Master of Science / Food Science Institute / Elizabeth Boyle / To evaluate the effect of extended post-harvest hanging time on pork sides and the microbial shelf-life of fabricated steaks, aerobic plate count (APC), Enterobacteriaceae (EB), yeast and mold populations, pH, and moisture content of pork sides hung for 21 days at 0±1°C was determined. After hanging, blade steaks fabricated from these sides were vacuum packaged, stored up to 35 days at 0±1°C, and evaluated for APC, EB, yeast and mold populations, and pH. Carcass cooler temperature and percent relative humidity, measured every hour during storage, averaged 0±1°C and 87.3% (66-100%), respectively. Pork carcass surface moisture content declined (P ≤ 0.05) from 65.1% on day 1 to 50.5% on day 21. The carcass pH was similar (P ≥ 0.05) at 5.88 on days 1, 7, and 14; however, by day 21 the pH declined (P ≤ 0.05) to 5.72. The flank, shoulder, and jowl were sampled on pork carcasses. There was no day effect for carcass APC; however, there was a location effect. The jowl had the highest (P ≤ 0.05) APC with 1.21 log CFU/cm². There was no carcass location or day effect for EB or mold populations, but there was a carcass location and day effect for yeast populations. The detection limit (DL) for EB and yeast and mold populations on pork carcass samples (n = 240) was 0.06 and 0.41 log CFU/cm² for the shoulder and flank, and jowl, respectively. For EB and mold populations, 98.8 and 97.9% of carcass samples, respectively, were below the DL. For yeast populations, 37.5, 45.0, and 63.8% were above the DL for flank, shoulder, and jowl, respectively. On days 1, 7, 14, and 21, 60.0, 55.0, 53.3 and 26.6% were above the DL, respectively, for carcass yeast populations; however, none were greater than 2.83 log CFU/cm². The pH of pork steaks was 5.69-5.89. There was a day effect for APC on pork steaks. The initial APC of steaks was 1.61 log CFU/g, increasing (P ≤ 0.05) to 5.06 log CFU/g on day 35. There was a day effect for EB and mold populations; but not for yeast populations. The DL for EB and yeast and mold populations on pork steaks (n = 102) was 0.70 log CFU/g. On days 0, 7, 14, 21, 28, and 35, the percent of EB populations above the DL on pork steaks were 0.0, 0.0, 23.5, 41.2, 94.1, 41.2%, respectively, however, none of the steak samples exceeded 4.40 log CFU/g. For mold populations, 100.0% of steaks were below the DL on days 0, 7, and 14. On days 21, 28, and 35, 18, 24, and 12%, respectively, were above the DL. None of the steak samples exceeded 2.68 log CFU/g for mold populations. For yeast populations, 56.8% of pork steaks samples were above the DL, but none were greater than 3.69 log CFU/g. These results indicate that pork carcasses and vacuum packaged shoulder blade steaks fabricated from these carcasses have acceptable quality for 21 and 35 days, respectively, when stored at 0±1°C after harvest.

Master of Science / Department of Animal Sciences and Industry / Travis G. O'Quinn / The objective of this study was to evaluate the impact of quality grade on beef eating quality of top sirloin steaks when cooked to multiple degrees of doneness (DOD). Beef top sirloin butts (N = 60; 15 / quality grade) were collected to equally represent 4 quality grades [Prime, Top Choice (modest00 – moderate100), Low Choice, and Select]. Top butts were cut into six consecutive steaks, and then divided laterally to get a total of twelve steaks per top butt. Steaks were assigned to one of three DOD: rare (60°C), medium (71°C), and well-done (77°C). Steaks within DOD were assigned to consumer sensory analysis, trained sensory analysis, fat and moisture analysis, and Warner-Bratzler shear force (WBSF). There were no interactions (P > 0.05) for all consumer ratings of palatability traits, indicating increases in DOD had the same impact across all quality grades. There was a difference (P > 0.05) within quality grade for consumer ratings of juiciness (P > 0.05). Prime steaks had greater (P < 0.05) juiciness ratings than all other quality grades, except for Top Choice. As DOD increased, consumer ratings and the percentage of steaks rated acceptable for each palatability trait decreased (P < 0.05; rare > medium > well-done). There was a quality grade × DOD interaction (P < 0.05) for trained sensory panel juiciness scores. When cooked to medium, Prime and Top Choice steaks were rated higher (P < 0.05) for juiciness than Low Choice and Select steaks. Similar to consumer ratings, trained panel ratings of tenderness decreased (P < 0.05) as DOD increased (rare > medium > well-done). Lastly, there were no quality grade by DOD interactions (P > 0.05) for Warner-Bratzler shear force. These results indicate that regardless of the DOD steaks were cooked to, quality grade had minimal impact on the palatability of beef top sirloin steaks. Therefore, unless cooked to a medium DOD, it is unnecessary for consumers, retailers, and foodservice to pay premium prices for higher quality top sirloin steaks, as the same eating experience will be given.

No description available.

High-pressure needleless injection (HPNI) is a process where small-diameter, high-velocity burst of liquid, penetrate foods at pressures ≤ 10,000 psi. The potential of HPNI as an enhancing technique for meat was studied. In study 1, HPNI translocated surface E. coli O157 into the interior of beef eye-of-round subprimals with an incidence of 40 (±7), 25 (±8), and 25 (±8)% for meat that had been surface-inoculated with a four-strain cocktail at 0.5, 1, and 2 log10 CFU/cm2, respectively. Run-off water contained 2, 2, and 3 log10 CFU/ml and was used for HPNI of additional subprimals, which resulted in a cross-contamination incidence of 83 (±4), 60 (±15), and 37 (±6) %, respectively. Incidence of translocation and cross-contamination was similar at all sampled levels below the inoculated surface. Study 1 results indicate that surface microflora will be translocated from the surface into the interior of HPNI-treated beef by the injection fluid and by cross-contamination with recycled fluid. In study 2, E. coli was undetected in cooked steaks (63˚C internal) cut from subprimals inoculated with 2 log10 CFU/cm2 and HPNI processed (study 1). Although cooking reduced E. coli counts, determination of complete kill was not possible because the detection limit for bacterial recovery was about 1 log10 CFU/g. Steaks cut from HPNI-processed subprimals took longer (p <0.05) to reach 63˚C with grilling or broiling, compared to control steaks, possibly due to increased moisture in enhanced steaks. In study 3, sensory acceptance of steaks was evaluated by a consumer panel. Appearance, flavor, and overall acceptance were similar among the untreated control, HPNI steaks, blade tenderized steaks (BT steaks), and steaks cut from subprimals that had been needle-injected with 0.35% (wt/vol) sodium tripolyphosphate using needle injection (NI-subprimal steaks) or HPNI (HPNI-subprimal steaks). Texture of BT steaks (6.5±1.9) was more liked than control steaks (5.8±1.8), while texture was similar for all other comparisons. Conversely, Warner-Bratzler shear force was NI-subprimal steaks < control < HPNI steaks = HPNI-subprimal steaks = BT steaks. Lack of correspondence between texture acceptance data and WBSF suggests that sensory scores were influenced by factors other than the force required for mechanical shear.