Why The Food 'Sniff Test' May Not Be As Accurate As You Think

In January, the British supermarket Morrisons decided to stop printing use-by dates on its milk cartons, reports The Guardian. The point, the chain argued, is that having a specific date creates an artificially hard deadline that causes people to throw away milk that can still be consumed in the next few days. Removing the best-by date would address millions of pints of food waste. Instead of relying on the date, customers are encouraged to give the milk the tried-and-true smell test.

When asked if this method would work in an exclusive interview with Mashed, Lynn Williams, a technical information specialist at the USDA's Food Safety and Inspection Service, explained that "spoiled foods can develop an off odor, flavor, or texture due to naturally occurring spoilage bacteria." However, she clarified that "pathogenic bacteria (the ones that can make you sick with foodborne illness), do not cause any changes to the food and are not detectable by human sight or smell." In other words, the smell test would work with spoiled milk in some cases but cannot be entirely relied upon as a way to check for harmful bacteria. Still, Williams points out that sell-by and use-by dates on food items are not "safety dates." Rather, they serve as guidelines for stores and customers to estimate when a food's quality is on the verge of decline.

Despite not being an indicator of milk's safety, entirely, a good sniff test will suss out the quality of the dairy product. Kristen Gibson, an associate professor of food science at the University of Arkansas, explained to HuffPost that if milk smells spoiled, "I think the experience [of drinking it] would not be very pleasant. But it shouldn't cause you harm." So, the Morrisons grocery chain has a point. It's just that the point's about quality, not safety. Still, our noses can inadvertently prevent us from consuming anything that's potentially harmful. As The Conversation notes, "Spoilage is a good indicator food has been left too long and 'bad' microorganisms, including pathogens, may also have grown."

For those wanting further guidance on food safety, Lynn Williams shares the USDA's recommendations for true best-by dates. Fresh meat should be eaten or frozen within one to five days of purchase, depending on the type. Leftover cooked food can be kept in the fridge for three to four days. Eggs are good for five weeks, and so on. If you combine this knowledge with the sniff test — and check for strange tastes and textures, such as mushiness or sliminess — you should be able to maintain a safe kitchen.