Beef Quality Beef Quality Grading

The USDA Quality Grade is determined by considering the degree of marbling, as observed in the cut surface of the ribeye between the 12th and 13th ribs, in relation to the overall maturity of the carcass. Marbling scores are assigned to the carcass depending on the degree of intramuscular fat that is present in the cut surface of the ribeye. Marbling scores have been established by the LSD and are referenced in the form of photographs[1] (Fig. 1). The marbling scores are Abundant, Moderately Abundant, Slightly Abundant, Moderate, Modest, Small, Slight, Traces, and Practically Devoid. Mean percent chemical fat has been determined in the ribeye muscle as 10.42%, 8.56%, 7.34%, 5.97%, 4.99%, 3.43%, 2.48%, and 1.77% for marbling scores of Moderately Abundant, Slightly Abundant, Moderate, Modest, Small, Slight, Traces, and Practically Devoid, respectively.1-4-1 Before the marbling score is evaluated, the USDA has mandated a ten-minute (minimum) bloom period between the time that the carcass has been ribbed until grading, to allow for consistency.1-1-1

Prior to assigning an official USDA Quality Grade, the maturity of the carcass must be evaluated and determined. Maturity scores of A, B, C, D, and E are assigned to each carcass. These scores correlate to the balance of skeletal maturity (the ratio of cartilage to bone in the cartilaginous buttons of the vertebral column) and the

Table 1 Beef muscle color and texture of each maturity group

Moderately Abundant

Modest

Slightly Abundant

Small

Moderate

Slight

Fig. 1 USDA standard marbling scorecards. Reproductions of the official USDA marbling photographs prepared by the National Livestock and Meat Board for the U.S. Department of Agriculture. (From Ref. 1.) (View this art in color at www.dekker.com. )

Maturity

Muscle color

Muscle texture

Table 1 Beef muscle color and texture of each maturity group

Maturity

Muscle color

Muscle texture

A

Light cherry red

Fine

B

Slightly dark red

Fine

C

Slightly dark red

Moderately fine

D

Moderately dark red

Slightly coarse

E

Dark red

lean maturity (based on the color and texture of the exposed ribeye). As an animal matures, the cartilaginous (soft, white, pliable) connective tissue of the skeletal system is changed into bone (hard, dense, spongy) via the ossification process. Such changes occur in a definite sequence so that the relative degree of ossification (cartilage to bone) is a reliable indicator of maturity.[6] A, B, C, D, and E scores for skeletal maturity have 0 10%, 11 35%, 36 70%, 71 90%, and greater than 90% ossification in the first three thoracic buttons, respective-ly.[6] A carcass in the A-lean maturity group has a bright, cherry-red color of lean with a very fine texture, while a carcass in the E-lean maturity group has a dark, moderately brown-colored lean with extremely coarse texture (Table 1). Carcasses with balanced maturity scores of A, B, C, D, and E are 9 30, 30 42, 42 72, 72 96, and greater than 96 months of age at slaughter, respectively.[6] Beef carcasses classified as B maturity and younger are considered to be young, and maturity scores of C and older are considered old.[6]

Marbling and maturity scores are combined to determine the overall USDA Quality Grade. These are combined as illustrated in Fig. 2[1] and may be referenced to result in different levels of the final USDA Quality Grades: Prime, Choice, Select, Standard, Commercial, Utility, Cutter, and Canner. An exception to this system includes carcasses classified as bulls, whose grade consists of yield grade only. Additionally, bull and bullock carcasses must be further identified.[1]

Even though wholesomeness, cleanliness, and nutritional value are often confused as aspects of quality, the eating quality or overall palatability of the beef is of primary concern when dealing with ''quality.'' USDA Quality Grades are assigned to beef carcasses with the intention of predicting overall palatability. The factors used to determine the USDA Quality Grade, including marbling and maturity scores, have been proven to have effects on palatability. Research shows that with increased marbling score, sensory panel ratings increase, including factors such as juiciness, tenderness, flavor desirability, and overall palatability.[7] In support of this, increasing marbling score also has shown lower shear force values (less resistance).1-7-1 Youthfulness (maturity) is also an

Relationship Between Marbling, Maturity, and Carcass Quality Grade*

Degrees of Marbling A***

Slightly Abundant

Moderate Modest Small Slight Traces

Practically Devoid

Maturity**

Degrees of E Marbling

Prime

Com m

srcial

Choice

Select

Utility

Cutter

Standard

' Assumes that firmness of lean is comparably developed with the degree of marbling and that the carcass is not a "dark cutter." * Maturity increases from left to right (A through E).

' The A maturity portion of the figure is the only portion applicable to bullock carcasses.

Slightly Abundant

Moderate

Modest

Small

Slight

Traces

Practically Devoid

' Assumes that firmness of lean is comparably developed with the degree of marbling and that the carcass is not a "dark cutter." * Maturity increases from left to right (A through E).

' The A maturity portion of the figure is the only portion applicable to bullock carcasses.

Fig. 2 USDA quality grading chart. (From Ref. 1.)

indicator of tenderness in beef carcasses due to the minimal cross-linking of connective tissues (collagen) in muscles of young animals.

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