There's nothing worse than giving foodborne illness to your ministry group. Most people think that once food is fully cooked the threat is gone; however, it is extremely important to correctly handle food after it is cooked. The nature of many of our events require that we often do food prep in the morning and let it sit for hours, but what's safe and acceptable?
What are the factors for controlling microorganism growth?
Disease causing microorganisms multiply between 41F and 135F (known as the temperature danger zone). Within that range, microorganisms grow most rapidly between 70F (room temp) and 125F.
Bacteria double every 20 minutes. The National Restaurant Association (NRA) set 4 hours as the limit for food in the temperature danger zone. At this point there are about 400,000% more bacteria and can potentially make someone ill. After 4 hours, restaurants are required by law to discard the food. These are strict standards to ensure safety, I wouldn't go much longer, but it is possible for food to still be safe after 4-5 hours if it isn't a potential hazardous food.
Microorganisms grow best at neutral or slightly acidic pH, which is most of what we eat.
Microorganisms need building blocks of proteins and carbs to grow. Once food is cooked, there is abundant access to these things. For example, potatoes can last for a long time when raw. But when cooked like in potato salad, the structure breaks down and bacteria now has access to broken down carbs and amino acids.
Microorganisms need water to grow. Unfortunately, most of the food we eat is moist and promote bacterial growth.
The 2 factors that people can control are time and temperature. One dangerous practice is to keep food warm by keeping it in a cooler for a long time. The food is kept within the danger zone for an extended time (warm means incubation temperature where bacteria thrive) and steam is trapped, keeping the environment humid and moist. This is fine if it is held for less than 4 hours; but beyond that, I would not recommend keeping food warm in a cooler.
For this reason, leftover food should be refridgerated immediately. If it has a funny smell, toss it! Depending on the food, it is possible to keep warm food safely beyond 4 hours; however, it's better to err on the safe side when planning your next event.