I don't know much about dry aging but thought this was a good explanation of the process from Wikipedia.
Dry aged beef is beef that has been hung to dry for several weeks. After the animal is slaughtered and cleaned, either an entire half will be hung, or primal cuts (large distinct sections) will be placed in a cooler. This process involves considerable expense as the beef must be stored at or near freezing temperatures. Also only the higher grades of meat can be dry aged, as the process requires meat with a large, evenly distributed fat content. For these reasons one seldom sees dry aged beef outside of steak restaurants and upscale butcher shops. The key effect of dry aging is the concentration of the flavor. The taste of dry-aged beef is almost incomparable to that of wet-aged, with dry-aged being far superior--depending on the duration of aging, with four weeks being a recommended minimum.
The process enhances beef by two means. First, moisture is evaporated from the muscle. This creates a greater concentration of beef flavor and taste. Second, the beef’s natural enzymes break down the connective tissue in the muscle, which leads to more tender beef.
Dry aging of beef is rare in the United States today due to the significant loss of weight in the aging process.
Dry Aged beef is different from wet aged beef, which is typically aged in a vacuum sealed bag, requiring only a matter of days with no loss of weight, and doesn't require the same precision in cooling. In contrast, dry-aging takes several weeks, with a significant portion of the meat mass lost due to mold growth and evaporation.
The process of dry-aging usually also promotes growth of certain fungal (mold) species on the external surface of the meat. This doesn't cause spoilage, but actually forms an external "crust" on the meat's surface, which is trimmed off when the meat is prepared for cooking.
In addition to
endogenous enzymes (those found naturally in the beef) which help tenderize and increase the flavor of the meat, these fungal species do so as well. The genus
Thamnidia, in particular, is known to produce collagenolytic enzymes which greatly contribute to the tenderness and flavor of dry-aged meat.