Increasingly, retail and foodservice operators are turning to food technology to save time and money and to increase food quality. One of those technologies is cook-chill processing. Cook-chill is a process where foods are cooked, bagged and rapidly chilled to extend shelf life. Alternatively, foods can be bagged, cooked in the bag and chilled, termed “sous vide.” Bagged foods are held refrigerated for a limited shelf life. Some of the benefits of the cook-chill process include increases in shelf life, consistency, portion control and quality of foods.

The cook-chill process also decreases labor, product handling and chances of cross-contamination of foods. Regulations for cook-chill processing in retail or foodservice operations are specified in the 2009 Food Code in 3-502.11.D and 3-502.12. Additional guidelines are found in Annex 3 §3-502.12 and Annex 6.2 of the Food Code.

A typical cook-chill process starts with assembling ingredients, followed by cooking. Cooking reduces or eliminates vegetative disease-causing microorganisms, reduces spoilage microorganisms and inactivates food enzymes that can lead to product quality loss. After cooking and while hot (at least 135 °F), foods are pumped or placed into impermeable bags. Air is expelled, and the bags are sealed. Bags are rapidly chilled and then placed into a refrigerator or freezer for storage until use.

Cook-chill Process Food Safety Concerns
The cooking step employed in cook-chill processing will not effectively destroy bacterial spores. Spores from the genera Clostridium and Bacillus can survive and cause foodborne illness. Therefore, special attention must be given to a proper rapid-cooling procedure to prevent the growth and toxin formation of these bacteria (Table 1). Secondly, bagging cook-chill foods creates a reduced-oxygen atmosphere, which is a requirement for the growth of Clostridium bacteria. Bagging and handling after cooking may provide an opportunity for cross-contamination with illness-causing bacteria. Lastly, some of these bacteria can grow slowly at refrigeration temperatures. These are described as psychrotropic and include some strains of Clostridium botulinum and all strains of Listeria monocytogenes. These two bacteria are considered the primary microbiological hazards in the cook-chill process.

The U.S. Food and Drug Administration (FDA) has recognized these hazards since the earliest versions of the Food Code in 1993. Earlier versions of Annex 6 specified that all operations using reduced-oxygen packaging, including cook-chill processing, were required to obtain a variance from their regulatory authority if refrigeration was the only barrier to C. botulinum. The newer versions of the Food Code provide conditions where an operation may package potentially hazardous foods using cook-chill processing without obtaining a prior approval variance. Foods that are not considered potentially hazardous do not require a Hazard Analysis and Critical Control Points (HACCP) plan or variance to cook-chill or otherwise package in a reduced-oxygen environment.

In general, an operation must have the following (see Table 2): 1) a valid HACCP plan addressing both C. botulinum and L. monocytogenes as hazards; 2) Standard Operating Procedures (SOPs) must be in place addressing required hazards and risk factors; and 3) cook-chill food must be prepared and consumed on the premises, or prepared and consumed off the premises but within the same business entity. Seafood can be cook-chill processed, but must be frozen before, during and after a reduced-oxygen packaging process due to the fact that it is often contaminated with the psychrotrophic C. botulinum bacteria.

HACCP-based Cook-chill Food Safety Programs
The FDA has published guidance for establishing a HACCP-based food safety program and cook-chill process in both the Food Code and in various documents available on the agency’s Web site. An operation must have both a HACCP plan and SOPs, which constitute the food safety management system. The HACCP plan should address cooking, cooling, chilling and any additional CCPs that could lead to the growth and toxin formation of all potential pathogens. Additionally, it must address sanitation, hygiene, refrigeration, labeling and employee training in the SOPs. Most individuals who have attended a HACCP workshop should have the knowledge to create the needed HACCP plan and SOPs. If the process appears too difficult, seek out the assistance of a qualified food safety professional.

Storage temperature and the microbial-inhibition properties of the food are the two key factors in determining the safe shelf life of cook-chill processed foods (Table 3). C. botulinum (psychro-trophs) will grow in foods at 38 °F and L. monocytogenes can grow at 34 °F. Therefore, there are refrigerated storage shelf-life limits to cook-chill processed foods that use refrigeration as the only barrier to growth. Frozen foods may be stored indefinitely or until quality loss.

There are generally four CCPs in a cook-chill process. These include cooking, bagging, cooling and chilling.

CCP1: Cooking
A cooking process that meets the requirements in the Food Code 3-401.11 will destroy non-spore-forming pathogens, including L. monocytogenes. Remember that the C. botulinum (a reduced-oxygen packaging hazard) is a spore former, and spores are not destroyed at these temperatures.

CCP2: Bagging
Transferring cooked foods into bags can be a source of environmental contamination. Bagging prior to cooking will eliminate this CCP. If bagging after cooking, minimize survival of contaminates by filling hot food (≥ 135 °F) into bags. Even at this temperature, there is a small risk that L. monocytogenes can be present and survive. Reheating bagged foods to 165 °F just prior to serving will also help destroy L. monocytogenes.

CCP3: Cooling
A cooling process that meets Food Code requirements (FC 3-501.14), such as 135 °F to 70 °F in 2 hours or less and 135 °F to 41 °F in a total of 6 hours of less, is required. Typically, operations strive for an even more rapid cooling process (≤ 41 °F in < 30 minutes). This can be accomplished in most operations by using a large tote bin filled with ice and water. Ice must be distributed throughout the tote and between bags. Fresh ice must be added periodically to maintain cooling temperatures. Bags in the tote bin should be rotated to provide even cooling. Larger operations may choose to use a tumble chiller designed for this purpose.

CCP4: Chilling
Once foods are cooled to 41 °F or less, they should be immediately refrigerated. Operators will need a cooler set for ambient temperatures below 38 °F or 34 °F. An interesting method employed by some operators to achieve temperatures of either 34 °F or 38 °F in a refrigerator set at 41 °F is to place foods in a food-grade bin on ice. Often the same bin used to cool foods can be subsequently used to store them on ice. Food temperatures must be monitored and go from 41–38 °F within 24 hours or from 41–34 °F within 48 hours. If an operation uses 41 °F as its refrigeration temperature (with a variance), this CCP may not be needed.

Barriers to Cook-chill Hazards
If an operator wishes to request a variance from their regulatory authority for cook-chill processing, they must consider barriers or hurdles to both C. botulinum and L. monocytogenes. Some possible barriers might include the following:

• Water activity (aw)
• Low pH (high acid)
• Salt, nitrite or nitrate content
• Cooking or reheating

Interpreting barriers in your HACCP plan to obtain a variance may be difficult; operators may wish to get the advice of a qualified food safety professional. Employing these hurdles will make the product safer, but they cannot be used to avoid creating a HACCP program and applying for a variance.

After addressing microbial hazards in the HACCP plan, a complete food safety management system requires SOPs to control risks inherent in the system. These are considered prerequisites to any reduced-oxygen packaging HACCP food safety program.

SOP 1: Dedicated area and sanitation
Since environmental contaminants can enter foods during any type of handling, the Food Code requires that a dedicated processing area be used. This area must be dedicated to handling cook-chill foods any time they have a risk of exposure to the environment (e.g., during bagging). This SOP should also describe how the area is cleaned and sanitized before and during use.

SOP 2: Prevention of cross-contamination
This SOP should describe how cross-contamination is minimized on food contact and non-contact surfaces. It should detail proper handling and bagging of foods in the cook-chill process. If product is pumped into bags, this SOP would detail how that equipment, especially hoses, are maintained to be clean and sanitary.

SOP 3: No bare-hand contact
This SOP defines that there should be no bare-hand contact with cook-chill foods after the cooking step. In some cases, employees will handle product with sanitized, heat-proof gloves or utensils. In that case, the gloves or utensils must be clean and sanitized before use.

SOP 4: Chilled foods storage
The Food Code requires some form of continuous electronic temperature monitoring of the ambient refrigerator temperature. However, it is recommended to monitor product temperature. If the ambient refrigerator temperature goes above the critical limit, the operator can ensure compliance by monitoring that the cook-chilled food remained below the critical temperature limit. Employees must also visually verify and record ambient (or product) temperature in refrigeration twice daily. Bagged product transported to a satellite location must also undergo continuous temperature monitoring.

There are several options available to monitor both the cooler temperature and food temperatures electronically. Options include a thermocouple data logger and thermometers with recording charts. Monitors with alarms or auto-dialers are recommended. If the operator chooses the ice bath method of storage mentioned above, then the ice bath temperature must be monitored instead of the ambient refrigeration temperature.

SOP 5: Labeling
Labels are required on all cook-chill processed foods. At a minimum, labels must indicate product identity, manufacture date, shelf-life expiration date and refrigeration statement, such as, “Must be kept refrigerated at or below 41 °F (38 °F or 34 °F) at all times until use.”

SOP 6: Employee training
Because of the severity of foodborne illness caused by C. botulinum and L. monocytogenes, employees who work with cook-chill processed foods must be provided adequate training. The training should identify the microbial hazards and emphasize the importance of measures taken to maintain safety. This would include an overview of a HACCP-based food safety system and all SOPs required to maintain safe production. The role of recordkeeping should also be emphasized.

SOP 7: Monitoring and recordkeeping
A proper monitoring and recordkeeping system is a requirement of any HACCP-based food safety program. This SOP should explain the monitoring activities of all CCPs and SOPs defined previously. Operators should create their own forms with employee marking instructions. This SOP will also define the minimum holding period for records (6 months) and the location of those records. The SOP should designate the person in charge of reviewing, approving and maintaining the records. Records should be backed up in a second, separate location. Lack of any records during an inspection will most likely result in your cook-chill process being revoked.

Update: At the April 2010 Conference for Food Protection, a committee was formed to examine reduced-oxygen packaging. The committee’s goal is to examine the science behind safe HACCP-based, reduced-oxygen packaging and make recommendations for updating the Food Code at the 2012 Conference for Food Protection.

Brian A. Nummer, Ph.D., is an extension food safety specialist and food microbiologist at Utah State University and director of the Retail-Foodservice Food Safety Consortium.