Refrigerators seem like such basic technology: Put cold food in, it stays cold. Put warm food in, it gets cold. Simple, right? They’re a bit trickier than that. Those drawers inside your refrigerator are actually at different temperatures than the rest of the space, and the overall temperature of the inside of your fridge is affected by how tightly you store the contents. When you throw in the added complication of temperature control knobs (what does a cold setting of 2 actually mean?), it further confuses the task at hand.
It may seem minor, but finding the perfect temperature is important for food safety. According to the Food and Drug Administration (FDA), the number of harmful bacteria in food kept at room temperature can double every 20 minutes. The FDA advises consumers to keep their fridge at 40 degrees Fahrenheit or lower and to keep the freezer set at 0 degrees.
However, Consumer Reports conducted tests that suggest the ideal temperature for a refrigerator is 37 degrees Fahrenheit. This temperature keeps food at a safe temperature but isn’t so cold that ice begins to form in your vegetables. Set your refrigerator to this temperature for the best-quality food — and the longest storage time.
Modern fridges allow you to set specific temperatures, but older models might still operate with the knob for atmosphere adjustment. In this case, invest in a refrigerator thermometer. A thermometer will let you know exactly how cold (or hot) your fridge gets on what setting. Just adjust the knob until the thermometer reads 37 degrees after a couple of hours.
Even with a modern fridge, a thermometer can be a good option. It will let you determine whether the temperature settings are accurate. Some refrigerators had a deviation of two or three degrees from the setting. This means that setting it at 37 degrees might result in a setting of 34 degrees or 40 degrees, depending on the direction of the variance.
It takes around two hours for bacterial growth to begin. All food, even to-go boxes taken from restaurants, should be chilled within that time. While you would probably be okay eating food that had been left out for a bit over two hours, the safest option is to store anything you purchase in the refrigerator before that time has passed.