Maturity

The maturity of the carcass has shown to be highly correlated to tenderness of the meat upon cooking.[5] As cattle mature, they become tougher due to an increased amount of connective tissue and less soluble collagen.[5] Therefore, the maturity of the carcass is considered in determining a USDA Quality Grade. Maturity is divided into two categories: skeletal maturity and lean maturity. The more important of the two is the skeletal or bone maturity, meaning that when there is a difference between the two factors, the overall maturity score is in the direction of the bone.[1] However, in no instance may the overall maturity score vary from the skeletal maturity score by more than 100.[1]

Moderately Abundant

Modest

Slightly Abundant

Small

Moderate

Slight

Fig. 1 Reproductions of the official USDA marbling photo graphs prepared by the National Cattlemen's Beef Association for the U.S. Department of Agriculture. (View this art in color at www.dekker.com. )

Skeletal Maturity

The skeletal maturity of a carcass is visually determined by the amount of ossification in the sacral, lumbar, and thoracic vertebrae of the carcass (Fig. 2).[4] Ossification is defined as the process by which cartilage progresses into bone.[4] Animals typically age from the hindquarter to the forequarter and would therefore reveal ossification in the sacral vertebrae first, and eventually in the thoracic vertebrae.[4] The five maturity groups correlate with the age of the animal as follows: A (9 30 months), B (30 42 months), C (42 72 months), D (72 96 months), and E (greater than 96 months).[4] In A-maturity, or very young carcasses, the cartilage at the ends of the thoracic vertebrae shows no ossification, the lumbar vertebrae all reveal some cartilage, and there is distinct separation in the sacral region.[1] Also, in a young animal the vertebrae appear red and porous, and the rib bones appear in a curvature configuration and still have a red tinge to them. However, as the animal ossifies or ages, the vertebral column appears very different. In more mature carcasses, ossification is notable at the ends of the thoracic vertebrae, the cartilage at the tips of the lumbar vertebrae is completely ossified, and the sacral vertebrae are completely fused, with no separation.[4] Additionally, the bone appears hard, flinty, and white.[1] Furthermore, the ribs become whiter in color and wider and flatter in appearance.[1]

Lean Maturity

The lean, or flesh, of the animal undergoes physiological changes as the animal matures, just as the skeleton does. However, the change in lean color is a more noted quality issue with consumers because they purchase their meat products on the basis of appearance. If a steak in a supermarket is dark in color, which is different from the preferred bright, cherry-red color of beef, they will not be as likely to purchase the product. For this reason, lean maturity is an important factor in determining an overall USDA Quality Grade. In a young A-maturity carcass, the lean typically has a fine texture and is a light, youthful, cherry-red color.[1] However, as the lean matures it appears dark red in color and coarse-textured.[1] It is important to note that the U.S. standards for quality grades relating to lean maturity refer only to changes in lean color due directly to changes in maturity of the animal. This is important because a condition called ''dark cutting beef'' can occur, causing the meat to appear very dark in color.[4] However, this condition is due to lack of glycogen in the muscle at time of slaughter, not due to the maturity of the animal.[4] This condition does not effect the palatability of the carcass in a negative way, but actually creates a more tender, juicy product with slight soapy off-flavors. Carcasses identified as dark cutters are therefore quality-graded according to their maturity and marbling scores to obtain a USDA Quality Grade. The final quality grade may be reduced by as much as one full grade because of the reduced acceptance of dark beef by consumers.[1]

RELATIONSHIP BETWEEN MARBLING, MATURITY, AND USDA QUALITY GRADE

A USDA Quality Grade is determined by the correlation between marbling and maturity as shown in Fig. 3. For instance, only carcasses of A and B maturity are eligible for the Prime, Choice, Select, and Standard USDA Quality Grades.[4] The chart also reveals that as maturity progressively increases, carcasses must have increasingly higher degrees of marbling to continue to grade in their respective grades.

Fig. 2 Location of cartilage and vertebrae for determination of maturity. (From Ref. 4.)

Degrees of Marbling

Relationship between marbling, maturing and carcass quality grade MATURITY **

Degrees of Marbling

Degrees of Marbling

Relationship between marbling, maturing and carcass quality grade MATURITY **

Degrees of Marbling

Fig. 3 Relationship between marbling, maturity, and carcass quality grade. (From Ref. [4].)

CONCLUSION

REFERENCES

USDA Quality Grades are determined through visual appraisal of the lean and skeletal maturity of the carcass, as well as the degree of marbling. Both factors have been associated with obtaining a USDA Quality Grade because of their high correlation to tenderness, juiciness, and flavor of the meat. Consumer acceptance is of great concern in the meat industry today, consequently making the assessment of USDA Quality Grades important as well. Although many factors other than marbling and maturity (e.g., diet and genetics) might affect the overall palatability of the meat, the degree of marbling and maturity may be visually determined on the carcass without any further background information about the animal. Thus, the U.S. standards recognize marbling and maturity as the measures used to assess USDA Quality Grades.

1. Anonymous. United States Standards for Grades of Carcass Beef; US Department of Agriculture, Agricultural Market ing Service, Livestock and Seed Division: Washington, DC, 1997; 1 16.

2. Smith, G.C. Relationship of USDA quality grades to palatability of cooked beef. J. Food Qual. 1987, 10 (2), 269 286.

3. Savell, J.W. National consumer retail beef study: Palatabil ity evaluations of beef loin steaks that differed in marbling. J. Food Sci. 1987, 52 (3), 517 519.

4. Burson, D.E. Quality and Yield Grades for Beef Carcasses; North Central Regional Extension Publication # 357: Lincoln, NE. http://www.ianr.unl.edu/pubs/Beef/rp357.htm (accessed December 2003).

5. Fry, G. Quality Grades; Bovine Engineering and Con sultion: Rosebud, AR. http://www.bovineengineering.com/ quality grades.html (accessed December 2003).

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