The objective of the current study was to evaluate the effects of aging on myoglobin chemistry of dark-cutting beef. Ten USDA Choice (mean pH = 5.6; normal pH beef) and 10 no-roll dark cutter (mean pH = 6.4) strip loins were obtained from a commercial packing plant within 3 d of harvest. Loins were cut into 4 sections, vacuum packaged, randomly assigned to 0-, 21-, 42-, and 62-d aging at 2°C in the dark. Following aging, loin sections were cut into 2.5-cm-thick steaks and were used to determine bloom development, oxygen consumption (OC), metmyoglobin reducing activity (MRA), and lipid oxidation. Surface color readings were measured using a HunterLab Miniscan XE Plus spectrophotometer. A significant muscle type × aging time interaction resulted for OC ( < 0.001). Normal pH steaks declined more ( < 0.001) in OC during aging than dark-cutting beef. On d 0, dark-cutting beef had a greater OC ( < 0.001) than normal pH beef. There was a significant muscle type × oxygenation time × aging period interaction for L* values, deoxymyoglobin (DeoxyMb), and oxymyoglobin (OxyMb). When dark-cutting sections were aged for 62 d, both 0 and 60 min bloom development L* values were greater ( < 0.0001) than 0 min dark-cutting sections aged for 21 or 42 d. At all aging periods, normal pH beef had greater OxyMb content and lower DeoxyMb ( < 0.0001) during bloom development than dark-cutting beef. An aging period × muscle type interaction was significant for % overall reflectance ( = 0.0017) and absorbance ( = 0.0038). Dark cutting and normal pH beef loin sections aged for 62 d had greater reflectance ( < 0.0001) than 21 d. On d 0, dark-cutting beef had greater ( < 0.0001) MRA than normal pH beef. There were no significant ( = 0.14) differences in MRA between 42 and 62 d between dark-cutting and normal pH beef. Dark cutting steaks had lower thiobarbituric acid reactive substances values ( < 0.0001) than normal pH steaks. The results indicate that characterizing the myoglobin chemistry during aging will help to design strategies to improve appearance of high pH beef.

In livestock science and meat science, muscle fiber characteristics have been evaluated based on a cross-sectional area (CSA) of muscle fiber. However, muscle fiber is not planar but cylindrical. Thus, muscle fiber volume and volume-based characteristics were evaluated in this study. In addition, their relationships to pork loin quality was assessed and compared with that of CSA-based muscle fiber characteristics. Muscle fiber type IIB was underestimated by CSA-based evaluations with 1.6 times in fiber size and 2.6 times in relative composition. The pennation angle, which ranged from 48.00° to 83.33°, determined the real CSA and total number of fibers (TNF) on the surface of a loin chop. Significant (P < 0.05) correlation coefficients were found: fiber volume (r = –0.37) and volume % (r = –0.37) of type IIX with loin length; volume % of type IIX with CIE L* (r = 0.40); volume % of types IIX (r = 0.39) and IIB (r = –0.39) with Warner-Bratzler shear force. Although those correlations to loin quality differed from those of CSA-based characteristics, the Z-scores did not show any significance between the 2 correlation coefficients, except for TNF. Therefore, the conventional methodology for muscle fiber characteristics can be used for evaluating the relationship to pork quality; however, the new methodology is more useful in estimating the characteristics of muscle fiber, which is elongated and cylindrical and to correct the underestimated fiber size and composition of type IIB.

The objective was to characterize the relationship between fresh loin quality with fresh belly or fresh and cured ham quality. Pigs raised in 8 barns representing 2 seasons [cold ( = 4,290) and hot ( = 3,394)] and 2 production focuses [lean ( = 3,627) and quality ( = 4,057)] were used. Carcass characteristics and other meat quality data were collected on 7,684 carcasses. All of the carcasses were evaluated for HCW, LM depth, tenth rib fat depth, leg (ham primal) weight, instrumental color on the gluteus medius and gluteus profundus of the ham face, and subjective loin quality. Instrumental loin color and ultimate pH (≥ 22 h postmortem) were collected on the ventral side of loins along with dimensions and firmness scores of fresh bellies from 50% of the carcasses. Ten percent of the boneless loins and fresh hams were evaluated for slice shear force (SSF) or cured ham characteristics. Correlation coefficients between traits were computed using the CORR procedure of SAS and considered significantly different from 0 at ≤ 0.05. Temperature decline, beginning at 31 min postmortem and concluding at 22 h postmortem, for the longissimus dorsi and semimembranosus muscles were evaluated on 10% of the carcasses. Ultimate loin pH was correlated with dimensional belly characteristics ( ≥ |0.07|; < 0.0001) fresh ham instrumental color ( ≥ |0.03|; ≤ 0.05), and semimembranosus ultimate pH ( = 0.33; < 0.0001). Further, ultimate loin pH was correlated ( ≤ 0.01) with pump retention ( = 0.087) and cooked yield ( = 0.156) of cured hams. Instrumental L*on the ventral surface of the loin was related to L* on both muscles of the ham face ( ≤ 0.0001). Even though significant relationships between the loin, belly, and ham were detected, the variability in belly and ham quality explained by variability in loin quality was poor (≤ 22.09%). Compositional differences between the loin and belly may have contributed to those poor relationships. Additionally, differences in temperature declines during chilling between the loin and ham likely contributed to the weak nature of relationships. Equilibration of longissimus dorsi temperature to ambient cooler temperature occurred at 14 h postmortem ( = 0.0005), yet the semimembranosus had not equilibrated with ambient (equilibration bay) temperature ( < 0.0001) at 22 h postmortem. Using loin quality to draw conclusions about fresh belly and fresh and cured ham quality may be misleading.

Rapid assessment of pork quality by packers necessitates using early postmortem (∼1 d) traits as an indication of aged pork quality (∼14 d). Efforts have been made to develop a grading system based on color and marbling of the ventral side of boneless loins. In order for this system to be successful, there must be a correlation between early postmortem quality traits observed by packers and the same traits observed by consumers after aging. However, the strength and direction of those correlations are unclear. It is also unknown if the correlations between early and aged postmortem quality differ between barrows (B) and gilts (G). Therefore, the objectives were to determine correlations between early postmortem loin quality characteristics and aged loin quality characteristics, and determine if those correlations differed between barrows and gilts. Early postmortem (∼1 d) quality traits included: instrumental and subjective color, marbling and firmness, and loin pH on the ventral surface of the loin. Loins were aged until 14 d postmortem in vacuum packages. Aged quality traits included traits evaluated early as well as shear force and cook loss. Correlations were compared between barrows and gilts using a Fisher's z test. Overall, early subjective firmness scores of barrows were greater (P &lt; 0.001) than those of gilts. No other early quality traits differed between sexes. Early pH was correlated with aged pH (r = 0.80 B; 0.75 G), ventral lightness (r = –0.57 B; –0.54 G), ventral yellowness (r = –0.55 B; –0.55 G), subjective ventral color (r = 0.55, B; 0.41 G), and subjective chop color (r = 0.42 B; 0.44 G). Correlations of early pH and aged quality did not differ between sexes. Early lightness was correlated with aged ventral pH (r = –0.56) and subjective color (r = –0.39) in barrows but not gilts (P ≤ 0.04). Early lightness was correlated with aged lightness (r = 0.60 B; 0.51 G) and yellowness (r = 0.49 B; 0.55 G), but was not correlated with to any aged chop quality traits. Early marbling was correlated with ventral color (r = 0.42) in barrows and ventral marbling (r = 0.67 B; 0.66 G) and chop marbling (r = 0.57 B; 0.59 G) in barrows and gilts. In summary, early pH and lightness were correlated with aged quality characteristics and correlations rarely differed between barrows and gilts. Sex does not need to be accounted for when relating early and aged quality characteristics.

The objective was to characterize ham and loin quality of carcasses ranging from 78 to 145 kg (average ∼119 kg). Hot carcass weight (HCW), back fat depth, and loin depth was measured on 666 carcasses. Loin pH, instrumental and visual color and iodine value of clear plate fat (all 3 layers) was measured on approximately 90% of the population. Quality measurements of the ham, 14 d aged loin and chop, and loin chop shear force (SSF) were evaluated on approximately 30% of the population. Myosin heavy chain fiber type determination was completed on 49 carcasses. Slopes of regression lines and coefficients of determination between HCW and quality traits were calculated using the REG procedure in SAS and considered significantly different from 0 at P ≤ 0.05. As HCW increased, loin depth (b1 = 0.2496, P < 0.0001), back fat depth (b1 = 0.1374, P < 0.0001), loin weight (b1 = 0.0345, P < 0.0001), and ham weight (b1 = 0.1044, P < 0.0001) increased. Estimated lean (b1 = –0.0751, P < 0.0001) and iodine value (b1 = –0.0922, P < 0.0001) decreased as HCW increased, where HCW accounted for 24% (R2 = 0.24) of the variation in estimated lean and 7% (R2 = 0.07) of the variation in iodine value. However, HCW did not explain variation in ham quality traits (P > 0.15) and did not explain more than 1% (R2 ≤ 0.01) of the variation in 1 d loin color or pH. Loins from heavier carcasses were more tender (decreased SSF; b1 = –0.0674, P < 0.0001), although HCW only explained 9% of the variation in SSF. Hot carcass weight did not alter (P > 0.22) muscle fiber type percentage or area. These results suggest that increasing HCW to an average of 119 kg did not compromise pork quality.