Understanding Temperature Control System (TCS) Controlling Time & Temperature during Cooking, Holding, Cooling, and Reheating

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Understanding Temperature Control / Cooking, Cooling & Reheating

All food can potentially carry harmful bacteria, but some foods are especially conducive to promoting bacterial growth. Several factors affect the rate at which bacteria grow in food, but time and temperature are two of the most easily-controlled factors in a food service kitchen. Food that requires time and temperature control for safety is referred to as TCS food. TCS food has several attributes that make it ideal for bacterial growth, such as moisture, protein, and a neutral or slightly acidic pH.

TCS food can be whole food, or it can be food that has already been prepared, like a casserole. TCS food can be from animal or plant sources. Foods that are considered TCS include:

  • Milk and other dairy products
  • Meat (beef, pork, lamb) or poultry (chicken, turkey)
  • Fish and shellfish
  • Eggs
  • Baked potatoes
  • Plant-based foods that have been heat-treated (cooked rice, beans, or vegetables)
  • Soy foods (tofu, textured soy protein/meat alternatives)
  • Sliced or cut fruits or vegetables (e.g. cantaloupe or melons, leafy greens, tomatoes, etc.)
  • Bean sprouts and sprout seeds
  • Untreated garlic-and-oil mixtures

Factors that Affect Bacterial Growth

There are six factors that affect bacterial growth on food. These are food, acidity, time, temperature, oxygen, and moisture. How acidic a food is, as measured by pH, can also influence how quickly bacteria can grow. Bacteria tend to grow in foods with a pH between 4.6 and 9.0. Low pH foods—those that are more acidic—include things like pickled foods, jams or jellies, honey, and fruits. High pH foods—those that do not have much acidity—include meats, milk, and vegetables. Most bacteria that cause foodborne illness grow well in conditions that do not have much oxygen, which is why it is important to control other factors that promote bacterial growth in food. Bacteria need moisture to grow, and the amount of moisture in a food is measured by water activity. The higher the moisture in a food, the better the conditions for bacterial growth. The water activity scale ranges from 0 to 1.0, with distilled water being 1.0. Most foods have a water activity of at least 0.95, meaning that bacteria have sufficient moisture to grow.

A food handler cannot control a food’s acidity, oxygen, or moisture; these properties are inherent to the food itself. However, in food service, the remaining two factors, time and temperature, can be controlled. Time and temperature are closely related. Bacterial growth in ideal conditions happen rapidly: the amount of bacteria can double every 15 to 20 minutes. This is especially true when the temperature of food falls in the temperature danger zone. The temperature danger zone ranges from 41 F to 135 F (5 C to 74 C). The longer a food stays in this temperature range, the higher the risk for bacteria to grow rapidly in a TCS food. It is recommended to limit the length of time a TCS food is in the temperature danger zone to no more than four hours.

Controlling Time & Temperature from Receiving through Preparation

Receiving Food

It is important to make sure you check the temperature of TCS food during the receiving process. This will help you gauge whether food was exposed to the temperature danger zone during transit. Document each food’s temperature on a designated temperature log. Refrigerated TCS foods should arrive at 41 F (5 C) or colder. Frozen TCS food should arrive at 0 F (-18 C) or colder. Hot TCS food should be received at 135 F (57 C) or higher; as with cold or frozen TCS food, be sure to document the temperature of hot TCS food upon receipt using a designated temperature log. Frozen TCS food with ice crystals or frozen liquid, fluids, or water stains should not be accepted. Additionally, any food that has passed its use-by or expiration date, has an off odor, abnormal color, or mold, or any meat, fish or poultry that is slimy, sticky, or dry should be rejected.

Storing Food

Maintaining proper temperature during storage of TCS food is very important. Temperatures should be checked and recorded regularly. Food storage time should be documented. This is accomplished through writing down the date a food was put into storage and when it should be used directly on the food itself. Labels are a good way to do this. Here are some safety tips for safely storing TCS food:

  • Refrigerated TCS food should be stored at 41 F (5 C) or colder so that the internal temperature of the food maintains this temperature.
  • Keep frozen food frozen; do not allow it to thaw.
  • Do not overcrowd freezers or refrigerators; this can cause the temperature inside the equipment to become warmer and expose the food to dangerous temperatures.
  • Minimize how often you have to open refrigerator and freezer doors.
  • Label TCS food when it goes into storage. The label should include the name of the food, the date it went into storage, and the date it should be used by. Ready-to-eat TCS food prepared on-site in your facility must be used within seven days if held at 41 F (5 C) or lower.
  • Be sure to rotate food during storage so that the food with the earliest use-by date is in front of foods with later dates. (As discussed in Lesson Four, this is called FIFO rotation, or first in, first out.)

The proper temperatures for kitchen equipment are as follows:

  • Refrigerators: 40 F (4 C) or colder
  • Freezers: 0 F (-18 C) or colder
  • Dry storage: 50 F to 70 F (10 C to 21 C), with relative humidity of 50 to 60 percent

Record the temperature of your facility’s walk-in refrigerators and freezers on an approved temperature log. Your program may use a specific form, or you can use the temperature log template below.

Thawing Food

There are four ways to properly thaw frozen food. Which method you use depends on the type of food you thaw. It is important to thaw food properly to minimize how much time the food is in the temperature danger zone to inhibit bacterial growth.

Thawing Method

  1. In the refrigerator

    Thawing food in the refrigerator takes at least 24 hours, so this method requires planning ahead. Place the food on a tray in case any fluids leak from the package. Food should be placed on the bottom shelf of the refrigerator to thaw. The temperature inside the refrigerator should be 40 F (4 C) or colder.

    The refrigerator method is the safest method for thawing meat and poultry.

  2. In cold water

    This method is quicker than the refrigerator method and usually takes several hours, depending on the weight of the food. Place the frozen food item in a watertight plastic bag and completely submerge the bag under cold running water, 70 F (21 C) or colder. If thawing using this method, the food must not be above 41 F (5 C) for more than four hours. Once thawed, food should be immediately cooked.

  3. In the microwave

    Use the microwave method for immediate thawing and cooking. To thaw food using the microwave, remove all original packaging and place the food in a microwave-safe container. Follow the instructions in the microwave’s user manual for thawing foods (or defrosting foods) in the microwave. (This method is not ideal for large meat items like roasts or turkey.)

    Once thawed, the food should be cooked immediately.

  4. As part of the cooking process

    Food can be thawed as part of the cooking process, such as when you cook a frozen hamburger patty. Cooking frozen food directly does add to the total cooking time required for the internal temperature of the food to reach the required temperature for that food.

Source: Academy of Nutrition and Dietetics, National Restaurant Association

Preparing Food

When preparing TCS food, make sure that the food is not exposed to the temperature danger zone for too long. The total amount of time that a TCS food can be in the danger zone is fewer than four hours. During preparation of TCS food, pay attention to how long the food is in the danger zone. Prepare TCS food in small batches, which helps prevent ingredients from being in the temperature danger zone for too long. Once the food is prepared, return it to the refrigerator as quickly as possible.

Controlling Time & Temperature during Cooking, Holding, Cooling, and Reheating

Cooking Food

To reduce the risk of foodborne illness, TCS food should be cooked to an internal temperature specific to the type of food item it is. The table below lists the minimum internal temperature for various TCS food categories, as well as how long each food should be at that temperature.


Holding Food

Once a TCS food has been cooked, it must be held at the correct internal temperature for that food. Cold TCS food must maintain a temperature of 41 F (5 C) or colder, while hot TCS food must maintain a temperature of 135 F (57 C) or hotter. Using covers whenever possible helps to maintain the proper temperature of TCS food. Temperatures of held TCS food should be taken every two hours. Any prepared food that falls in the temperature danger zone (41 F - 135 F) for more than four hours should be thrown out.

Cooling Food

Guidelines for cooling TCS food are as follows: first, bring the food down from 135 F (57 C) to 70 F (21 C) within two hours. If the food does not reach 70 F within two hours, it will need to be reheated to 135 F (57 C) and then cooled again. Next, bring the temperature down from 70 F (21 C) to 41 F (5 C) within four hours. The total cooling time should not exceed six hours. The best ways to cool foods rapidly include using an ice bath, transferring the food to a shallow pan, and dividing dense foods, like lasagna or casserole, into smaller portions. Record the temperature of the food during the cooling process on a temperature log to ensure that it cools properly.

Reheating Food

When reheating food, the internal temperature of the food must reach 165 F (75 C) within two hours. Take the temperature to ensure the food has reached 165 F (74 C) for 15 seconds. Once this minimum temperature has been reached, the food should be held at 135 F (57 C) or warmer.

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