Can You Trust The "Sniff Test" On Leftovers?

Does your nose know?

Young woman on kitchen during quarantine. Hold plasti foot tray opened with bed smell. Unfresh food. Woman feel sick because of bed smell. Stand in front of opened fridge.
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Reaching into the depths of your fridge, you find a container of homemade mac and cheese. Your mind wanders. Was that from last week? Perhaps even the week before? Opening the lid, you see no signs of mold, and take a whiff before diving in.

Most of us are raised on the sniff test, the old wife's tale that supposes that if food still smells "alright," it must be safe to eat. But is that really the case? To find out, Southern Living interviewed several food scientists to ask whether the sniff test is based on evidence.

Can the Sniff Test Determine Food Safety?

Yes and no.

Slimy, spoiling foods exhibit many characteristics like changing colors (for example, blue mold), wilting leaves, and a putrid smell. These foods that have passed their prime are typically gross to us.

Dr. Donald Schaffner, extension specialist in food science at Rutgers University, told Southern Living, "I think that the sniff test is generally a reliable indication for spoilage. Even that has some limitations. For example, when I made a cup of coffee today, the cream smelled fine, but when I added it to the coffee, it curdled, and it did not taste good, although I had no indication from the smell."

While it's unlikely you'll swig back a cup full of curdled coffee, good news if you do: It won't make you sick, according to Dr. Karen Schaich, associate professor of food science at Rutgers University. She explained, "First, let me differentiate between safety and spoilage. The odors, off-flavors, souring, colors, and slimes on food are caused by large numbers of food spoilage organisms (yeasts, molds, bacteria), and these are not the same as the organisms that cause food poisoning (bacteria). Spoilage organisms will make the food inedible but not make you sick."

In fact, certain foods are beloved because they are spoiled; think yogurt and kimchi, fermented milk and cabbage, respectively, to create new dishes. Spoilage is in the eye of the beholder.

Contaminated Foods Don't Smell

Unlike spoiled food, foods contaminated with a pathogen, like a Salmonella or E. coli, don't have a specific smell or bad taste.

Dr. Schaich explained, "Unfortunately, food poisoning organisms do not produce odors, flavors, colors, slimes, or other indicators that can tell you they are present. I do not know of a useful common test for the presence of food poisoning organisms."

Ali Manning, a food scientist and consultant, recommends following safe food handling protocols to prevent foodborne illnesses. She said, "The best line of defense is your senses, so when cooking, it's important to store foods at appropriate temperatures, prevent cross-contamination, and cook foods properly."

The Food and Drug Administration (FDA) have a set of guidelines on best practices such as temperatures for doneness, washing, and storing.

What Can the Sniff Test Tell Us?

Essentially the sniff test is one of many sensory cues that can tell whether food is spoiled. Manning explained, "The sniff test is a simple trick to determine the quality of a food, not safety. Foods naturally degrade or spoil over time, so important to not only evaluate the product but check the "expiration- sell by- use by" dates on the packaging, as well. Food quality is not to be confused with food safety because greater measures go into place in case of a spike in foodborne illnesses."

Is There Another Test?

While the sniff test works for spoiled food, there isn't an at-home test to check for contaminated foods. Microbiologists test with cultures in Petri plates to determine whether there is an outbreak.

If you find yourself throwing out a lot of rotten food, try one of the many apps that help track and adequately store your fridge, like the FoodKeeper App. Or donate your extras before they turn to mush and help fight food insecurity with apps like Too Good To Go or Food Rescue Us.

What's the Safe Method with Leftovers?

The FDA recommends storing most leftovers in an airtight container in the refrigerator and consuming them within three to four days after preparing.

Certain items, like baked goods, have a longer shelf-life due to their ingredients; sugar preserves the dish and can be kept for longer. Other dishes, like ground meat and raw sausage, last much less time, only one to two days.

Manning said, "The preparation of the item, temperature storage, and moisture content are all essential factors to consider. If there's any doubt, throw it out or consider composting as an alternative to food waste going to the landfill."

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