J. Brad Morgan
Department of Animal Science
Oklahoma State University
"The U.S. cattle industry cannot expect improvements in demand for its products/byproducts when 'quality' doesn't warrant such increases. We the beef cattle industry must measure our quality defects so they can be managed." Those were the words of Dr. Darrell Wilkes (then Vice-President of the National Cattlemen's Association), during the development phase of the initial National Beef Quality Audit (NBQA). From that 1991 audit, the take home message was that the U.S. beef industry must attack waste by reducing excessive external fat, decreasing excessive seam fat (fat located between muscles), improving overall cutability and increasing our understanding of the value of closer-trimmed beef products. During the past four years, economic pressures to reduce carcass waste fat have certainly been successful. According to the recently completed NBQA 1995, the average adjusted fat thickness of beef carcasses harvested in the U.S. has decreased from .59 inches in 1991 to .47 inches today (Smith, 1995). However, these efforts on attacking waste fat have now challenged the livestock and meat industries to seek ways of producing meat products that will enable the consumer to receive maximum palatability at the lowest cost. Listed below are quotes and findings from several key research projects to document the variation in tenderness which currently exists in the U.S. fed cattle/carcass population.
Approximately 41% and 63% of
all chuck and round cuts, respectively, displayed shear force values categorized
In regard to "middle meats," steaks from the top sirloin received sensory panel ratings less than moderately tender.
Postmortem aging times, as a method to assure meat tenderness, ranged from three to 90 days.
One tough beef carcass could affect as many as 542 consumers.
Beef is being cooked to a greater degree of doneness today than in previous years because of concerns about E. coli 0157: H7.
One out of every four steaks is less than desirable in tenderness/palatability.
Bad dining experience can spread
via word of mouth to as many as 950 potential customers.
During 1995, problems associated with beef toughness cost the U.S. beef industry more than $250 million.
According to retailers, restaurateurs and purveyors, "Due to the enormous emphasis directed to attacking waste fat, U.S. beef has lost ground in the palatability attributes associated with the taste of fat."
In order to fulfill the beef
industry goal of "100% customer satisfaction," a technique(s) must be
developed which overcomes the dilemma between the production of lean meat,
which is not very tender, or providing tender meat which contains too
The general objective of this article is to reiterate the importance of beef tenderness to today's consumer, overview the sources of variation associated with beef tenderness, discuss potential mechanical and genetic approaches for controlling and predicting the observed variation in beef tenderness and discuss potential incentives as well as possible obstacles associated with the implementation of objective tenderness determination of beef muscle.
Inconsistency in beef tenderness at the consumer level has been identified as one of the major problems facing the entire beef industry. If we reminisce back to the original National Beef Quality Audit 1991 (Smith et al., 1991), I overviewed a "real-world" beef toughness experience regarding a head meat buyer of a prominent West Coast supermarket chain (annual beef sales in excess of $200 million). In that scenario, the meat buyer stated that "typically, carcasses were shipped from slaughter plants in Southern California, Arizona and the Texas Panhandle to a centrally located fabrication facility." He continued by stating that, "following fabrication, subprimals were aged for a minimum of 14 days prior to delivery at retail stores. Once at the retail store, all round, loin and rib retail cuts were blade tenderized prior to retail store display." The policy of this particular retail chain was that if customers were not 100% satisfied with any particular product, including beef, a full-value monetary refund would be issued to that unsatisfied customer. During the years between 1988 through 1991, the meat department at this particular retail chain issued approximately $7,000 per week to unsatisfied customers. Of the $364,000 annually refunded to customers by their meat department, approximately 78% ($286,000 annually) were directly related to inconsistent or inadequate beef tenderness.
During the past few years, I have been involved primarily through conversations with the above mentioned meat buyer, trying to improve the consistency associated with their beef products. During one of our conversations, I asked him the question, "Really, how important is beef tenderness to your operation?" He quickly responded by stating, "Meat, no let me rephrase that, BEEF sales are extremely important to our retail operation." He continued by explaining to me how BEEF is a primary store item in that when customers purchase beef from their stores, they the customer typically also purchase secondary items such as soft drinks, potato chips, vegetables and beer from those stores as well. He concluded answering the question by stating, "BEEF is essential to our existence!" With these thoughts in mind, I quickly realized how important it was to reduce and hopefully eliminate the beef toughness dilemma faced by this West Coast retail chain. (General Note: Procedures used to reduce/eliminate this problem will be latter discussed).
A second example which demonstrates the importance of beef tenderness to consumers and to the entire beef industry is the fact that beef retail cuts are priced according to their expected tenderness level. Using data from the National Beef Tenderness Survey (Morgan et al., 1991), Jeff Savell from Texas A & M University plotted the mean retail price of four beef cuts representing a wide range in tenderness against their mean Warner-Bratzler shear values. Tenderloin steaks command between a $2.00 to $3.00/pound premium over top loin steaks despite the fact that these steaks are similar in composition. The price differential between these cuts is directly a reflection of the tenderness advantage associated with tenderloin steaks.
Results from a very interesting study conducted by Boleman et al. (1995) at Texas A & M University suggests that consumers can discern between beef tenderness levels and are willing to pay a premium for guaranteed tenderness. In this three-phase study, top loin steaks from strip loin subprimals were cooked, and a tenderness value was determined using a Warner-Bratzler shearing device. The remaining steaks were placed into one of the following categories based on their respective shear force values: 1) 5 to 7.9 pound; 2) 9 to 11.9 pound; and 3) 13 to 15.9 lb. Category 1 steaks were color-coded with red labels, category 2 steaks with white labels, and category 3 steaks with blue labels. During phase 1, consumers rated red-coded steaks highest for tenderness, flavor and overall satisfaction compared to blue- and white-coded steaks. Even with a $1.00/pound premium, 94.6% of the consumers chose to purchase "guaranteed-tender" red-coded steaks. Results from this project suggest that consumers can detect and are willing to pay for differences between levels of tenderness. This research demonstrates that an economic incentive is currently present for "guaranteed-tender" beef, and until some measure of real, not perceived, tenderness is identified, the beef industry cannot and will not search for, manage and (or) market "guaranteed-tender" beef.
To reduce variation in tenderness of aged beef, one must first understand the mechanisms involved. Many researchers have had the impression that all animals (i.e., carcasses) probably had the same tenderness level when slaughtered. Differences in the "ultimate tenderness" were the result of carcasses responding to the aging process (i.e., tenderization) at various rates. This phenomenon has been documented by researchers at the Meat Animal Research Center (Wheeler and Koohmaraie, 1994) in that they demonstrated that there are minor differences in meat tenderness at the time of slaughter and that, indeed, the observed differences in 1-day shear force are generated during the first 24 hours after post-slaughter. Thus, there are some animals that go through the tenderization process rapidly and could be consumed after 3, 7, or 14 days, and still others would not be acceptable from a tenderness standpoint even after extended postmortem storage. As pointed out by Dr. Koohmaraie, "I have suggested that differences between the rate and extent of postmortem tenderization are the cause of variation in meat tenderness after postmortem storage."
The development of a method of predicting meat tenderness requires sound knowledge of the mechanisms that influence and (or) regulate meat tenderness. Listed below are a few major factors which influence or help control tenderness variation.
Genetics Contributions: Many scientists as well as producers have suggested that controlling genetics of the slaughter cattle population would entirely solve the beef industry's tenderness dilemma. Certainly, genetics makes a large contribution to the total tenderness puzzle. However, analyses indicate that genetic and environmental factors make about an equal contribution to variation in tenderness. The best estimates indicate that, within a single breed, genetics controls about 30% of the variation in beef tenderness. This 30% represents the heritability (additive gene effects) of tenderness within a breed. Therefore, within a breed, 70% of the variation is explained by environmental and non-additive gene effects. Due to the fact that between-breed variation is less variable than within-breed variation, approximately 46% of the variation in tenderness is accounted for through genetics, and 54% is environmental. Thus, significant improvements in meat tenderness can be made by controlling factors responsible for environmental effects such as time on feed, stress, carcass chilling, postmortem aging time, cooking method and end point degree of doneness.
It has been well documented that some breeds of cattle produce tender meat while other breeds produce meat with inferior tenderness ratings (Wheeler et al., 1996). Many researchers have concluded that the mean sheer force and variation in shear force increases as the percentage of Bos indicus inheritance increases (Figure 1, Crouse et al., 1989).
Figure 1. Shear force by breed type and marbling score. The thickest line connects the mean for each marbling score. The percentages at the bottom represent the percentage of animals with a shear force greater than 6.0 kg.
Management Practices: Research shows that numerous management practices influence beef tenderness/palatability. For example, animal age/maturity, energy level of the diet, time on feed, use of growth promotants and gender of the animal (bull, steer, heifer, heiferette) have all been documented to influence beef tenderness. As you are aware, the USDA implemented on January 31, 1997 a change in the way B-maturity carcasses (approximately 30 to 42 months of age) are assigned a U.S. Quality grade. In brief, these B-maturity carcasses (approximately 980,000 carcasses) having small or slight marbling scores will no longer be eligible for the U.S. Choice or Select but will be quality graded as U.S. Standard. Excluding these carcasses from the low end of U.S. Choice and U.S. Select Quality grades potentially will decrease the variation in palatability and provide for improvement in overall quality.
An industry debate has emerged over the question: "Do carcasses from calf-fed steers and heifers produce steaks with more desirable and more consistent tenderness values than carcasses from yearling-fed cattle, regardless of marbling?" Recent studies involving cattle of predominantly British breeds concluded that beef from carcasses of steers slaughtered at 13 months of age is not more tender than beef from carcasses of steers slaughtered at 15, 17, 19 or 21 months of age. Currently, the industry does not have sufficient evidence to warrant changing the maturity x marbling compensations in the USDA Quality grading system for animals which were calf- versus yearling-fed animals.
Today's cattle feeding industry tends to feed cattle long enough to ensure that minimum requirements for time-on-feed are met consistently. Few grass-fed cattle go to slaughter, and few cattle are on feed less than the 76 to 100 days necessary to achieve consumer acceptability. The bottom line: most current feeding practices maximize the tenderness potential of beef produced in the United States.
A degree of concern has developed regarding the role that growth-promoting compounds play in the reduction of USDA Quality grade and meat tenderness. Growth implants androgens, estrogens and a combination of androgens and estrogens are commonly used in most feedlot cattle to increase feed efficiency and growth, and some compounds also increase lean production and (or) reduce fat deposition. Certain studies suggest that implants have little or no effect on the quality grade of beef carcasses or the tenderness of the finished products when implanting procedures follow the manufacturer's recommendation.
Progeny Testing: Traditional animal breeding theory indicates that the most effective genetic selection is made through progeny testing. Due to the time required, progeny testing may not be a practical method to improve tenderness. Lets make the following assumptions:
It would take 12.0 years and 40.7 years to improve shear force by 1.0 kg by selection for shear force or marbling, respectively. If we increase the cow herd to 500 cows, the above estimates will be 6.8 and 23.1 years, respectively. Undoubtedly, it would be impossible to select heavily for tenderness without compromising other economically important traits.
Calcium-Activated Tenderization: In 1988, a method calcium infusion or injection was developed, which ensured meat tenderness (Koohmaraie et al., 1990). Calpains require calcium for activity. But, conditions in postmortem muscle are not always optimum for calcium to be available to activate calpains. But exogenous (i.e., foreign or additional) calcium can be added to meat, thus activating calpains and inducing more rapid and extensive tenderization. The process known as Calcium-Activated Tenderization (CAT) consists of injecting cuts of meat (either pre- or post-rigor) with a 5% (by weight) of a 2.2% solution of food-grade calcium chloride. Following injection, cuts are vacuum packaged and refrigerated for seven days prior to storage. The beauty of this process is that in addition to a 30% to 40% increase in tenderness, a "built-in" control system exists, so meat is never over-tenderized as it is with other proteinases such as papain.
In a recently published research project entitled "Beef Customer Satisfaction" (Reagan et al., 1995), it was discovered that 58% of American consumers are now cooking beef steaks to a degree of doneness of medium-well or greater. Of course food safety concerns regarding E. coli 0157:H7 in ground beef have probably encouraged consumers to prepare all meat items to higher degrees of doneness. Certainly, in most cases, as degree of doneness increases, meat palatability (i.e., tenderness) decreases in a linear fashion. Wulf and co-workers (1996) demonstrated that as strip and round steak degree of doneness increased, the tenderness improvement associated with one CAT increased, or in other words, CAT lessened the toughening effects of heating (Figure 2, Wulf et al., 1996).
Figure 2. Effects of calcium-activated tenderization (CAT) and degree of doneness on shear force of cooked steaks
In my opinion, there are few, if any, barriers to commercial application of the CAT process for ensuring desirable meat tenderness regardless of the product source. Meanwhile, research groups seek a long-term solution to tenderness variation problems by looking for ways to produce tender meat consistently and to identify tough meat.
Palatability Assurance Critical Control Points (PACCP): All within the business sector business schools, training conferences and consultants are capitalizing on a new obsession with quality. Total Quality Management (TQM) is being adopted throughout the marketing chain of many products by major corporations in the food industry. While TQM has primarily focused on production, the new idea is to "integrate at each production interface." In other words, all production sectors in the beef industry cow/calf, stocker, feeder, packer, retailer, food service must identify their quality shortcomings and work as a team to increase the value of their product at each interface. This concept can be applied in the development of a "vertically cooperative" Palatability Assurance Critical Control Points (PACCP) system to monitor beef palatability (Figure 3).
Figure 3. Palatability Assurance Critical Control Points Production Scheme
Let's shift gears and remember back to the meat buyer from the West Coast supermarket chain and the refunds, lost sales and headaches he was facing on a daily basis; he finally became tired of this problem. After a thorough screening of the research materials, the meat buyer decided to incorporate beef which had been produced using the PACCP production system. Some of the Critical Control Points (CCP) which were incorporated and monitored into their system are listed below.
CCP 1: Breed Influence on Palatability. As mentioned previously, the beef carcasses utilized in their original system were harvested from southern-tier states where Bos indicus breeds/crosses are utilized in crossbreeding programs to counteract the heat/humidity associated with semitropical climates. With this in mind, the West Coast supermarket chain decided to utilize California calf-fed Holsteins in their PACCP-based production scheme.
CCP 2: Time on Feed. According to West Coast supermarket personnel, all of the calf-fed Holstein calves will be fed for at least 300 days.
CCP 3: Postmortem Aging Time. As mentioned above, postmortem aging is very important for the production of consistently tender beef production. Today's meat packing and transportation industries have become so efficient that much of the beef is not allowed to age to the extent that it did 10 years ago. For example, in 1991, when the National Beef Tenderness Survey was conducted, approximately one-quarter of the beef cuts sold in retail stores across the U.S. were aged for 7 days or less. Customers purchasing beef from this West Coast supermarket chain are guaranteed that all cuts have aged for at least 14 days.
Finally, what has the PACCP production scheme done for the West Coast supermarket chain? According to the head meat buyer, the following has been accomplished.
Refund Policy: The $286,000 of beef toughness-related refunds granted to unsatisfied customers in 1991 was reduced to less than $2,000 refunded during 1995. He concluded by stating, "Instead of always taking claims from angry customers, our meat market managers can now sell and market beef."
Meat Image: The "meat image" of their stores has improved dramatically. "If our meat image improves, the entire image of our operation also improves," said the meat buyer.
Positive Employee Feedback: "People working in our retail meat markets really enjoy working with the beef from the PACCP production system," stated the meat buyer. He concluded, "If they feel good about the product, they're going to be more loyal to their job."
Increased Sales: The bottom line to the success of this program has been that beef sales have increased by 7.5% (measured by the pounds of beef purchased/1,000 customers).
Boleman, SJ, SL Boleman, JW Savell, RK Miller, HR Cross, TL Wheeler, M Koohmaraie, SD Shackelford, MF Miller, RL West and DD Johnson. 1995. Consumer evaluation of beef of known tenderness level. J. Anim. Sci. Abstr. (In Press).
Crouse, JD, LV Cundiff, RM Koch, M Koohmaraie and SC Seideman. 1989. Comparison of Bos indicus and Bos taurus inheritance for carcass beef characteristics and palatability. J. Anim. Sci. 67:2661.
Koohmaraie, M. 1990. Inhibition of postmortem tenderization in bovine carcasses through infusion of zinc. J. Anim. Sci. 68:1476.
Koohmaraie, M. 1994. Muscle proteinases and meat aging. Meat Sci. 36:93.
Morgan, JB, JW Savell, DS Hale,
RK Miller, DB Griffin, HR Cross and SD
Shackelford. 1991. National beef tenderness survey. J. Anim. Sci. 69:3274.
National Cattlemen's Association. 1994. National Beef Tenderness Plan: "Staking A Claim." A Report from the National Beef Tenderness Task Force, National Cattlemen's Association, Englewood, CO.
Reagan, JO. 1995. National Beef Customer Satisfaction Study, A Report from the National Livestock & Meat Board, Chicago, IL.
Smith, GC. 1991. Improving the Consistency and Competitiveness of Beef: A Blueprint for Total Quality Management in the Fed-Beef Industry. The Final Report of the National Beef Quality Audit 1991, National Cattlemen's Association, Englewood, Colo.
Smith, GC. 1995. Improving the Consistency and Competitiveness of Beef: A Blueprint for Total Quality Management in the Fed-Beef Industry. The Final Report of the National Beef Quality Audit 1995, National Cattlemen's Association, Englewood, Colo.
Wheeler, TL, LV Cundiff, RM Koch and JD Crouse. 1996. Characterization of biological types of cattle (cycle IV): carcass traits and longissimus palatability. J. Anim. Sci. (In Press).
Wulf, DM, JD Tatum, RD Green, JB Morgan, BL Golden and GC Smith. 1996. Genetic influences on beef palatability in Charlois- and Limousin-sired steers and heifers. J. Anim. Sci. 74:2394.