The idea behind thawing food before putting it into a slow cooker is to reduce the amount of time the food is in the “danger zone,” which is between 40 and 140 degrees. That’s when any bacteria that might be on or in the food could multiply quickly and become a food safety concern. Food should move through the danger zone within two hours.
Meat is more dense than vegetables are, and if you put it in a slow cooker when it’s still frozen, it could stay in that danger zone for too long. Vegetables thaw more quickly, so it’s less of a concern to use frozen vegetables in a slow cooker.
Food safety is especially important to take into account if the food will be eaten by people most at risk from foodborne illness: older adults, children, pregnant women, or anyone undergoing cancer treatment or dealing with a chronic illness, such as diabetes. They are most at risk for developing serious complications from the intestinal problems that could result from food bugs.
Although slow cookers use low temperatures — generally between 170 degrees and 280 degrees — to cook food, the lengthy cooking time and steam produced in the cooker combine to destroy bacteria. That said, it’s especially important to use some type of liquid (to generate steam) and to keep the lid on the slow cooker as much as possible during cooking. The temperature can dip 10 to 15 degrees when the lid is removed.
To assure safety when using the slow cooker:
- If you’re planning to cook a roast or other large cut of meat or poultry in the slow cooker, consult the manufacturer’s recommendations to be sure the meat is heated thoroughly quickly enough. Or, just cut the meat into smaller chunks first.
For the first hour, use the high setting. That will move the food through the danger zone more quickly. After that, you can switch to a lower setting if the food will be cooked all day.
- You may want to test the heating capacity of your slow cooker. To do that, fill the crock in the slow cooker one-half to two-thirds full of water. Put on the lid and turn the heat to low, or 200 degrees if you have a model with a temperature display. After eight hours, check the temperature of the water with a meat thermometer. Be sure to do so quickly, as the water will cool significantly as soon as the lid is removed. The water should be 185 degrees. If the temperature is below that, the slow cooker may be unsafe to use.
If you’re not home during the entire cooking process and the power goes out, throw away the food even if it looks done.
For more information about slow cooker food safety, see the U.S. Department of Agriculture’s fact sheet.
Chow Line is a service of Ohio State University’s College of Food, Agricultural, and Environmental Sciences and its outreach and research arms, Ohio State University Extension and the Ohio Agricultural Research and Development Center. Send questions to Chow Line, c/o Martha Filipic, 2021 Coffey Road, Columbus, OH 43210-1043.