How Long Cooked Food Can Sit: A Holding Bound from the Cooling Curve and a Growth Account

Cooked food left standing does not cool to safety. A pot cooling toward room temperature enters the 5 to 60 °C band and, at the ambient temperatures considered here, never leaves it, because its temperature approaches the ambient temperature and stops there. This paper computes how long two stated pots can stand before a stated spore-forming organism grows from a stated post-cooking survivor load to a stated threshold. The pots are 4.0 kg of cooked rice and 6.0 kg of stew, each leaving cooking at 95 °C and cooling by Newton's law with stated constants for covered and uncovered pots, at ambient temperatures of 20, 28, and 35 °C. The organism is Bacillus cereus, starting at 100 per gram and counted as reaching concern at 100,000 per gram, an allowance of 9.97 doublings with stated doubling times by temperature band. The shortest computed standing limit is 8.01 hours, for uncovered rice at 35 °C, whose count reaches 98,911.9 per gram by 8.0 hours; the longest is 12.54 hours, for covered stew at 35 °C, which stays hot enough to suppress growth for much of its cooling. No pot reaches 5 °C at any of the three ambient temperatures. Applying a stated safety factor of two gives a simple standing rule: at most 5.0 hours at 20 °C and at most 4.0 hours at 28 °C or 35 °C, measured from the end of cooking. Reheating does not reset an exceeded limit for the heat-stable toxin considered here: two hours past the limit, uncovered rice at 35 °C carries a toxin index of 16.2 times the threshold level, and reheating to 75 °C leaves that index at 16.2 while reducing vegetative cells. SIMULATED, NOT MEASURED.