There is a new awareness regarding beef quality. Today consumers are more discriminating, more selective and harder to please than ever before. They want beef that is superior in taste, tenderness and juiciness. And they want every cut to provide the same high-quality eating experience every time they buy it.
The Certified Angus Beef™ (CAB®) brand was created in 1978 to promote the Angus advantage for producing high-quality beef products that exceed consumer expectations time and time again. Specifications for the brand were set using sound, repeatable, scientific information that ensures beef identified with the Certified Angus Beef mark will be consistently tender and juicy and satisfy the consumer’s appetite for that classic beef flavor. Whether at the retail or restaurant level, consumers have come to rely on brands as an assurance of beef quality and consistency. The ever-increasing demand for CAB product is testimony to the effectiveness of the CAB brand to provide consumers with the eating experience they both expect and deserve.

The Angus advantage
The sustainability and growth of any branded beef program is a direct function of two key factors: (1) consumer acceptability and (2) availability of product. In today’s beef industry, no beef breed outside Angus can simultaneously achieve both of these criteria. This fact alone sets the Angus breed apart with respect to its importance in the production of high-quality beef.
A closer look at the Angus breed reveals several production advantages, including superior maternal ability and reproductive efficiency, but it also emphasizes the production of high-quality end products desired by the meat industry and consumers. Unquestionably, marbling ability has always been a strength of the Angus breed. Data collected from Certified Angus Beef LLC licensed packers and fabricators suggests that approximately 80% of USDA Prime carcasses are from Angus and Angus-type cattle. Being genetically predisposed to marbling deposition, the Angus breed can inherently produce beef that is more likely to be tender, juicy and flavorful when compared to cattle of other breeds.
A review of eight research studies conducted at South Dakota State University (SDSU) reveals that the average genotypic and phenotypic correlations of marbling to shear-force value (a measure of tenderness), are -0.44 and -0.21, respectively. This means that as marbling increases, shear-force values decrease. Lower shear-force values indicate greater tenderness. The fact that the genotypic correlation is significantly more negative than the phenotypic correlation suggests that when selection pressure is placed on genetically enhancing marbling deposition, the breeder is simultaneously selecting for enhancements in tenderness. Although the exact mechanism through which this occurs is not fully understood, by combining the breed’s inherent ability to marble with genetic selection for carcass merit, the Angus breed’s impact on consumer acceptability is amplified.
We know that usage of Angus genetics is steadily increasing within the industry. Licensed packers and fabricators indicate that more than 40% of all harvested cattle at federally inspected facilities are Angus and Angus-type cattle. Predictions indicate that this number will exceed 50% by 2003. Although no other beef breed can singly supply an equivalent volume of product, the increased presence and improvement of Angus genetics within the beef industry is critical to maintaining and growing product availability.

CAB® carcass specifications
A consumer’s perception of the combined effects of flavor, juiciness and tenderness determine overall beef palatability. Genetics, carcass composition, nutrition, time on feed and a host of postmortem variables influence these components. The CAB carcass specifications are based on scientific evidence that has been shown to reduce the variability in beef palatability. Carcasses from Angus and Angus-type cattle must meet eight important criteria before they are stamped “Accepted as Specified” by USDA graders and identified with the CAB mark. These uncompromising standards help ensure that CAB product exceeds the consumer’s expectations. The eight CAB carcass specifications are:

(1) A modest or higher degree of marbling
A review of scientific literature provides sound evidence that as the amount of marbling increases from “Practically Devoid” (USDA Standard) to “Slight” (USDA Select) to “Small” (low-Choice) to “Modest” (minimum for CAB) to “Slightly Abundant” (USDA Prime), desirability of tenderness, juiciness and flavor of cooked beef increases progressively.
However, with respect to tenderness, several contradictions exist. Marbling has been reported to account for less than 25% of the variation in tenderness among steaks cooked to a medium degree of doneness. Yet, it is important to note that tenderness represents only one of three key palatability attributes, and a review of research provides no evidence that marbling is detrimental to beef tenderness. In fact, increased marbling has been identified to improve beef tenderness four ways: (1) bulk density reduction, (2) lubrication effect, (3) connective tissue strain and (4) enhanced resistance to temperature abuse.
The bulk density effect is based on the density differences between low-density fat and higher-density heat-denatured protein (cooked beef). As fat levels increase proportionally to the unit volume of beef, the overall density of any given bite of beef decreases. Thus, beef that has a higher fat content is more tender.
Additionally, as fat content within beef muscle increases, intramuscular fat is deposited between muscle fibers, and fat stores within the muscle fiber increase. Therefore, muscle fibers are surrounded or bathed in fat to a greater extent in beef with higher fat content. Upon cooking and chewing, fat is released, which stimulates salivation and the perception of juiciness and tenderness. Beef with a higher amount of fat is perceived as juicy and tender because of the lubrication effect of fat.
It has also been shown that marbling is deposited within perimysium muscle connective tissue. As fat deposition increases, the strength of the connective tissue decreases and the subsequent beef is more tender. The added strain placed on connective tissue by fat deposits makes collagen/reticulin more susceptible to steam-gelatinization during the cooking process. When cooked to higher degrees of doneness (medium-well and well-done), marbling becomes even more influential in preserving the inherent tenderness of beef, protecting against the effects of temperature abuse and overcooking.
Marbling and juiciness are also positively related. The juiciness of cooked beef increases almost linearly as the amount of marbling in the muscle increases. The feel of juice released in the mouth upon chewing and the subsequent stimulation of the salivary gland by fat influences the perceived juiciness of beef. Additionally, beef products with a higher amount of marbling will sustain the feeling of juiciness in the oral cavity.
Higher levels of marbling also provide an insulatory effect for beef during cooking. High temperatures used in cooking degrade protein, which results in the release of water. Fat conducts heat at a slower rate than lean tissue, and lean tissue is about 75% water. Therefore, fat slows down the migration of heat and decreases the shock effect of high heat on protein degradation and moisture release. The result is that meat containing higher fat content does not cook as rapidly; therefore, the amount of water and fat lost during cooking is reduced. Simply put, beef with more marbling can be cooked to a higher degree of doneness yet still be perceived as “juicy” to the consumer than can beef with less marbling.
Along with juiciness, flavor increases as marbling increases. The desirability of the flavor and aroma of cooked beef is determined by species-specific carbonyl compounds that are located in the marbling of beef muscle. In addition to species differences, beef flavor is influenced by both nutrition (grain- vs. forage-based rations) and days on feed. As the amount of marbling increases, there are progressive increases in the desirability and/or intensity of flavor in cooked beef.
The 1995 National Beef Quality Audit indicates that only 13.0% of all fed cattle harvested exhibit a “Modest” degree of marbling or better. Lowering the minimum degree of marbling required for certification would increase the supply of cattle available to produce CAB product. However, it would also increase the variability in eating satisfaction. Research reveals that the odds of getting a steak that is slightly undesirable or worse in overall palatability from the various USDA Quality Grades are:
Prime 1 in 26
Upper 2/3 Choice (CAB) 1 in 19
Lower 1/3 Choice 1 in 7
Select 1 in 5
Standard 1 in 2
Science has identified a “Modest” degree of marbling as the threshold where variability in overall palatability is dramatically reduced. As a result, a “Modest” degree of marbling is required for certification.

(2) Medium or fine marbling texture
Scientific evidence reveals that the finer the marbling deposits and the more even the distribution throughout the muscle, the greater the likelihood that the beneficial effects of marbling on palatability will be exhibited in each and every bite. Therefore, carcasses must exhibit medium or fine marbling texture rather than coarse marbling to be certified.

(3) “A” maturity range
Volumes of evidence relate increasing animal maturity to beef toughness with the primary contributor being connective tissue. Connective tissue functions as the framework for all muscles and harnesses the power generated by muscle fibers during contraction. As an animal becomes increasingly older, both the amount and stability (extent of cross-linkages) of connective tissue proteins increases. Within the muscles of older animals, cross-linkages occur within the molecules of collagen (and reticulin) fibrils, rendering them no longer susceptible to heat-transformation into gelatin. In beef from older cattle, the heavily cross-linked connective tissue does not soften during cooking and remains as “gristle” even after thorough chewing.
In addition to advantages in tenderness, younger cattle tend to produce beef with superior color, texture and firmness. The color and texture of the lean undergo progressive changes with advancing maturity. In more mature carcasses, the texture of the lean becomes progressively coarser and the color of the lean becomes darker red.
To account for the effects of the maturing process on beef tenderness, evaluations of carcass maturity are used in determining USDA Quality Grades. There are five maturity groupings, designated as “A” through “E.” Approximate ages corresponding to each maturity classification are:
A 9-30 months
B 30-42 months
C 42-72 months
D 72-96 months
E > 96 months
The detrimental effects that advanced physiological maturity can impart on beef palatability provides the scientific basis for restricting certification to only those carcasses that classify as “A” maturity.

(4) USDA Yield Grade 3.9 or leaner
Since 1976, the beef industry has assessed differences in carcass composition using USDA yield grades. Yield grades (YG) estimate beef carcass cutability, which is defined as the combined yield of closely trimmed, boneless retail cuts (CTBRC) from the round, loin, rib and chuck. This is an estimate of the relative amount of lean, edible meat from a carcass. Yield grades range from 1 (highest cutability) to 5 (lowest cutability). Simply put, the lower the numerical value, the higher the percentage of CTBRC. The expected percentages of CTBRC for each USDA Yield Grade are:
YG 1 52.3%
YG 2 50.0-52.3%
YG 3 47.7-50.0%
YG 4 45.4-47.7%
YG 5 < 45.4%
The yield grade of a beef carcass is determined by evaluating the following factors: (1) external fat thickness over the ribeye (12th-rib cross-section), (2) ribeye area, (3) percentage of kidney, pelvic and heart fat (%KPH), and (4) hot carcass weight. Increases in external fat thickness, %KPH, and hot carcass weight typically reduce cutability, while increases in ribeye area often result in improvements in cutability and lower numeric USDA yield grades.
Excessive carcass fatness was listed as a primary quality concern by both the retail and foodservice segments of the beef industry during the 1991 and 1995 National Beef Quality Audits. When beef carries too much fat, either external or seam fat (fat between muscles), product yields decrease. As a result, retailers attempt to recoup their additional trim losses by adding it to retail prices, and restaurants simply lose customers or customers choose other entrées. To ensure a quality product and reduce the variability in trim loss due to excessive “waste” fat, CAB carcasses must be USDA YG 3.9 or leaner.

(5) Moderately thick or thicker muscling characteristics
All carcasses that are ultimately certified must exhibit beef muscling characteristics as opposed to dairy-type muscle conformation. Superior muscle thickness implies a higher and more desirable proportion of lean tissue to bone. Additionally, carcasses exhibiting those typical beef muscling characteristics produce strip loin and sirloin steaks that are more desirable to the foodservice industry as they are more symmetrical in shape and result in a more appealing plate presentation.

(6) No hump on the neck exceeding 2 inches in height
To be accepted as CAB product, carcasses must not exhibit a hump on the neck exceeding 2 inches in height. This restriction eliminates those cattle heavily influenced by Brahman (Bos indicus) genetics. To better grasp the significance of this specification, as it relates to differences in breed and biological types of cattle, it is first necessary to establish a general understanding of postmortem aging and the inherent mechanisms that dictate ultimate beef tenderness.
Postmortem tenderization of muscle occurs as a result of protein degradation or proteolysis. Immediately following harvest, endogenous chemical catalysts (proteolytic enzymes) called calpains, begin to degrade individual myofibrils (muscle fibers) by creating disruptions in the structure (at the Z-lines) of the sarcomere, the repeating contractile unit of the muscle fiber. Tenderness is therefore enhanced since degraded/disrupted muscle fibers fragment more readily during chewing than do intact muscle fibers. An endogenous inhibitor to calpain is calpastatin (calpain stopper). Calpastatin slows and/or stops the activity of calpain enzymes. As a result, the comparative amounts/activities of calpain and calpastatin within the same muscle determine the extent of Z-line degradation during postmortem aging of beef.
With regard to tenderness differences between breeds of cattle, research indicates that Brahman cattle tend to produce beef with more variation in tenderness than other breeds. Scientists at the U.S. Meat Animal Research Center (MARC) at Clay Center, Neb., discovered that cattle of Bos taurus species have less calpastatin in their muscles than do Bos indicus species of cattle. As a result, carcasses of Bos taurus species, such as Angus, experience greater improvements in tenderness during postmortem aging than do carcasses of Bos indicus species, such as Brahman. Additionally, research conducted in Australia reported that the most important contributor to toughness of Australian beef was the percentage of Bos indicus genetics in the cattle from which the beef was derived.
Inconsistency in beef tenderness at the consumer level has been identified as one of the major problems facing the entire beef industry. One way to reduce the variation in tenderness is to remove from the supply those carcasses of cattle that are genetically predisposed to producing beef unacceptable in tenderness. As a result, carcasses exhibiting excessive Brahman influence, as determined by hump height, are excluded from certification.

(7) No evidence of internal hemorrhages in the ribeye muscle (at the 12th-rib cross-section)
Internal hemorrhages, also referred to as “pin-point bleeding” or “blood splash,” occur when small capillaries within the muscle rupture, resulting in the appearance of small spots of blood in the muscle tissue. This carcass defect most often occurs immediately after the animal has been rendered unconscious and prior to exsanguination (bleeding). It is at this point in the harvest process that the animal is shackled and elevated to a vertical position. In this position, the pressure placed on the capillaries and vessels is increased as gravity dictates the flow of blood to the lower extremities. Minimizing the duration between rendering the animal unconscious and bleeding most effectively controls the occurrence of this defect. This humanely and effectively reduces the blood pressure and decreases the likelihood of capillary rupture.
These small blood spots do not affect palatability. Yet they greatly detract from the product’s visual appearance. It is important to note that appearance is one of the primary sensory properties upon which purchasing decisions are based. From the perspective of CAB, it is key to exceed all the consumer’s expectations for quality, both palatability and eye appeal. Thus, carcasses exhibiting this defect are excluded from certification.

(8) Free of dark-cutting characteristics
“Dark-cutting” beef is characterized by a color that ranges from dark red to nearly black and is the direct result of low muscle glycogen (a complex form of stored sugar) levels immediately prior to harvest. The amount of glycogen stored in muscle is critical, as it ultimately dictates muscle pH and color. The scientific term, pH, when used with meat, indicates the relative acidity of the muscle. A lower pH (closer to 1.0) is more acidic than a higher pH (closer to 7.0).
Under normal conditions, glycogen is converted to lactic acid during rigor mortis, resulting in an ultimate muscle pH of 5.5 to 5.6. At this pH, beef muscle typically exhibits a normal bright cherry red color. In cases where glycogen levels have been depleted prior to harvest, less lactic acid is produced, a higher ultimate muscle pH is obtained and a darker color results. Post-rigor muscle pH values equal to or greater than 6.0 typically result in some degree of dark-cutting beef. This explains why dark-cutting beef is occasionally referred to as “high-pH beef.”
Glycogen depletion in muscles of cattle can typically be associated with stress prior to harvest. Dramatic and quick weather changes, commingling, poor cattle-handling practices, lengthy transport and holding times, and withholding feed for extended periods (1-2 days) immediately prior to harvest can each induce or magnify the incidence of dark cutters. The incidence of dark-cutting beef in grain-finished steers and heifers generally averages from 1% to 5%.
With regard to palatability, dark-cutting beef is typically more tender and juicy than normal-pH beef. The higher pH is
more conducive to proteolytic “tenderizing” enzyme activity during postmortem aging and increases the water-holding capacity of the muscle. However, dark-cutting beef is more susceptible to bacterial growth and, as a result, exhibits significantly shorter shelf life. Yet, the greatest problem with dark-cutting beef is consumer rejection because of its color. In the consumers’ eyes, dark-cutting beef is an inferior product when displayed in the fresh meatcase. This perception is backed by science and, as a result, eligible carcasses exhibiting dark-cutting characteristics are excluded from yielding CAB product.

Conclusions
As long as people eat beef, there will be those who insist upon having the finest beef available. Consumers should not be asked to gamble with their beef dollar. Desirable tenderness, juiciness and flavor should be inherent attributes consistently present in the beef they purchase. CAB product has provided consumers with such consistency. Not by chance, but rather through science.