This should not be confused with inter-muscular fat, or seam fat, that lies between muscle fibers. Marbling is evaluated visually in the ribeye muscle between the 12 th and 13 th ribs. Studies have shown that marbling explains about 5 to 20 percent of the variation in tenderness when evaluated by shear force within a marbling score. However, marbling contributes to overall taste panel tenderness by enhancing flavor and juiciness. Consumer taste studies indicate that the chance of receiving an undesirable steak decreases as quality grade increases from Standard to Prime.
Maturity refers to the physiological age of the animal.
As an animal ages chronologically, it is believed that the cartilaginous tips on the backbone will gradually turn to bone. Maturity scores range from A-E with A maturity being the youngest and E maturity being the oldest. The marbling score and the maturity score combine to form the quality grade. B-maturity carcasses require a Modest degree of marbling to reach the Choice grade and have no chance of grading Select. B maturity carcasses that have a Small degree of marbling grade Standard.