Midwestern Meats

Beef Quality Grades

A quality grade is a composite evaluation of factors that affect palatability of meat (tenderness, juiciness, and flavor). These factors include carcass maturity, firmness, texture, and color of lean, and the amount and distribution of marbling within the lean. Beef carcass quality grading is based on (1) degree of marbling and (2) degree of maturity.

Marbling

Marbling (intramuscular fat) is the intermingling or dispersion of fat within the lean. Graders evaluate the amount and distribution of marbling in the ribeye muscle at the cut surface after the carcass has been ribbed between the 12th and 13th ribs. Degree of marbling is the primary determination of quality grade.

Degrees of Marbling

Each degree of marbling is divided into 100 subunits. In general, however, marbling scores are discussed in tenths within each degree of marbling (e.g.,Slight 90, Small 00, Small 10).

Grade Marbling Score
Prime + Abundant 00-100
Prime ° Moderately Abundant 00-100
Prime - Slightly Abundant 00-100
Choice + Moderate 00-100
Choice ° Modest 00-100
Choice - Small 00-100
Select + Slight 50-100
Select - Slight 00-49
Standard + Traces 34-100
Standard ° Practically Devoid 67-100 to Traces 00-33
Standard - Practically Devoid 00-66

In addition to marbling, there are other ways to evaluate muscle for quality. Firmness of muscle is desirable, as is proper color and texture. Desirable ribeyes will exhibit an adequate amount of finely dispersed marbling in a firm, fine textured, bright, cherry-red colored lean. As an animal matures, the characteristics of muscle change, and muscle color becomes darker and muscle texture becomes coarser.

Maturity

Maturity refers to the physiological age of the animal rather than the chronological age. Because the chronological age is virtually never known, physiological maturity is used; and the indicators are bone characteristics, ossification of cartilage, color and texture of ribeye muscle. Cartilage becomes bone, lean color darkens and texture becomes coarser with increasing age. Cartilage and bone maturity receives more emphasis because lean color and texture can be affected by other postmortem factors.

Cartilage evaluated in determining beef carcass physiological maturity are those associated with the vertebrae of the backbone, except the cervical (neck). Thus the cartilage between and on the dorsal edges of the individual sacral and lumbar vertebrae as well as the cartilage located on the dorsal surface of the spinous processes of the thoracic vertebrae (buttons). Cartilage in all these areas are considered in arriving at the maturity group. The buttons are the most prominent, softest and least ossified in the younger carcasses. As maturity proceeds from A to E, progressively more and more ossification becomes evident. Ribs are quite round and red in A maturity carcasses, whereas E maturity carcasses have wide and flat ribs. Redness of the ribs gradually decreases with advancing age in C maturity, and they generally become white in color because they no longer manufacture red blood cells and remain white thereafter. Color and texture of the longissimus muscle are used to determine carcass maturity when these characteristics differ sufficiently from normal.

There is a posterior-anterior progression in maturity. Thus, ossification begins in the sacral region and with advancing age proceeds to the lumbar region and then even later it begins in the thoracic region (buttons) of the carcass. Because of this posterior-anterior progression of ossification, even young A maturity carcasses will have some ossification in the sacral cartilage.

In terms of chronological age, the buttons begin to ossify at 30 months of age. Determine age using thoracic buttons. When the percentage ossification of the cartilage reaches 10, 35, 70, and 90 percent, the maturity is B, C, D, and E, respectively.

Carcasses are stratified into five maturity groups, based on the estimated age of the live animal

Carcass maturity Approximate live age
A 9 – 30 mos.
B 30 – 42 mos.
C 42 – 72 mos.
D 72 – 96 mos.
E > 96 mos.

Skeletal Ossification

  • Sacral vertebrae (first to ossify)
  • Lumbar vertebrae
  • Thoracic vertebrae (buttons – last to ossify)
  • Size and shape of the rib bones
  • Condition of bones

 

Ossification of the vertebral column

 

  Maturity Group
Vertebrae A B C D E
Sacral Distinct separation Completely fused Completely fused Completely fused Completely fused
Lumbar No ossification Nearly completely ossified Completely ossified Completely ossified Completely ossified
Thoracic No ossification Some ossification Partially ossified Considerable ossification (outlines of buttons are still visible) Extensive ossification (outlines of buttons are barely visible)
Thoracic buttons 0-10% 10-35% 35-70% 70-90% >90%

Condition of the bodies of the split chine bones:

  • A- Red, porous and soft
  • B- Slightly red and slightly soft
  • C- Tinged with red, slightly hard
  • D- Rather white, moderately hard
  • E- White, nonporous, extremely hard

Appearance of the ribs:

  • A- Narrow and oval
  • B- Slightly wide and slightly flat
  • C- Slightly wide and moderately flat
  • D- Moderately wide and flat
  • E- Wide and flat

Lean Maturity:

Color and Texture – As maturity increases, lean becomes darker in color and coarser in texture

 

Lean Maturity Descriptions

 

Maturity Lean Color Lean Texture
A0 Light cherry-red Very fine
B0 Light cherry-red to slightly dark red Fine
C0 Moderately light red to moderately dark red Moderately fine
D0 Moderately dark red to dark red Slightly coarse
E0 Dark red to very dark red Coarse

Balancing lean maturity and bone maturity:

  1. Use a simple average when bone and lean maturities are within 40 units of each other.
  2. When there is more than 40 units difference in lean and bone maturity, average the two maturities and adjust the average 10% toward the bone except when:
Crossing the B/C line
  1. If the average of the lean and bone maturities doesn’t move across the B/C line from the bone maturity side (e.g., Bone = B and Lean = C with the average being B or Bone = C and Lean = B with the average being C); average the two maturities and adjust the average to the nearest 10% toward the bone.
  2. If the bone and lean maturities are not considerably different, but one is in B maturity and the other in C maturity and the average of the two moves across the B/C line from the bone maturity side, the overall maturity will be on the side of bone maturity — it will be either B-100 or C-00.
  3. In no case may overall maturity be more than one full maturity group different than bone maturity. A80 lean + D20 skeletal = C20 overall.

Determination of Final Quality Grade:

After the degree of maturity and marbling has been determined, these two factors are combined to arrive at the Final Quality Grade. The fundamentals involved in applying quality grades are learning the degrees of marbling in order from lowest to highest and minimum marbling degrees for each maturity group and understanding the relationship between marbling and maturity in each quality grade.

Step-Wise Procedure for Quality Grading Beef Carcasses

1. Determine carcass skeletal maturity by evaluating the degree of skeletal ossification in the top three thoracic vertebra (buttons), and the sacral and lumbar vertebra. Also evaluate the color and shape of the ribs. Determine lean maturity by evaluating the color and texture of the lean in the ribeye exposed between the 12th and 13th ribs.

 

Skeletal Maturity + Lean Maturity = Overall Maturity

 

A60 + A40 = A50 (Simple Average)

B60 + A80 = B30 (>40; 10% to bone)

C60 + B10 = C00 (B/C line)

D60 + B20 = C60 (<=100% from bone)

2. Evaluate the marbling in the ribeye and determine the marbling score.

 

Overall Maturity + Marbling Score = USDA Quality Grade

 

A70 + Sm40 = Ch-

B60 + Md40 = Cho

3. Determine lean firmness to ensure that the minimum degree of firmness specified for each maturity group is met.

Table illustrating the minimum marbling score requirements for USDA quality grades within each final maturity group

Final maturity score
USDA Quality Grade A00B00C00D00E00
Prime + AB00 AB00
Prime o MAB00 MAB00
Prime - SLAB00 SLAB00
Choice + MD00 MD00
Choice o MT00 MT00
Choice - SM00
Select + SL50
Select - SL00
Standard+ TR00 TR00
Standard- PD00 PD00
Commercial+ MD00 SLAB00 AB00
Commercialo MT00 MD00 SLAB00
Commercial- SM00 MT00 MD00
Utility+ SL00 SM00 MT00
Utilityo TR00 SL00 SM00
Utility- PD00 TR00 SL00

AB = Abundant; MAB = Moderately Abundant; SLAB = Slightly Abundant; MD = Moderate; MT = Modest; SM = Small; SL = Slight; TR = Traces; PD = Practically Devoid.
Carcasses with B, C, D, or E final maturity scores require an increasing amount of marbling as maturity increases to remain in the same quality grade.
Carcasses having B final maturity scores with Small and Slight marbling must grade U.S. Standard. There is no U.S. Select grade for B maturity carcasses.

 

Written by Rod McConnell — July 11, 2013

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