What’s up with beef that’s aged 28 days? Why are they bragging about that? It sounds so gross!

There are two reasons—flavor and tenderness. In the 6 to 12 hours after a steer is slaughtered, rigor mortis causes its muscles to seize up. During the aging process, enzymes already present in the muscle cells start to break down the connective tissue between them, making the meat tender.

Most supermarket cuts are aged 5 to 7 days, though many upscale steakhouses and specialty grocery stores offer beef aged longer. Meat stops getting tender after 10 to 16 days, but after that it continues to get more flavorful.

Beef is about 70 percent water. Immediately after slaughter, a carcass will lose 2 to 3 percent of its weight due to evaporation, and then another 1 to 1.5 percent each week after that. As it ages and water continues to evaporate, flavors get concentrated. This is the reason why aged beef is more expensive—the same animal produces fewer pounds of meat.

There are two ways to age beef. In the more common wet aging, also called bag aging, beef is cut into primal cuts (the large pieces, like the chuck and loin, from which steaks and roasts are cut) and vacuum sealed. The advantages of this method are that less moisture (and thus weight) is lost, and the beef can be aged while in transit.

In dry-aging, an entire side of beef hangs unwrapped in a cooler at 30°F to 35°F and 85 percent humidity, and may develop a layer of mold that is cut off and discarded before serving or sale. Because more water evaporates out of the meat, the slightly gamy flavor of the beef is more concentrated. Dry-aged beef tends to be very expensive, so usually only high-quality USDA prime or choice beef is dry-aged.

Dry-aged and wet-aged beef taste different. Eaters in a Journal of Food Science study were more satisfied with wet-aged beef. They said it had fewer “off” or unfamiliar odors and flavors.

The study also found that the predominant bacteria in dry-aged beef are members of the aerobic (oxygen-using) pseudomonas genus, while those in wet-aged beef are anaerobic (non-oxygen-using) lactobacilli. While the study didn’t look at how the different bacteria affected flavor, the two bacteria do utilize different chemicals for food and produce different byproducts—for example, lactobacilli break down lactose into lactic acid, while pseudomonas do not.

See more articles