This is something that’s been bugging me. I teach food safety, primarily to food service managers and folks that work in restaurants. Occasionally I do work with consumer groups. If you teach these topics you know that there are a couple differences in what we teach the restaurant folks vs. what we teach consumers. Why?
According to the FDA Food Code food service operations are allowed to keep TCS (or potentially hazardous) food in the temperature danger zone (TDZ) of 41 degrees to 135 degrees F for up to FOUR hours.
But, when you teach it to consumers it’s the TWO HOUR RULE. According to the United States Department of Agriculture: “Never leave food out of refrigeration over 2 hours. If the temperature is above 90 °F, food should not be left out more than 1 hour.” https://www.fsis.usda.gov .
And if you really want to get “picky” their TDZ is a bit different, too. They say 40 degrees to 140 degrees F.
Food doesn’t instantly go bad at either two hours or four hours. Again, according to the USDA “leaving food out too long at room temperature can cause bacteria (such as Staphylococcus aureus, Salmonella Enteritidis, Escherichia coli O157:H7, and Campylobacter) to grow to dangerous levels that can cause illness. Bacteria grow most rapidly in the range of temperatures between 40 °F and 140 °F, doubling in number in as little as 20 minutes.”
Why the difference? I don’t really have an “official” scientific reason. According to the folks at the USDA Meat and Poultry hotline they are leaving an abundance of caution with the conservative consumer recommendations.
While teaching I try to explain to folks that the four hours allowed for restaurants/food service is making the assumption that these folks are following recommended FDA food safety practices. These include lots of hand washing and gloves, use of sanitizers, working to prevent cross-contamination and using timers and thermometers.
This conservative approach might be a great idea for consumers. A lot of things can happen (or not happen) in a home kitchen. I’m hoping that they do wash their hands before cooking and do use some good food safety procedures. Not many folks in home kitchens use sanitizers but let’s hope they use lots of hot soapy water. Does the dog or cat climb on that counter when they are alone in the house? Did mom get called away and thinks it’s two hours, when really it was more? Food in restaurants are delivered in refrigerated trucks and put away quickly, while sometimes food stays in the TDZ longer than planned between the grocery store and the home refrigerator. I also wonder how many home refrigerators have thermometers.
What I think is really important…if it’s two or four…. follow good food safety practices all of the time.
Cheryle Jones Syracuse, MS
Professor Emeritus, The Ohio State University