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Time Matters to Keep Food Safe

Janet Hackert, Regional Nutrition and Health Education Specialist, Northwest Region, University of Missouri Extension


When it comes to food safety, time matters. The reason has a lot to do with how the microorganisms that cause food-borne illness move and grow. Let’s look at the 10-second rule and the 2-hour rule.

Have you seen this? Someone drops a piece of food on the floor. They pick it up, laugh and say, “10-second rule!” as they brush it off and eat it. And it’s funny. Or is it? Let’s consider a similar situation to see how long it takes to make food dirty. Let’s say I have a piece of banana and I drop it on a saw-dust-covered floor … One-Mississippi, two-Mississippi ... Or I drop a cracker in a mud puddle … Three-Mississippi, four-Mississippi ... I’m still within the “10-second rule” but is my food already contaminated? Sure it is. Just as quickly, germs we cannot see transfer from a dirty surface to food.

How about the 2-hour rule that says not to leave perishable food out at temperatures between 40 and 140F for more than two hours? What makes two hours so special? It is because microorganisms that can make us sick grow and multiply quickly. Again let’s look at an example. Let’s say we have a Thanksgiving turkey, a Super Bowl pizza or an everyday meat-and-cheese sandwich. And let’s say that food has just two small, disease-causing microorganisms on it. Chances are pretty good that most people’s immune systems can handle that and not get sick.

Now let’s say the food is left out at room temperature, say 68F, for a half hour. Those two will have multiplied into eight microorganisms. In an hour, there will be 32. After an hour and a half, they have grown to 128 strong. In just two hours, the two, barely noticeable microorganisms we started with would have exploded into a whopping 512 microorganisms living on that left-out food. Could these make a person sick? It would be much more difficult for a person’s immune system to fight these and avoid disease. And this is assuming just two to begin with.

So ditch the 10-second rule and follow the 2-hour rule to avoid food-borne illness this holiday season and throughout the year!




Last Updated 10/29/2009




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