J. Sci. Food Agric. 1979,30,493-498
The Influence of Breed on the Carcass and Eating Quality of Pork Jeffrey D. Wood, Eric Dransfield and Douglas N. Rhodes ARC Meat Research Institute, Langford, Bristol
(Manuscript received 6 September 1978)
Twelve gilts from four breeds were reared from 30 to 65 kg liveweight and assessed for carcass, muscle and eating quality. The breeds were Large White (LW), Gloucester Old Spot (GOS) Crossbreed 1 (Cl) and Crossbreed 2 ((22). The latter two were commercial products from breeding companies. There were small differences in quality between the breeds. C1 had about 2 % more lean than the others. GOS had shorter carcasses, a higher proportion of total lean in the fore limb and thicker backfat but were not fatter overall. C1 and C2 had lower pH1 measurements than LW or GOS but similar colour and drip loss measurements in M . longissimus lumborum. There were positive but weak relationships between pH1 and percentage fat ( r = f0.1 to +0.3). C1 had the more tender meat. When all breeds were pooled, about 9 % of the variation in toughness was accounted for by variation in percentage lean or fat. There was no suggestion that the pure breeds or fatter pigs had meat of better eating quality. 1. Introduction
In the United Kingdom, pork and lamb are meats derived from animals slaughtered at relatively young physiological ages and are intrinsically tender. Tenderness is overwhelminglythemost important factor in the eating quality of meats, and the popularity of pork and lamb depends to a large extent on the ability of the housewife to use the quick methods of cooking-grilling and frying-for them. The pig was traditionally a source of animal fat and the trend to reduce the human intake of fat during the last 30 years has forced continuous efforts in husbandry to reduce fatness in the pig carcass. Fears have been expressed that reduction in the fatness of pork would be accompanied by increases in toughness, in the belief that the substitution of a soft fat by a more coherent protein must produce tougher meat. Much research has shown that this effect, if apparent, is very small; estimates of the correlation coefficient between fatness and tenderness show a wide range, both positive and negative, and overall about 10% of the variability in the texture of the lean of meat (pork and beef mostly) is accounted for by the level of fatness of the carcass1 Pig carcasses have become leaner as a result of improvements in breeding and management, the average backfat thickness of pigs in the classification scheme operated by MLC in Great Britain having decreased by about 2.0 mm between 1971 and 1976. This comparatively small difference is much less than the range over which experimental work has demonstrated little or no effect of fatness on texture (correlation coefficients < 0.25).l Nevertheless, concern continues to be expressed by quality meat retailers that modern pork is less tender than that produced 25 years ago and the present work was undertaken to study the eating quality differences between pork from a traditional breed now infrequently used (Gloucester Old Spot), a conventional breed (Large White) and two commercially developed cross breeds. At the same time other aspects of carcass and meat quality were investigated. 2. Materials and methods
Each breed was represented by 12 pigs. Pure bred Large White (LW) and Gloucester Old Spot 0022-5142/79/050@0493 $02.00
01979 Society of Chemical Industry 493
J. D. Wood et al.
494
(GOS) gilts were obtained from sources used in previous work at MRI2 and crossbred gilts, products of different breeding companies designated C1 and C2 were obtained from commercial sources. Gilts of approximately 30 kg liveweight (8Ck90 days of age) were housed in mixed breed groups of twelve and fed individually on the same diet at one of two feeding levels: to appetite for 1 h twice daily or to a scale designed to provide about 80 % of appetite. The diet was a proprietary pelleted one containing 18.5 % crude protein. At approximately 65 kg liveweight, the pigs were laired overnight (17-19 h) without food and slaughtered by electrical stunning and exsanguination. The hot carcass weight, PZfat measurement (6.5 cm from the midline opposite the head of the last rib and excluding skin thickness) and pH in the M . longissimrcs lumborum (LD) at 45 min post-slaughter (PHI) were recorded. The carcasses were then chilled at 5°C for 18 h and split down the midline. Backfat thickness (excluding skin) measurements were made and the left side was used for determination of tissue composition using the 'total tissue' dissection procedure3 which involves removal of subcutaneous fat followed by dissection of four 'anatomical joints' into lean, bone and intermuscular fat. The right side was used for quality assessments. Drip was measured on a chop containing the 7th-9th thoracic vertebrae after storage at 1"C for 48 h. Colour (Hunter Colour Difference Meter), ultimate pH and pigment concentration4 were measured on the LD from the 4th-6th thoracic vertebrae, 3 days after slaughter. Six to eight days after slaughter ajoint from the 10th thoracic to 6th lumbar vertebrae was roasted at 180°C to an internal temperature of 80°C. The eating quality of the L D was assessed by taste panelists and texture was determined instrumentally. Flavour was assessed on an 8-point scale: dislike extremely, dislike very much, dislike moderately, dislike slightly, like slightly, like moderately, like very much, like extremely and scored - 7, - 5, -3, - 1, 1 , 3, 5,7, respectively. Tenderness was judged on an 8-point scale: extremely tough (scored -7), very tough (- 5 ) , moderately tough (- 3), slightly tough ( - l), slightly tender (l), moderately tender (3), very tender (5) extremely tender (7) and juiciness: dry (O),slightly juicy (l), moderately juicy (2), extremely juicy (3). Analysis of the results was done using scores from 7 panelists who gave 284 assessments of each attribute (31 missing values were inserted to reduce the residual mean square). Toughness was determined instrumentally on the roast LD by measuring the total work done to compress uniform samples between blunt jaws.5
3. Results
Analysis of variance was done with the main effects breed, level of feeding and their interaction. Although pigs fed to appetite consumed more feed per day (2045 us 1675 g s.e.d. 43.2) and grew more quickly (786 u s 708 g day-1 s.e.d. 24.0) than the scale-fed pigs there were no significant feeding level or interaction effects on any aspect of composition or quality. Therefore the results for breed alone are given (Table 1). The average values for feed intake per day were 1882, 1846, 1941 and 1825 g in LW, GOS, C1 and C2, respectively. GOS had short carcasses and GOS (particularly) and C2 had thick backfat. C1 had the thinnest backfat and the leanest carcasses. GOS had more lean in the fore limb and less in the hind limb compared with the other breeds. pH1 was lower in C l and C2 than in LW and GOS whereas ~ H F was the same in all breeds. Cl were the most tender whilst LW were the least tender, although the difference was only one point on the eight point scale. All other measurement of muscle or eating quality were unaffected by breed. The breed means for backfat thickness at C (directly above maximum depth (B) of eye muscle) and hot PZ (6.5 cm from midline) were similar. PZ was also measured on the cold carcass and a slight reduction from the hot value was observed. Overall means (mm+s.d.) were: hot PZ 12.475 3.13 ; cold PZ 1I SO? 2.71. Carcass length also declined during the process of cooling from 722 +_ 17 to 716k19 (mm+s.d.). Correlation coefficients, pooled within subgroups, are given in Table 2. There was no correlation between feed intake per day and any aspect of carcass or meat quality. Carcass length was negatively correlated with backfat thickness, percentage subcutaneous and total fat and positively
Carcass and eating quality of pork
495
Table 1. Carcass measurements, carcass composition, lean distribution, muscle quality and eating quality in pigs from four breeds Breed
-
Carcass measurements
Hot carcass weight (kg) Leg length (mm) Carcass length (mm) Shoulder depth (mm) Shoulder width (mm)
LW
GOS
50. l b
48.6% 516a 69ia 292b 122%
529b 720b 293b l18a
c1 50.2b 527b 725'1 299 122"
C2 48.8a 512a 716b 279a 130a
S.e.d. and significance 0.59* 6.0* 6.6*** 5.5* 7.1n5
Backfat thickness
Mid-rump (mm) Mid-back (mm) Shoulder (mm)
16.48 14.6% 31.7%
19.6b 17.7" 33.2b
13.9% 14.6% 29.68.
19.1b 16.3a 32.7h
1.42*** 1.04* 1.50NS
Eye muscle measurements
Width (A) (mm) Depth (B) (mm) Fat thickness (C) (mm) Fat thickness (K) (mm) Hot PZ (mm)
84.38 44.5% 11 .4a 18.4% 11.88
81.6" 45.4% 14.4'' 19.5% 14.4b
83.Y 47.9% 11.5' 18.9 10.7a
83.2& 44.98 12.9" 20.7% 12.88
2.57NS 2.06NS 1.10* 1.20NS 1.17*
Carcass compositiona
Lean Bone Subcutaneous fat Total fat
53.97ab 11.58b 22. lob 30. 38ab
53. 3ga 10.868 21.33ab 30.62ab
55. 86b 1 1 .24ab 19.39a 28. 40a
53.40% 10.86s 22.62b 31.50"
1.17** 0.30NS 1.03* 1.22NS
Lean distributionb
Fore limb Neck and thorax Lumbar and abdomen Hind limb
13.17s 37.02" 12.758 33.14b
13.87" 37.38% 13.34% 31.76%
13.08& 37.968 12.51a 32.438
13.328 36.708. 12.42a 33.92b
0.23** 0.63NS 0.54NS 0.37***
Muscle quality
pH1 PHF Intramuscular fat (%) Haem pigment (parts Drip 48 h (%) Lightness raw muscle
6.4b
6.5b 5.6" 2.0% 38.3& 1.28 50.8%
6. l a 5.4= 2.08 36.58 1.3a 51.2'
Eating quality
Toughness (J) Tenderness ( - 7 to 7) Flavour (- 7 to 7) Juiciness (0 to 3)
+
+
5.5%
2.1% 34.7% 1 .O& 51 .O& 0.20b
0.18ah
0.16"
0.5%
1.3b 2.9 1.2"
1.P
2.38 1.28
2.28 1.28
6.18
0.11**
5.53
0.05NS 0.23NS 2.84NS 0.22NS
1.98 36.3a 1.4s 51.1% 0.19b 1. lab 2.48 1.18
1.35NS
0.011** 0.35** 0.30NS O.1lNS
*** P
The Influence of Breed on the Carcass and Eating Quality of Pork Jeffrey D. Wood, Eric Dransfield and Douglas N. Rhodes ARC Meat Research Institute, Langford, Bristol
(Manuscript received 6 September 1978)
Twelve gilts from four breeds were reared from 30 to 65 kg liveweight and assessed for carcass, muscle and eating quality. The breeds were Large White (LW), Gloucester Old Spot (GOS) Crossbreed 1 (Cl) and Crossbreed 2 ((22). The latter two were commercial products from breeding companies. There were small differences in quality between the breeds. C1 had about 2 % more lean than the others. GOS had shorter carcasses, a higher proportion of total lean in the fore limb and thicker backfat but were not fatter overall. C1 and C2 had lower pH1 measurements than LW or GOS but similar colour and drip loss measurements in M . longissimus lumborum. There were positive but weak relationships between pH1 and percentage fat ( r = f0.1 to +0.3). C1 had the more tender meat. When all breeds were pooled, about 9 % of the variation in toughness was accounted for by variation in percentage lean or fat. There was no suggestion that the pure breeds or fatter pigs had meat of better eating quality. 1. Introduction
In the United Kingdom, pork and lamb are meats derived from animals slaughtered at relatively young physiological ages and are intrinsically tender. Tenderness is overwhelminglythemost important factor in the eating quality of meats, and the popularity of pork and lamb depends to a large extent on the ability of the housewife to use the quick methods of cooking-grilling and frying-for them. The pig was traditionally a source of animal fat and the trend to reduce the human intake of fat during the last 30 years has forced continuous efforts in husbandry to reduce fatness in the pig carcass. Fears have been expressed that reduction in the fatness of pork would be accompanied by increases in toughness, in the belief that the substitution of a soft fat by a more coherent protein must produce tougher meat. Much research has shown that this effect, if apparent, is very small; estimates of the correlation coefficient between fatness and tenderness show a wide range, both positive and negative, and overall about 10% of the variability in the texture of the lean of meat (pork and beef mostly) is accounted for by the level of fatness of the carcass1 Pig carcasses have become leaner as a result of improvements in breeding and management, the average backfat thickness of pigs in the classification scheme operated by MLC in Great Britain having decreased by about 2.0 mm between 1971 and 1976. This comparatively small difference is much less than the range over which experimental work has demonstrated little or no effect of fatness on texture (correlation coefficients < 0.25).l Nevertheless, concern continues to be expressed by quality meat retailers that modern pork is less tender than that produced 25 years ago and the present work was undertaken to study the eating quality differences between pork from a traditional breed now infrequently used (Gloucester Old Spot), a conventional breed (Large White) and two commercially developed cross breeds. At the same time other aspects of carcass and meat quality were investigated. 2. Materials and methods
Each breed was represented by 12 pigs. Pure bred Large White (LW) and Gloucester Old Spot 0022-5142/79/050@0493 $02.00
01979 Society of Chemical Industry 493
J. D. Wood et al.
494
(GOS) gilts were obtained from sources used in previous work at MRI2 and crossbred gilts, products of different breeding companies designated C1 and C2 were obtained from commercial sources. Gilts of approximately 30 kg liveweight (8Ck90 days of age) were housed in mixed breed groups of twelve and fed individually on the same diet at one of two feeding levels: to appetite for 1 h twice daily or to a scale designed to provide about 80 % of appetite. The diet was a proprietary pelleted one containing 18.5 % crude protein. At approximately 65 kg liveweight, the pigs were laired overnight (17-19 h) without food and slaughtered by electrical stunning and exsanguination. The hot carcass weight, PZfat measurement (6.5 cm from the midline opposite the head of the last rib and excluding skin thickness) and pH in the M . longissimrcs lumborum (LD) at 45 min post-slaughter (PHI) were recorded. The carcasses were then chilled at 5°C for 18 h and split down the midline. Backfat thickness (excluding skin) measurements were made and the left side was used for determination of tissue composition using the 'total tissue' dissection procedure3 which involves removal of subcutaneous fat followed by dissection of four 'anatomical joints' into lean, bone and intermuscular fat. The right side was used for quality assessments. Drip was measured on a chop containing the 7th-9th thoracic vertebrae after storage at 1"C for 48 h. Colour (Hunter Colour Difference Meter), ultimate pH and pigment concentration4 were measured on the LD from the 4th-6th thoracic vertebrae, 3 days after slaughter. Six to eight days after slaughter ajoint from the 10th thoracic to 6th lumbar vertebrae was roasted at 180°C to an internal temperature of 80°C. The eating quality of the L D was assessed by taste panelists and texture was determined instrumentally. Flavour was assessed on an 8-point scale: dislike extremely, dislike very much, dislike moderately, dislike slightly, like slightly, like moderately, like very much, like extremely and scored - 7, - 5, -3, - 1, 1 , 3, 5,7, respectively. Tenderness was judged on an 8-point scale: extremely tough (scored -7), very tough (- 5 ) , moderately tough (- 3), slightly tough ( - l), slightly tender (l), moderately tender (3), very tender (5) extremely tender (7) and juiciness: dry (O),slightly juicy (l), moderately juicy (2), extremely juicy (3). Analysis of the results was done using scores from 7 panelists who gave 284 assessments of each attribute (31 missing values were inserted to reduce the residual mean square). Toughness was determined instrumentally on the roast LD by measuring the total work done to compress uniform samples between blunt jaws.5
3. Results
Analysis of variance was done with the main effects breed, level of feeding and their interaction. Although pigs fed to appetite consumed more feed per day (2045 us 1675 g s.e.d. 43.2) and grew more quickly (786 u s 708 g day-1 s.e.d. 24.0) than the scale-fed pigs there were no significant feeding level or interaction effects on any aspect of composition or quality. Therefore the results for breed alone are given (Table 1). The average values for feed intake per day were 1882, 1846, 1941 and 1825 g in LW, GOS, C1 and C2, respectively. GOS had short carcasses and GOS (particularly) and C2 had thick backfat. C1 had the thinnest backfat and the leanest carcasses. GOS had more lean in the fore limb and less in the hind limb compared with the other breeds. pH1 was lower in C l and C2 than in LW and GOS whereas ~ H F was the same in all breeds. Cl were the most tender whilst LW were the least tender, although the difference was only one point on the eight point scale. All other measurement of muscle or eating quality were unaffected by breed. The breed means for backfat thickness at C (directly above maximum depth (B) of eye muscle) and hot PZ (6.5 cm from midline) were similar. PZ was also measured on the cold carcass and a slight reduction from the hot value was observed. Overall means (mm+s.d.) were: hot PZ 12.475 3.13 ; cold PZ 1I SO? 2.71. Carcass length also declined during the process of cooling from 722 +_ 17 to 716k19 (mm+s.d.). Correlation coefficients, pooled within subgroups, are given in Table 2. There was no correlation between feed intake per day and any aspect of carcass or meat quality. Carcass length was negatively correlated with backfat thickness, percentage subcutaneous and total fat and positively
Carcass and eating quality of pork
495
Table 1. Carcass measurements, carcass composition, lean distribution, muscle quality and eating quality in pigs from four breeds Breed
-
Carcass measurements
Hot carcass weight (kg) Leg length (mm) Carcass length (mm) Shoulder depth (mm) Shoulder width (mm)
LW
GOS
50. l b
48.6% 516a 69ia 292b 122%
529b 720b 293b l18a
c1 50.2b 527b 725'1 299 122"
C2 48.8a 512a 716b 279a 130a
S.e.d. and significance 0.59* 6.0* 6.6*** 5.5* 7.1n5
Backfat thickness
Mid-rump (mm) Mid-back (mm) Shoulder (mm)
16.48 14.6% 31.7%
19.6b 17.7" 33.2b
13.9% 14.6% 29.68.
19.1b 16.3a 32.7h
1.42*** 1.04* 1.50NS
Eye muscle measurements
Width (A) (mm) Depth (B) (mm) Fat thickness (C) (mm) Fat thickness (K) (mm) Hot PZ (mm)
84.38 44.5% 11 .4a 18.4% 11.88
81.6" 45.4% 14.4'' 19.5% 14.4b
83.Y 47.9% 11.5' 18.9 10.7a
83.2& 44.98 12.9" 20.7% 12.88
2.57NS 2.06NS 1.10* 1.20NS 1.17*
Carcass compositiona
Lean Bone Subcutaneous fat Total fat
53.97ab 11.58b 22. lob 30. 38ab
53. 3ga 10.868 21.33ab 30.62ab
55. 86b 1 1 .24ab 19.39a 28. 40a
53.40% 10.86s 22.62b 31.50"
1.17** 0.30NS 1.03* 1.22NS
Lean distributionb
Fore limb Neck and thorax Lumbar and abdomen Hind limb
13.17s 37.02" 12.758 33.14b
13.87" 37.38% 13.34% 31.76%
13.08& 37.968 12.51a 32.438
13.328 36.708. 12.42a 33.92b
0.23** 0.63NS 0.54NS 0.37***
Muscle quality
pH1 PHF Intramuscular fat (%) Haem pigment (parts Drip 48 h (%) Lightness raw muscle
6.4b
6.5b 5.6" 2.0% 38.3& 1.28 50.8%
6. l a 5.4= 2.08 36.58 1.3a 51.2'
Eating quality
Toughness (J) Tenderness ( - 7 to 7) Flavour (- 7 to 7) Juiciness (0 to 3)
+
+
5.5%
2.1% 34.7% 1 .O& 51 .O& 0.20b
0.18ah
0.16"
0.5%
1.3b 2.9 1.2"
1.P
2.38 1.28
2.28 1.28
6.18
0.11**
5.53
0.05NS 0.23NS 2.84NS 0.22NS
1.98 36.3a 1.4s 51.1% 0.19b 1. lab 2.48 1.18
1.35NS
0.011** 0.35** 0.30NS O.1lNS
*** P
