The Corner Forum
Saturday, Nov. 2, 2002
Issue #4

It's All About Keeping Harmful Bacteria From Growing on Food

By Eleanora Isles

Associate Professor, Nutritional Sciences Department, Howard University

Dr. Isles, what I need your help for is to explain why some of these things are important. Could you start by telling me why does it matter if food is found at the wrong temperatures?

Okay. Well, we have in food safety, there is the idea that temperature between 40°F [45°F, under D.C. regulations] and 140°F is what is referred to as the danger zone. Room temperature is around 70. So that falls right in the middle there.

And when food is held at those temperatures, certain types of bacteria proliferate. And that is why we recommend that food should either be kept refrigerated — that is, below 40°F [45°F, under D.C. regulations] — or it should be served or held hot, above 140°F, so that it will be out of that danger zone where these bacteria proliferate very rapidly.

Are there some types of foods where this is more important than for other types of foods?

Well, yes, because there are some foods that do not need to be refrigerated. For instance, fruits in particular, you do not need to refrigerate, because bacteria don't grow very rapidly in fruits. But foods such as meats and milk and egg dishes, those foods support the growth of bacteria, so these cooked foods should be held at the proper temperature.

So for example if they found chicken at 110°F or 125°F —

The other thing I should have said, is that foods can be held at this zone for a short period of time — for about two hours. But above that, it should be refrigerated. For example, if you're preparing your food, and you're serving it, it could stay within that zone for a limited period of time. And also you mentioned about chicken. When we talk about temperature, it's also very important to cook food to the proper internal temperature.

For example, if you were cooking chicken, and poultry, it should be cooked to an internal temperature of 180°F. And there are also internal temperatures given for cooking things like hamburgers. Because chicken and hamburgers and other meats may have bacteria in them, and you would have to cook it sufficiently to destroy the bacteria. And from time to time we hear reports of food-borne illness that is caused by not cooking foods to the proper temperature.

What you said about the two hours — that it's okay — that's very important, because when our city inspectors go, they measure the temperature of foods, and if it looks like foods are being kept out at room temperature, then they make a violation, but it sounds like you're saying it depends also on how long they're kept there — if it's just a short time, that's okay?

Yeah, see the thing is if you have food left out at room temperature, if the food was heated, it would have destroyed the bacteria, and it might not have grown and developed within that short period of time, and that is why you can leave it out for a short period.

I see. Since cooking kills the bacteria, why can't you leave out food almost forever, as long as you cook it well?

Because bacteria might recontaminate the food. In the four-hour period that you left the food out, it could grow and develop. The bacteria may have been killed, but there's bacteria in the air — people's hands may have bacteria, to recontaminate the food. And, of course, there are some people who are more susceptible to bacteria than others. I know for a fact that people who have impaired immune systems, would, of course, be more susceptible.

Tell me about roaches. People think they're disgusting, and things like that. But why does the city care if they find roaches at a place?

Well, roaches — they carry bacteria with them. Roaches would walk almost anywhere in a sewer, outside in the yard in the dirt and the dust and they may pick up bacteria as they do that, and then when they come, they would contaminate the food. So that's a reason right there why we shouldn't have roaches and rodents and this sort of thing around our food.

Finally, cleanliness. For instance, the cutting boards — why does it matter there?

Well, cuttin' boards — we often talk about cross-contamination. For example, if you were to cut up poultry, which is notorious for having salmonella bacteria — and you would not wash and sterilize that board properly, and then you went and cut some foods that were not going to be cooked to high temperatures, then the salmonella could be transmitted to that food. That's why we talk about havin' your boards thoroughly cleaned before you use it with other foods.

And also, as we talked about hygiene, one of the problems that we have found in food services is that one of the main sources of contamination is from people not washin' their hands properly.

Something as simple as that, but that's a major cause of bacterial contamination — food handlers not following proper procedures. §