marbling

Marbling refers to the intermixture of fat and lean within a cut of meat, especially when it's evenly distributed. This intramuscular fat plays a crucial role in the eating quality of meat, contributing to its tenderness, juiciness, and flavor. During cooking, the fat melts, acting as a lubricant that enhances the overall tenderness of the meat.123

The amount and distribution of marbling are significant factors in meat grading systems. In the United States, for example, higher marbling levels, particularly when finely textured and evenly distributed, improve the USDA quality grade of beef, with Prime being the highest. While lean muscle typically consists of about 73% water, 21% protein, and 5% fat, these proportions can change as an animal is fattened, with increased fat often leading to decreased percentages of protein and water.24