Cryovac® OS2000™ Polymeric Oxygen Scavenging Systems

Presented at Worldpak 2002

Brian L. Butler - Cryovac Division, Sealed Air Corporation

Abstract

Common problems associated with the presence of oxygen in food products include color degradation, microbial spoilage, nutrient loss, as well as flavor and odor changes. Removal of headspace oxygen and prevention of its ingress has been shown to minimize these negative effects. Previously developed iron based oxygen scavenging systems require moisture for activation and often appear as foreign object in the package. Cryovac® OS2000™ polymer based oxygen scavenging film absorbs oxygen in modified atmosphere (MA) packages and also serves as a total oxygen barrier when activated. The OS Film™ is clear, moisture independent, and unlike other oxygen scavenging systems remains inactive until the scavenging reaction is triggered with UV light. When used as a headspace scavenger, OS2000™ film removes residual headspace oxygen including trapped oxygen, which may emanate from the product. The active barrier properties of the film work to absorb ingress oxygen before it can reach the food product.

The Effects of Oxygen on Food Products and Packaging

The deleterious effects of oxygen on food products are well documented. Changes in product color, odor, and taste are the most easily detected effects of oxidation. Nutrient loss, product rancidity and microbial spoilage play an equally important role in product degradation over time and are all controlled, in part, by the presence of oxygen. Reduction or total removal of headspace oxygen along with the prevention of ingress has been shown to minimize the oxidative effects and prolong product shelf life while improving quality.

In nearly all forms of packaging, oxygen is introduced to the food product from three major sources. The most obvious source of oxygen is the headspace gas, which surrounds the product in all non-vacuum packages. A modified atmosphere package (MAP) environment is commonly used with oxygen sensitive products. In a MAP situation, the initial air is removed from the package and replaced with a single gas or mixture of gasses, usually with reduced oxygen. With even the best MAP flushing systems, it is difficult to remove all of the oxygen from the package headspace. The result is free oxygen in the package, which is available to interact with the product.

The second source of oxygen is ingress oxygen through the package itself. Although barrier technology has advance greatly over time, the perfect oxygen barrier for flexible polymeric films remains elusive. Glass and metal are considered to be total oxygen barriers but their incorporation into flexible packaging has consistently posed problems. Over the shelf life of a product, oxygen is constantly permeating into the package. The reduced oxygen environment in vacuum and MAP packages creates a partial pressure difference and a driving force, which can in effect increase the rate of oxygen permeation into the package. Even with the use of high barrier packaging materials, extended shelf lives can result in detrimental amounts of oxygen reaching the product.

Air, which is entrapped in the product itself, is the final source of oxygen available for oxidative reactions. Entrapped or dissolved oxygen is commonly overlooked or ignored during the packaging process. Over time, this trapped oxygen can migrate out of the product and into the headspace resulting in elevated oxygen levels. Increased microbial activity or color change reactions are a common result. Oxygen that remains trapped in the food product can accommodate accelerated oxidation reactions due to the autocatalytic nature of these reactions.

Why Use Oxygen Scavenging

The benefits of oxygen scavenging are numerous. Today’s consumers above all else demand convenience. They want their products and packages to be functional. The food in these packages needs to be fresh, natural, and flavorful. The right oxygen scavenging technology will help deliver foods that match these consumer demands.

Reduced oxygen enhances freshness, protects nutrients, preserves color and flavor components of food products. The formation of oxidative by-products which may affect product flavor are similarly decreased. Use of chemical preservatives such as BHA, BHT, sulfur dioxide, sorbates, or benzoates can be reduced or eliminated.

Types of Oxygen Scavengers

There are primarily three forms of oxygen scavenging chemistries in use today. The most conventional approach is the use of a metal-based scavenger such as iron. In these systems, the finely powdered activated metal enters the oxide state when exposed to the appropriate humidity condition, effectively binding oxygen in the process. Metal-based scavengers can exist in several forms. The most common form is the sachet, where the ground metal is packaged in a highly permeable pouch. Other metal-based scavengers include labels, coatings and extrusion additives, which incorporate the metal compound.

The second approach to oxygen scavenging is the use of low molecular weight organic compounds. The most common forms are ascorbic acid or sodium ascorbate, which bind oxygen by oxidizing carbon-carbon double bonds

Polymer Based Oxygen Scavengers

The third method of oxygen scavenging incorporates a polymeric based oxygen scavenging resin along with a catalyst into a film structure. The polymeric systems bind oxygen through oxidation of the polymer chain or pendulant groups.

The needs for polymer based oxygen absorbers vary from producer to consumer. Producer needs include polymer-based resins, which are extrudable, clear or invisible, flexible or rigid, and won’t change package look or feel. These products also need to fit the existing supply chain, as well as conform to existing packaging processes and equipment.

Market needs include low cost affordable products that bring value. These products should be invisible or transparent to the customer, and apply to a broad range of applications.

Cryovac® OS2000™ Oxygen Scavenging Film

Cryovac® Oxygen Scavenging Film is the result of over ten years of extensive research and development and was recently awarded the Flexible Packaging Association’s highest achievement award for having contributed most to the advancement of the industry.

OS Films™ are designed to defeat the harmful effects of oxygen on food. OS2000™ absorbs residual headspace oxygen that even the best gas flushing and vacuum systems cannot remove. Entrapped or dissolved oxygen is pulled away from the food product resulting in improved flavor and color profiles in highly oxygen sensitive products. Finally, OS Films™ act as a total active barrier layer, stopping oxygen ingress before it reaches the food product.

OS Films™ address both consumer and producer needs. The scavenger is invisible and does not change the package appearance. Product quality is enhanced through reduced oxidative reactions, providing fresher, more natural food products, without the use of chemical antioxidants.

OS2000™ can be used with a broad range of food and non-food packaging applications. The system is easy to use and moisture independent thanks to a patented triggering concept which activates the film just prior to the packaging process. The OS2000™ system is similarly built to fit into the existing supply chain and work with existing packaging equipment.

Finally, the system is hearty, reducing headspace O2 levels from 1% to ppm levels in 4-10 days - comparable with oxygen scavenging sachets. The system works in a wide range of environments from ambient storage to refrigeration. No moisture or external stimulus is needed to sustain the reaction and the reaction is not affected by the presence of other headspace gasses such as nitrogen or carbon dioxide.

Film Structure

The secret to the Cryovac® Oxygen Scavenging System lies in a discreet oxygen scavenging layer (OSL) which is extruded into a multilayer film. The patented technology incorporates an oxidizable polymer with a transition metal catalyst and a photoinitiator. The OSL is incorporated into the multilayer film and is invisible to the naked eye.

Other layers in the film include a sealant layer and bulk layers to provide the film with mechanical and physical properties such as tear and puncture resistance, moisture barrier, stiffness, etc. Another important attribute of the film structure is oxygen barrier. The oxygen barrier can be included in the multilayer co-extrusion or added through lamination of a skin layer. The amount of barrier and composition of the skin layer can be tailored to suit the packaging application. A wide range of graphics or labels can be applied to OS2000™ film through trap or surface printing.

How OS2000™ Works

OS2000™ film incorporates "scavenging on command". Unlike metal based or organic scavengers, which may begin to absorb oxygen immediately upon contact with air, OS Films™ remain dormant until activated. A patented activation system exposes the film to a specific spectrum of UV light, which initiates the scavenging reaction.

The activation system, which has been developed and manufactured by Cryovac, is designed to adapt to current packaging equipment. The Series 4100 Scavenging Initiation System (SIS) is installed directly on the processor’s packaging line. The film is activated just prior to sealing of the package. After initial activation, the scavenging reaction continues with no further external stimulus until the scavenging capacity of the film is exceeded.

Benefits Of Using OS2000™ Film

OS2000™ vs. Sachets and Iron Based Films

The benefits of using an oxygen scavenging film versus a sachet are numerous. The most obvious benefit is that the oxygen scavenger in OS2000™ does not appear as a foreign object in the package. Many producers are concerned with introducing a foreign object into their package. There is inherent liability in the consumer ingesting the sachet or mistaking the sachet for a product additive such as a flavoring packet. This liability can extend past the individual product and endanger the entire brand name.

Some producers have chosen to secure the sachet to the inside of the package or incorporate a label type sachet. Others have chosen iron-based coatings or extrusion additives, which can make the film opaque and have a tendency to change the appearance of the package. OS2000™ film is clear, allowing superior product presentation with unobstructed viewing.

Iron based oxygen scavengers (films or sachets) generally are dependent on moisture to initiate and maintain the scavenging reaction. Cryovac® OS Films™ are completely independent of moisture.

Metal detectors are a vital part of most production lines. OS Films™ have no effect on metal detection systems. With OS Films™, the producer can be sure that each package is equipped with oxygen scavenging, reducing reliability issues associated with sachet systems.

Since the OS2000™ system is dormant until activated, the film does not begin to scavenge oxygen until it becomes part of the package. Waste of unused sachets is eliminated. OS2000™ is priced competitively and offers a cost reduction from the use of sachets, on a per package basis. In summary, the use of Cryovac® OS2000™ film can greatly reduce production complexity with increased reliability.

Shelf Life Increases - Improved Production Efficiency

For those producers who are not currently using oxygen scavenging, the benefits can mean great increases in the profitability of the product line. Oxygen scavenging has been proven time and time again to increase the effective shelf life of both food and non-food products.

Longer shelf life can lead to wider distribution areas. Producers can now afford to ship their products into new areas, which were previously inaccessible. Reduced spoilage claims and product buy-backs from retailers can also positively affect the bottom line. At the manufacturing level, shelf life increases provide for extended production campaigns, resulting in better production efficiency. Finally, the presence of an oxygen scavenger can reduce the need for achieving extremely low oxygen levels in MAP packages. The reduction in gas flush time can result in accelerated line speeds and higher production rates.

Applications For OS2000™ Films

Food Related

Headspace Scavenging: OS Films™ have been proven effective in removing headspace oxygen from a wide range of MAP products and packages. Cryovac® OS Films™ have been shown to provide benefit to a wide range of food products including, fresh pasta, dried or smoked meat products, processed meats, shredded cheese, dried fruits and nuts, pet food, and cereal bars. Other MAP products are currently being evaluated.

Total Active Barrier: Cryovac® OS Films™ have also shown benefits in extending the shelf life of products, which do not have a package headspace. Functioning as an "active barrier", OS Films™ absorb oxygen as it permeates into the package. Oxygen, entering the package, is effectively stopped before it can reach the product. Studies have indicated that color changes in vacuum packaged meats are greatly reduced when OS2000™ film is used to prevent ingress of atmospheric oxygen. When incorporated into VFFS style pouches containing tomato based sauces, the OS Films™ greatly extended shelf life of these products by reducing color change (darkening) and flavor degradation.

Non - Food Applications

OS Films™ are also currently being tested with highly oxygen sensitive consumer and medical products, which require total oxygen barrier along with product visibility.

Summary

Cryovac® OS2000™ Oxygen Scavenging Film has been designed to meet a wide range of consumer and producer needs. Consumers are provided with a convenient, functional package, which enhances the freshness of the food product without the use of chemical preservatives. Producer needs are met with a clear package incorporating an invisible scavenger which doesn’t change the package look or feel. As an added benefit, the OS2000™ system has been designed to fit existing packaging processes and equipment and to improve production efficiencies.

The OS2000™ Oxygen Scavenging System has been proven to protect nutrients, color and flavor components in food products while reducing or eliminating the formation of oxidative by-products. Extended shelf life can be a benefit to both consumers and producers.

OS2000™ remains dormant until activated and does not require any further external stimulus after activation. The liability of foreign objects in the package is eliminated and the reliability of scavenging in every package is gained. Whether used as a headspace scavenger, total active barrier, or both, Cryovac® OS2000™ Oxygen Scavenging Film is the clear choice for any oxygen scavenging application.