I have adapted this post from :
All fresh beef is aged for at least a few days and up to several weeks to allow enzymes naturally present in the meat to break down the muscle tissue, resulting in improved texture and flavor. These days, most beef is aged in plastic shrink-wrap -- a process known as wet-aging.
Dry aged beef, on the other hand, is exposed to air, so dehydration can further concentrate the meat's flavor. Because the meat loses weight from dehydration, and it also must be trimmed of its completely dried exterior, it is more expensive than wet-aged meat, and harder to find.
The first step to making dry aged beef at home is actually a food safety note. Home refrigerators aren't as consistent or as cold as commercial meat lockers.
Before making dry aged beef at home, get a refrigerator thermometer and make sure your fridge is set to and can maintain a temperature below 40 F. Cook or freeze the meat within seven days of beginning the dry-aging process.
Next, buy a prime USDA boneless beef rib or loin roast from the best meat source in your area. USDA Prime meats are produced in limited quantities for use in the finest restaurants, hotels and gourmet markets. They are well marbled and have thick coverings of firm fat. Your local grocery store will not carry this type of meat.
Unwrap the beef, rinse it well, and pat it dry with paper towels. Do not trim. Wrap the roast loosely in a triple layer of cheesecloth and set it on a rack over a rimmed baking sheet or other tray.
Refrigerate for three to seven days; the longer the beef ages, the tastier it gets. After the first day, carefully unwrap and then rewrap with the same cheesecloth to keep the cloth fibers from sticking to the meat.
When you are ready to roast, unwrap the meat and, with a sharp knife, shave off and discard the hard, dried outer layer of the meat. Shave away any dried areas of fat, too, but leave behind as much of the good fat as possible. Roast whole, or cut into steaks.
cambridgedr, do you do this in the lowest left rear corner of your frig? Has it succeeded at other than 34 degrees for you? I ask because i recently talked to a pro chef who said that " above 34 and fuzzy stuff grows on it immediately". (He told me about the day that a steak restnt where he worked- had their dedicated 34 degree Dry Aging walk-in- go above 34. They threw out $10,000 of product and immediately had installed an alarm that would go off if temp veered from 34.) Now that was a huge restaurant where law suits are 'the great white whale' , and you are doing these dry aged steaks for yourself; so that's why i'm curious about the flexibility of 'below 40 degrees' and 34 degrees precisely. th much.
p.s. this same pro chef said that they trim off about 20-25% of the end product because the outside of the dry aged meat gets dry/tough(they don't throw it away; it is given to the Boston Food Bank who really appreciates the donated protein among their burgeoning potatoes and pasta donations). When i asked if he would cut it off if he were making it for himself at home, he said yes. He also said that that loss is what keeps the restaurant from dry aging individual steaks and instead they age sides of beef- because the cumulative loss is less.