Note: This is the first article of a three-part series covering plastics in barrier packaging (1) trends, (2) material/process advances and (3) applications.

Value and health are currently driving barrier technology in food packaging. Increasingly busy lifestyles are reflected in growing consumer demands for convenience foods, ready meals and eating "on the go," resulting in high growth in food packaging.

With the increasingly global customer base of food retailing, food packaging requires longer shelf life and monitoring of food safety/quality based on international standards. The rising popularity of convenience foods means global demand for food packaging will reach $140 billion by year end 2016.

Consumers expect not only product protection from packaging, but they also want to see the food they buy; they want it to be safe to eat; they want it to stay fresh for a longer period; and above all they want it to be tasty. Food-purchasing decisions are based not only on convenience but also on taste and appearance, making excellent barrier quality to maintain product freshness vital in food packaging, not only to extend shelf life but also to protect brand image.

Food safety is the number one issue with the public, and active/barrier packaging that can help prevent spoilage or contamination is in strong demand. Recalls can be particularly damaging to both brand image and the company's bottom line. Most companies understand the added expense of improving packaging to help prevent recalls or a liability case is often far less than the cost of losing many customers because of an unhealthy or unsafe product.

Consumers insist on easy-to-open, see-through, economical packaging while also requiring protection against oxygen, water vapor and aromas. Environmental, regulatory and public policy issues are also impacting the design of barrier plastic packaging. Packaging waste is a growing environmental concern, and consumers are seeking ever more sustainable packaging choices driving food packagers to look for bioplastic materials with good barrier properties.

The presence of oxygen-sensitive unsaturated fats is fueling development of active/barrier packaging in flexible and rigid formats, as the result of trends toward natural/organic foods featuring heart-healthy fats. Active packaging interacts chemically with the food inside the package to safeguard against product degradation from exposure to oxygen and/or moisture.

By making use of a combination of active and barrier packaging, processors can increase shelf life, protect flavor profiles and maintain the food's appearance/texture — all without adding preservatives to the product formulation.

Plastic barrier packaging product examples.

Modern innovations have made it possible to keep food fresh for a much longer time, without changing the taste or aroma. While proven barrier materials extend product shelf life by impeding O2 ingress into a package, O2 scavengers "capture" O2 within a sealed package to ensure it does not react with the food product.

Nanotechnology is increasingly used to enhance packaging barrier properties. The rapid use of nano-based packaging in a wide range of consumer products has also raised a number of safety, environmental, ethical, policy and regulatory issues.

New, clear barrier materials are being developed to replace aluminum foil and other opaque barrier materials, resulting from a trend toward packaging food products in clear materials. In rigid high-barrier packaging, there is a trend toward mono-layer PET (polyethylene terephthalate) bottles, away from co-injection/stretch blow-molded and coated PET containers.

Using barrier resin blends with oxygen-scavenging capability, rigid mono-layer bottles with excellent O2 barrier can be produced on standard injection machines. There is significant interest in developing barrier containers that do not cause recycled PET to yellow.

A lightweighting trend in the beverage industry adds another dimension to the barrier coating challenge as thinner walls result in increased permeation in nonbarrier bottles. Use of bioplastics in food packaging is advancing barrier bioplastic system development.

Let's take a more detailed look at innovation in equilibrium modified atmosphere packaging (EMAP), which is simply packaging used to extend fresh produce shelf life. EMAP packaging film allows ready-to-eat fresh fruit, vegetables and herbs to stay fresher longer and travel further. This packaging makes use of selectively breathable films that offer high clarity, good sealing and anti-fog properties.

While EMAP technology is not new, innovative systems have been developed to optimize EMAP for specific produce. Because fresh fruit and vegetables are still "alive" and respiring, traditional gas-flushed barrier modified atmosphere packaging (MAP) used for meat is unsuitable for the produce industry. By correctly manipulating O2 and CO2 (carbon dioxide) concentrations within the packaging, EMAP enables produce to last longer by delaying respiration and reducing ethylene production and ripening.

Anaerobic respiration (left), aerobic respiration (center), EMAP in action (right).

Going left to right in the above graphic, in a gas-tight container, living vegetable material will modify the atmosphere due to respiratory O2 uptake and CO2 output, thus creating anaerobic conditions that will cause off-odors and off-flavors. Continuing, with highly permeable packaging materials, the in-package atmosphere will be similar to the composition of the external atmosphere, and produce respiration will not be reduced.

Finally, in EMAP packaging, equilibrium concentrations of O2 and CO2 become established with rates of gas transmission through the packaging material equaling the produce respiration rate. This in turn reduces enzymatic browning, retards softening, preserves vitamins and extends the overall freshness of the packaged produce. EMAP allows processors to extend shelf life without using chemicals, so it is also ideal for packaging organic produce.

EMAP films must be specifically designed to match the handling conditions, ethylene sensitivity and respiration rate of the produce to be packaged. The oxygen level within the produce package is regulated by microperforations in the package film. Each type and variety of produce has unique physical and biological characteristics that will require different film perforations to optimize film permeability. Film permeability is a critical control point for fresh produce quality assurance.

EMAP produce film.

The best practice in fresh produce EMAP packaging is when film perforation is controlled by the processor because:

  • Film thickness variations cause hole size variability
  • Produce respiration changes throughout the season and with growing conditions

In-line laser perforation supplied by PerfoTec allows the number of holes, hole size and location to be adjusted so film permeability can be optimized unlike standard laser preperforated films. Use of a laser system with in-line camera control gives full control over permeability of the packaging film. A new respiration meter developed by PerfoTec allows produce respiration to be determined within four hours to better optimize EMAP film permeability.

EMAP film equipment (left), in-line laser film perforation (top right), produce respiration meter (bottom right).