7.1 Reheating Procedures

Reheating requirements in a food service operation depend entirely on what happens to the food AFTER reheating: whether it will sit in a hot-holding unit for an extended service period, or go straight to a customer's plate. The FDA Food Code treats these as two different food safety events, each requiring its own control.

The 165°F/15-Second Rule for Hot Holding

Under the FDA Food Code, TCS (Time/Temperature Control for Safety) food that is reheated in order to be placed into hot holding must reach an internal temperature of 165°F for 15 seconds within 2 hours.

This is the critical exam point: reheating for hot holding is a separate control point from the food's original cooking step. It does not matter what temperature the food reached the first time it was cooked — once it has been cooled, refrigerated, and is now being brought back up to be hot-held again, it must reach 165°F for 15 seconds, full stop.

Example: A prime rib roast was originally cooked using the Food Code's extended-time alternate method to a lower internal temperature (such as 130-145°F, held for a specified time to achieve the same pathogen destruction as a higher instant temperature) and served immediately — this was fully compliant at the time. But if that same roast is cooled, refrigerated overnight, and then reheated the next day to go into a carving station's hot-holding unit, the earlier 145°F cook does not carry forward. It must be reheated to 165°F for 15 seconds before it goes into hot holding.

Why Reheating for Hot Holding Gets Its Own Rule

Original cooking temperatures are tailored to the specific food (165°F for poultry, 155°F for ground meats, 145°F for whole-muscle cuts and eggs, and so on) because each time/temperature combination is scientifically validated to destroy the pathogens of concern for that food. But food that has since been cooled and stored may have picked up new contamination, or may harbor spore-forming organisms such as Clostridium perfringens or Bacillus cereus whose spores survive cooking and can germinate during slow cooling or extended refrigerated storage. Reheating to a single universal high benchmark — 165°F for 15 seconds — gives a reliable checkpoint that destroys vegetative pathogens regardless of the food type, without requiring staff to remember each food's original cook requirement a second time.

The 2-Hour Window: Why It Exists

The temperature danger zone is 41°F-135°F, the range in which most foodborne pathogens multiply rapidly — bacteria can double in number in as little as 20 minutes under favorable conditions. Requiring food to reach 165°F within 2 hours forces the use of active, high-power reheating methods (stovetop, oven, steamer) rather than a slow warm-up, and it caps how long the food can realistically spend passing through the danger zone during the reheating trip.

A hot-holding unit is not a reheating appliance. Hot-holding equipment is built to maintain a temperature that has already been reached — not to raise a cold or lukewarm food up to temperature. Placing food into a hot-holding unit to "finish heating" leaves it stalled in or near the danger zone far longer than the 2-hour limit allows.

If 165°F Isn't Reached Within 2 Hours

If a TCS food has not reached 165°F for 15 seconds by the 2-hour mark, it must be discarded — not given extra time on the heat. There is no allowance for "it's close, just a few more minutes." The 2-hour window is a hard limit, and continuing to heat past it does not retroactively make the earlier danger-zone time safe.

Exception: Commercially Processed Ready-to-Eat Food

Ready-to-eat food that comes from a commercially processed, hermetically sealed container (such as a canned soup or a vacuum-sealed pouch from an inspected processing plant) and is reheated for hot holding only needs to reach 135°F — the same temperature required simply to maintain hot-held food, not the 165°F pathogen-destruction benchmark. This lower bar is allowed because the food has already undergone a validated commercial process (such as a canning retort cycle) that provides its own safety margin, and it has not been opened or exposed to the establishment's kitchen environment until this point. The moment the product is opened and combined with other ingredients, the standard 165°F/15-second rule applies again.

Reheating for Immediate Service

When food is reheated and served right away, with no subsequent hot-holding step, the 165°F/2-hour rule does not apply. For example, a cook pulling a single refrigerated portion of soup and reheating it to order on the stovetop before plating it for an already-seated guest is not required to hit 165°F for 15 seconds. The food still must be reheated to a temperature that is safe and hot for service — the Food Code does not eliminate the need for a proper reheat — but the specific hot-holding benchmark and its 2-hour clock are not triggered, because there is no extended holding period afterward during which any surviving organisms could multiply.

Microwave Reheating

Microwaves heat unevenly, leaving potential cold spots even when a probe reading elsewhere shows a safe temperature. Because of this, the Food Code adds a specific rule for microwave reheating of TCS food for hot holding: the food must be heated to 165°F, covered, and then allowed to stand for 2 minutes before it is hot-held or served. The cover traps heat and steam, and the 2-minute stand time allows the heat to equalize throughout the food by conduction, resolving cold spots that a single probe check might have missed the moment active heating stopped.

Practical Application for the Food Safety Manager

• Keep a calibrated probe thermometer at every reheating station and check the thickest part or geometric center of the food.
• Track elapsed reheating time with a timer or logged start time — do not estimate.
• Never use a hot-holding unit to finish bringing cold food up to temperature.
• Train staff that "it was already cooked once" is never a substitute for verifying 165°F/15 seconds before hot holding.
• Enforce the discard-at-2-hours rule consistently, even during a rush.