Food Protection Connection: Reduced Oxygen Packaging
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(reprinted from Dietary Manager, November/December 2010)
People are always looking for ways to increase the shelf life of their food. We have sought out canning, pickling, freezing, adding preservatives, and many other methods to extend the life of our food supply since the beginning of recorded history. Reduced oxygen packaging (ROP) is one of those methods . This method of preservation has many unique advantages, but comes with significant microbiological concerns. In this article we will explore what ROP is; its benefits and downfalls; what methods of ROP are commonly used; and most importantly safety concerns and controls. Anyone considering ROP packaging should contact their regulatory agency for requirements, guidelines, and approvals before they begin to process in this manner.
What is ROP?
Packaging using an ROP method can be used to describe any packaging process in which a sealed product has an environment that is reduced in oxygen. ROP is an all-inclusive term used to describe methods such as Controlled Oxygen Packaging (CAP), Modified Atmosphere Packaging (MAP), Cook-Chill, Vacuum Packing (VP), and Sous Vide. Each form of ROP has its unique methods and outcomes, but all have one thing in common: the final product will be in a sealed package in which there is little or no oxygen present.
The process of modifying the atmosphere within a package followed by use of agents (or sachets of compounds that emit gas) to bind or absorb oxygen to maintain the atmosphere within the package is called Controlled Oxygen Packaging, or CAP. When you open a package of shelf-stable food and find that little packet of stuff marked “Do Not Eat” you have just opened a CAP product.
MAP, Modified Atmosphere Packaging, is achieved by flushing a package with a one-time gaseous compound so the atmosphere within the package, once sealed, is different from outside air. This is done by reducing the amount of available oxygen in the package by replacing it with another gas, thus making a reduced oxygen or anaerobic environment. An example would be refrigerated fresh-cut produce in consumer bags.
With the Cook-Chill method, you simply fill a plastic bag with a hot cooked food, expel the air, and close the bag with a plastic/metal clip which creates a reduced oxygen atmosphere. This also seems like an easy and harmless enough process to the unaware cook. This process is similar to Hot-Pack home canning, except in Cook-Chill a bag is used instead of a canning jar. This is a common method used for refrigerated bagged soups for the foodservice industry.
Have you ever purchased a home-use vacuum sealer? Is so, you are Vacuum Packing your food products. VP reduces the amount of air within the package using an air vacuum machine and hermetically seals the package—usually by heat sealing the bag while the vacuum is still running. The resulting package will have a virtually perfect vacuum seal.
The method of Sous Vide is a specific process of ROP utilized for food that requires refrigeration/freezing after packaging—usually potentially hazardous foods (PHF). The process of Sous Vide does reduce the initial bacterial load of a product to lower levels, but not low enough to make the food shelf stable. The process generally has several steps: preparation of the raw materials (which may include partial grilling or a similar step); packaging the product by use of vacuum sealing; cooking/pasteurizing the product to the desired cooking temperature while in the package; rapid cooling/freezing; reheating to 165ºF for hot holding or any temperature for immediate service. This method is said to retain the color, texture, moisture, and flavor of the final product.
Each method of ROP has its own unique mix of drawbacks and benefits. Generally, extension of shelf life and food preservation is one the greatest benefits and one that is shared among all methods. One can prevent the growth of aerobic spoilage organisms by creating an anaerobic condition within a package. The creation of slime, texture changes, and unpleasant odors is generally caused by organisms such as pseudomonads, aerobic yeasts and molds, all of which need oxygen to grow. Additionally, by removing oxygen from the environment you slow degradation and the oxidative process that food goes through as it ages. Reducing oxygen will help retain the brilliant color of foods, especially meats. Sealing food in ROP packaging will also maintain moisture content to specific desired levels, for taste and texture.
The methods of CAP, MAP, and VP allow for extended shelf life for food displayed at retail sale. Cook-Chill and Sous Vide products can be utilized within a facility, but cannot be wholesaled or given directly to the consumer (due to inability to verify temperature controls). The final cooking step must be accomplished by the facility that prepared the products. Although there are limits to these methods, their use within a food facility does extend product shelf life and help retain the quality of the food over extended periods of time. Other benefits include: allowing a facility to batch prepare food ahead of time; lessening of mess and dirty utensils; decreasing time to prepare; and helping maintain portion control. Together these facility benefits ultimately create economic benefits.
All good things, of course, come with a few downfalls. For ROP foods that require refrigeration or freezing (non-shelf stable foods), there are increased safety concerns. Clostridium botulinum and Listeria monocytogenes are among the two most concerning pathogens. These can both have deadly consequences if control methods are not in place. These are not, of course, the only organisms of concern. Pathogens such as Staphylococcus aureus, Bacillus cereus, and Salmonella spp, are among those that can grow slowly in ROP products as well. Extended shelf life can allow for their unacceptable growth level over time. This article is not going to explore the biology of these pathogens. For the purpose of this article, simply know each can bring about severe foodborne illness and/or death. As such, at least one barrier or multiple barriers/hurdles needs to be incorporated into a written production process. The use of multiple barriers creates a hurdle effect that is required to make certain the final food product is safe to consume even though none of them would, individually, be enough to control these pathogens.
In shelf stable ROP products (non-potentially hazardous food (PHF)/time/temperature controlled for safety (TCS), such as beef jerky, there are added preservatives, low available water, high salt content, and in some cases low pH to serve as barriers to microbiological growth. However, not all products have these control factors and/or intrinsic properties; thus, they become the products of most concern. For these products (PHFs/TCS) there must be strict control methods in place, which start with refrigeration. Refrigeration is the primary barrier and must be maintained throughout the entire ROP process and shelf-life, hence the strict requirement that the label must have “KEEP REFRIGERATED” on it. Even for products that have been adequately heat treated, the chance for post-processing contamination by pathogens is high. According to the Food and Drug Administration (FDA), “refrigeration practices at retail need improvement” therefore, consideration for post-processing contamination must be considered. Processors for products that will only use refrigeration as the sole barrier for food safety must build in extra preventative measures such as, but not limited to, strict temperature controls and checks, an aggressive cleaning and sanitizing schedule, and good employee hygiene practices to assure a safe product.
Documentation of testing and verification may be required by the regulatory agency depending on the food and the safety barrier of choice. Most food safety regulatory agencies require that anyone packaging under ROP have a written HACCP (hazard analysis critical control point) program in place and get approval before processing begins.
The science and technology behind ROP is intricate and extensive enough that all aspects of it could not possibly be covered within this article. Anyone considering ROP processing should research the topic well before beginning. The general parameters for safe ROP packaging by processors and retailers are outlined in the accompanying sidebar.
Now, let’s revisit your home vacuum package machine that you got for the holidays last year. Are you a bit more leery of using it? You should be. Most home-use machines come with instructions to freeze the products after you VP them. This is a safe method as freezing is a safety barrier. You need to consider if there is another safety barrier as described herein if you do not want to freeze the food. These machines have a place in our homes, but they need to be utilized properly.
Reduced oxygen packaging is a useful tool and has its benefits. However, anyone considering entering into this type of production must research their product, its specific requirement for ROP packaging, and approved methods for applying the technology. ROP packaging should not be entered into lightly. When done right, is has great benefits. When done wrong, it can be deadly.
General Parameters for Safe ROP Packaging by Processors and Retailers
Safety Barriers: Refrigeration is the primary safety barrier. Each food must possess one or more of the following secondary barriers:
Refrigeration: All non-shelf stable ROP foods must be maintained at 41ºF or below or frozen. Raw or processed fish must be frozen before, during, and after ROP.
Labeling: All products must be labeled “keep refrigerated” and have a use-by date not to exceed 14 days from production (except certain cheeses 30 days), unless otherwise approved by a regulatory agency. After the expiration date, food must be discarded or frozen. Those items that are frozen must be labeled, “Keep frozen, use within 4 days of thawing.” Raw or processed fish (frozen as required) must be labeled “Keep frozen. Thaw under refrigeration immediately before use.” Smoked fish must be labeled to “Keep refrigerated at 38ºF or below.”
Sanitation: Strict cleaning and sanitizing procedures must be in place.
Employee training: All employees involved in ROP should be adequately trained.
HACCP: All ROP processing should have a written HACCP plan that is approved by the regulatory agency.
- 2009 FDA Food Code
- US Department of Agriculture, Food Safety Inspection Service
- AFDO, The Vision for Food Safety Reform Resource Binder, 2009
Association of Food and Drug Officials, York, PA
- NPDA, 1989, Guidelines for the Development, Production & Handling of Refrigerated Foods
National Food Processor's Association, Washington DC
by Melissa Vaccaro, MS, CHO
Melissa Vaccaro, MS, CHO is a Food Program Specialist for the PA Department of Agriculture and an Executive Board Member for the Central Atlantic States Association of Food Drug Officials (CASA). Contact her at email@example.com.