Of the three safe methods for thawing ground beef, defrosting meat in the microwave is by far the fastest. But be aware that it's also the most limiting and the most damaging to the quality of your finished recipe. It's limiting in that you must promptly cook the meat. You can't refreeze it because when you defrost hamburger in the microwave, it starts partially cooking, making it susceptible to rapid bacteria growth. And, it's damaging because the beef loses a significant amount of moisture, turns a little rubbery and often ends up unevenly cooked since portions get a head start during thawing.
Thawing Meat in the Microwave
You can freeze ground beef in its store packaging, but you can't defrost hamburger in the microwave in it because neither plastic wrap nor foam trays are microwave safe. Unless you've already frozen the meat in a microwave-safe container, transfer it to a microwave-safe plate.
The defrost function on microwaves generally aren't all that reliable, so skip it. Instead, microwave the frozen ground beef at 50 percent power for two minutes, flipping it over once halfway through. Check it, remove thawed portions, and rearrange the remaining meat into a layer of even thickness as best as you can. Then, continue microwaving the meat at 30 percent power, checking it every 30 seconds or so and removing thawed sections until it's defrosted.
It's OK if there are some small areas of meat that are mostly, but not entirely thawed. The less time in the microwave, the better. Remember, now you need to cook the meat right away.
Defrosting Ground Beef in Cold Water
If you need to thaw the ground beef fairly quickly, but not quite as quickly as defrosting the meat in the microwave, consider the submersion method. Depending on the quantity of meat, it typically takes between half an hour and two to three hours, and it doesn't result in nearly as much loss of quality.
Keep the ground beef in its airtight packaging and submerge it completely in a large bowl or pot of cold water. Dump the water out and refill with fresh, colder water every 30 minutes. Ground beef thawed in this way must still be cooked right away, and it should be fully cooked before refreezing any portion of it.
Thawing Ground Beef in the Refrigerator
Whenever you're able to plan far enough ahead, defrost ground beef by putting it in the refrigerator 24 hours ahead of time. While it's much slower than thawing meat in the microwave or submersion thawing, it results in the least loss of moisture and quality. Plus, you can keep it in the fridge for a day or two between thawing and cooking, and you can refreeze unused portions without cooking them first.
Unsafe Defrosting of Ground Beef
Raw meat should never be left out at room temperature for more than two hours or for one hour in an environment over 90 degrees Fahrenheit. And when meat is held between 40 and 140 F, it's considered to be in the danger zone where bacteria multiplies rapidly. With enough time in the danger zone, bacteria can grow beyond the point where the food is rendered safe by cooking.
This means that you can't defrost ground beef by just letting it sit out on the kitchen counter. Another unsafe option is to use warm or hot water for the submersion method in an attempt to speed up the thawing process. Both of these methods can easily keep the meat in the danger zone for too long.