The key to thawing or defrosting meat is timing. The best method for pork tenderloin is by slow thawing at a cold temperature. Thawing meat in the refrigerator is the safest method because it eliminates the chances of bacteria that can grow at room temperature or warmer. There are several methods for defrosting, and the one you choose depends on how much time you have.
Place the frozen tenderloin on a plate with dipped edges or in a shallow baking dish. Leave the frozen pork wrapped.
Tent a piece of aluminium foil or plastic cling wrap over the plate and place in the fridge.
Defrost in the refrigerator. The defrosting time depends on the size of the tenderloin. Smaller cuts take between 5 to 7 hours while larger cuts can take from 12 to 20 hours. For the best results, place the pork in the fridge the night before or first thing in the morning.
Keep the thawed pork in the refrigerator for 3 to 5 days. If you decide to not cook the meat within this time, it can be refrozen but the quality of the pork deteriorates every time you freeze it.
Fill the sink or a large bowl with cold water. Do not use warm or hot water as it unevenly thaws the meat, and is more likely to result in the growth of bacteria.
Place the pork tenderloin in a large zip lock bag. Make sure the bag is properly sealed. Squeeze out as much air as possible.
Submerge the bag completely under the water. Allow to thaw for 30 minutes to 2 hours depending on the size. Feel to make sure it is completely defrosted. If more than 30 minutes are required, make sure to change the water every 30 minutes to help prevent bacteria growth.
Cook the meat immediately after thawing.
Remove all wrappings from the pork and place on a shallow dipped plate or baking dish.
Microwave according to your microwave defrost setting. Oftentimes, you can type in the weight of the meat and the microwave will set the time. It is best to defrost for 2 minutes followed by a 2 minute rest. Flip the meat and repeat until it is soft.
Use the tenderloin immediately after thawing in the microwave; the meat cannot be refrigerated or refrozen since it's possible that it started to cook during the defrosting process.