Bacteria that cause food poisoning grow slowly at refrigerator temperatures and are largely controlled by proper hot holding, but in between they can double in number in a short time. Common food safety guidance treats about 5 °C to 60 °C as the danger zone, though different authorities draw the edges slightly differently. The aim is to keep cold food at or below about 5 °C, keep hot food hot, and move food quickly through the zone when cooling or reheating it.
Time matters as much as temperature. A plate of cut fruit at 25 °C for ten minutes is far lower risk than a pot of rice left to cool on the counter for three hours. That is why kitchens track not just storage temperatures but also cooling times, how long food sits on a pass or buffet, and how quickly display cases recover after restocking.
In a 42 °C Delhi kitchen in June, anything left out sits in the most dangerous part of the range. A wedding caterer cooking hundreds of portions in advance must plan blast chilling, cold storage and hot holding so food is never left at room temperature waiting.