Effects of simulated dry and wet chilling and aging of beef fat and lean tissues on the reduction of Escherichia coli O157:H7 and Salmonella.

The efficacy of dry and wet chilling and aging of beef as methods for the reduction of Escherichia coli O157:H7 and Salmonella on lean and fat tissues was studied. Samples were obtained from a harvest facility prior to antimicrobial interventions and were inoculated with a cocktail mixture of E. coli O157:H7 or Salmonella to achieve a target inoculation of 6 log CFU/cm(2). Wet chilled and aged samples were then suspended, sprayed (10 °C) continuously for 15 min and then sprayed for 1 min every 17 min for 17 h, and vacuum packed after 48 h. Dry chilled and aged samples were suspended in refrigeration (3 °C) with an air velocity of 0.25 m/s and a relative humidity of 80%. A large initial reduction of E. coli O157:H7 and Salmonella was observed, regardless of tissue type and chilling method. Fewer E. coli O157:H7 microorganisms were detected on wet chilled samples at 24 and 36 h; however, plate counts were higher from wet aged samples excised at 7 through 28 days. The final plate counts were 1.03 and 3.67 log CFU/cm(2) for dry and wet aged samples, respectively. Fewer E. coli O157:H7 microorganisms were detected on fat samples from each sampling time, with the exception of 28 days, compared with lean samples. Similar trends were observed in the reduction of Salmonella for chilling or aging method and tissue type, resulting in final plate counts of 1.25 and 3.67 log CFU/cm(2) for dry and wet aged samples, respectively. The findings reaffirmed wet or dry chilling and aging as potential interventions for small plants as a critical control point.

Effects of zilpaterol hydrochloride with or without an estrogen-trenbolone acetate terminal implant on carcass traits, retail cutout, tenderness, and muscle fiber diameter in finishing steers.

Our objective was to determine the effects of feeding zilpaterol hydrochloride (ZH), a beta-agonist, for the final 30 d of the feeding period, with or without a terminal estrogen + trenbolone acetate (TBA) implant (Revalor-S; 24 mg of estradiol-17beta and 120 mg of TBA; REV) on meat tenderness and carcass cutout yields. Crossbred steers (n = 2,279) were divided into 6 BW blocks and 24 pens. Within each block, pens were assigned randomly to 1 of 4 treatments: 1) no terminal implant (control); 2) a terminal REV given 91 d before slaughter; 3) no terminal implant plus ZH; and 4) a terminal REV implant plus ZH (REV+ZH). All cattle received Component TE-IS (16 mg of estradiol and 80 mg of TBA) on d - 61 of the feeding period [corrected]. Zilpaterol hydrochloride was added to the diets at a concentration of 8.38 mg/kg (DM basis) during the final 30 d of the feeding period, followed by a 3-d period before slaughter in which ZH was withdrawn from the diet. Carcasses (n = 30/treatment) were selected from the 2,279 cattle and fabricated into subprimal cuts as per Institutional Meat Purchase Specifications. Strip loins were collected, cut into 2.54-cm steaks, and aged 7, 14, and 21 d, after which Warner-Bratzler shear force (WBSF), collagen content, desmin degradation, and muscle fiber diameter measurements were determined. Feeding ZH increased (P < 0.05) yield of the #112A ribeye roll, #116B chuck mock tender, #167A peeled knuckle, #169 top inside round, #171B outside round, #171C eye of round, #180 strip loin, #184 top sirloin butt, and #189A full tenderloin for ZH treatment. Longissimus muscle WBSF at 7, 14, and 21 d postmortem was increased (P < 0.001) with ZH supplementation. Desmin degradation at 7, 14, and 21 d postmortem was not affected with REV or ZH supplementation compared with controls. Zilpaterol hydrochloride had an additive effect with REV on increasing LM fiber diameter (P < 0.001). When fed to cattle that received a terminal implant of REV, ZH potentially increased LM WBSF as a result of induced muscle hypertrophy. During the 21-d aging period, WBSF decreased with aging, suggesting that carcasses from cattle supplemented with ZH might require longer aging time to ensure that acceptable levels of tenderness are reached.

Spoilage and safety characteristics of ground beef packaged in traditional and modified atmosphere packages.

Two separate studies, one with pathogen-inoculated product and one with noninoculated product, were conducted to determine the safety and spoilage characteristics of modified atmosphere packaging (MAP) and traditional packaging of ground beef patties. Ground beef patties were allotted to five packaging treatments (i) control (foam tray with film overwrap; traditional), (ii) high-oxygen MAP (80% 02, 20% CO2), (iii) high-oxygen MAP with added rosemary extract, (iv) low-oxygen carbon monoxide MAP (0.4% CO, 30% CO2, 69.6% N2), and (v) low-oxygen carbon monoxide MAP with added rosemary extract. Beef patties were evaluated for changes over time (0, 1, 3, 5, 7, 14, and 21 days) during lighted display. Results indicated low-oxygen carbon monoxide gas flush had a stabilizing effect on meat color after the formation of carboxymyoglobin and was effective for preventing the development of surface discoloration. Consumers indicated that beef patties packaged in atmospheres containing carbon monoxide were more likely to smell fresh at 7, 14, and 21 days of display, but the majority would probably not consume these products after 14 days of display because of their odor. MAP suppressed the growth of psychrophilic aerobic bacteria when compared with control packages. Generally, control packages had significantly higher total aerobic bacteria and Lactobacillus counts than did modified atmosphere packages. In the inoculated ground beef (approximately 10(5) CFU/g) in MAP, Escherichia coli O157 populations ranged from 4.51 to 4.73 log CFU/g with no differences among the various packages, but the total E. coli O157:H7 in the ground beef in the control packages was significantly higher at 5.61 log CFU/g after 21 days of storage. On days 14 and 21, the total Salmonella in the ground beef in control packages was at 5.29 and 5.27 log CFU/g, respectively, which was significantly higher than counts in the modified atmosphere packages (3.99 to 4.31 log CFU/g on day 14 and 3.76 to 4.02 log CFU/g on day 21). Data from these studies indicate that MAP suppresses pathogen growth compared with controls and that spoilage characteristics developed in MAP packages.

Effects of supplemental manganese on performance of growing-finishing pigs and pork quality during retail display.

Crossbred barrows and gilts (n = 168) were used to test the effects of supplemental Mn during the growing-finishing period on performance, pork carcass characteristics, and pork quality during 7 d of retail display. Pigs were blocked by BW and allotted within blocks to pens (5 pigs/pen in blocks 1, 2, 5, and 6, and 4 pigs/pen in blocks 3 and 4). A total of 36 pens was randomly assigned to 1 of 6 dietary treatments, where the basal diets were formulated with (PC) or without (NC) Mn in the mineral premix, and supplemented with 0 or 350 ppm (as-fed basis) of Mn from MnSO4 or a Mn-AA complex (AvMn). Pigs were slaughtered at a commercial pork packing plant when the lightest block of pigs averaged 113.6 kg. During fabrication, boneless pork loins were collected and transported to Oklahoma State University, where 2.5-cm-thick LM chops were packaged in a modified atmosphere (80% O2 and 20% CO2) and subsequently placed in display cases (2 to 4 degrees C) under continuous fluorescent lighting (1,600 lx) for 7 d. Pig performance was not (P > or = 0.44) affected by supplemental Mn; however, during the grower-II phase, pigs fed the basal diets including Mn consumed less (P < 0.02) feed and tended to be more efficient (P < 0.09) than pigs fed the basal diets devoid of Mn. Throughout the entire feeding trial, neither dietary nor supplemental Mn altered (P > or = 0.22) ADG, ADFI, or G:F. Chops from pigs fed the diets supplemented with MnSO4 received greater (P < or = 0.05) lean color scores and had a redder (greater a* and hue angle values), more vivid color than chops from pigs fed the diets supplemented with AvMn. Additionally, LM chops from pigs fed the PC diets supplemented with MnSO4 were darker (lower L* values; P < 0.05) than chops from pigs fed the NC diets or PC diets supplemented with 0 or 350 ppm of AvMn. Even though discoloration scores were similar during the first 4 d of display, chops from pigs fed the PC diets supplemented with MnSO4 were less (P < 0.05) discolored on d 6 and 7 of retail display than chops from pigs fed the PC or NC diets and diets supplemented with AvMn (dietary treatment x display time, P = 0.04). Results of this study indicate that feeding an additional 350 ppm of Mn from MnSO4 above the maintenance requirements of growing-finishing pigs does not beneficially affect live pig performance but may improve pork color and delay discoloration of pork during retail display.

Influence of ceftiofur sodium biobullet administration on tenderness and tissue damage in beef round muscle.

The effect of a biobullet (BB) containing freeze-dried ceftiofur sodium antibiotic on the presence of injection lesions, tissue damage, and histological properties, as well as Warner-Bratzler shear force (WBSF), of the biceps femoris was investigated. Steer calves (n = 25) were individually identified and assigned randomly to a product administration treatment date (7, 14, 21, 28, or 35 d before slaughter). At each pre-slaughter ceftiofur BB administration time, identified steers (n = 5) were humanely placed into a standard commercial restraining chute, where a BB implant was administered from a distance of 6.09 m. Following a standard finishing period (120 d), steers were transported to a commercial beef processing and humanely slaughtered. Following a 36-h postmortem chilling (1 degree C) period, carcasses were graded and fabricated according to industry-accepted procedures. Paired muscle samples were individually identified, collected, and aged for 14 d postmortem. Muscles were dissected into 1.27-cm strips, followed by observation and palpation for the presence of injection site lesions. Preslaughter administration times of 7 and 14 d resulted in the presence of injection lesions (80 and 20%, respectively). In addition to the control samples, no muscle damage was observed in cattle treated with BB implants 21, 28, or 35 d before slaughter. Warner-Bratzler shear force measurements taken near lesions of BB steaks and in areas 5.08 cm from lesions of control steaks tended to be higher (P < 0.10) than for other BB and control sample locations. Concentrations of insoluble and soluble collagen were higher (P < 0.05) at the site of the lesion center in lesion-afflicted vs. with control steaks. Histological determinations of the relative proportions of muscle, connective tissue, and fat were altered (P < 0.05) in BB lesion-afflicted steak cores; however, these differences were negated outside the core location of BB-treated and control steaks. It seems that using the ceftiofur BB implant system within 14 d of slaughter does create injection site lesions and increase WBSF; however, when the BB implant system, containing 100 mg of freeze-dried ceftiofur sodium, was used according to the recommended procedure (> or = 30 d preslaughter), tissue damage, alterations in histological and collagen properties, and increased meat toughness were not observed.