Technologies for Value Assessment of Beef
Duane M. Wulf, Ph.D.
South Dakota State University

INTRODUCTION

The value of any product is determined by a customer’s willingness to pay for that product, which is determined by that customer’s wants and needs. The value of beef is therefore ultimately determined according to beef customers’ desires. There are three basic beef carcass characteristics that affect carcass value. These are shown in Table 1.

PRODUCT SIZE

Product size is the easiest value-influencing beef carcass characteristic to assess. Product size can be determined by simply obtaining a hot carcass weight. Most packers have determined that carcasses weighing less than 550 pounds or greater than 950 pounds are of lower value because they don’t match customer wants and needs. Although 550 to 950 pounds represents a substantial range for U.S. beef producers to shoot for, certain markets, representing certain customers, may desire a smaller, more defined product size range.

PRODUCT CUTABILITY

"Cutability" is defined as the proportion of muscle to the proportion of fat and bone, or the percentage of closely-trimmed boneless retail cuts. Carcass cutability is a significant factor in determining carcass value because it affects the amount of product that can be sold at high prices versus the amount of fat and bone, that must be discarded or sold at much lower prices. Beef carcass cutability is predicted by USDA yield grades as shown in Table 2.

The current USDA yield grading system is quite accurate at predicting cutability if the yield grades are accurately assigned as shown in Table 3. Instrument grading to predict cutability has shown promise with two technologies, VIA and TOBEC. VIA stands for video image analysis and consists of a computer that analyzes images, or pictures, obtained from a video camera. TOBEC is an electromagnetic scanning instrument that measures electro-conductivity by passing a beef hindquarter through a cylinder surrounded by a coil that generates a magnetic field.

The problem with the current USDA yield grade system, if there is a problem, is that it is difficult for a human grader to accurately assign yield grades at industry chain speeds of 300 to 400 head per hour. Researchers from Texas Tech University recently reported USDA line graders stamp the correct yield grade on only 73.6% of beef carcasses (Kerth et al., 1999). In other words, one out of every four beef carcasses is mis-yield graded. A study conducted by Colorado State University and USDA personnel found that the line graders were fairly accurate at determining fat thickness (r² = .83), but were not at all accurate at determining rib eye area (r² = .23) (Belk et al., 1998). These researchers concluded that the assignment of USDA yield grades to beef carcasses would be more accurately accomplished if the line grader was provided with a rib eye area measurement. The determination of rib eye area could probably be accomplished by using video image analysis (VIA).

PRODUCT QUALITY (Appearance and Eating quality)

Beef is offered for sale to the consumer at generally higher prices than other protein sources. The relatively higher retail price of beef is mainly a result of inherent disadvantages in cattle production efficiency, such as longer gestation periods, lower prolificacy, and reduced feed conversion as compared to pigs and poultry. Although beef producers should strive to reduce production costs and retail beef prices, the industry must rely on superior quality to increase demand for its product because beef will, inevitably, always be priced higher than pork and poultry. According to the Beef Customer Satisfaction Study, consumers perceive beef to be better tasting than either chicken or pork (NLSMB, 1995). However, several studies have documented wide variation in the quality of beef currently produced in the United States (Morgan et al., 1991; Savell et al., 1991).

The United States Department of Agriculture (USDA) Grading Service attempts to sort through this diversity in the cattle population and assign carcasses into grades of expected eating quality. These USDA quality grades are based primarily on evaluations of carcass maturity and the amount of intramuscular fat (marbling) present in the longissimus muscle (USDA, 1989). Both of these factors, maturity and marbling, have been shown by numerous researchers to significantly impact beef palatability. Increased maturity has been associated with decreased palatability (Romans et al., 1965; Breidenstein et al., 1968; Prost et al., 1975; Smith et al., 1982; Smith et al., 1988). The largest study of maturity effects on palatability was conducted by Smith et al. (1982) and utilized beef from 1,005 carcasses of all maturity groups (A through E). Substantial decreases in palatability and tenderness were found with increased maturity. However, the vast majority of carcasses within the fed steer and heifer population are classified into the "A-maturity" group (Lorenzen et al., 1993), and Smith et al. (1982) found little association between maturity and palatability within the "A-maturity" group (r² = 0 for longissimus muscle, r² = .18 for semimembranosus). Furthermore, USDA grades are assigned independent of differences in carcass maturity within the "A-maturity" group (USDA, 1989). Therefore, we can assume that, for most of the fed steer and heifer population, maturity is a constant and marbling is the sole determinant of USDA quality grade.

The impact of marbling level on beef palatability has also been extensively examined (Blumer, 1963; Romans et al., 1965; McBee and Wiles, 1967; Smith et al., 1984; Savell et al., 1987). Similar to the research on beef maturity, the effects of marbling on palatability have been studied across the extreme range of marbling scores. Smith et al. (1984) utilized 1,005 carcasses with marbling scores from "practically devoid" to "moderately abundant" and found a moderate relationship between marbling and palatability (r² = .34 for longissimus muscle, r² = .07 for semimembranosus) within the "A-maturity" group. However, The National Beef Quality Audit (Smith et al., 1995) reported that 84% of all carcasses from the fed steer and heifer population had marbling scores of "small" or "slight". Smith et al. (1984) reported no significant differences between means for "small" and "slight" for all 14 palatability attributes examined. With the majority of the fed steer and heifer slaughter being in a narrow maturity range (A-maturity) and in a narrow marbling range (slight and small), the USDA quality grades do not effectively segregate these carcasses into uniform palatability groups. However, substantial palatability differences do exist within this narrow maturity:marbling window. Therefore, the beef industry must seek other methods of distinguishing carcasses with palatable beef from carcasses with unpalatable beef, and continue to strive towards improving palatability.

Two ready-to-use on-line methods of assessing the palatability of beef carcasses appear promising. For the purpose of this paper, these two methods will be referred to as: 1) the Tenderness Classification System and 2) the Colorimeter System.

The Tenderness Classification System was developed by USDA researchers at the U.S. Meat Animal Research Center (MARC) in Clay Center, Nebraska (Shackelford et al., 1997a). The shear force of cooked meat has long been used by researchers in the laboratory to assess meat tenderness. The Tenderness Classification System uses this shear force technology, but in an accelerated manner which therefore makes it adaptable to on-line use in a packing plant. In this system, a one-inch-thick rib steak is removed from each carcass and trimmed of all fat and bone. This steak is then cooked on a belt grill, which cooks both sides simultaneously, for a period of 7 minutes. Following cooking, a 0.4 inch by 2.0 inch slice is removed from the steak and the force required to shear this slice is measured on an electronic testing machine. The entire process, from cutting the steak to shearing the steak can be accomplished in 10 minutes. This system could be utilized at chain speeds of 400 head per hour (Goering, 1999). The Tenderness Classification System has been shown to explain 46 to 56% of the variation in aged beef tenderness (Shackelford et al., 1997b).

The Colorimeter System was first tested at Colorado State University (Wulf et al., 1997) and later at The Ohio State University (Wulf et al., 1998). Research to integrate color measurements to predict tenderness along with cutability prediction in a single VIA instrument is currently ongoing at Colorado State University (Goering, 1999). The Colorimeter System, as defined by the Ohio State research uses three factors to predict eating quality: marbling, hump height, and colorimeter readings. Hump height is a measure of the neck hump on beef carcasses and can be used to sort out those tenderness problems associated with Bos indicus (eared breeds) genetics. If those carcasses with humps of greater than 3.5 inches are excluded, eating quality can be improved. Colorimeter readings are very simple to measure. It requires only 3 seconds to obtain a colorimeter reading on the surface of the rib eye muscle. The one critical factor that must be taken into account is bloom time, because bloom time will dramatically affect muscle color. Carcasses with a darker shade of muscle color (not necessarily dark cutters) have been shown to have less tender beef than carcasses with a brighter muscle color. In the Ohio State research, marbling explained 12% of the variation in eating quality, hump height explained 8% of the variation in eating quality, and colorimeter readings explained 24% of the variation in eating quality. Putting these three factors together in a single grading system explained 39% of the variation in eating quality (Wulf et al., 1998).

Table 4 shows a comparison of systems at predicting eating quality. The Tenderness Classification System is the most accurate system and will probably always be the most accurate system because it is a direct measure of tenderness, whereas the other systems are indirect measures of tenderness and/or eating quality. However, the Tenderness Classification System is an evasive system (it uses one steak from each carcass) and is also quite expensive to operate in its present form. The other two system are not evasive and are both relatively simple to operate. Therefore, one must weigh accuracy versus expense when deciding which system to use.

As the beef industry moves towards a more consumer-oriented approach to decision making, beef producers must increase product quality and consistency. Currently, however, it is very difficult for beef producers to improve product eating quality because a rapid, accurate method of measuring palatability is not being used. How can we improve quality when we can’t measure it? The beef industry cannot hit a target that it can’t see. These new systems reviewed here may or may not be implemented into the USDA grading system. However, at a minimum, they hold much potential for a branded beef program to differentiate its products. And if used, these systems would allow a more true value assessment of beef.

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