Dry aging is basically controlled decomposition. It typically starts with whole subprimals: large cuts with bones and fat caps left fully intact. These are held in humidity-controlled refrigerated rooms where air can circulate around the beef, pulling moisture from its exposed surfaces. Meanwhile, muscle enzymes in the beef slowly soften muscle protein and connective tissue and change flavor, and desirable molds grow on the meat’s surface, creating additional protein-snipping enzymes. At the end of aging, a thin pellicle of dried, hardened flesh will have formed on the meat’s exterior; this, along with the molds and oxidized fat, are trimmed away, and the beef is then cut into individual steaks.

Between moisture evaporation and the trimming away of dried moldy parts, a subprimal cut can lose more than 30 percent of its original weight. This, along with the time spent in dedicated refrigerators, contributes to dried-aged beef’s premium price. 

As the beef ages, water evaporates out of it, which concentrates its flavor. Meanwhile, enzymes break down collagen and muscle protein, enhancing tenderness. The breakdown of protein and fat also generates a slew of new nutty, savory, and even desirably cheesy flavors and aromas that deepen and transform the beef’s taste.

To track beef dry-aged from two to eight weeks, we bought a refrigerator designed for dry aging. Staying at the low end of the recommended ranges, we set it to 34 degrees and 76 percent relative humidity and turned on its fans. We purchased five prime-grade prime rib roasts from the same purveyor, staggering their delivery so that we could start aging a roast every two weeks. After 60 days, we had roasts that had dry-aged for zero days, two weeks, four weeks, six weeks, and eight weeks. We trimmed each roast of desiccated flesh and some of its fat (including the oxidized portions) and then broke it down to create 1½-inch-thick rib-eye steaks. We cooked all the steaks sous vide to 130 degrees (medium-rare) and tasted some straight from the sous vide bath (to detect flavor differences without the distraction of browning) and some after searing them to develop browning. 

• After two weeks of dry aging: Steaks were barely more tender than the unaged beef and tasted very similar.
• After four weeks: The meat was “melt‑in‑your‑mouth” tender and noticeably more savory and complex.
• At six weeks: The beef was only slightly more tender than at four weeks, but its flavors had continued to develop, becoming more “nutty” and “funky.” 
• At eight weeks: The meat was no more tender than at six weeks, but it had a “blue cheese” aroma and intensely gamy flavors with “mushroomy,” “cheesy” notes that “barely resembled beef.”

Dry-aged beef is expensive, so you should know what you’re buying. For our money, the sweet spot for dry aging is four to six weeks. That’s when the meat will have become significantly more tender, with richer, beefier flavors. But if you’re up for the heightened gamy, cheesy flavors of more advanced dry aging, look for meat that’s been aged for more than six weeks. As for steak dry-aged for just two weeks—why bother? You’ll be paying a lot more for a product that’s barely different from steak that hasn’t been dry-aged.