FOOD SCIENCE 
Tender Steaks 
http://www.cooksillustrated.com/printfoodscience.asp?foodscienceid=223&bdc=2676

	
In a side-by-side test, our steaks tasted both juicier and more tender. If traditionally cooked steaks have more juice in them, why don’t they taste juicier?

Meat consists of groups of cells that are covered by long sleeves of collagen. As meat is heated above 140 degrees, the collagen shrinks, bursting the cells within. The liquid that was held within these cells now floats freely in the meat. This is what’s happening in the gray zone, and when eaten, the liquid inside will flow out copiously with the first couple of chews, leaving you with not much more than a wrung-out sponge in your mouth. On the other hand, if meat is kept between 120 and 140 degrees (as with our method), the cells remain intact and the juice stays put until pressure is placed upon them, resulting in a steak that slowly releases its juices with each chew. It turns out that less juice released more slowly provides a greater sensation of juiciness than more juice released all at once.

This explains the juiciness, but what about the tenderness? Meat contains active enzymes called cathepsins, which break down connective tissues over time, increasing tenderness (a fact that is demonstrated to great effect in dry-aged meat). As temperature rises, these enzymes work faster and faster, until they reach 122 degrees, where all action stops. While our steaks are slowly heating up, the cathepsins are working overtime (in effect “aging” and tenderizing our steaks within half an hour). When steaks are cooked by conventional methods, their final temperature is reached much more rapidly, denying the cathepsins the time they need to properly do their job