Trichinosis is no longer a threat in commercially raised pork, so it isn't a high-risk meat any more. It doesn't automatically need to be cooked to well done, and in general can be treated like beef, lamb or any other meat. That being said, the usual rules of safe food handling still apply to pork. That's especially true when you're thawing frozen pork cuts.
Never thaw pork or any other meat by leaving it on the counter. At temperatures between 40 degrees and 140 degrees Fahrenheit, the food safety danger zone, any bacteria in the meat can multiply rapidly. The outer portions of your piece of pork will reach room temperature well before the middle is thawed, creating an unnecessary risk of foodborne illness.
Slow and Steady
The safest place to thaw any piece of pork is in your refrigerator. It's a slow method, because the fridge's temperature is only a few degrees above freezing, but that's exactly why it's safest. Your pork never reaches an unsafe temperature, so it remains safe for a few days after thawing or can even be refrozen -- at the cost of a slight loss of quality -- if you change your mind the next day.
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Most chops and small cuts will thaw overnight in the refrigerator, but you might need to allow 36 to 48 hours for a large roast.
The Water's Fine
If you didn't leave yourself time for refrigerator defrosting, the next-best method is a cold water bath. Put the pork in a waterproof bag, and then into a deep bowl or pot. Run enough cold water to fully submerge the pork, and replace it every 30 minutes to keep it fresh and cold. Chops frozen in a single layer can thaw in as little as 30 minutes, while a 3-pound roast can take 2 to 3 hours. Once you thaw the pork in cold water it must be cooked the same day, though you can refrigerate it for a couple of hours -- if necessary -- along the way.
Fast and Furious
If you're really pressed for time, you can also defrost pork in the microwave. This is a riskier option from the quality standpoint, because microwave ovens heat unevenly and can produce hot spots where the pork thaws quickly, or even becomes grey and cooked. Some are better than others at defrosting, but it's always worth a try. In general, if your microwave has a sensor-defrost option, use that instead of defrosting by time or weight. Open the microwave door periodically and turn the pork, to help the microwave warm it evenly.
Pork defrosted in the microwave must be cooked immediately, because it will already be in the danger zone by the time it's thawed.
For Best Results
If you're packaging pork for the freezer, keep in mind that the smallest, flattest packages are the quickest to freeze and thaw. That minimizes any loss of quality in the pork itself. It also makes thawing faster and more convenient.
Another threat to quality is air left inside the packaging, which causes freezer burn and shortens the usable life of pork. Use a vacuum sealer if you have one, otherwise squeeze as much air as possible from the package before you freeze it.
The same rules of freezing and thawing apply to cooked pork, though they should be heated differently at mealtime. Raw cuts of pork should be cooked to at least 145 F, but cooked pork like any other leftovers -- must be heated to an internal temperature of 165 F.