Food Protection Connection: The Cold Facts on Cooling

(reprinted from Nutrition & Foodservice Edge, April 2012)

The Center for Food Safety and Applied Nutrition (CFSAN) continues to report improper cooling as a major cause of foodborne illness. Despite the studies, outbreaks, news and food safety education available on cooling, many food facility employees do not understand the importance of proper cooling and routinely fail to accomplish cooling correctly. Does your facility cool its food properly?  Has the process ever been verified? 

Proper cooling is one of the most labor-intensive operational steps in a food facility and therefore is often ignored, not monitored, or simply given short cuts. Improper cooling of cooked potentially hazardous foods will provide an ideal environment for the growth of spore-forming bacteria and production of toxins.  Additionally, if post-cook contamination occurs and pathogens are reintroduced into food, improper cooling will lead to an environment that is ideal for growth of pathogens to sufficient numbers to cause foodborne illness.

THE HAZARD
There is a big misconception that cooking food to high temperatures, ‘cooking it to death,’ will keep food safe. False! Some bacteria have the ability to go dormant and turn into endospores (spores) as a means of protection. Spores are resistant to heat, freezing, chemicals, and other adverse environmental conditions that food undergoes during preparation. When conditions are favorable, spores can reactivate and become viable vegetative cells again. If the cooking step prior to cooling is adequate and no recontamination of the food occurs, spore-forming bacteria such as Clostridium perfringens and Bacillus cereus will indeed be killed. However, if these pathogens formed spores, danger is still lurking.  Heat treatment will not eliminate bacterial spores.

These pathogens, and other similar pathogens, are also toxigenic, meaning vegetative cells in large numbers can produce harmful. Toxins are also not destroyed by heating.  To prevent the growth and multiplication of spore-forming toxigenic organisms, food must be cooled rapidly after cooking. If cooling is not controlled, these spores will germinate and the new vegetative cell can multiply to dangerous levels causing illness, especially for persons classified as a ‘highly susceptible population.’ In sufficient numbers, these new vegetative cells can produce toxins that will additionally lead to illness. It is imperative that these spore-forming toxigenic organisms be effectively controlled and not allowed to grow.

Substandard sanitary conditions or poor employee practices could result in recontamination of the food by other pathogens as well, such as Salmonella or Listeria monocytogenes.  Though not spore-formers, if food becomes contaminated post-cook, these pathogens and pathogens like them could multiply to dangerous levels if the food is allowed to remain in the temperature danger zone (135°F – 41°F) too long. Cooling requirements, as documented in the FDA Food Code, are based on growth characteristics of organisms that may survive cooking or become post-cook contaminants, which under certain conditions of temperature abuse can rapidly multiply to levels that would cause illness.

Cooling Requirements
Cooling requires control of both time and temperature.  Cooling is a critical control point with measurable control limits.  The FDA Food Code requires:

• Cool hot food from 135°F to 41°F in 6 hours, with cooling from 135°F to 70°F within the first 2 hours
• Cool foods prepared from ambient temperature ingredients (~70°F), such as canned tuna, to 41°F in 4 hours

With rapid cooling occurring within the first two hours and a total of six hours for total cooling, flexibility exists in how you can accomplish cooling effectively.  For example, if you can cool hot food in 30 minutes to 70°F by using an ice bath, you now have an additional 5.5 hours to take the food from 70°F to 41°F. If it takes the full two hours to reach 70°F, then you only have four hours to go from 70°F to 41°F.

Cooling Methods
You will need to select a proper cooling method that best suits your operation.  Every operation is different. Cooling is not a ‘one method fits all’ process.  Some cooling methods may include:

• Place food in shallow containers (less than 4 inches deep), keeping the food uncovered and put it in your walk-in or reach-in cooler in the coldest location within the cooler that has good air circulation.
• Use a quick chill unit such as a blast chiller.
• Use an ice bath method and stir food often.
• Use an ice stick/rod to stir cooling food.
• Use containers whose material facilitates heat transfer, such as stainless steel pans.
• Add potable ice as an ingredient at the end of the cooking process.
• Cut food into smaller, thinner portions before placing in a cooler.
• Chill ingredients before making salads such as tuna or chicken salad.

Things to remember when cooling foods:

• Coolers/refrigerators are not meant to cool food.  They are meant to hold foods cold, not cool large volumes of food. Do not over-tax your units. If you only have small coolers you may need to use an alternative method of cooling to get your food to a more reasonable temperature before placing it into a small cooler.
• Foods should remain uncovered while they are cooling. Tightly covered containers will slow the rate of heat transfer. No inspector should debit a violation of having food uncovered in a cooler if the food is undergoing cooling.  Although protecting food by covering is important, in this case, rapid cooling far outweighs placing a cover or lid on a cooling product. The FDA Food Code specifically allows for food to be uncovered or loosely covered while in the cooling stage. Once at 41°F, then cover the product.
• Evaluate bulk or batch cooking to assure you can adequately cool the volume of food you intend to make.
• Mass and volume of food will affect cooling rate. Thick soups will take longer to cool than thin broth-based soups. A large roast will cool slower than a portioned roast. Alter your cooling methods as needed to adjust for these variations.
• A clean, sanitary facility and good employee practices will be important to control post-cook contamination of any pathogen.

Monitoring and Validating
Whatever methods of cooling you choose to use, the methods must be validated and monitored.  Does the method you have chosen really work?

• Try your intended cooling process to make sure it actually works within the cooling parameters required in the FDA Food Code for the specific food and specific volume of food you plan to prepare. Foods cool at different rates, so one method will not work for all food items. Verify that your methods actually work.
• Always use a cleaned, sanitized, and calibrated thermometer when checking food temperatures.
• Take temperatures frequently during the cooling process.
• Keep a record or log of times and temperatures. Good record-keeping will verify that you are keeping an eye on your process. They can also provide a trend analysis of methods or steps within the method that may need to be altered or adjusted.
• Immediately respond to any deviations in the cooling method or if any critical limits are exceeded. Staff should notify managers or the person in charge if a corrective action is needed. The person in charge should oversee the corrective action procedures.
• Record any corrective actions you take, including reheating or disposal of food on your log sheets.

If a specific cooling method has been shown to work, the frequency at which you record temperatures and monitor your process can be re-evaluated. Management staff should occasionally validate that the cooling process is working as required and employees are following the prescribed procedures and record keeping.

Corrective Actions
What do you do when something goes wrong?  Do you have a plan in place?  The goal of corrective actions is not to discard food.  The goal is to assure the food is safe to consume. If there is a way to right the wrong, go for it. If not, don’t take chances—throw it away. Following are various corrective actions you could apply.

• Re-heat cooked hot food to 165°F for 15 seconds and begin the cooling process again using a different cooling method if:
  • The food is above 70°F and 2 hours or less into the cooling process
  • The food is above 41°F and 6 hours or less into the cooling process
• Discard cooked  hot food when food is:
  • Above 70°F and more than 2 hours into the cooling process
  • Above 41°F and more than 6 hours into the cooling process
• Use a different cooling method for prepared ready-to-eat foods, such as salad items, when the food is above 41°F AND less than 4 hours into the cooling process. Do not exceed a total of 4 hours in the danger zone when you alter your cooling method.
• Discard prepared ready-to-eat foods prepared from ambient temperature ingredients, such as tuna salad, when the food is still above 41°F and more than 4 hours into the cooling process.

Cool, But Cool Correctly
Food must move through the temperature danger zone rapidly during the cooling process—the faster the better. Improperly cooling food can begin a spiral effect that cannot be stopped. Even with proper cooking or reheating, toxins released by bacteria after cooking and improper cooling may not be destroyed to levels safe enough for human consumption. Post-cook contamination through employee practices or unsanitary conditions must be controlled as well. Though labor intensive, cooling must be done right. Don’t cut corners with this food safety hazard.

Sources
1.            US Department of Health and Human Services, Food and Drug Administration. 2009 FDA Food Code and Annex, www.cfsan.fda.gov
2.            US Department of Agriculture, Food and Nutrition Services & National Food Service Management Institute. HACCP Based Standard Operating Procedures: Cooling Potentially Hazardous Foods,. www.nfsmi.org 

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 mvaccaro@state.pa.us.