Stew Science: Why You Shouldn't Cook Your Beef All Day
Geege Schuman stashed this in Food Hacks
When connective tissue in the beef first breaks down, it creates a very concentrated zone of gelatin within the meat. This gelatin thickens juices, which helps them stay put inside the meat along with helping them to coat your tongue and mouth. More importantly, as the muscle structure continues to break down within the meat, it has a hard time hanging on to the moisture it has. Think of it as being like the difference between a net full of water balloons and a net full of sponges. Both may have the same amount of moisture, but press down on the sponges and that liquid comes gushing out all at once, leaving behind a dry shell. The water balloons, on the other hand, take a little more effort to break, releasing their juices in discrete bursts—in the same way that juicy meat should release juice steadily as you chew, not gush out all its moisture at once.
Well that's a vivid image. Okay, must not overcook beef.