The Flat-Iron That Costs Less

Two muscles sit at the top of every beef tenderness ranking. The first is the tenderloin. The second is a 250-gram seam tucked under the shoulder blade that, until twenty-three years ago, was sold as stew meat.

The seam has a Korean name long before it had an English one. Buchaesal — fan meat — named for the way it spreads under the blade when the connective sheet down its middle is split. On a Seoul menu, it sits beside the loin and the rib without apology. In American supermarkets it was ground or braised for a century. Then a research program gave it a different name, and a different price.

The cut the research found

Between 1998 and 2001, a U.S. beef-industry program — funded by the Beef Checkoff and run jointly by the University of Nebraska and the University of Florida — set out to profile every muscle in the chuck and round for tenderness. The teams measured roughly 5,600 samples across 39 muscles. The Warner-Bratzler shear-force test, which records how many kilograms of force a blade needs to slice through a cooked piece of beef, is the discipline’s standard measure of tenderness.

One muscle in the chuck — the infraspinatus, attached to the outside face of the shoulder blade — landed second. Only the psoas major, the tenderloin, sat ahead of it. Compiled tenderness data published by the U.S. Beef Checkoff places the infraspinatus among the muscles with the lowest shear force values, below 3.9 kg. The American industry renamed it the flat iron. Korean butchers had been calling it buchaesal since long before any of the data existed.

What the math says next

If the second-most tender muscle on a carcass sells for less than a sixth-ranked muscle, the gap is telling a story about market knowledge, not about the meat. U.S. boxed-beef pricing tracked by the USDA Agricultural Marketing Service has placed wholesale ribeye averages around $28 per pound, and wholesale flat iron averages near $20 per pound, across recent reporting cycles. The spread is consistent.

A 30% price gap between the second and the sixth most tender muscle is not a quality gap. It is a knowledge gap.

Why Korea never lost the cut

Korean butchery has a different relationship with the chuck. In the ten-primal Korean fabrication map, the shoulder (apdari, 앞다리) and the chuck (moksim, 목심) are sliced into named cuts the same way the loin is — not ground into a uniform mince. Buchaesal is one of those named cuts. The lengthwise connective sheet that runs down the centre of the muscle — the same sheet American butchers had to learn to butterfly past — is something Korean kitchens have been splitting for generations. Slice thin across the grain, both halves cook in under thirty seconds on a charcoal grate.

What this means at the table

It means buchaesal is the order that asks the room to look past the menu hierarchy. The chadol opens the table because the fat seasons the grate; the rib follows because the marinade is timed for it; the buchaesal earns its slot on the grill because the price is wrong about the cut. To carry the same logic home, see the takeaway selection — the chuck cuts pack as well as the loin, often better, because the fascia keeps the slice flat in transit.

Marbling, covered in a separate piece on intramuscular fat as the predictor of palatability, explains why the loin commands its premium. The buchaesal is the cut that proves the rule has an exception — a tender muscle the loin’s market never absorbed, and a knowledge gap a Korean grill closes by ordering it.

Source: “Ranking of Beef Muscles for Tenderness,” Beef Checkoff Program / Cattlemen’s Beef Board, compiling six decades of Warner-Bratzler shear force and sensory data across 40 beef muscles. Wholesale price spread cross-referenced with USDA Agricultural Marketing Service boxed-beef cutout reporting.