We’ve been eating through our share of burgers, ‘cue and jerky recently — we’re literate in beef. But when it comes to aging meat, you need to talk to the beef cognoscenti, and Pat LaFrieda is a card-carrying member: butchery goes back more than 100 years in his family. He shared this excerpt from his new book, Meat: Everything You Need to Know.

Dry aging is a process where steaks are hung or put on racks in a temperature- and humidity-controlled room for 21 to 120 days in order to tenderize the meat and make it more flavorful. Through the process of dry aging, the moisture is drawn out of the meat, so the flavor becomes concentrated. Also, in the process of aging, the steak’s natural enzymes work to break down collagen in the meat, essentially decomposing it. Collagen is what makes muscle tough, so when it starts to break down, the meat becomes tender. An aged steak can be so tender that you could stick your finger right through it. Dry-aged beef has a sweet, corn-like smell similar to that of cooked beer.

7-Days-Gear-Patrol7 days: The collagen has just begun to break down, but the steak won’t have the flavor or texture qualities that you are looking for in a dry-aged steak. Steak is not sold aged to this stage. The meat is still fairly bright, but it will darken as it ages and becomes drier.

21-Days-Gear-Patrol21 days: The steak loses 10 percent of its weight in the first three weeks through evaporation. The water seeps out the front and the back of the meat, but the fat and bone on the sides of the steak make the sides waterproof. Because the meat shrinks, the steak will become more concave as it ages. Although the fat doesn’t shrink, it does darken in the aging process.

30-Days-Gear-Patrol30 days: This is the most commonly requested age in steaks. The steak has developed the flavor and texture qualities associated with dry-aged meat: It is very tender, with a flavor I can best describe as a mix of buttered popcorn and rare roast beef. At this point the steak has lost 15 percent of its total weight.

45-Days-Gear-Patrol45 days: The steak has a little bit more funk than one aged to 30 days. The steak has lost only a fraction more weight, and the flavor of the fat changes before the meat does, so it’s important not to trim off all the fat before you cook it.

90-Days-Gear-Patrol90 days: The white striations on the surface of the meat are good mold and also salt, which is extracted from the meat along with the water. The crust that develops around the meat protects it in the same way a rind does with cheese. The exterior crust is shaved off before the meat is sold. What you’re left with is a steak that is slightly darker and drier in appearance than fresh steak, but to the untrained eye the two might be indistinguishable.

120-Days-Gear-Patrol120 days: This is the longest we age steaks, and it’s about four times as long as aged steaks you’d find at most restaurants and butcher shops. Only a handful of very high-end restaurants buy it. The steak has lost 35 percent of its original weight. A steak aged this long has a very funky flavor and it’s also very expensive, so it is for someone who really appreciates an intense beef flavor.