Safely using reduced oxygen packaging for school food service

While limiting the amount of oxygen in a package is beneficial in slowing down spoilage microorganisms and enzymes, there are pathogens that can survive and grow in reduced oxygen environments. The two pathogens of concern in ROP foods are Clostridium botulinum and Listeria monocytogenes. The practices and actions used in your food service department must control the growth and prevent the toxin formation of Clostridium botulinum, and the growth of Listeria monocytogenes.

Both pathogens thrive in:

• Environments that have little or no oxygen.
• Foods with a high water activity (water molecules are available for pathogens to use for growth and survival).
• Foods with a low acidity (high pH).
• Foods held in the Temperature Danger Zone. Listeria monocytogenes can survive in temperatures as low as 34 degrees F.

If given enough time, the number of pathogens present can increase to levels that will cause foodborne illness when the food is consumed.

It is important to understand what foods can be safely preserved in reduced oxygen packaging, and how to handle these foods to minimize risks.

Vacuum packaged foods

Foods that will be preserved using vacuum packaging must: 

• Maintain an internal temperature of 41 degrees F or below. Store these foods in the refrigerator or freezer. Pathogen growth is slowed at temperatures at or below 41 degrees F.
• Meet at least one of the following food characteristics to minimize the survival and growth of pathogens:
  • Water activity (a_w) of 0.91 or less. Water activity measures the number of water molecules in a food that are free or available to interact with pathogens. Pathogens need water to survive and grow. Foods with a low a_w can minimize pathogen survival and growth. Examples of these foods include jams and jellies, many baked goods, grains, nuts, and dehydrated produce.
  • Acidity (pH) of 4.6 or less. The pH of a food is a measurement of acidity. Foods with a pH of 4.6 or less are considered acidic or acidified. Acidic foods can minimize pathogen survival and growth. Many fruits are naturally acidic (have a pH less than 4.6). Tomato products can be acidified (an acidic ingredient is added to lower the pH).
  • Raw meat, raw poultry or raw vegetables. These foods have other naturally present microorganisms that will compete with pathogens for the nutrients they need to survive and grow. This can minimize the risk of a pathogen growing to an amount large enough to cause foodborne illness. 
  • Cured meat or poultry product that was processed in a USDA-regulated facility. These foods have a low a_w because the water molecules are interacting with salts and/or preservatives. 
• The refrigerated shelf life is limited to no more than 30 days from packaging. Research has shown that if the pathogens of concern are present in a reduced oxygen environment where other food safety factors (a_w, acidity and temperature) are controlled, there is a low risk of reaching levels high enough to cause foodborne illness when consumed if not held for more than 30 days. These ROP foods can be stored and maintained frozen. The time frozen does not count towards the 30 days.

Fish can be preserved using vacuum packaging if it is frozen before packaging and maintains its frozen state during packaging and storage. When the frozen ROP fish is ready to use, it must be removed from the ROP package and thawed following an approved thawing procedure. Research has shown that certain strains of Clostridium botulinum that are found in fish can grow and produce the toxin that causes botulism to a sufficient level at a temperature as low as 38 degrees F after 25 days.

Certain cheeses may be preserved using vacuum packaging as long as they are produced in a commercial manufacturing plant and the food service department does not add additional ingredients before packaging. 

Cook-chill or sous vide foods

In addition to safe food handling practices to minimize the risk of cross-contamination, continuous temperature control and monitoring are essential for the safety of cook-chill and sous vide foods. 

Cook-chill foods

The food must be kept out of the Temperature Danger Zone. The food is cooked to its safe minimum internal temperature and held at or above 135 degrees F during packaging. Once packaged, the food is rapidly chilled following an approved cooling procedure. To rapidly cool food, use a blast chiller following the manufacturer's instructions, or place the packaged food in a single layer on a perforated tray or rack in a standard freezer unit. This will allow the cold air to circulate around all sides of the food. Do not stack the packaged food until it is cooled to 41 degrees F or below.

Cook-chill foods stored in a refrigerator and that maintain an internal temperature of 41 degrees F or below must be used within seven days of packaging. The shelf life is limited to seven days as Listeria monocytogenes can grow at refrigerated temperatures. To increase the shelf life to 30 days from packaging, the cook-chill food must be cooled from 41 degrees F to 34 degrees F or below within 48 hours of the initial cooling.

The cook-chill food must then maintain an internal temperature of 34 degrees F or below. To achieve this temperature control, the food service department may need to designate a refrigerator unit specifically for holding cook-chill foods as the ambient air temperature of the unit will need to be set at a lower temperature than the primary refrigerator unit.

Cook-chill foods can be held frozen with no limitations on shelf life. Once the frozen cook-chill food is removed from the freezer unit for thawing, you must follow the shelf life limitations.

Sous vide foods

Foods prepared using the sous vide method must be cooked to the safe minimum internal temperature. There are many time and temperature sous vide cooking charts available that recommend temperatures that are in the Temperature Danger Zone. Thoroughly sous vide foods.

Before using ROP methods in your school, contact your local health inspector. Provide the health inspector with a list of all the foods you plan to preserve using ROP and by which method(s). If you plan to use multiple ROP methods, you may need to write separate HACCP (Hazard Analysis Critical Control Point) plans.

Your health inspector will assist with questions about your HACCP plan. The food service or nutrition services director must write and submit the HACCP plan.

A HACCP plan is different from your department’s Food Safety Plan. A Food Safety Plan contains the day-to-day policies and procedures related to food handling, sanitation, employee hygiene and illness, training, and other topics needed to prepare and serve safe food.

A HACCP plan pertains to a specific food preparation or handling process and contains the specific actions needed to minimize any food safety risks not addressed in your Food Safety Plan.

The ROP methods are appropriate for different foods and have different intended uses. Cook-chill and sous vide methods require additional temperature control steps compared to vacuum packaging. Vacuum packaging might be a part of your cook-chill plan. This is why separate plans may be needed. 

Prepare to begin the process:

• Assemble your team: at least one person should have completed training in HACCP principles. This may be a food service director.
  • An Extension food safety educator may be able to support your team.
  • Your local health inspector and the Minnesota Department of Health (MDH) HACCP Plan Coordinator will assist your team with questions throughout the process.
• Describe all foods you plan to preserve using an ROP method(s), their intended use, and how long they will be stored before serving.
• Map the flow that food and other supplies, like packaging, will follow in the department.
  • Start with receiving and storage, then continue with the preparation steps, including the ROP method used, storage and service.
  • Physically walk through the department to verify the flow.

Your local health inspector will provide you with a plan template. There are seven principles or components of a HACCP plan. Each of these should be completed with the entire HACCP team. Your plan will be unique to your food service department.

To write your HACCP plan:

1. Conduct a hazard analysis. Identify all the potential food safety risks (biological, chemical and physical) at each step in the flow of the produce and supplies.
2. Determine the critical control points (CCPs). Identify which risks are not minimized by the policies and procedures in your Food Safety Plan.
3. Establish critical limits for each CCP. Set food safety parameters and processes to minimize the risks for each CCP.
4. Establish a monitoring system for each CCP. Create a plan for how each critical limit will be monitored throughout the process. This includes the specific actions that will be used to test and who will be responsible for testing.
5. Establish corrective actions. Write plans for how the produce will be handled if the critical limit is not met. This may include reprocessing or discarding the produce.
6. Establish verification procedures. Identify who will be responsible for checking the final product.
7. Establish documentation and record-keeping procedures. Identify the production logs needed, and include training plans and frequency.

Considerations for your HACCP plan

Monitoring and verification procedures are critical to the safety of ROP foods.

Employee training and schedules

• Limit the number of employees responsible for performing ROP tasks to minimize the risk of errors. A chef, production supervisor, lead cook or prep cook would be appropriate.
• The cook-chill method requires detailed cooling time and temperature documentation. Foods preserved using this method should be done earlier in the shift to allow for a trained employee to test and record the temperatures at set times.
• For cook-chill products intended to be held in the refrigerator for more than seven days before serving, plan to prepare and preserve these earlier in the work week.
  • After being cooled to 41 degrees F or below within six hours, these foods must be cooled to 34 degrees F or below within an additional 48 hours.
  • These foods should not be preserved on a Friday afternoon if the food service department is closed on Saturday and Sunday as no trained employee will be present to monitor and record the time and temperature.

Equipment and supplies

• Develop and use date-marking labels specific to your ROP foods that include handling instructions.
• Temperature control is important in maintaining the safety of your ROP foods.
  • Review your current refrigerator and freezer temperature monitoring system with your local health inspector to determine if it meets the requirements for continuous monitoring.
  • You may need to invest in an electronic system that continuously monitors the temperature of the refrigeration unit and logs the data.
• Review your current transportation procedures with your local health inspector if you plan to transport ROP foods to kitchens or satellite locations throughout the school district. Determine if you need to purchase different cold-holding equipment or temperature-monitoring devices.

Throughout the entire process, keep notes on your conversations with your local health inspector and others assisting you. Detailed note-taking can help answer questions that arise.

Once you have finished your HACCP plan, submit it to your local health inspector and the MDH HACCP Plan Coordinator to review. Be sure to ask for a review timeline, and follow-up periodically if you do not receive an update.

Wait to begin using ROP methods until you have received approval from your local health inspector.

Once you have received approval, you can begin to train your staff. Training should be ongoing to ensure ROP methods are followed and food is preserved safely.

If you need to modify your HACCP plan, contact your local health inspector before making a change. A change could include purchasing a new piece of equipment, adding another ROP method, or adding more foods to your existing plan.

Your local health inspector will verify adherence to the HACCP plan during future routine inspections.