Marbling
Fine flecks of fat within the lean of beef, used in grading meat.
Also: intramuscular fat, shimofuri
Marbling is fat laid down inside the muscle, between the fibres, so that a cut of beef shows white flecks and threads through the red. It differs from the fat that covers the outside of a carcass. Marbling depends on breed, age, feeding and time on feed. The Japanese Wagyu breeds lay down the most, and Japan grades beef on a marbling scale from 1 to 12; the Aberdeen Angus is noted for it among Western breeds. The United States, Australia and other countries use their own grading systems in which marbling is a main factor. Lean breeds and grass-fed cattle usually show less.