Quality attributes and color characteristics in three-piece boneless hams

Meat Science 95 (2013) 59–63

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Quality attributes and color characteristics in three-piece boneless hams Russell O. McKeith, T. Dean Pringle ⁎ Department of Animal Dairy Science, University of Georgia, 425 River Rd., Athens, GA 30602, United States

a r t i c l e

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Article history: Received 8 October 2012 Received in revised form 17 January 2013 Accepted 3 April 2013 Keywords: Ham Quality Color pH

a b s t r a c t One hundred and fifty hams were selected on visual assessment of quality into normal (C) and two-tone (TT) groups. CIE LAB color and pH measurements were collected at the plant 48 h postmortem on the gluteus medius (GM), gluteus profundus (GP), and rectus femoris (RF), and again at 72 h on the semimembranosus (SM), biceps femoris (BF), semitendinosus (ST), and RF. Data were analyzed using GLM procedures of SAS, and correlations between color scores, pH, and drip loss were calculated. Plant and fabrication pH were lower (P b 0.01) in GM from TT hams compared with C. Muscles from TT hams had lower (P b 0.01) L* and a* values compared with C. The GM L* and GM pH values were correlated (P b 0.05) with L* values for all other muscles and drip loss in SM. These data show that GM color and pH are accurate predictors of pork quality attributes in the muscles of a three-piece boneless ham. © 2013 Elsevier Ltd. All rights reserved.

1. Introduction It has been determined that color and appearance are the two most important factors determining consumers' meat selection preferences (Francis, 1977). Pork is ideally grayish-pink in color, but deviations from this are very common in the retail display case (Cannon et al., 1995; Wilson, Ginger, Schweigert, & Aunan, 1959). There is a phenomenon known as two toning in hams, which is the contrast in pigmentation both within muscles and between adjacent muscles. In pork, this primarily occurs at the junction between the longissimus dorsi and psoas major and between the different muscles found within the ham. Wilson et al. (1959) suggested that the degree of two toning was related to differences in the amount of myoglobin in the adjacent muscles; however, this theory may not fully explain two-tone color within muscles. It has been reported that pale, soft, and exudative (PSE) pork has been associated with two toning due to the abundance of white or intermediate muscle fibers (Miller, Garwood, & Judge, 1975). Pale, soft and, exudative pork is defined as pork that has unacceptably high lightness values (L*) and reduced water holding capacity, resulting in excessive cooking and processing losses (Forrest, Gundlach, & Briskey, 1963). Furthermore, PSE pork is a pH- and temperature-based phenomenon, meaning that it develops in muscle due to an accelerated rate of glycolysis early during postmortem metabolism while the carcass temperatures are still high (Bowker, Grant, Forrest, & Gerrard, 2000). The ultimate pH of PSE pork can range from 5.5 to 4.8 (Lawrie, 1958). Researchers have determined that muscles from PSE carcasses have a higher ratio of light muscle fibers to dark muscle fibers compared with muscles from normal carcasses (Dildey, Aberle, Forrest, & Judge, ⁎ Corresponding author. Tel.: +1 706 542 0997. E-mail address: [email protected] (T.D. Pringle). 0309-1740/$ – see front matter © 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.meatsci.2013.04.020

1970). From this, it has been suggested that the size and number of light muscle fibers are the most important factors related to two-tone ham color. The current literature describing the level of two-tone ham color in the U.S. pork industry is limited; however, a national survey conducted in the 1950s determined that 46.9% of the 584 pork carcasses evaluated expressed two-tone color (Self, Bray, & Reierson, 1957). In the pork chain quality audit conducted by Cannon et al. (1996), two-toned muscle color was observed in 12.7 % of the loins and 14.7% of the hams. For packers today, two toning in fresh pork is still an issue. Therefore, the objective of this study was to investigate quality attributes in hams that vary in visual quality. 2. Materials and methods 2.1. Ham collection Fresh whole hams (NAMP, 401; n = 150; 75/treatment) were collected 24 h postmortem on three different days (n = 50) from a large, commercial pork plant located in the southeastern United States. Hams were evaluated immediately after separation from the remainder of the pork carcasses and were selected into two quality categories. The two categories developed were normal (C) and two tone (TT) based on visual muscle color uniformity in the butt-face of the ham. Approximately 45 min after selection, hams were again visually evaluated to confirm the prior selection decision. Hams that were not confirmed as TT were returned to the fabrication line, and additional hams were evaluated and selected, if necessary. The selection process continued until there were 25 hams/ treatment/day. Following selection and confirmation, objective CIE (CIE, 1976) measures (L*, a*, and b*) were collected on the gluteus medius (GM) and gluteus profundus (GP) using a Hunter Lab Miniscan XE Plus spectrophotometer (Model 45/0 LAV, 2.54-cm-diameter aperture, 10°

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standard observer, Illuminate D65; Hunter Associated Laboratories Inc., Reston, VA) and pH (Cole-Parmer meter, model 05669-00) was measured in the GM. Hams were then boxed and shipped to the University of Georgia Meat Science and Technology Center. At 48 h postmortem, CIE color (L*, a*, and b*) values on the GM, GP, and RF were collected along with ultimate pH measurements in the GM. 2.2. Ham fabrication yields Following color and pH determination, hams were fabricated according to the National Association of Meat Purveyors specifications (NAMP, 2007). Specifically, whole ham (NAMP, 401) weights were recorded. Hams were then skinned and trimmed to 0 cm subcutaneous fat (NAMP, 402A), and weights were collected. Hams were then fabricated into the outside (NAMP, 402E), inside (NAMP, 402 F), and knuckle (NAMP, 402H) to make a fresh ham (NAMP, 402G). The light butt was also removed. Weights of each piece were recorded individually. The percent lean cuts was determined using the equation [(inside + outside + knuckle + light butt) / skinned ham weight], and the percent three-piece boneless ham yield was determined using the equation [(inside + outside + knuckle)/skinned ham weight]. 2.3. Color of ham muscles Approximately 72 h postmortem, CIE (L*, a*, and b*) values were collected on the semimembranosus (SM), biceps femoris (BF), semitendinosus (ST), and RF. The SM was divided into the anterior region (A) and posterior region (P), whereas the BF was divided into the dorsal (D) and ventral (V) regions, and the RF was divided into the inside (I) and outside (O). 2.4. Drip loss A 1.27-cm slice was taken and trimmed free from subcutaneous fat and epimyseal connective tissue for drip loss analysis on the SM muscle following the procedures of Carr et al. (2005) with modifications. Samples were weighed and suspended in a bag for 24 h at 4 °C to collect any purge loss. Chops were then gently blotted and weighed, and the percent purge loss was calculated using the following equation [(Initial wt − Final wt) × 100%]. 2.5. Lipid determination From the previously fabricated SM, a 1.27-cm slice was cut, vacuum packaged, and frozen for subsequent analysis. Samples were powder homogenized, and lipid content was measured in duplicate using the procedure of Folch, Lees, and Sloane Stanley (1957) with modifications. Tissue samples (2.5 g ± 0.1 g) were homogenized with 10 mL of methanol and 5 mL of chloroform (2:1 methanol–chloroform mixture) and allowed to stand for 1 h at 25 °C. Chloroform (5 mL) and 1 M KCl (5 mL) were added and samples were vortexed. Samples were then placed in an ice bath for 5 min and centrifuged at 2,000 ×g for 10 min at 0 °C. The aqueous layer was discarded. The remaining lipidcontaining layer was then dried overnight in a fume hood. After drying, samples were weighed and percent lipid was calculated using the following equation [((pan with lipid weight – pan weight)/sample weight) × 100%]. 2.6. Moisture determination From the same powder homogenized SM sample, moisture was measured in duplicate (AOAC, 1990). Disposable aluminum drying pans were dried overnight in a 90 °C oven. Tissue samples (1.0 g ± 0.1 g) were placed in pre-weighed, dried aluminum pans and in a 90 °C oven

for 48 h. After drying, samples were cooled and weighed and the percent moisture was calculated using the following equation: ((wet sample weight − dry sample weight) / (wet sample weight)) × 100%. 2.7. Statistical analysis Data were analyzed as a completely randomized block design using the GLM procedures of SAS (SAS Inst., Inc., Cary, NC), comparing two ham types (C and TT). The effect of day was tested and found to be non-significant. This was expected because the selection days occurred over a 5-week period in January and February. Least squares means were generated and separated using the LSD procedure with a significance level of P ≤ 0.05. Pearson correlation coefficients were also calculated between CIE color scores for all muscles, plant pH, fabrication pH, % moisture, and % purge loss. Regression analyses were conducted comparing prefabrication GM L* values to L* values from the various muscles in the three-piece boneless ham. 3. Results and discussion 3.1. Whole ham pH and color Two-tone hams had a significantly lower pH at 24 and 48 h postmortem compared with normal hams (5.73 vs. 5.61 and 5.75 vs. 5.57; Table 1). Similarly, pale two-toned hams (pH 5.42) and non-pale two-toned hams (pH 5.53) have been reported to have lower pH values than dark, firm and dry hams (pH 6.07) at 24 h postmortem (Briskey, Bray, Hoekstra, Phillips, & Grummer, 1959). Moreover, at 45 min postmortem, it has been documented that pH is significantly lower in PSE pork compared with normal pork (Bendall & Wismer-Pedersen, 1962; Briskey, 1964; Dildey et al., 1970; Josell, von Seth, & Tomberg, 2003; Lawrie & Gatherum, 1962). Other research determined that PSE longissimus lumborum muscles had significantly lower ultimate pH (pHu 5.50) compared with red, firm, and non-exudative muscle (pHu 5.73) (Warner, Kauffman, & Russel, 1993).

Table 1 pH measurements in the GM at 24 and 48 h postmortem from two-tone (TT) and normal hams (C) and color measurements in the gluteus medius (GM), gluteus profundus (GP), and rectus femoris (RF). Item

pH 24 h 48 h GM (24 h) L*a a*b b*c GM (48 h) L*a a*b b*c GP (24 h) L*a a*b b*c GP (48 h) L*a a*b b*c RF (48 h) L*a a*b b*c a b c

Treatment C

TT

Pr > F

SEM

5.73 5.75

5.61 5.57

b0.01 b0.01

0.02 0.02

44.61 10.13 14.12

47.97 8.91 15.02

b0.01 b0.01 b0.01

0.42 0.17 0.19

49.09 10.95 17.41

53.83 9.80 17.61

b0.01 b0.01 0.32

0.36 0.18 0.14

38.40 13.69 14.24

40.86 13.55 15.29

b0.01 0.57 b0.01

3.99 1.49 1.73

41.12 14.27 18.15

43.38 14.10 18.56

b0.01 0.58 0.10

0.46 0.17 0.20

48.71 8.87 15.95

56.31 7.57 16.56

b0.01 b0.01 0.05

0.36 0.27 0.22

L* = lightness, where 0 equals black and 100 equals white. a* = redness, from red (+) to green (−). b* = yellowness, from yellow (+) to blue (−).

R.O. McKeith, T.D. Pringle / Meat Science 95 (2013) 59–63

Gluteus medius CIE L* and a* values were significantly different between C and TT hams at 24 and 48 h postmortem (Table 1). The L* values indicate differences in lightness with 0 equaling black and 100 equaling white, a* represents measurements from red (+) to green (−), and b* represents measurements from yellow (+) to blue (−) (Mancini & Hunt, 2005). From the GM, L* values were lighter and a* values were less red for TT hams compared with C hams. Two-tone hams were also more yellow (higher b*) at 24 h postmortem than C hams; however, b* values measured at 48 h postmortem did not differ between groups (Table 1). These data are in agreement with Warner et al. (1993), who reported differences between ham quality classifications where GM L* values from red, firm, and non-exudative hams were 46.2; pale, soft, and exudative L* values were 53.0; and dark, firm and dry L* values were 40.5. Gluteus profundus L* values were significantly lighter in TT compared with C at 24 and 48 h postmortem, and b* values were significantly more yellow at 24 h for TT hams than C hams, but there were no differences in b* values between the groups at 48 h (Table 1). Likewise, there were no differences in a* values between groups at either time point (Table 1). In the RF at 48 h postmortem, L* values were significantly lighter, a* values were significantly less red, and b* values were significantly more yellow for TT hams compared with C hams (Table 1).

3.2. Ham fabrication yields Whole ham (401), trimmed ham (401A), and skinned ham (401C) weights were not significantly different between treatments (Table 2). The inside, outside, and light butt were significantly heavier for C hams compared with TT hams, whereas the knuckle was heavier (P b 0.05) for the TT hams compared with C hams (Table 2). Although differences in individual muscle weights existed, the percentage of three-piece boneless hams and the percentage of ham lean cuts were not different among ham quality groups (Table 2).

3.3. Drip loss and proximate analysis Water holding capacity (WHC) is an important trait in ham muscle because these muscles are used extensively in further processed products. Weight loss (g) and percent purge loss were higher (P b 0.05) for the SM from TT hams when compared with C hams (Table 3). In another study it was reported that PSE pigs expressed significantly greater longissimus muscle drip loss (3.8%) compared with normal pigs (2.3%) (van Laack, Faustman, & Sebranek, 1993).

Table 2 Fabrication yields of normal hams (C) and two-tone (TT) hams. Item

Ham yields 401 Ham, kg 402A Trimmed ham, kg 402A Skinned ham, kg 402G Ham Inside, kg Knuckle, kg Outside, kg Light butt, kg Three-piece ham, % a Lean cuts, % b

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For proximate analysis, neither moisture (%) nor fat (%) were significantly different among ham quality groups (Table 3). 3.4. Color of the three-piece boneless ham muscles The anterior location of the SM muscle had significantly higher values for L* and b*, whereas a* values was significantly lower for TT hams compared with C hams (Table 4). In the posterior region of the SM, TT hams had higher (P b 0.01) L* and lower (P b 0.01) a* values compared with C hams (Table 4). Schilling et al. (2004), reported that SM samples from PSE carcasses had significantly higher L* values (57.6) compared with L* values (45.8) of red, firm, and non-exudative SM muscle. The anterior region of the SM from TT hams had higher b* values compared with C hams, and the posterior region of TT hams tended (P = 0.07) to be more yellow than the C hams (Table 4). For the dorsal and ventral regions of the BF and the ST, TT hams had significantly higher L* and b* color values and lower (P ≤ 0.03) a* values compared with C hams (Table 4). For the RF, both the inside and the outside regions of the TT hams had higher (P b 0.01) L* and lower a* values compared with C hams, but b* values were not different (P = 0.84) between groups (Table 4). Because of the large differences in L* values between the inside and the outside regions of the RF, pH was measured in the two regions (Table 4). The pH was lower (P b 0.01) in the inside location, which had higher (P b 0.01) L* values than the outside (Table 4). Warner et al. (1993) reported that at 2 h postmortem, low-quality RF muscles had a significantly lower pH than RF muscle from normal quality ham with pH values of 5.46 and 6.12, respectively. 3.5. Pearson correlations between quality measures Correlation coefficients were calculated between muscle pH, muscle color, % fat, % moisture, and % purge loss (Table 5). There were (P b 0.01) correlations (Table 5) between L* values for the SM (anterior and posterior regions), BF (dorsal and ventral regions), and RF (inside and outside regions) when compared with GM L* values and pH (24 h and 48 h). As expected, the correlations between L* values and pH measurements were inversely related, confirming the fact that ham color is negatively impacted as muscle pH decreases. A study conducted by Warner et al. (1993) reported negative correlations between L* and pH in the GM (r = − 0.78), ST (r = − 0.80), BF (r = − 0.71), RF (r = − 0.75), and SM (r = − 0.62). Moreover, percent purge loss was inversely correlated (P b 0.01) with both pH measurements (Table 4). Warner et al. (1993) reported a correlation value of − 0.76 between exudates and pHu. These results also concur with van der Wal, Olsman, Garrson, and Engel (1992), who reported drip loss values for pork loins exhibiting dark, firm, and dry; normal; and pale, soft, and exudative characteristics of 1.7%, 3.0%, and 5.0%, respectively. These findings were expected because as pH approaches

Treatment C

TT

Pr > F

SEM

11.17 11.15 9.22

10.93 10.82 9.00

0.21 0.08 0.18

0.79 0.79 0.54

2.23 1.30 2.57 0.24 66.04 68.66

2.12 1.41 2.42 0.22 65.97 68.43

0.04 b0.01 b0.01 0.02 0.94 0.65

0.19 0.12 0.21 0.03 0.20 0.30

Table 3 Purge loss and proximate analysis of normal hams (C) and two-tone (TT) hams.

a Percent three-piece ham was calculated using the formula: ((inside + outside + knuckle) / 402a skinned ham). b Percent lean cuts was calculated using the formula: (inside + outside + knuckle + light butt) / 402a skinned ham).

Item

Purge Loss Initial wt, g Final wt, g Loss wt, g Purge loss, % a Proximate analysis Moisture, % Fat, %

Treatment C

TT

Pr > F

SEM

48.54 47.15 1.38 2.86

48.70 46.78 2.00 4.09

0.85 0.66 b0.01 b0.01

0.61 0.59 0.07 0.13

73.07 2.93

73.61 2.74

0.13 0.18

0.25 0.10

a Percent purge loss was calculated using the formula: ((weight loss (g) / initial weight (g)) × 100).

R.O. McKeith, T.D. Pringle / Meat Science 95 (2013) 59–63

Table 4 Ham color measurements collected on the semimembranosus, biceps femoris, semitendinosus, and rectus femoris for two-tone (TT) and normal hams (C). Item

Semimembranosus Anterior L*a a*b b*c Posterior L*a a*b b*c Biceps femoris Dorsal L*a a*b b*c Ventral L*a a*b b*c Semitendinosus L*a a*b b*c Rectus femoris Inside L*a a*b b*c pH Outside L*a a*b b*c pH a b c

Treatment C

TT

Pr > F

SEM

42.07 11.96 15.44

48.43 10.59 16.47

b0.01 b0.01 b0.01

0.40 0.20 0.19

49.51 10.66 16.67

53.53 9.16 17.05

b0.01 b0.01 0.07

0.42 0.21 0.14

41.71 13.58 16.97

46.61 12.60 18.10

b0.01 b0.01 b0.01

0.36 0.18 0.17

40.29 14.10 16.89

45.21 12.88 17.88

b0.01 b0.01 b0.01

0.36 0.18 0.17

40.42 14.64 16.75

43.37 13.82 17.23

b0.01 0.03 0.04

0.51 0.26 0.16

40.98 12.19 14.91 6.08

47.37 9.10 14.96 5.88

b0.01 b0.01 0.84 b0.01

0.42 0.22 0.16 0.03

36.16 16.75 15.62 6.24

40.07 13.28 15.71 6.12

b0.01 0.05 0.69 0.01

0.39 1.23 0.16 0.04

L* = lightness, where 0 equals black and 100 equals white. a* = redness, from red (+) to green (−). b* = yellowness, from yellow (+) to blue (−).

the isoelectric point (pI) of muscle proteins, a resulting increase in purge loss occurs. The pI for pork is the pH where the positive and negative charges on the muscle proteins are equal in magnitude and the pI in pork occurs between pH 5.2 and 5.4 (Aberle, Forrest, Gerrard, & Mills, 2001). These charges attract to one another, so

Table 5 Correlation coefficients comparing pH measured at 24 and 48 h and gluteus medius (GM) 48 h L* values with L* values of the GM, gluteus profundus (GP), semimembranosus (SM), biceps femoris, (BF), rectus femoris (RF), composition, and purge loss. Item

pH 24 h

pH 48 h

GM 48 h

GM 24 h L*a GM 48 h L*a GP 24 h L*a GP 48 h L*a SMA L*a SMP L*a DBF L*a VBF L*a RFI L*a RFO L*a Percent fat Percent moisture Percent Purge loss

−0.25⁎ −0.30⁎ −0.37⁎ −0.37⁎ −0.37⁎ −0.30⁎ −0.43⁎ −0.42⁎ −0.31⁎ −0.18⁎

−0.29⁎ −0.37⁎ −0.43⁎ −0.40⁎ −0.47⁎ −0.38⁎ −0.50⁎ −0.46⁎ −0.34⁎ −0.24⁎

0.51⁎ — 0.44⁎

−0.07 0.01

−0.01 0.01

0.03 0.07

a

−0.49⁎

−0.56⁎

L* = lightness, where 0 equals black and 100 equals white. ⁎ P b 0.05.

0.36⁎ 0.73⁎ 0.46⁎ 0.67⁎ 0.55⁎ 0.50⁎ 0.47⁎

0.46⁎

fewer charged groups are available to attract and bind water (Huff-Lonergan & Lonergan, 2005). When the pH decreases below the isoelectric point (pI), water binding capacity increases because there are more positively charged groups in the muscle proteins that repel one another. In contrast, when the pH increases above the pI, water binding increases due to an increase in the negatively charged groups on the proteins. As the pH moves away from the pI, there are greater percentages of bound or immobilized water within the muscle cell (Aberle et al., 2001). Correlations between GM L* values, measures at 48 h postmortem, and L* values of the SM at the anterior and posterior locations, BF at dorsal and ventral locations, and RF at the inside and outside locations were significant (Table 4). These correlations were positive, indicating that as lightness in the GM muscle increased, so did lightness in other muscles. Regression analysis showed that the GM 48 h L* values were predictive of L* values for the various muscles of the three-piece boneless ham. More specifically, the R 2 values when comparing GM 48 h L* values to the L* values of the SM, measured in the anterior and posterior regions of the muscle, were 0.48 (Fig. 1) and 0.21 (Fig. 2), respectively. Comparison of GM 48 h L* values to L* values of the BF measured in the dorsal and ventral regions of the muscle, showed R 2 values were 0.39 and 0.19, respectively. Finally, when comparing the L* values of the RF, measured in the inside and outside regions of the muscle, to GM 48 h L* values, the R 2 values were 0.27 and 0.22, respectively. Furthermore, there were not significant correlations between GM 48 h L* values, and % moisture, or % fat (Table 4). These data show that it is possible to accurately predict the lightness of the SM and BF muscles using L* values from the GM. This should allow hams to be sorted, prior to fabrication, based on the L* value of the GM muscle into quality-based groups.

4. Conclusions In this study, poor-quality ham muscles were more likely to express two toning than normal hams. This two toning is considered a quality defect and was strongly related to pH. The decreased pH found in two-tone ham muscle resulted in increased drip loss and higher L* values. Muscle pH appeared to be a good predictor of two toning in ham muscles, and lightness (L*) in the GM muscle appeared to be a good predictor of lightness in the muscle groups of a three-piece boneless ham. This is important because these muscles are not very visible prior to fabrication. Future experiments should be conducted to determine whether myoglobin oxidation or denaturation varies within muscles that differ in quality, along with interventions to increase pH and improve pork quality.

65

Semimembranosus Anterior

62

60 55

y = 0.9132x- 1.6633 R² = 0.4771

50

L* 45

Linear (L*)

40 35 30 40

45

50

55

60

65

Gluteus medius Fig. 1. The relationship between L* values from the anterior region of the semimembranosus and L* values from the gluteus medius.

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Semimembranosus Posterior

70 65 60

y = 0.4596x + 27.917 R² = 0.2136

55 50 L* Linear (L*)

45 40 35 30 35

40

45

50

55

60

65

Gluteus medius Fig. 2. The relationship between L* values from the posterior region of the semimembranosus and L* values from the gluteus medius.

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