Beef Tenderness and the Shear Force Test

Tenderness is critical to the meat-eating experience. Nobody enjoys sinking their teeth into a tough steak.

A tried-and-true method of testing beef tenderness is the plain old taste test. These days, however, there are ways to objectively measure the precise tenderness of a cut of beef.

The Warner-Bratzler Shear Force Test

The Warner-Bratzler shear force test is named for the two men who worked together to create it. Kenneth F. Warner, a USDA research scientist, invented the test equipment in 1928. Lyman J. Bratzler, a K-State graduate, standardized the equipment and the test procedure a few years later.

The test is very simple. The scientists performing the test collect a one-inch-thick steak from the 12th rib of the animal and trim it free of fat and bone. They vacuum seal the steak and allow it to age for 14 days at temperatures at or just above freezing. After aging, the steak is then frozen for 14 days. Prior to testing, the steak is completely thawed in a refrigerator and broiled to medium doneness.

Once the cooked steak has cooled off, the scientists collect six to eight core samples, each half an inch (1.27 cm) in diameter. They measure the pounds or kilograms of force required to shear the cores completely in half using a steel blade specifically design to mimic the action of the human jaw. The mean for all the cores is the shear force for the animal.

On the Warner-Bratzler system, beef tenderloin typically has a shear force of around 5.7 lbs. (2.6 kg). A top round steak has a shear force of around 11.7 lbs. (5.3 kg).

The Genetics of Tenderness

Tenderness is a heritable trait, and it is one that is heavily influenced by breed. Cattle breeds with the gene for double-muscling, such as the Belgian Blue, are extremely tender. At the other end of the spectrum, zebu breeds such as the Brahman tend to be on the tough side. Between the two extremes lie British breeds such as the Angus.

But there is typically some variation within each breed for the tenderness trait. Those seeking to improve the shear force test results of their cattle will do well to seek out bulls with bred-in tenderness genes. A sire’s genetic potential for tenderness can be determined through progeny testing. With the Brahman and Simmental breeds, cattlemen can refer to the shear force EPD.

Management Factors Affecting Tenderness

Of course, poor management will ruin even the best beef genetics. Tenderness largely depends on intramuscular fat, not marbling. Marbling is only used as a measure of tenderness because it is typically associated with the presence of intramuscular fat, which is microscopic and nearly impossible to measure in the home kitchen.

Intramuscular fat resides in special fat cells that develop as cattle reach early adolescence. These cells must fill up if an animal is to produce tender beef. This means that the animal must steadily gain weight during the finishing process, whether on grain or grass. If the cattle lose weight while finishing, this is an indicator that the intramuscular fat levels have decreased and the meat has toughened. Steady weight gains require optimum nutrition, including adequate energy intake and properly balanced vitamin and mineral levels. Grain can fill up the fat cells faster than grass. However, it is entirely possible to produce tender beef on forage alone with proper planning.

Note that growth hormones do not increase beef tenderness—they simply increase muscle mass.

Younger animals are normally more tender than older animals, as they have had less time to develop connective tissue. However, there is a trade-off here, because younger animals also have had less time to deposit intramuscular fat. A beef animal that has reached the critical balance point between intramuscular fat and connective tissue is considered finished. This is where frame scoring comes into play. A large-framed animal grows slowly and takes much longer to finish than a small- or moderate-framed animal.

Post-Harvest Factors Affecting Tenderness

One of the most important management factors influencing beef tenderness is the procedure at the slaughter facility. Stress will cause adrenaline levels to spike and muscles to tense. Low-stress transport and a quick, humane kill are necessary for keeping meat at its most tender.

Even after slaughter, the beef carcass must still be handled properly to ensure tenderness. Aging is a key factor, as it allows natural enzymes to begin the process of softening up the muscle. Aging takes place at low temperatures to prevent problems with bacterial growth. The carcass is typically placed in a plastic bag during the aging process to avoid oxidation.

The final step of producing tender beef is left up to the consumer, and that is cooking. As beef is cooked to higher levels of doneness, it becomes steadily tougher. Intramuscular fat is required to keep a steak tender when cooked to well done. Very lean beef and low-grade cuts can still provide an enjoyable eating experience when slow cooked. This gives the collagen holding the steak together time to melt.