Effects of long spray-chilling on water pocket development in ribeyes.

Water Pocket (WP) is a defect on beef that may lead to significant economic losses. Our hypothesis is that longer spray-chilling time increases WP incidence on ribeyes (M. longissimus thoracis). Ribeyes (28,801) were visually evaluated for the presence of WP after 24 or 72h of spray chilling. Additionally, 252 beef sides were evaluated prior to chilling to predict WP development after 24h of spray chilling. Also, the 12th rib fat thickness was measured on 313 sides and the sides were assigned to two categories of WP or no WP to evaluate fat thickness as an indicator for WP. Subcutaneous fat softness is not related to WP development, longer spray-chilling does not increase the incidence of WP in ribeyes, and thinner subcutaneous fat is an indicator for WP development.

Light microscopy and image analysis of thin filament lengths utilizing dual probes on beef, chicken, and rabbit myofibrils.

Image analysis procedures for immunofluorescence microscopy were developed to measure muscle thin filament lengths of beef, rabbit, and chicken myofibrils. Strips of beef cutaneous trunci, rectus abdominis, psoas, and masseter; chicken pectoralis; and rabbit psoas muscles were excised 5 to 30 min postmortem. Fluorescein phalloidin and rhodamine myosin subfragment-1 (S1) were used to probe the myofibril structure. Digital images were recorded with a cooled charge-coupled device controlled with IPLab Spectrum software (Signal Analytics Corp.) on a Macintosh operating system. The camera was attached to an inverted microscope, using both the phase-contrast and fluorescence illumination modes. Unfixed myofibrils incubated with fluorescein phalloidin showed fluorescence primarily at the Z-line and the tips of the thin filaments in the overlap region. Images were processed using IPLab and the National Institutes of Health's Image software. A region of interest was selected and scaled by a factor of 18.18, which enlarged the image from 11 pixels/microm to approximately 200 pixels/microm. An X-Y plot was exported to Spectrum 1.1 (Academic Software Development Group), where the signal was processed with a second derivative routine, so a cursor function could be used to measure length. Fixation before phalloidin incubation resulted in greatest intensity at the Z lines but a more-uniform staining over the remainder of the thin filament zone. High-resolution image capture and processing showed that thin filament lengths were significantly different (P < 0.01) among beef, rabbit, and chicken, with lengths of 1.28 to 1.32 microm, 1.16 microm, and 1.05 microm, respectively. Measurements using the S1 signal confirmed the phalloidin results. Fluorescent probes may be useful to study sarcomere structure and help explain species and muscle differences in meat texture.

Nulliparous versus primiparous crossbred females for beef.

Feedlot and carcass traits of nulliparous and primiparous females representing eight breed types, including Bos taurus and Bos indicus x Bos taurus crosses, were evaluated. Nulliparous females (heifers) were in the feedlot for 4 mo; primiparous females (heiferettes) were fed for 2 1/3 mo after their calves were weaned at 6 mo of age. Heifers averaged higher (P less than .01) in dressing percentage, percentage of kidney fat, carcass grade (P less than .10), and color of lean (P less than .05) compared with heiferettes. Heiferettes exceeded the nulliparous group in feedlot ADG (P less than .01), fat thickness (P less than .05), and percentage of steak, roast, and bone (P less than .01). Parity effects on carcass weight, longissimus area, marbling, pH, and shear force value were not statistically significant. Dam breed types differed in several traits, including marbling (P less than .05) and percentage of steak (P less than .10), roast (P less than .01), and bone (P less than .01). Dam breed x parity interactions were nonsignificant. Results show that beef derived from heiferettes is competitive with heifer beef.

Growth traits and composition of two- and three-way-cross intact male progeny of Bos taurus and Bos indicus X Bos taurus dams.

Feedlot traits, carcass traits and distribution of commercial cuts of crossbred intact male progeny (n = 556) from young and mature Hereford, Red Poll, Hereford X Red Poll, Red Poll X Hereford, Angus X Hereford, Angus X Charolais, Brahman X Hereford and Brahman X Angus dams were evaluated. First-calf heifers were bred to Red Angus bulls; Santa Gertrudis sires were used for each cow's second and third breeding seasons. Calves from these young dams were slaughtered at 13 mo. Calves of mature dams were all sired by Limousin bulls and slaughtered at 12 mo. Dam breed was a major source of variation in most bull traits. Progeny of Brahman-cross dams were inferior (P less than .01) in daily gain, final weight, carcass weight and in edible cuts/day of age compared with progeny from Bos taurus dams. Intact male progeny of Angus X Charolais dams ranked highest in longissimus area, cutability, and edible cuts/day of age. The range of dam breed means in percentage of steak, roast, bone-in cuts (chuck short ribs and back ribs), short plate and thin cuts, and lean trim was just over 1%. Greater variation among dam breeds existed in fat measurements. Analyses in which Hereford-Red Poll diallel data for young dams and mature dams were combined showed positive maternal heterosis for dressing percentage (P less than .05), carcass weight (P less than .05), carcass weight/day of age (P less than .05), estimated carcass fat (P less than .05), fat thickness (P less than .01) and marbling score (P less than .01). Reciprocal effects were inconsequential. Results illustrate the importance of dam breed-type effects in formulating breeding strategies for commercial beef herds.

Quadratic relationship between early-post-mortem glycolytic rate and beef tenderness.

Post-mortem (PM) glycolytic rate in beef M. longissimus thoracis et lumborum (LTL) was controlled by applying low-voltage electrical stimulation (ES) for 1 min at different stages along the slaughter line. The ES treatments were as follows: (1) No electrical stimulation (NES); (2) 75 V to one side of the carcass immediately after splitting; (3) 20-40 V during exsanguination; (4) 75 V either during or following exsanguination. The study utilized 40 bulls and 40 steers. Loin steaks were aged in vacuum pouches 2, 4, 8 and 16 days PM. Quadratic equations utilizing pH at 3 h (pH(3)) gave the best estimate of Warner-Bratzler (WB) shear force for 2, 4, 8 and 16 day steaks. The rate of glycolysis is the primary determinant of LTL tenderness in this study. Temperature may only be important through its influence on early PM glycolytic rate. Optimum tenderness was produced by stimulating carcasses or sides to produce a pH(3) of 6·0. ES application to the carcass either just before or after splitting (treatment 2) produced more desirable and consistent pH(3) responses than either NES or ES during exsanguination. Aging has a differential effect whereby the WB shear values from tougher (leaner bulls) 2 day steaks improve to a greater degree, so they are not different from more tender (fatter steers) steaks by 16 day PM.

Effects of early-postmortem glycolytic rate on beef tenderness.

Electrical stimulation (ES) was applied at 500 V to one side from each of 60 beef carcasses at 30 to 40 min postmortem. Wide ranges of early-postmortem glycolytic and cooling rates were produced in the musculature by use of three different forms of ES (in addition to non-ES treatment of the contralateral sides) and application of chilling routines of four different degrees of severity. Panel and Warner-Bratzler shear evaluations of loin steaks from all 120 sides showed that tenderness was highest when glycolysis had proceeded at an intermediate rate (corresponding to the attainment of a 3-h pH of about 6·1) and was appreciably lower on both sides of this mid-value. The toughening effect of rapid glycolysis (relative to that of a moderately increased glycolytic rate) persisted through 14 days of aging at 2°C. These observations appear to be incompatible with the view that lysosomal enzymes contribute significantly to ES-induced tenderization. They also indicate that the effect of ES on tenderness is highly dependent on the subsequent cooling rate, very slow chilling sometimes accelerating the already high rate of pH fall to such an extent that the tissue is significantly toughened. Finally, they suggest that the goal of maximizing the early-postmortem rate of pH decline in bovine muscle is misguided and, if attained, will cause sub-optimal tenderness.

Effect of sampling fat location and cooking on fatty acid composition of beef steaks.

To investigate the impact of sampling fat location and cooking on fatty acid composition of beef steaks, 21 raw steaks from crossbred steers were dissected to obtain outer (OSC) and inner subcutaneous fat (ISC), seam fat, marbling, and lean muscle. Twenty-one cooked steaks were dissected to obtain OSC, ISC, seam fat, surface and inner muscle. Trans-vaccenic acid and c9, t11-CLA percentages were lower (P<0.05) in lean muscle than subcutaneous (s.c.) fat or marbling. Monounsaturated: saturated fatty acid ratios were lower (P<0.05) in seam fat and marbling than s.c. fat or lean muscle. Linoleic and linolenic acid levels were highest in lean muscle and longer chain n-6 and n-3 fatty acids were only detected in lean muscle. Cooking did not change fatty acid composition dramatically except that n-6: n-3 ratio in s.c. and seam fat decreased after cooking (P<0.05).

The influence of forage diets and aging on beef palatability.

To investigate the influence of diet and aging on beef palatability, lipid oxidative stability, and fatty acid composition, crossbred steers were assigned to Feedlot S (alfalfa and grain), Forage TR (triticale and annual ryegrass), Forage TK (triticale and kale), or Forage+Feedlot (grazing ryegrass, fescue and orchardgrass, finished on alfalfa and grain) dietary treatments. Heifers were finished on Feedlot H (alfalfa and grain). Longissimus and tricep muscles were sampled from these animals for steaks and ground beef, respectively. Steaks were either dry- or wet-aged for 14 d. Ground beef was dry-aged, wet-aged for 14 d, or not aged. Trained sensory panelists evaluated palatability attributes of steaks and ground beef. Diet did not influence sensory attributes of steaks or ground beef. Aging impacted (P<0.05) sensory attributes of ground beef. Diet and aging had no impact on lipid oxidative stability but affected fatty acid composition of raw ground beef.