Muscle: Bone Ratio and Fat Percentage as Measures of Beef Carcass Composition
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Beefiness Carcass Grading and Evaluation
thirty July 2007
By David R. Jones and William C. Stringer, Food Science and Nutrition Department, University Of Missouri Extension. Evaluation of beefiness quality and composition is important to cattle producers, meat packers and retailers, and consumers.
Consumers desire cuts of beef that are lean, nutritious, and possess desirable eating characteristics. Meat researchers take developed reliable methods for measuring the factors that influence eating characteristics and factors affecting yield of lean cuts. Using these evaluation techniques, producers and packers tin produce and sell carcasses that meet consumer demand.
This guide provides information about standard U.Southward. Department of Agriculture beef carcass yield and quality grading systems. Other useful and accurate evaluation procedures will also exist introduced.
Beef carcass grading is divided into quality grading and yield grading.
Quality grading
Quality grades indicate the factors related to the sensory characteristics of tenderness, flavor, color, texture and juiciness. The quality grade is intended to reflect the cooked production'south overall acceptability.
The USDA quality grades for steer and heifer carcasses are prime, choice, expert, standard, and utility. These grades are adamant by balancing maturity and degree of marbling.
Maturity refers to the physiological age of the live creature. Maturity in the carcass is adamant by the caste of ossification (os development) of the separate chine bones (back bones) and the color and texture of the cutting lean surface.
Cartilage changes into bone every bit the animal matures. This process of ossification proceeds from the back toward the front portion of the vertebral column. The degree of ossification in the vertebral buttons well-nigh the thorax, which is the cavity containing center, lungs, etc., is the near useful in evaluating maturity. Rib bones also become flatter and whiter as the animal matures.
Meat from young animals is lighter colored and effectively textured compared to older beef. Generally, a fine-textured lean will be more tender than a coarse textured lean. Carcass maturity is closely related to beef tenderness. As the animal matures, changes in the connective tissue cause the meat to exist less tender.
| The degrees of maturity are A, B, C, D and E. Age ranges for these maturity groups are approximately | |
| Maturity grouping | Age |
|---|---|
| A | nine to 30 months |
| B | 30 to 42 months |
| C | 42 to 72 months |
| D | 72 to 96 months |
| E | more than 96 months |
Nighttime-cut beef is non necessarily from older animals just tin too result from cattle that were physiologically stressed before slaughter. Dark-cut beef is highly discriminated against by consumers and retailers. Nighttime-cutting beef may exist reduced up to one full quality grade.
Marbling is fatty within the muscle and is evaluated in the rib heart betwixt the 12th and 13th ribs. The 10 USDA degrees of marbling are abundant, moderately arable, slightly abundant, moderate, modest, pocket-size, slight, traces, practically devoid, and devoid. Marbling has a strong correlation with the juiciness and flavour of beef.
Last quality grades are arrived at by a blended evaluation of maturity and marbling (Effigy 1).
Figure 1 Human relationship between marbling, maturity, and carcass quality grade
Yield grades
Yield grades estimate the quantity or the amount of closely trimmed boneless retail cuts from the loin, round, chuck and rib. At that place are v USDA yield grades, 1 through five. Yield form one carcasses have the highest yield of retail cuts and yield grade 5, the lowest.
The expected boneless retail yield from the round, loin, rib and chuck is as follows:
| Yield grade | Percent of carcass weight in boneless, uniformly trimmed retail cuts |
|---|---|
| one | more 52.iii |
| two | 52.three to 50.1 |
| three | l.0 to 47.eight |
| 4 | 47.seven to 45.5 |
| 5 | less than 45.v |
These yield figures are sometimes used in carcass bear witness results as a mensurate of cutability.
Yield form too tin be used to predict the total retail cuts from a carcass or quarter.
| Total percent retail cuts (closely trimmed, semi-boneless) | |||
| Yield grade | Carcass | Forequarter | Hindquarter |
|---|---|---|---|
| 1 | 82. 0 | 84.0 | 79. 9 |
| two | 77 4 | 79.0 | 74.ix |
| 3 | 72 8 | 75.6 | 69.nine |
| 4 | 68.two | 71.4 | 64.9 |
| five | 63.6 | 67.ii | 59 9 |
The USDA yield course is based on four factors:
- Hot carcass weight (pounds)
- Rib center area at the twelfth rib (square inches)
- Adjusted fat thickness over the rib eye at the twelfth rib (inches)
- Per centum kidney, pelvic, and heart (percentage of carcass weight).
These measurements are used in the official USDA formula as follows:
Yield class = two.5 + [(ii.50 x adjusted fat thickness, inches) + 0.two pct of kidney, pelvic, and heart + (0.0038 ten hot carcass weight, pounds) - (0.32 x area rib eye, square inches)]
When calculating yield grades, any decimal is dropped; yield grades are presented equally whole numbers. Care and accuracy of these measurements are essential to derive reliable estimates of the cutability. The USDA grader, in practice, estimates the factors and uses a short-cut formula.
Fat thickness
The corporeality of fat on a beef carcass has the greatest effect on the percent retail yield. As the pct fatty increases, the per centum musculus decreases. Fat thickness is measured at a point iii-fourths of the length of the rib eye (longissmus) muscle from the chine os, perpendicular to the surface fatty, at the twelfth rib. This measurement may be adapted according to the total corporeality of fat on the carcass.
Rib centre surface area
Total square inches of rib eye is used to estimate muscular development of a beef carcass. This measurement can be taken objectively between the 12th and 13th rib. A calibrated transparent plastic grid placed over the rib middle is normally used to determine the area.
An culling method is to trace the perimeter of the rib centre on acetate paper and calculate the expanse with a compensating planimeter, which is an instrument that measures area of irregularly shaped objects.
Hot carcass weight
Hot carcass weight, or 102 per centum x chilled carcass weight, is the weight of the carcass later slaughter. The carcass weight has an inverse upshot on the percent retail yield.
Kidney, pelvic, and heart fat
The amount of kidney, pelvic and heart fatty is fatty accumulated in the body cavity of the carcass. The weight is reported as a percent of the carcass weight. The range of kidney, pelvic and heart fat is one to viii per centum (with a typical average of 3.5 percent).
Yield grades estimate the proportions of lean and fatty. Meat graders make up one's mind yield grades with fast, simple visual appraisals of fat and musculus of the carcass. Fatty thickness, hot carcass weight and rib centre area are objective measures with kidney, pelvic and heart fatty being a subjective measure.
USDA grading is washed on a voluntary ground by the packer. The packer absorbs the cost. When a carcass is submitted for grading, it must be both quality and yield graded.
USDA grades should not be confused with the USDA inspection for wholesomeness.
Beef carcass evaluation
The purpose of beef carcass evaluation is to assistance beef producers in:
- Producing high-quality beefiness carcasses
- Producing high-yielding beefiness carcasses
- Identifying superior lines of breeding stock
- Promoting a desirable, marketable product.
Improving the efficiency of beef cattle production is important to feeders, cow/calf ranchers and seed stock producers. Feeders can evaluate their feeding and direction practices with cutability scores or the percentage or number of their cattle grading choice. moo-cow/dogie ranchers may use grades to rank or functioning-exam their stock. Seed stock producers can ultimately utilize quality and yield grades in sire evaluation.
Some other guidelines or indexes that may be useful in beef carcass evaluation are a growth cistron or loin middle index.
Growth factors can be used to express the composition of growth. Expressing the pounds of retail cuts per solar day of historic period is one method.
This figure is determined by this formula: pounds of trimmed retail cuts per day of age = (carcass weight x cutability) divided past age in days.
Example
A 600-pound carcass, 400 days old with a yield grade iii (50 percent retail yield) produces 0.75 pounds of retail cuts per day of age:
(600 x 0.five) ÷ 400 = 0.75 pounds of retail cuts per twenty-four hour period of age.
Loin eye area has been highly correlated to the percent musculus in a carcass. A goal of progressive beefiness producers is to produce cattle yielding at least 2 square inches loin eye area per 100 pounds of carcass.
Case
A 550-pound carcass with a 12.5 square inch loin eye would yield 2.27 foursquare inches loin center expanse per 100 pounds of carcass (12.5 ÷ five.v = ii.27 square inches loin heart area per 100-pound carcass).
Use of the USDA's Beef Carcass Data Service is a service designed to provide carcass data to breeders or others who don't own the animals at the time of slaughter. Cattle are ear tagged with USDA ear tags and upon slaughter the proper quality and yield grade data are forwarded to the purchaser of the ear tags. This is especially helpful to seed stock producers.
For information on source of ear tags and cost of the service, contact Livestock Division, Agricultural Marketing Service, U.Due south. Department of Agriculture, Washington, DC 20250.
Terminal updated: June 2007
Source: https://www.thecattlesite.com/articles/1081/beef-carcass-grading-and-evaluation/
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