Injection-site lesions in beef muscles and study of the chemistry responsible for green discoloration

Abstract

Numerous factors affect consumer acceptability of meat products sold via retail outlets. These factors include product quality, color, and packaging systems. Quality defects, such as injection-site lesions, have a negative impact on consumer acceptability. The desirability of the color of muscle can be assured or improved by presence/concentration of antioxidants (such as α-tocopherol) and by the packaging system in which retail products are displayed.

Damaged beef muscle tissue resulting from intramuscular injections of animal-health products represents a “quality control” problem and an economic loss to the beef industry. Audits were conducted in 1998, 1999, and 2000 on 3,190 rounds from cow carcasses in seven different states. Outside round muscles were cut into 1.25-cm slices to identify and characterize lesions. In 1998, 31% and 60% of rounds from carcasses of beef cattle and dairy cattle, respectively, had an injection-site lesion. Frequency of lesions in rounds from carcasses of beef cattle declined 5 percentage points (P < 0.05) between 1998 and 1999, and 6 percentage points (P < 0.05) between 1999 and 2000. Frequency of lesions in rounds from carcasses of dairy cattle declined 9 percentage points (P < 0.05) between 1998 and 1999, and 16 percentage points {P < 0.05) between 1999 and 2000. Frequencies of injection-site lesions in muscles of rounds from carcasses o f beef cattle were significantly lower than those in muscles of rounds from carcasses of dairy cattle in all three years. Injection-site lesions were most common between the hooks and pins of the hindquarter of beef cattle, and between the pins and hocks of the hindquarter of dairy cattle. Clear lesions and woody calluses exceeded 89%, and occurred more frequently than did other kinds of lesions in muscles of rounds from carcasses of beef and dairy cattle in 1998, 1999, and 2000. Of all injection-site lesions, between 3% and 5% were cystic in muscles of rounds from beef carcasses, and between 2% to 4% were cystic in muscles of rounds from dairy carcasses.

Fifteen individual and sequential national audits of injection-site lesions in fed beef top sirloin butts have been conducted at the steak provisioner/cutting level between November 1995 and July 2000. The national incidence of injection-site lesions in top sirloin butts (n = 240,080) decreased (P < 0.05) between November 1995 (11.4%) and July 2000 (2.1%). From November 1995 to July 1997, mean weight per injection-site lesion, across all lesion classes, increased (P < 0.05) from 192.5 g to 435.8 g, respectively; mean weight per lesion subsequently decreased (P < 0.05) to 249.8 g in July 2000, but was still heavier (P < 0.05) than in November 1995.

During the 2000 National Beef Quality Audit, concern was raised by one of the major packers relative to a ‘greening’ of injection-site lesions located in muscles of chuck steaks and/or roasts packaged in a high-oxygen environment. Supplementation o f vitamin E has been shown to enhance retail caselife by maintaining bright, cherry-red color of muscles. Fifty steers were vaccinated with Conquest 5K and were allocated to one of two groups; control or vitamin E supplementation for 60 days. Following boxed storage and retail display, 80% of control steaks and 96% of vitamin E steaks had a green injection-site lesion present. Of those steaks that exhibited greening, 39.5% of the steaks did not have a visible lesion at the time of packaging. Color attributes; L*, a*, and b*; o f muscle tissue did not differ between control and vitamin E steaks prior to packaging or after retail display, nor were there difference in L*, a* or b* in injection-site lesions after retail display. Thiobarbituric acid values were greater (P < 0.05) in control steaks at the site of the green injection-site lesion and at a point 6 cm away from the injection-site lesion. Histological evaluation verified the presence of injection-site lesions; the tissue contained fibrous connective tissue/scarring, sheet of macrophages, lymphoid follicles, atrophied muscle fibers, fat cells, and adjuvant. Although results suggested that vitamin E supplementation may delay onset of the chemical reaction causing greening o f injection-site lesions when packaged in high oxygen modified atmosphere, and may reduce the degree of oxidative rancidity formation, supplementation does not have the potential to eliminate the ‘greening’ reaction.

Combinations of myoglobin (Mb), copper sulfate (CuS04), hydrogen peroxide (H2O2), vaccine, and aluminum hydroxide were made and subjected to high partial pressures of oxygen. In phase II, combinations of Mb, copper (Cu), sodium sulfide (NaS), sodium sulfite (NaSO3), sodium sulfate (NaSO4), and H2O2 were made at pH 7.2 or 5.5 and subjected to either low or high partial pressures of oxygen. All combinations and extracted lesions were evaluated using spectrophotometry. The pigments from the green lesions from control and Vitamin E supplemented cattle displayed, on average, a 164.5 and 621.3 percent increase at 656 nm as compared to 654 nm, respectively. The absorbance for the lesions from control and supplemented cattle declined 75 and 109 percent, respectively, from 656 to 658 nm. These changes in absorbance matched the changes in absorbance observed in the sulfmyoglobin and hydroperoxymetmyoglobin pigments made in phase I. Based on the results from phase I, it was concluded that the green color could be a result of CuSO4 or H2O2. Combinations, in phase II, which exhibited a positive percent change from 654 to 656 nm and a negative percent change from 656 to 658 nm were Mb+NaSO4, Mb+Cu+H2O2, Mb+SO3, Mb+Cu+NaS, and Mb+Cu+NaSO3, all at pH 7.2 under low partial pressures of oxygen; Mb+NaS04, Mb+NaS, and M b+NaS03, all at pH 7.2 under high partial pressures of oxygen; and Mb+Cu+NaSO4 at pH 5.5 under high partial pressures of oxygen. Results indicated that the ‘greening’ reaction observed in injection-site lesions of the chucks was a result of the reaction between myoglobin and sulfur, and, as such, suggest that there is an increase o f sulfur at the site of the injection-site lesion.