Characterization of color uniformity
of the cut lean surface in fresh ham
M.T. See and B.A. Belstra
North Carolina State University, Department of Animal Science
Summary
Data were collected on fresh hams to evaluate quality characteristics across groupings with decreasing uniformity of visual color. Carcasses were identified and hot carcass weight (87.8 kg), fat depth and loin depth were collected at 45 m postmortem from pigs representing nine producer lots. Hams were fabricated under normal commercial conditions at 24 h postmortem. Hams were visually classified as normal (n = 140), slightly two-toned (n = 77), moderately two-toned (n = 29) or two-toned/PSE (n = 13). Ultimate pH, Minolta L* value, and fluid loss were measured on the cut lean surface of the gluteus medius, psoas major and quadriceps femoris. As a check on visual classification, color difference was calculated for each ham as the sum of the squared deviations of the Minolta L* value of each muscle from the average Minolta L* value of all three muscles. Hot carcass weight, fat depth, and ham weight did not differ (P > 0.05) across color classifications. However, loin muscle depth increased linearly (55.2, 54.3, 57.9, 57.3 ± .8; P < 0.01) with decreasing color uniformity. Calculated color difference was in strong agreement with visual color classification showing a linear increase 53, 74, 92, 106 ± 7; P < 0.001) as visual uniformity decreased. For the quadriceps femoris, ultimate pH decreased linearly (6.01, 5.96, 5.96, 5.86 ± .03; P < 0.05), and Minolta L* value (52.5, 54.2, 54.8, 58.3 ± .6; P < .001) and fluid loss percentage (2.1, 2.5, 3.1, 3.3 ± .2; P < 0.001) linearly increased with decreasing uniformity of color in the ham face. Likewise for the gluteus medius, ultimate pH decreased linearly (5.92, 5.87, 5.84, 5.75 ± .02; P < 0.001), and Minolta L* value (47.8, 49.0, 51.8, 55.2 ± .7; P < 0.001) and fluid loss percentage (2.6, 2.8, 3.5, 3.8 ± .2; P < 0.001) linearly increased with decreasing uniformity of color in the ham face. However, no differences (P > 0.05) were observed across color classifications for ultimate pH, Minolta L* value or fluid loss percentage of the psoas major. These results indicate that differences in color uniformity are more closely related to quality differences of the gluteus medius and the quadriceps femoris than the psoas major.
Introduction
Fresh meat color has a subtle but important impact on consumer purchase decisions. Most consumers prefer a bright reddish-pink color in fresh pork (Minolta color = 49). Pork cuts that are too dark (Minolta color = 31), too pale (Minolta color = 61), or too variable in color within a package, product or within the meat case, may lower the consumer’s perception of quality. Therefore the objective of this project was to characterize fresh hams with varying uniformity of color across the cut surface by objective measures of the gluteus medius, psosas major and quadriceps femoris.
Materials and Methods
Carcasses (n = 259) were selected and identified from 9 producer lots delivered to commercial pork processing plant in eastern NC. Hot carcass weight, fat depth and loin depth were collected at 45 min. postmortem. Hams were fabricated under normal processing conditions at 24 h postmortem. Hams were visually classified (Figure 1) as either normal (n = 140), slightly two-toned (n = 77), moderately two-toned (n = 29) or two-toned / PSE (n = 13). Ultimate pH, Minolta L* value and fluid loss (filter paper method; Kauffman et al., 1986) were measured on the cut lean surface of the gluteus medius, psoas major and quadriceps femoris. Color difference was calculated for each ham as the sum of the squared deviations of the Minolta L* value of each muscle from the average Minolta L* value of all three muscles. The statistical analysis model included fixed effects of producer lot and color uniformity classification. Hot carcass weight and order of measurement were included as covariates for composition and quality traits, respectively. Linear contrasts were evaluated across color uniformity classifications.
Figure 1. Visual color uniformity classifications.
Results and Discussion
Hot carcass wt, fat depth, and ham wt did not differ across color uniformity classifications (Table 1), except for Normal vs. STT for fat depth. However, loin muscle depth increased linearly with decreasing color uniformity. This would indicate that the weight of the pig does not influence color uniformity in the ham face. However, pigs with higher lean content, especially larger loin muscle, have decreased color uniformity in the ham face. Calculated color difference was in strong agreement with visual color classification showing a linear increase as visual uniformity decreased. This indicates that the subjective visual classifications did agree with the objective measurements indicating valid classifications.
Table 1. Least Squares Means for Carcass Composition and Color Difference by Color Uniformity Classification
|
|
Color Uniformity Classification |
|||
|
Measure |
Normal |
STT |
MTT |
TT / PSE |
|
Hot Carcass Wt, kg |
87.4 ± 0.5 |
87.4 ± 0.6 |
87.6 ± 1.0 |
89.0 ± 1.5 |
|
Fat Depth, mm |
21.2 ± 0.4 a |
19.6 ± 0.5 a |
20.5 ± 0.8 a,b |
20.3 ± 1.1 a,b |
|
Loin Depth, mm * |
55.2 ± 0.5 b,c |
54.3 ± 0.6 c |
57.9 ± 1.0 a |
57.3 ± 1.4 a,b |
|
Ham Wt, kg |
10.8 ± 0.1 |
10.9 ± 0.1 |
11.0 ± 0.1 |
10.9 ± 0.2 |
|
Color Difference * |
53 ± 4 a |
74 ± 5 b |
92 ± 9 b,c |
106 ± 13 c |
|
* Linear effect across color uniformity classification P < 0.01 a,b,c Values with different superscripts in the same row are significantly different P < 0.05 |
||||
For the quadriceps femoris (Table 2), ultimate pH decreased linearly and Minolta L* value and fluid loss percentage linearly increased with decreasing uniformity of color in the ham face. For the gluteus medius (Table 3), ultimate pH decreased linearly and Minolta L* value and fluid loss percentage linearly increased with decreasing uniformity of color in the ham face.No significant differences were observed across color classifications for ultimate pH, Minolta L* value or fluid loss percentage of the psoas major (Table 4). Observed differences in relationships between muscles in measures of color, fluid loss, and pH and color classification indicate that the quadriceps femoris and gluteus medius are strongly related color uniformity in the ham face. However, less variation was observed for the psoas major indicating that this muscle does not contribute to observed color uniformity.
Table 2. Least Squares Means for Minolta L* Ultimate pH, and Fluid loss of the Quadriceps Femoris by Color Uniformity Classification
|
|
Color Uniformity Classification |
|||
|
Measure |
Normal |
STT |
MTT |
TT / PSE |
|
Minolta L* value * |
52.5 ± 0.4 a |
54.2 ± 0.4 b |
54.8 ± 0.7 b |
58.3 ± 1.0 c |
|
Ultimate pH * |
6.01 ± 0.02 a |
5.96 ± 0.03 a,b |
5.96 ± 0.04 a,b |
5.96 ± 0.06 b |
|
Fluid Loss, % * |
2.1 ± 0.1 a |
2.5 ± 0.2 a |
3.1 ± 0.3 b |
3.3 ± 0.4 b |
|
* Linear effect across color uniformity classification P < 0.01 a,b,c Values with different superscripts in the same row are significantly different P < 0.05 |
||||
Table 3. Least Squares Means for Minolta L* Ultimate pH, and Fluid loss of the Gluteus Medius by Color Uniformity Classification.
|
|
Color Uniformity Classification |
|||
|
Measure |
Normal |
STT |
MTT |
TT / PSE |
|
Minolta L* value * |
47.8 ± 0.4 a |
49.0 ± 0.6 a |
51.8 ± 0.9 b |
55.2 ± 1.3 c |
|
Ultimate pH * |
5.92 ± 0.01 a |
5.87 ± 0.02 b |
5.84 ± 0.03 b,c |
5.75 ± 0.04 c |
|
Fluid Loss, % * |
2.5 ± 0.1 a |
2.8 ± 0.2 a |
3.5 ± 0.3 b |
3.8 ± 0.4 b |
|
* Linear effect across color uniformity classification P < 0.01 a,b,c Values with different superscripts in the same row are significantly different P < 0.05 |
||||
Table 4. Least Squares Means for Minolta L* Ultimate pH, and Fluid loss of the Psoas Major by Color Uniformity Classification
|
|
Color Uniformity Classification |
|||
|
Measure |
Normal |
STT |
MTT |
TT / PSE |
|
Minolta L* value * |
44.5 ± 0.3 |
44.4 ± 0.4 |
43.8 ± 0.6 |
46.1 ± 0.9 |
|
Ultimate pH * |
6.22 ± 0.02 |
6.21 ± 0.02 |
6.17 ± 0.04 |
6.12 ± 0.05 |
|
Fluid Loss, % * |
1.6 ± 0.1 |
1.7 ± 0.2 |
2.1 ± 0.2 |
2.4 ± 0.3 |
|
* Linear effect across color uniformity classification P < 0.01 a,b,c Values with different superscripts in the same row are significantly different P < 0.05 |
||||
Implications
These results indicate that differences in color uniformity are more closely related to quality differences of the gluteus medius and the quadriceps femoris than the psoas major.
Reference
Kauffman, R.G., G. Eikelenboom, P.G. van der Wal, B. Engel, and M. Zaar. 1986. A comparison
of methods to estimate water-holding capacity in post-rigor porcine muscle. Meat Sci. 18:307-322.
