Colour differences among carcasses graded with similar score for conformation and fatness

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1 Animal (2008), 2:7, pp & The Animal Consortium 2008 doi: /s animal Colour differences among carcasses graded with similar score for conformation and fatness G. Indurain 1,V.Goñi 1, A. Horcada 2, K. Insausti 1, B. Hernández 1 and M. J. Beriain 1 1 Escuela Técnica Superior de Ingenieros Agrónomos, Universidad Pública de Navarra, Campus de Arrosadía 31006, Pamplona, Spain; 2 Escuela Universitaria de Ingeniería Técnica Agrícola, Universidad de Sevilla, Carretera de Utrera Km 15, 41013, Sevilla, Spain (Received 6 June 2007; Accepted 18 March 2008) In a population of 268 yearling bulls, those carcasses graded as U 2,U 0 or U 1 for beef carcass conformation (n 5 240) and those graded as 2 2,2 0 or 2 1 for beef carcass fatness (n 5 213) were selected to study the efficiency of carcass weight, carcass dimensions and instrumental colour of latissimus dorsi, rectus abdominis and subcutaneous fat, to discriminate among these carcass grades, in a population of highmuscled and very lean carcasses from young bulls. The increase in conformation grade meant an increase in carcass weight and perimeter of the leg. Classifiers use attributes characterizing muscular development and carcass profiles from a general impression of the whole carcass. There were no significant differences for carcass weight or carcass dimensions, among the carcasses classified according to the three fat classes. The a* and b* coordinate values for the latissimus dorsi muscle were observed to decrease significantly as the carcass conformation score increased (P, 0.05). However, muscle and subcutaneous fat of fatter carcasses showed higher a*, b* colour coordinates and chroma (C*) values than leaner carcasses. The CIE (Commission International de l Éclairage) L*, a* and b* colour coordinate measurements taken on the carcasses 45 min post mortem varied significantly from the readings taken after hanging for 24 h (P, 0,001). The higher a* and b* values on the carcasses chilled for 24 h could be caused by oxygenation of both subcutaneous fat, and latissimus dorsi and rectus abdominis muscles in the time elapsing after slaughter and after carcass exposition to circulating air in the cooler for 24 h. Lightness of the latissimus dorsi muscle underwent a decrease, compared with an increase in the rectus abdominis muscle. Hardening of the subcutaneous fat during cold storage may exert an influence on the decrease in lightness observed. These differences in carcass colour during chilling storage would suggest that the relationship between carcass colour and conformation grades was higher shortly after slaughter. Both L* colour coordinate of fat colour (P, 0.01) and a*, b* and C* colour coordinates of latissimus dorsi muscle (P, 0.05) were related to conformation classification. Colour was more efficient to differentiate conformation than fat cover classes. Sixtytwo percent of carcasses were correctly classified for conformation by colour differences but only 37% of carcasses were correctly classified for fatness by colour. Keywords: beef, carcass classification, colour Introduction The Spanish Beef market demands animals in the early stage of puberty or young animals, with highmuscled carcasses, a high percentage of lean meat and a certain degree of fatness to prevent weight loss during cold storage, while maintaining sensory quality (Alberti et al., 2005). The beef industry has become increasingly interested in implementing strategies for improving and reducing variation in carcass and meat quality. A successful tool to achieve this has been the implementation of Protected Geographical Indications (PGI), which try mjberiain@unavarra.es to promote beef consumption from local breeds and traditional handling (European Commission, 2007). The consequence of marketing beef from a specific breed and handling method is that the range of carcass conformation and fatness degrees becomes narrow, also reducing the variation in carcass quality. The European Union set up a bovine carcass conformation and fatness classification system, EUROP scales, to be applied in the entire EU territory for bovines heavier than 300 kg of live weight (Regulation EEC No. 1021/91) to provide a basis for determining the market price within each carcass weight range, facilitate the relationship between market operators and supplying markets with 1093

2 Indurain, Goñi, Horcada, Insausti, Hernández and Beriain quality products. Because the scheme depends on human judgement, it is criticized by some as being subjective and, although classifiers do a complex training procedure before carrying out commercial classifications in order to avoid substantial individual differences in assessment, repeatability of carcass classifications tends to be low. Besides, carcass classification is criticized because it is a visual evaluation and carcass classes are described in a very broad manner (Díez et al., 2006). Cannell et al. (2002) concluded that the fast pace of classification in commercial packing plants caused inaccuracies in applications of grades by linegraders, thus affecting market confidence. To avoid errors in carcass classification, there have been attempts to develop automatic classifiers of carcass grading (Steiner et al., 2003), but only video image analysis has been applied for the online classification of beef carcasses according to the EUROP scale for conformation and fat cover (Allen and Finnerty, 2001; Goyache et al., 2001). Colour measurements have been used as a tool to estimate beef palatability (Wulf and Page, 2000; Wyle et al., 2003), and specifically, consumers assess the freshness and tenderness of veal based on lean colour; thus the veal industry relies heavily on lean colour for carcass grading and for determining carcass value (Denoyelle and Berny, 1999; Lagoda et al., 2002). Klont et al. (1999) found in veal carcasses that the majority of the muscle colour parameters measured at different times post mortem were not significant and only L* values 45 min post mortem were significantly lower for the heavier carcasses compared with the lighter ones. However, there is lack of information on the relationship between carcass colour and classification for conformation and fatness classes in older and nonsuckling animals. Thus, the aim of this paper is to study whether there are colour differences among close carcass conformation and fatness classes and whether instrumental colour measurements could improve carcass classification in a narrow range of conformation and fatness grades of carcasses coming from a population of highmuscled and very lean carcasses. Material and methods Animals A total of 268 Pirenaica yearling bulls were born and raised on three private farms located in Northern Spain. After weaning at around 6 months of age, calves were fed with concentrate (containing corn gluten feed, soybean meal, copra, corn, wheat, beans, palmist, mineral salts and vitamins), which contained 90% dry matter, 16% crude protein, 6% crude fibre and 5% crude fat, and straw, both ad libitum (Association of Official Analytical Chemists, 2000). Animals were slaughtered and dressed in an officially approved slaughterhouse. Animals were transported approximately 60 km from each farm the same day of slaughter. Animals were slaughtered using standard commercial procedures, according to European welfare codes of practice. Animals were slaughtered on arrival using a captive bolt stunner followed by sticking and bleeding. Just after bleeding they were hung from their hocks. Animals were slaughtered at kg live weight and days of age. This is the most usual commercial type of carcass produced in Spain from young bulls slaughtered for beef consumption (Alberti et al., 2005). Carcass classification, weight and dimensions Before carcasses were placed in the cooler for ageing, 45 min post mortem, three licensed technicians classified carcasses for conformation and fatness according to the European beef carcass classification system (Regulation EEC No. 1021/91). When one of the technicians disagreed in the classification from the other two, his classification was discarded. When the three grades gave three different classifications, the average was used. For conformation score, thickness, width and length of carcass are estimated. A carcass considered wellconformed shows good muscling and convex and transversal profiles, and is wide, short and compact. Conformation classification has six grades, which form the word SEUROP, with S being those carcasses with superior conformation, E excellent, U very good, R good, O fair and P being poor. Fatness degree is related to the amount of subcutaneous and thoracic fat. Fatness classes are 1 for low, 2 slight, 3 average, 4 high and 5 for very high. Conformation and fatness categories can be subdivided up to three subcategories (1, 0 and 2) to improve the accuracy of classification. Hence, for conformation, carcasses were scored from 18 for S1 to1forp2. For fatness, carcasses were scored from 15 for 51 to 1 for 12. Table 1 shows that 80% of carcasses graded 2 in fatness score (22, 28 or 21) (n 5 213) and 90% of carcasses graded U in conformation score (U2, U8 or U1) (n 5 240). To test a homogenous dataset group of carcasses and to try to identify the major factors affecting conformation and fatness classification, for statistical analysis it was decided to leave out of this study carcasses with conformation scores higher or lower than U (classes E, R and O), and fatness scores higher or lower than 2 (classes 1 and 3). Immediately after classification, the carcasses were hung in a cold store at 48C for chilling. After chilling, the left half of the carcass was sectioned at the sixth thoracic rib and the ph and temperature of the longissimus dorsi muscle were measured (ph24 h and T a 24 h) using a portable Crison model 507 ph meter equipped with a penetration electrode and a temperature probe (ISO, 1974). After chilling, carcasses were weighed and carcass measurements were recorded according to de Boer et al. (1974) and Alberti et al. (2005). > Length of carcass, measured from the anterior edge of the symphysis pubis to the middle of the anterior edge of the visible part of the first rib. > Length of the hind leg, measured from the medial malleolus of the tibia in a straight line to the anterior edge of the symphysis pubis. 1094

3 Colour differences in beef carcasses Table 1 Percentage of carcasses by conformation and fatness grades of the European beef carcass classification system (n 5 268) Grades Conformation O1 R R1 U U1 U2 E2 E Fatness Carcass conformation and fatness scores by comparison with the official conformation standards of the European Union beef carcass classification system. > Width of the leg, measured as the horizontal distance between the outermost points on the medial and the lateral surface of the leg. > Perimeter of the leg, the maximum measurement of the horizontal contour of the leg at the symphysis pubis level. > Depth of the chest, measured from the last sternebra to the dorsal tip of the spinous process of the sixth thoracic vertebra. A blockiness index was calculated as the ratio between cold carcass weight and carcass length. Length and perimeter measurements were taken by a tape measure, whereas width measurements were taken by a caliper. Colour measurement At the end of the slaughter chain (45 min post mortem) and before the carcasses were placed in the cooler, instrumental colour measurements were taken on two accessible muscles on the carcass surface: latissimus dorsi muscle at the 8th thoracic rib (LTD45 min) and on the outer portion of the rectus abdominis muscles (RA45 min). No cut or incision was made to measure the colour of these muscles. Carcass fat colour was measured on the subcutaneous fat covering longissimus dorsi muscle, at the 10th rib (FAT45 min). After hanging in a cold store for 24 h, colour readings were taken again on the LTD (LTD24 h) and RA (RA24 h) muscles, and on the subcutaneous fat (FAT24 h). The LTD muscle was chosen as one of the most easily accessible muscles on the carcass, while the RA muscle was chosen because it was recommended for measurement by Legras (1981) and the American Meat Science Association (2001). Meat colour was measured instrumentally using a spectrocolorimeter (model CM2002; Minolta, Osaka, Japan) (l: 400 to 700 nm, Dl: 10 nm, D65, 108) calibrated with a white plate and a light trap supplied by the manufacturer. Colour was expressed using the Commission International de l Éclairage (CIE) L*, a* and b* colour system (CIE, 1976) together with hue angle (H*) and chroma (C*). A total of five spectral readings were taken for subcutaneous fat and for each muscle, turning the spectrocolorimeter Statistical analysis Oneway analysis of variance (ANOVA), taking time elapsed after slaughter as the fixed effect, was run in order to measure Table 2 Descriptive statistics for live weight, carcass weight, carcass dimensions, ph and temperature of yearling bull carcasses (n 5 268) Minimum Maximum Mean 6 s.d. Live weight (kg) Cold carcass weight (kg) Length of carcass (cm) Length of hind leg (cm) Perimeter of leg (cm) Width of leg (cm) Depth of chest (cm) Blockiness index ph24 h post mortem T a 24 h post mortem (8C) Length of carcass: distance from the anterior edge of symphysis pubis to the middle of the anterior edge of the visible part of the first rib. Length of hind leg: distance from the medial malleolus of the tibia in a straight line to the anterior edge of the symphysis pubis. Width of leg: The horizontal distance between the outermost points on the medial and the lateral surface of the leg. Perimeter of leg: the maximum measurement of the horizontal contour of the leg at the symphysis pubis level. Depth of chest: distance from the last sternebra to the dorsal tip of the spinous process of the sixth thoracic vertebra. Blockiness index: ratio between cold carcass weight and carcass length. carcass colour evolution during the first 24 h post mortem. Tukey s test was used for the comparison of means. Oneway ANOVA was used to examine the differences among U conformationgrade levels (U2, U8 and U1) and among 2 fatnessgrade levels (22, 28 and 21) depending on carcass weight, dimension, colour, ph and temperature. Discriminant function analysis was used to determine which variables measured on the carcass discriminate between the grades of conformation and grades of fatness. Owing to the high number of parameters measured, only those that showed significant differences among conformation or fatness classes were included in the discriminant analysis. The statistical package used was SPSS v.13.0 (SPSS Inc., Chicago, IL, USA). Results and discussion Carcass characteristics and colour evolution Data from the carcasses studied could be considered a representative sample of the actual distribution of weights, conformation and fatness existing in the beef market under the Protected Geographical Indication Ternera de Navarra. Table 1 shows that the cattle used in this study produced mediumhigh conformed and lowfat carcasses: conformation score U or very good and fatness score 2 or slight. Data from the carcasses studied (Table 2) could be a representative sample of Pirenaica young bulls raised and slaughtered similarly, because they were similar to those reported for different authors (Goñi et al., 1999; Gorraiz et al., 2002; Alberti et al., 2005). Table 3 lists the colour coordinate values characterizing the subcutaneous fat, LTD and RA muscles on the day of slaughter (45 min post slaughter) and after chilling for 24 h. 1095

4 Indurain, Goñi, Horcada, Insausti, Hernández and Beriain Table 3 Least Square Mean and standard error values for the instrumental CIE L*, a* and b* colour coordinates, chroma (C*) and hue (H*), for the subcutaneous fat, latissimus dorsi and rectus abdominis muscles 45 min post mortem and after hanging for 24 h in a cold store in yearling bull carcasses (n 5 268) 45 min post mortem 24 h post mortem Subcutaneous fat L* *** a* *** b* *** C* *** H* *** Latissimus dorsi L* *** a* *** b* *** C* *** H* *** Rectus abdominis L* *** a* *** b* *** C* *** H* ns The results for the colour coordinates a* and b* for the RA muscle in this study are similar to those described by Klont et al. (1999) and Lagoda et al. (2002). In contrast, lightness (L*) values were substantially lower (10 to 15 units). This difference may be attributed to the fact that these authors studied veal cattle (16 to 30 weeks old) whereas in the current study yearling bulls were used (1year old). The CIE L*, a* and b* colour coordinate measurements taken on the carcass at the time of slaughter (45 min post mortem) varied significantly from the readings taken after hanging for 24 h (P, 0.001). The higher a* and b* values could be caused by oxygenation of both subcutaneous fat and the LTD and RA muscles in the time elapsing after slaughter. The change in L* was different for the two muscles: Lightness of the subcutaneous fat and LTD muscle underwent a decrease, compared with an increase in the RA muscle. Eikelenboom et al. (1992) and Lagoda et al. (2002) also observed an increase in lightness for the RA muscle, and this may be due to an increase in the amount of light dispersed by the muscle myofibrils as a consequence of rigor mortis of the muscle (MacDougall, 1982). Barnier et al. (1998) pointed out that the decrease in lightness taking place in the LTD muscle could be explained in terms of changes in myoglobin concentration and the final ph value, but these two factors could not fully explain it. Besides, if the carcass surface was exposed to the circulating air in the cooler for close to 24 h, moisture loss and surface hardening of the latissimus dorsi muscle surface and subcutaneous fat could have occurred, and this factor could contribute to the occurrence of darker carcasses during storage as compared to the early post mortem evaluation of colourless exposed muscle to circulating air such as rectus abdominis. Differences among conformation grades Table 4 presents the ANOVA results for carcass weight, carcass dimensions, ph, temperature, colour coordinate readings (L*, a*, b*, C* and H*) for the subcutaneous fat, latissimus dorsi and rectus abdominis muscles from the yearling bull carcasses measured at 45 min and 24 h post mortem according to subclasses (U2, U8 and U1) of conformation class U. The cold carcass weight, perimeter of the leg, width of the leg and the blockiness index increased as the carcass conformation score increased (P, 0.05). The general impression of the whole carcass affects the classification, as it is reflected by the increase in carcass weight and blockiness index with conformation grade (Díez et al., 2003). Although carcass weight is not properly included in the conformation rules, these results suggest that this trait exerts a major influence on classification performance. There were no differences in carcass dimensions related to length, so the grader tried to reflect the differences in the proportions of the moredesirable (round) to lessdesirable part of the carcass, and so the graders scored higher for conformation of those carcasses with a higher perimeter of the leg, that is, the wide and compact carcasses with more convex and transversal profiles. This relationship between perimeter of the leg and carcass conformation agrees with results of Díez et al. (2003), who found that in yearling bulls, classifiers apply conformation classification rules rigorously and use only attributes characterizing muscular development and carcass profiles. In the same way, Alberti et al. (2005) found that variables related to the volume of the leg were highly and significantly correlated with conformation in yearling bulls. However, these results do not mean that classifiers always take into account the muscular development of the leg. Firstly, carcass classification presents highly nonlinear patterns because the behaviour of classifiers seems to be quite different when dealing with different types of carcasses. For example, muscular development of the leg is taken into account when carcasses from yearling bulls with a very good conformation (conformation U) are judged. Secondly, when the grader classifies carcasses over a wide range of carcasses, then attributes characterizing body size or skeletal development, such as depth of the chest or length of the carcass, acquire considerable importance, overriding the attributes characterizing muscular development (Díez et al., 2006). Klont et al. (1999) observed higher temperature and lower ph at 24 h post mortem in veal carcasses with best conformation. Although in the current research there were no differences in the final ph or temperature values among conformation grades, the heavier carcasses had lower ph values than the lighter carcasses (r ; P, 0.05). At constant temperature, heavier carcasses delay cooling, with higher carcass temperatures for longer periods being conducive to acid formation in the muscle, in turn hastening the onset of rigor mortis. The a* and b* coordinates and chroma (C*) values for the LTD muscle, 45 min post mortem, was observed to 1096

5 Colour differences in beef carcasses Table 4 Carcass weight and dimensions, ph, temperature and colour readings for subcutaneous fat, latissimus dorsi and rectus abdominis muscles, measured 45 min (45 min) and 24 h (24 h) post mortem for the subclasses of the beef carcass conformation class U (n 5 240) (least square mean 6 s.e.) Carcass conformation classes U2 U U1 Carcass weight (kg) a b c *** Length of carcass (cm) ns Length of leg (cm) ns Perimeter of leg (cm) a b c *** Width of leg (cm) a a b * Depth of chest (cm) ns Blockiness index a b c *** ph24 h ns T a 24 h (8C) ns Subcutaneous fat 45 min L* a a b ** a* ns b* ns C* ns H* ns Latissimus dorsi 45 min L* ns a* a a b ** b* a b b * C* a b c *** H* ns Rectus abdominis 45 min L* ns a* ns b* ns C* ns H* ns Subcutaneous fat 24 h L* ns a* ns b* ns C* ns H* ns Latissimus dorsi 24 h L* a b b * a* ab a b 1 b* a ab b 1 C* a ab b 1 H* ns Rectus abdominis 24 h L* ns a* ns b* ns C* ns H* ns For a description of carcass dimensions see Table 2. Different superscript letters within row indicate significant differences. decrease significantly as the carcass conformation score increased (P, 0.05). After 24 h, beef carcasses scoring U2 for conformation showed a tendency to have higher L*, a*, b* and C* values than carcasses scoring U1 (P, 0.5). Regarding subcutaneous fat colour, there were only significant differences in the lightness (L*) at the 45 min post mortem when carcasses graded as U1 showed higher L* values (P, 0.01). Carcass colour evolutes during chilling (Table 3) and carcasses with higher conformation scores would show a more pronounced decrease in L*. Carcass colour variables measured shortly after slaughter were closely related to conformation score than colour variables measured after 24 h of chilling (Table 4). The higher conformation values are usually associated with more highly developed white muscle fibre content, which are less pigmented and it could account for the decrease in a* and C* (Jurie et al., 1995). Besides, the lower colour coordinates in those carcasses with high conformation grade would be linked to a higher final ph value (Guignot et al., 1994; Wulf et al., 1997). When defining groups by conformation score, two discriminant functions were obtained, with 69% of carcasses 1097

6 Indurain, Goñi, Horcada, Insausti, Hernández and Beriain Table 5 Correlation coefficients between canonical discriminant functions and carcass parameters on groups defined by conformation score % Variance 80.0% 20.0% Function 1 Function 2 Perimeter of leg a Blockiness index a Carcass weight a LTD45 min b* a Width of leg a LTD45 min a* a FAT45 min L* a LTD24 h L* a C* coordinate was not included because it is a combination of a* and b* coordinates. For a description of carcass dimensions see Table 2. a Largest absolute correlation between each variable and any discriminant function. correctly classified (Table 5). Function 1 separated low from highconformation score due to differences on muscular development of the leg, blockiness, carcass weight, and colour coordinate b* measured at the latissimus dorsi muscle, taken 45 min post mortem. Function 2 separated medium from high and lowconformation scores, on the basis of colour coordinate a* of latissimus dorsi muscle measured 45 min post mortem and L* of subcutaneous fat 45 min post mortem and latissimus dorsi muscle after carcass chilling (24 h post mortem). Of the total, 62.1% of cases were correctly classified. No carcass with conformation U2 was classified as U1, but 35.7% were classified as U. Again, 16.2% and 23.2% of carcasses with conformation U were classified as U2 and U1, respectively. Finally, 11.9% and 23.8% of carcasses with conformation U1 were classified as U2 and U, respectively. Allen and Finnerty (2001) found that video image analysis classified correctly between 58.3% and 48.7% of carcass for conformation depending on the type of video image system. These authors studied a carcass population that presented all the conformation score and they found that between 94% and 97% of predictions were within one subclass of the reference panel score. Differences among fatness grades Table 6 presents the ANOVA results for carcass weight, carcass dimensions, ph, temperature and colour coordinate readings (L*, a*, b*, C* and H*) for the subcutaneous fat, latissimus dorsi and rectus abdominis muscles from the yearling bull carcasses measured at 45 min and 24 h post mortem according to subgrades (22, 28 and 21) of fattening grade 2. There were no significant differences for carcass weight, carcass dimensions, carcass ph and temperature among the carcasses classified according to the three degrees of fattening. Alberti et al. (2005) found that carcass fatness had a weaker relationship with carcass dimensions than conformation in a heterogeneous population of yearling bulls. A higher carcass temperature would be expected in those fatter carcasses, due to the protection that subcutaneous fat provides against cooling. However, the low fattening level of the carcasses in the present study would not provide differences in the carcass cooling. At 45 min post mortem, the RA muscle in the fatter carcasses showed lower lightness (L*) (P, 0.1), but higher a* colour coordinate and chroma (C*) values than leaner carcasses (P, 0.05). At 24 h post mortem, LTD muscle colour in the fatter carcasses was not only redder (a*) and had higher chroma (C*), but also had higher b* (P, 0.05). At 24 h post mortem, subcutaneous fat of carcasses with fatness score 21 tended to show lower L* but higher b* andc* values (P, 0.05) than leaner carcasses. Conformation and fatness were negatively correlated (r ; P, 0.05, data not shown). Those carcasses with higher conformation would be leaner and have muscles surface with lower a*, b* and C* values than those fatter carcasses with lower conformation scores (Tables 4 and 6). Due to the thin subcutaneous fat layer (3.2 mm at the 6th rib), light of the spectrocolorimeter couldexceedthefatlayerandhigherb* andc* valuesof subcutaneous fat 24 h post mortem of those fatter carcasses could be influenced by the colour of the muscle that covers (longissimus dorsi). When defining groups by fatness score, two discriminant functions were obtained, but only 37.1% of carcasses were correctly classified (Table 7). Function 1 separated low and medium against high fatness score due to differences in the b* colour coordinate of fat and LTD muscle 24 h post mortem and the a* coordinate of RA 45 min post mortem. Function 2 separated medium from low fatness scores, on the basis of the a* coordinate of LTD after carcass chilling. Around 72.2% of carcasses with fat class 22 were correctly classified but 22.2% and 5.6% were classified as 2 and 21, respectively. Also, 72% of carcasses with fatness score 2 were incorrectly classified, 46.5% as 22 and 25.6% as 21. Finally, 60.9% of carcasses with fatness score 21 were correctly classified but 30.4% and 8.7% were classified as 22 and 2, respectively. Allen and Finnerty (2001) found that video image analysis classified correctly between 34.8% and 30.2% of carcass for fatness depending on the type of video image system. These authors studied a carcass population that presented all the fatness classes and they found that between 74.4% and 79.6% of predictions were within one subclass of the reference panel score. These authors attribute the lower efficiency of video image systems to correctly classify carcasses by fatness class to the greater variation in beef carcasses fat class scores compared with the conformation class scores in the population they studied. However, they pointed out that it may reflect greater difficulty in determining the correct fat class by the carcass graders. Some authors have reported that tougher beef was associated with darkercoloured lean measured at the ribbed longissimus dorsi (lower L*, a* and b* values) 1098

7 Colour differences in beef carcasses Table 6 Carcass weight and dimensions, ph, temperature, colour readings for the subcutaneous fat, latissimus dorsi and rectus abdominis muscles, measured 45 min (45 min) and 24 h (24 h) post mortem for the subgrades of the beef carcass fatness grade 2 (n 5 213) (least square mean 6 s.e.) Carcass fatness classes Carcass weight (kg) ns Length of carcass (cm) ns Length of leg (cm) ns Perimeter of leg (cm) ns Width of leg (cm) ns Depth of chest (cm) ns Blockiness index ns ph24 h ns T a 24 h (8C) ns Subcutaneous fat 45 min L* ns a* ns b* ns C* ns H* ns Latissimus dorsi 45 min L* ns a* ns b* ns C* ns H* ns Rectus abdominis 45 min L* a ab b 1 a* a a b * b* ns C* a a b * H* ns Subcutaneous fat 24 h L* ab a b 1 a* ns b* a a b * C* a a b * H* ns Latissimus dorsi 24 h L* ns a* a a b * b* a a b * C* a a b ** H* ns Rectus abdominis 24 h L* ns a* ns b* ns C* ns H* 36.47a ab b * For a description of carcass dimensions see Table 2. Different superscript letters within row indicate significant differences. (Wulf and Page, 2000; Wyle et al., 2003; Goñi et al., 2007). The relationship between colour and tenderness has been explained by the effect of animal feeding with tenderness, e.g. more carotenoids (higher b* values) in grassfed animals (Vote et al., 2003). However, Goñi et al. (2007) found that those carcasses with higher b* colour values in LTD and higher a* in RA yielded tougher cooked meat in a group of animals fed with the same diet based on concentrate. Although the relationship of fat and lean colour with tenderness could be different regarding the type of muscle, carcass management or animal feeding, differences in carcass colour among carcasses could be helpful both to grade carcasses for fatness and conformation more accurately and as an indicator of palatability. Conclusion There was an increase in the a* and b* colour coordinates during the first 24 h post mortem both in subcutaneous fat and in carcass surface muscles. However, L* values evolution was different depending on the muscle. Even in very close conformation grades, the carcasses with a high conformation score were heavier and had higher perimeter of 1099

8 Indurain, Goñi, Horcada, Insausti, Hernández and Beriain Table 7 Correlation coefficients between canonical discriminant functions and carcass parameters on groups defined by fatness score the leg. Besides, they exhibited lower L*, a* and b* colour coordinates than those carcasses with a lower conformation score. This relationship was more pronounced in latissimus dorsi muscle at the time of slaughter and it supports the conventional practice of classifying carcasses very shortly after slaughter. Colorimetric readings intending to differentiate carcasses based on their degree of fattening should be made on the LTD muscle 24 h post mortem, once cooling and hardening of the fat is well under way. So, colour measurements on the carcass at the early post mortem period might be helpful to meat industry and to producers in order to discriminate among carcass classification grades. Anyway, it would be interesting that the method would be taken on to further trials to test the strength of its predictive ability. This would help to establish a more objective price for this type of carcasses that are very homogeneous for official classification. References Alberti P, Ripoll G, Goyache F, Lahoz F, Olleta JL, Panea B and Sañudo C Carcass characterisation of seven Spanish beef breeds slaughtered at two commercial weights. Meat Science 71, Allen P and Finnerty N Mechanical grading of beef carcasses. Enof Porject Reports Teagasc ISBN The Irish Agriculture and Food Development Authority, Dublin, Ireland. American Meat Science Association Meat evaluation handbook. American Meat Science Association, Savoy, IL, USA. Association of Official Analytical Chemists Official method of analysis, 17th edition. AOAC, Washington DC, USA. 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