The Two-Hour Rule for Reheating Food
According to the FDA Food Code and USDA food safety guidelines, the maximum amount of time allowed for safely reheating food is two hours. Specifically, food must be reheated from refrigeration temperature to an internal temperature of 165°F (74°C) within two hours. If the food fails to reach this temperature within the two-hour window, it must be discarded to prevent the risk of foodborne illness.
This two-hour rule is a critical food safety standard that applies to all commercial food establishments, including restaurants, cafeterias, catering operations, and institutional kitchens. While home cooks are not subject to the same regulatory enforcement, following this guideline at home is equally important for protecting your family from foodborne pathogens.
The reason for the two-hour limit is rooted in bacterial growth patterns. When food is in the temperature danger zone between 40°F (4°C) and 140°F (60°C), bacteria can multiply rapidly, doubling in number every 20 minutes under optimal conditions. The longer food remains in this danger zone during the reheating process, the greater the risk of bacterial contamination reaching levels that can cause illness.
Why 165°F Is the Magic Number
The target internal temperature of 165°F (74°C) is not an arbitrary number but is based on extensive food science research into the thermal death points of the most common foodborne pathogens. At 165°F, virtually all harmful bacteria, including Salmonella, E. coli O157:H7, Listeria monocytogenes, and Clostridium perfringens, are destroyed within seconds.
This temperature provides a substantial safety margin that accounts for variations in food density, composition, and the accuracy of home and commercial thermometers. While some pathogens are destroyed at lower temperatures, 165°F ensures a comprehensive kill of all common foodborne bacteria regardless of the specific food being reheated.
It is crucial to measure the internal temperature of the food rather than relying on surface temperature or visual cues. A food thermometer should be inserted into the thickest part of the food, away from bone, fat, or gristle, to get an accurate reading. Steam rising from food or a bubbling surface does not necessarily indicate that the interior has reached 165°F.
Proper Reheating Methods
Different reheating methods vary in their efficiency and speed, which directly affects your ability to meet the two-hour requirement. Understanding the strengths and limitations of each method will help you choose the best approach for different types of food.
Stove-top reheating is one of the fastest and most effective methods for soups, sauces, gravies, and other liquid or semi-liquid foods. Heat the food over medium to medium-high heat, stirring frequently to ensure even temperature distribution. The stirring action helps eliminate cold spots where bacteria could survive. Use a food thermometer to confirm the food has reached 165°F throughout.
Oven reheating is ideal for casseroles, large cuts of meat, and baked dishes. Preheat the oven to at least 325°F (163°C) and place the food in an oven-safe container. Covering the food with foil helps retain moisture and promotes more even heating. Oven reheating tends to be slower than stove-top methods, so plan accordingly to stay within the two-hour window.
Microwave reheating is the fastest method for small to medium portions of food. However, microwaves can heat food unevenly, creating hot spots and cold spots within the same dish. To promote even heating, rotate the food halfway through the heating cycle, stir periodically, and allow the food to rest for one to two minutes after heating to allow temperatures to equalize. Always check the internal temperature with a thermometer at multiple points.
Foods That Require Extra Caution
Certain foods pose higher risks during the reheating process and require extra attention to ensure safety. Poultry products, including chicken, turkey, and duck, are among the most frequently implicated in foodborne illness outbreaks. Always reheat poultry to 165°F and verify with a thermometer.
Stuffing, whether cooked inside a bird or prepared separately, must also reach 165°F during reheating. Stuffing has a dense texture that can trap cold pockets, so thorough stirring and temperature verification at multiple points are essential.
Rice is a commonly overlooked reheating risk. Bacillus cereus, a spore-forming bacterium, can survive cooking and multiply in cooked rice that is held at room temperature. When reheating rice, ensure it reaches 165°F and consume it promptly. Do not reheat rice more than once.
Eggs and egg-based dishes, such as quiche, frittata, and egg casseroles, must be reheated to 165°F. These protein-rich foods provide an ideal environment for bacterial growth if not handled properly.
Common Reheating Mistakes
One of the most dangerous reheating mistakes is using a slow cooker, steam table, or chafing dish to reheat food. These devices are designed to hold already hot food at serving temperature, not to bring cold food up to safe temperatures. The slow heating process of these devices allows food to remain in the temperature danger zone for extended periods, dramatically increasing the risk of bacterial growth.
Another common mistake is reheating food multiple times. Each time food is cooled and reheated, it passes through the temperature danger zone, providing additional opportunities for bacteria to multiply. The safest approach is to reheat only the portion you plan to consume and keep the remainder refrigerated.
Relying on visual or tactile cues rather than a thermometer is another frequent error. Food can appear to be steaming hot on the surface while remaining cold in the center. The only reliable way to confirm that food has reached a safe internal temperature is to use a calibrated food thermometer.
Failing to break up large portions into smaller pieces before reheating can result in uneven heating and extended reheating times. Large, dense foods like roasts and casseroles should be cut into smaller portions or spread into shallow containers to promote faster, more even heating.
Special Considerations for Commercial Food Service
In commercial food service settings, the two-hour reheating requirement is strictly enforced by health inspectors and is a critical component of a food establishment's Hazard Analysis Critical Control Point (HACCP) plan. Violations of reheating time and temperature requirements can result in citations, fines, and in severe cases, temporary closure.
Commercial kitchens should maintain temperature logs documenting the start time and temperature of all reheating operations, as well as the final temperature and the time it was achieved. These records demonstrate compliance with food safety regulations and provide documentation in the event of a health inspection or foodborne illness investigation.
Staff training is essential for ensuring consistent compliance with reheating requirements. All kitchen staff should be trained on proper reheating procedures, thermometer use, and the importance of the two-hour time limit. Regular refresher training helps maintain awareness and prevent complacency.
Tips for Efficient and Safe Reheating at Home
To ensure safe and efficient reheating at home, follow these practical tips. Always thaw frozen food in the refrigerator before reheating, rather than at room temperature. Thawing at room temperature allows the outer layers of the food to warm into the danger zone while the interior remains frozen, extending the total time needed to reach 165°F.
Use shallow containers when storing leftovers in the refrigerator. Shallow containers allow food to cool more quickly and reheat more evenly than deep containers, reducing the time the food spends in the danger zone.
Invest in a reliable instant-read food thermometer. Digital thermometers provide fast, accurate readings and are inexpensive. Insert the thermometer into the thickest part of the food and check multiple locations to ensure even heating.
When reheating soups and gravies, bring them to a rolling boil and maintain the boil for at least one minute. The rolling boil ensures that the entire liquid has reached a temperature well above the 165°F minimum.
Conclusion
The maximum amount of time allowed for safely reheating food is two hours, during which the food must reach an internal temperature of 165°F (74°C). This standard, established by the FDA and USDA, is designed to minimize the time food spends in the temperature danger zone where harmful bacteria multiply rapidly. By choosing efficient reheating methods, using a food thermometer, avoiding common mistakes, and following proper food handling practices, you can ensure that reheated food is both delicious and safe to eat.
