Not everything can truly be dumped into a slow cooker for dinner.

I have always been a slow cooker evangelist. My husband would tell you that I have something of a "problem" when it comes to slow cookers, as I am currently in possession of no fewer than 14. They range in size from an adorable trio model with three half-quart inserts, perfect for a dark, milk, and white chocolate fondue situation, or a triumvirate of warm sauces, all the way up to an eight-quart model, which will cook a vat of chili large enough to serve an army.

In my defense, we entertain a lot, and a slow cooker is an entertainer's dream appliance: You can reheat pre-prepped dishes and hold things warm without watching the stove or worrying about burning, and a slow cooker can even serve as a plate warmer if you need one. When serving large parties, especially over extended periods of time, slow cookers can go right on your buffet and keep everything at optimal temps. When cooking coursed meals, which might need the soup hot at the start, and a sauce for the roast equally hot anywhere from 15 to 45 minutes later, depending on the speed your guests might eat and how lively the conversation, slow cookers to the rescue.

A snowy, frosty frozen beef prime rib roast in the snow.
Credit: skhoward/Getty Images

But slow cookers are not without their limits, so it is important to know that one of the things they cannot and should not do is heat up frozen food.

Why You Shouldn't Cook Frozen Meat in a Slow Cooker

It sounds like such a great idea, I know: Grab that bag of pre-chopped, pre-packaged stew or marinated pot roast out of the freezer, plop it in your handy slow cooker, and a few hours later you have dinner on the table. Except you might also have foodborne illness on the table, which is much less desirable.

According to the U.S. Department of Agriculture (USDA), slow cookers' max temperatures generally reach between 170 and 280 degrees F (77 and 138 degrees C). That's high enough to kill most bad bacteria, but the USDA still recommends thawing all foods completely before placing them in a slow cooker. Why? This has to do with the timing of how slow-cooked foods and possible bacteria growth intersect.

Bacteria has a sweet spot for growth. At temps between 41 degrees F (5 degrees C) and 135 degrees F (57 degrees C), especially in a moist environment, bacteria can grow and multiply rapidly; the serious danger zone is between 70 degrees F (21 degrees C) and 125 degrees F (52 degrees C). Above 140 degrees F (60 degrees C), food is too hot to provide such an environment.

The USDA recommends that any food you cook achieve a proper temp outside the danger zone (that is, above 140 degrees F/60 degrees C) within two hours. Frozen food, which starts at 0 degrees F (-18 degrees C), will take too long to come up to temperature in the low-heat slow cooker, so frozen meat will sit in the danger zone for bacteria growth for far too long to be considered safe.

All food headed for a slow cooker should be fully thawed in the refrigerator first, the USDA says, even for recipes that require long, slow cooking over several hours. The agency also suggests you still cook your meal on your slow cooker's highest temperature setting for the first hour. Then you can reduce the heat to the desired level to finish cooking. This will ensure that your food reaches a safe temperature within a reasonable timeframe and keeps it out of the danger zone for bacterial growth. If you have commercially packaged frozen slow cooker meals, it is recommended that you follow the package directions carefully.

How to Thaw Meat Rapidly

So, what if you have forgotten to thaw what you need beforehand and dinner will be a failure if you don't get that roast in the slow cooker before you leave for work? Use a convection thawing method to rapidly and safely thaw your food.

  1. Place the meat that needs thawing in a zip-top bag with as much air pressed out as possible. Put the bag into a vessel large enough to hold it submerged, but without too much extra space. Place the vessel in your sink, being sure it does not block the drain; elevating it on a wire rack can help with this. Fill the vessel with your coldest setting tap water. Weigh down the bag with a plate or other object if it wants to float; you want it fully submerged.
  2. When the vessel is overflowing with the cold water, reduce the stream to a thin trickle. You want the water running as minimally as you can but in a steady flow. This trickle of water, and the constant overflow of the vessel will create a convection of water around your frozen item that will speed up thawing tremendously, while still keeping things at a safe temperature.
  3. Depending on the size and thickness of the meat you are thawing, it can take as little as 20 minutes or up to an hour to thaw something completely. Solid large proteins, like whole chickens or roasts, will take the longest. After the first 20 minutes, check every 10 to 15 minutes to see if your food has thawed enough to proceed with your recipe.

While it might seem counterintuitive to use cold water for this process, do not try and speed up the thrawing with warm or hot water. You risk partially cooking the exterior of whatever you are thawing and bringing the surface into the bacteria danger zone while the center is still frozen.

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