This is because meat in the quick-freezing process, its combination of juices contained in the proteins and organic acids are also completely moved into ice, the meat slowly thawed, the crystallization of such juices will be re-slowly melted.
Restore the juice into the meat fibers, so that the meat to restore the original nature of the meat to maintain the meat's original nutrients and delicious, if thawed with hot water, meat juice crystals melt quickly, too late to penetrate into the meat fibers and loss of white, thus losing some of the proteins and aromatic substances, the use of this meat made of food, nutritional value is not high, the taste is not good.