With dedicated capacity and supply of APET now available, with uniform gloss and clarity and improved gauge control, thermoformers can achieve superior levels of productivity, significantly higher yields and consistent end tray quality. With gauge held to less than one per cent variation -- a new standard in APET sheet -- packaging manufacturers now know precisely how many trays they will produce per ton of APET without the worry about unpredictable thin spots. This reduces per piece end tray costs for packaging manufacturers

Taken together, this can mean savings of three to eight percent for thermoformers dramatically improving the economics of delivering APET clear rigid packaging and facilitating conversion to APET in applications where its benefits make it the material of choice.