The effect of vitamin E supplementation on discoloration of injection-site lesions in retail cuts and the greening reaction observed in injection-site lesions in muscles of the chuck

Concern has been raised about green discoloration of injection-site lesions in chuck muscles in modified-atmosphere packages. Objectives were: 1) to recreate green lesions, 2) to compare the severity of discoloration of injection-site lesions in chucks from carcasses of control or vitamin E-supplemented steers, and 3) to identify pigment(s) responsible for discoloration via in vitro color reactions. In Exp. 1, 23 steers (BW = 415 kg; 37 d before harvest) were injected with one of 12 pharmaceuticals, following label directions for route and dose, with the exception of a 5-mL maximum dose, to identify a product that could result in discoloration. Two vaccines (Products A and B) resulted in greening. In Exp. 2, 50 steers were injected (i.m.) with Product A and assigned to the control or vitamin E (1,000 IU/steer daily for 60 d) group. After retail display, 80 and 72% of steaks from the control and treatment groups, respectively, were discolored. Although vitamin E did not reduce (P = 0.53) greening, there was a trend (P = 0.10) toward delay discoloration of lesions from the treatment group. In Phase I of Exp. 3, pigments extracted from green lesions obtained from Exp. 2 were compared with solutions, exposed to a high partial pressure of oxygen (ppO), of myoglobin (Mb), copper sulfate, hydrogen peroxide ([H.sub.2][O.sub.2]), vaccine, and aluminum hydroxide either alone or in combination. In Phase II of Exp. 3, solutions of two or more of Mb, Cu, sodium sulfide, sodium sulfite, sodium sulfate ([Na.sub.2]S[O.sub.4]), and [H.sub.2][O.sub.2] were made at pH 7.2 or 5.5 and exposed to low or high ppO. Normal muscle tissue displayed a 3.2 and 56.7% decrease in absorbance/[micro]g of protein as wavelength changed from 654 to 656 nm and 656 to 658 nm, respectively. Pigments from control and treatment group green tissue displayed a 164.5 and 621.3% increase, respectively, in absorbance/[micro]g of protein as wavelength changed from 654 to 656 nm. As wavelength changed from 656 to 658 nm, the absorbance/ [micro]g of protein for control and treatment group lesions decreased by 75 and 109%, respectively. The Mb+Cu+[Na.sub.2]S[O.sub.4] solution, at pH 5.5 and high ppO, exhibited similar absorbance trends as green lesions indicating that greening may result from a Mb, Cu, and [Na.sub.2]S[O.sub.4] interaction. Results indicated that greening varies with pharmaceuticals and oxidation of tissue cannot be controlled with vitamin E supplementation. Research on the causative agents of green discoloration, with an emphasis on compounds containing sulfate or Cu, is needed. Key Words: Discoloration, Intramuscular Injection, Muscle Tissue, Subcutaneous Injection, Vitamin E