Master of Science / Department of Animal Sciences and Industry / Michael E. Dikeman / Objectives were to determine the effects of needle-free (NF) versus needle (N) injection methods and/or solutions for enhancement of beef longissimus lumborum muscle (LM) on color, instrumental tenderness, sensory attributes, pump yields, and cooking losses. In experiment 1, LM (n=15) at 9 d postmortem were halved before random assignment to N or NF injection enhancement with a solution containing 2.2% salt, 4.4% sodium tripolyphosphate (STPP), and 1.5% K lactate. Different steaks from each loin half were either placed on a 5 d color display, frozen for later sensory analysis, or aged until d 13 postmortem for LM slice shear force measurements. Pump yields tended (P=0.08) to be higher for NF injection. Needle injected steaks were darker (P<0.05) on day 1, but not after that. Discoloration was not different (P>0.05) between treatments. The NF treatment had greater (P<0.05) instrumental tenderness and intensity of off-flavors but less (P<0.05) cooking loss and beef flavor. In Experiment 2, LM (n=28) at 5 d postmortem were halved before random assignment to one of four treatments: 1) N, or 2) NF injection with a solution containing 2.2% salt, 4.4% STPP, 15% K lactate, and 0.58% rosemary; 3) N, or 4) NF injection with a solution containing 2.4% Ca lactate and 0.58% rosemary. Steaks from each loin half were either frozen for later sensory analysis or aged until d 14 postmortem for LM slice shear force measurements. Loins phosphate enhanced with the NF injector had the highest (P<0.05) pumped yields with no differences (P>0.05) among other treatment combinations. Instrumental tenderness was not different (P>0.05) between N and NF treatments but was higher with the phosphate solution than the Ca lactate solution. The NF treatment had lower (P<0.05) cooking losses when the phosphate solution was used, which resulted in less (P<0.05) cooking loss than the Ca lactate solution. More (P<0.05) off-flavors and abnormal texture resulted from NF injection. The phosphate solution resulted in greater (P<0.05) myofibrillar and overall tenderness, juiciness, off-flavors and abnormal texture with less (P<0.05) connective tissue than the Ca lactate solution. Enhancing beef LM with a phosphate solution and NF injection might improve yields, tenderness, and juiciness while harming texture and flavor.

Doctor of Philosophy / Department of Animal Sciences and Industry / Michael E. Dikeman / The objectives were to determine the effects of packaging and injection-enhancement on beef sensory attributes, postmortem proteolysis, and color. Muscles from USDA Select, A-maturity carcasses were fabricated into 2.54-cm steaks on d 7 postmortem. In Experiment 1, longissimus lumborum (n=14 pairs) muscles were used. Packaging treatments were: vacuum packaging (VP); 80% O2/20% CO2 (HiO2); 0.4% CO/35% CO2/64.6%N2 (ULO2CO); 0.4% CO/99.6% CO2; 0.4% CO/99.6% N2; or 0.4% CO/99.6% Ar. In Experiment 2, longissimus lumborum (n=12 pairs); semitendinosus (n=12 pairs); and triceps brachii (n=24 pairs) muscles from one carcass side were injection-enhanced or non-enhanced. Steaks were packaged into VP, HiO2, or ULO2CO MAP. Steaks packaged in HiO2 MAP were in dark storage (2°C) for 4 d and all other steaks for 14 d. Steaks were displayed under fluorescent lighting for 7 d. Trained color panelists assigned color scores. Steaks for tenderness, cooked color, and sensory were cooked to 70°C. Steaks packaged in VP or ULO2 with CO MAP had little or no discoloration. Steaks packaged in HiO2 MAP discolored faster (P < 0.05) and more (P < 0.05) than steaks in other packaging treatments. Steaks packaged in HiO2 MAP were less tender (P < 0.05) than other treatments at the end of display, but had 10 d less aging due to shorter dark storage. Steaks packaged in HiO2 had the lowest (P < 0.05) a* values for internal cooked color of all treatments and exhibited premature browning. Enhanced steaks were more tender (P < 0.05) than non-enhanced steaks. Sensory panelists found that non-enhanced steaks packaged in ULO2CO MAP or VP were more tender (P < 0.05), had more (P < 0.05) beef flavor, and had less (P < 0.05) off-flavors than steaks packaged in HiO2 MAP. Off-flavors for steaks packaged in HiO2 MAP often were described as oxidative and rancid. Enhanced steaks had more (P < 0.05) off-flavors than non-enhanced steaks. Postmortem proteolysis measured by desmin degradation was not affected (P > 0.05) by packaging. Steaks packaged in ULO2 plus CO MAP had superior color stability, tenderness, and sensory attributes compared to steaks in HiO2 MAP.