Using Measurements of Muscle Color/pH/Water-Holding Capacity to
Augment the Current USDA Beef Carcass Quality Grading
Standards and Improve the Accuracy and Precision of Sorting Beef Carcasses into Palatability Groups: Executive Summary
Duane M. Wulf, Jennie K. Page, and Tracy R. Schwotzer

One way to increase profits for the U.S. beef industry and U.S. beef producers is to increase consumer demand for beef. If product quality and consistency is improved, it is likely that demand for that product at all pricing levels will increase. Currently, however, it is very difficult for beef producers to improve product eating quality because a rapid, inexpensive, accurate, non-destructive method of measuring palatability does not exist. How can we improve quality when we can’t measure it? The beef industry cannot hit a target that it can’t see. Therefore, this research was conducted to develop a system which could accurately sort beef carcasses with respect to palatability. Phase I of this project involved data collection on 1,000 carcasses in Texas, Illinois, and Ohio and was conducted to define the U.S. beef carcass population with regard to muscle color and muscle pH. Phase II involved the selection of 100 beef carcasses from Texas, Illinois, and Ohio to represent the full range of muscle color observed in Phase I. Steaks from these 100 carcasses were used to determine shear force (tenderness) on eight beef cuts and taste panel ratings (tenderness, juiciness, and flavor) on three beef cuts. It was discovered that the darkest colored 20 to 25% of the beef sampled was less palatable and considerably less consistent than the other 75 to 80% of the beef sampled. Marbling score, by itself, explained 12% of the variation in beef palatability; hump height, by itself, explained 8% of the variation in beef palatability; measures of muscle color or pH, by themselves, explained 21 to 24% of the variation in beef palatability. When combined together, marbling score, hump height, and some measure of muscle color or pH explained 36 to 42% of the variation in beef palatability. This compares favorably to the MARC Tenderness Classification System which explains 46 to 56% of the variation in beef tenderness (Shackelford et al., 1997). Alternative quality grading systems were then proposed to improve the accuracy and precision of sorting carcasses into palatability groups. The two alternative grading proposed resulted in the palatability improvements shown below:

These grading systems, which included requirements for maturity, marbling, hump height, and colorimeter readings resulted in substantial decreases in palatability inconsistency and substantial decreases in the number of unpalatable carcasses as compared to our current USDA quality grading system. Colorimeter readings, while not highly effective at distinguishing those carcasses with exceptional palatability, appear to be effective at sorting out a group of carcasses which are quite undesirable in palatability. This relationship between dark colored muscle and unpalatable beef was the strongest within the Select grade. Therefore, the greatest palatability improvements could be made within USDA Select by using a colorimeter specification. The beef industry could implement one of these proposed systems into the current USDA beef quality grading standards and improve the accuracy and precision of sorting beef carcasses into palatability groups. At the least, measurements of muscle color or pH could be used in a branded-beef program to increase the palatability consistency of its beef products.