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Relationship between collagen characteristics, lipid content and raw and cooked texture of meat from young bulls of fifteen European breeds
Meat Science 87 (2011) 61–65
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Meat Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m e a t s c i
Relationship between collagen characteristics, lipid content and raw and cooked texture of meat from young bulls of fifteen European breeds Mette Christensen a,⁎, Per Ertbjerg a, Sebastiana Failla b, Carlos Sañudo c, R. Ian Richardson d, Geoff R. Nute d, José L. Olleta c, Begoña Panea e, Pere Albertí e, Manuel Juárez b, Jean-François Hocquette f, John L. Williams g,1 a
Department of Food Science, University of Copenhagen, DK-1958 Frederiksberg C, Denmark CRA-PCM, Via Salaria 31, 00016 Monterotondo, Italy Departamento de Producción Animal y Ciencia de los Alimentos, Universidad de Zaragoza, 50013 Zaragoza, Spain d Division of Farm Animal Science, University of Bristol, Langford, Bristol, BS40 5DU, United Kingdom e Centro de Investigación y Tecnología Agroalimentaria, Gobierno de Aragón, 50059 Zaragoza, Spain f INRA, UR1213, Unité de Recherches sur les Herbivores, Equipe Croissance et Métabolisme du Muscle, INRA-Theix, 63122 Saint-Genes Champanelle, France g Roslin Institute (Edinburgh), EH25 9PS, United Kingdom b c
a r t i c l e
i n f o
Article history: Received 2 July 2010 Received in revised form 31 August 2010 Accepted 1 September 2010 Keywords: Cattle M. longissimus thoracis Sarcomere length Intramuscular fat Shear force Compression
a b s t r a c t Variations in texture were determined for 10 day aged raw and cooked Longissimus thoracis (LT) muscle from 436 bulls of 15 European cattle breeds slaughtered at an age of 13–16 months. Variations in texture were related to differences in pH 24 h post-mortem, sarcomere length, collagen characteristics and lipid content. The shear force of cooked meat samples varied from 43.8 to 67.4 N/cm2. Simmental, Highland and Marchigiana cattle had the highest shear force values and Avileña-Negra Ibérica, Charolais, Casina and Pirenaica cattle had the lowest values. Cooked meat toughness showed a weak negative correlation to lipid content (P b 0.001) but no correlation to collagen characteristics. Raw meat texture measured by compression correlated positively (P b 0.001) with total and insoluble collagen. In conclusion, collagen characteristics showed correlation to raw meat texture but not to cooked meat toughness of LT muscle in European young bulls. © 2010 The American Meat Science Association. Published by Elsevier Ltd. All rights reserved.
1. Introduction To produce high quality meat, it is necessary to evaluate variables related to animal production, such as genetics and management which regulate muscle gene expression (Hocquette, Lehnert, Barendse, CassarMalek, & Picard, 2007), as well as variables associated with the processing of meat (Short et al., 1999). Breed is an important factor that can influence the characteristics of the raw muscle tissue (Cuvelier et al., 2006) and hence of the finished product (Vieira, Cerdeño, Seffano, Lavín, & Mantecón, 2007). A large number of genetically distinct cattle breeds exist in Western Europe, and this genetic diversity could produce meat with many different qualities (Albertí et al., 2008). Meat quality of different beef breeds has been evaluated in several studies (Barkhouse et al., 1996; Mandell, Gullett, Wilton, Kemp, & Allen, 1997; Seideman, Koohmaraie, & Crouse, 1987; Sherbeck, Tatum, Field, Morgan, & Smith, 1995; Vieira et al., 2007). However to date, variation in meat quality
⁎ Corresponding author. Tel.: +45 35 33 32 02; fax: +45 35 33 33 41. E-mail address: [email protected] (M. Christensen). 1 Present address: Parco Tecnologico Padano, via Einstein, 26900, Lodi, Italy.
among the main Western European beef, dairy or dual purpose breeds has not been compared within the same study. Tenderness is one of the most important quality attributes of beef and depends on many physical, chemical and biochemical factors. Inconsistency in beef tenderness is one of the major factors affecting consumer satisfaction and has been identified as one of the major problems facing the beef industry (Koohmaraie, 1994). Two of the main components contributing to meat toughness are the myofibrils and connective tissue (Maltin, Balcerzak, Tilley, & Delbay, 2003). The total amount and chemical composition of collagen is believed to contribute to the background toughness reached after optimal ageing time (Purslow, 2005). Differences in toughness can be caused by a variety of factors such as differences in fibre type proportions (Geay, Bauchart, Hocquette, & Culioli, 2001; Gil et al., 2001), sarcomere length, pH, marbling (Barker, Mies, Turner, Lunt, & Smith, 1995), connective tissue characteristics (Campo et al., 2000) and rate of tenderisation (Campo, Sañudo, Panea, Albertí, & Santolaria, 1999; Monsón, Sañudo, & Sierra, 2004; Shackelford, Wheeler, & Koohmaraie, 1997). The aim of the present study was to determine the variation in beef texture parameters of Longissimus thoracis muscle within and among 15 European cattle breeds reared under comparable management conditions. Furthermore, the effect of lipid content and collagen characteristics on texture was investigated.
0309-1740/$ – see front matter © 2010 The American Meat Science Association. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2010.09.003
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2. Materials and methods 2.1. Animals and rearing conditions The study used 436 young bulls obtained from 15 different European cattle breeds. Bulls from Jersey, South Devon, Aberdeen Angus and Highland were raised in the United Kingdom; Holstein, Danish Red Cattle and Simmental in Denmark; Asturiana de los Valles, Casina, AvileñaNegra Ibérica and Pirenaica in Spain; Piemontese and Marchigiana in Italy and Limousin and Charolais in France. The number of animals per breed varied from 20 for Simmental to 31 for Jersey, Casina, Pirenaica and Limousine (Albertí et al., 2008). Animals were reared under intensive conditions with ad libitum access to concentrate. Feed composition and management details are described in Albertí et al. (2008). At approximately 15 months of age, when the breed had reached about 75% of the mature bull weight, animals were slaughtered in either commercial or experimental abattoirs, depending on the experimental facilities of each country. All animals were without feed before slaughter for less than 24 h and had free access to water; transportation of animals did not exceed 8 h. Mixing of unfamiliar animals was avoided during lairage. During lairage, animals were kept in groups of 6 to 8 for less than 12 h. Stunning of animals was performed using captive bolt pistol and no electrical stimulation of carcasses was performed. Live weight, body size and carcass characteristics of the fifteen different breeds were reported by Albertí et al. (2008).
in a water bath. The tube was cooled to 40 °C and homogenised for 1 min using an Ultra Turrax Mixer T25 at 9500 rpm (IKA-WERKE, Stanfen, Germany). Distilled water (10 mL) was used to flush the homogeniser and then added to the tube. The homogenate was centrifuged for 15 min at 4000 ×g. The supernatant was filtered through paper into a second glass centrifuge tube and the filter was added to the pellet. Thirty mL of 6.0 M HCl was added to the supernatant and 50 mL of 6.0 M HCl was added to the pellet. Both were then hydrolyzed overnight in a sand bath at 110 °C (Harry Gestigkeit GmbH type ST32, Düsseldorf, Germany). The concentration of hydroxyproline was determined according to the NMKL method described by Kolar (1990). The amount of heat-soluble collagen was calculated from the hydroxyproline concentration using a conversion factor of 7.14. The total collagen content was calculated from the sum of the hydroxyproline concentration in the pellet (insoluble collagen) and in the supernatant (soluble collagen) and expressed in mg per gram wet tissue (Kolar, 1990). The collagen in the supernatant was expressed as the percentage of the total collagen content. 2.5. Determination of total lipid content Fat was extracted by the method of Folch, Lees, and Stanley (1957) separated into neutral lipid and phospholipid, methylated, separated by GLC and the individual peaks identified and quantified as described in detail by Scollan et al. (2001). Total lipid content, was taken as the sum of the neutral lipid and phospholipid fractions.
2.2. Sampling 2.6. Texture measurements After slaughter carcasses were chilled at +4 °C for 24 h. At 24 h postmortem the Longissimus thoracis (LT) muscle was excised from the left side of the carcass between the 6th and the 13th rib and a sample taken immediately and frozen for chemical analysis including fat concentration. The remainder was stored at +2 °C ± 1 °C until 48 h post-mortem. A section was then subdivided into slices, a sample taken for collagen analysis, vacuum packed, and frozen at −18 °C. The remaining section was aged to 10 days post-mortem before being subdivided, vacuum packed and frozen. Samples were taken from the 48 h post-mortem section to determine collagen characteristics and total lipid content. Samples were taken from the 10 day aged section for Warner–Bratzler shear force and compression analysis of instrumental texture. Samples for the individual analysis were taken from the same position on LT from all animals. Samples were vacuum packed and frozen and transported on dry ice to the CRA-PCM (Italy) for shear force determination, to the Universidad de Zaragoza (Spain) for compression test and sarcomere length measurement, to the Department of Food Science, University of Copenhagen (Denmark) to test collagen characteristics and to the Division of Farm Animal Science, University of Bristol (United Kingdom) to determine total lipid content. 2.3. pH and temperature determination pH was determined 24 h post-mortem (pH24) in LT between the 9th and 10th rib using a Radiometer pHM201 pH meter with a insertion-electrode ME 6.0226.100 (Metrohm, Herisau, Switzerland). Temperature was measured at the same location using a Testo 110 digital thermometer. Calibration of the pH meter was performed at the same temperature as the internal temperature of LT at 24 h postmortem (Karlsson & Rosenvold, 2002). 2.4. Determination of total, heat-insoluble and heat-soluble collagen content Heat-insoluble and heat-soluble collagen was determined using a slight modification of the method described by Kristensen et al. (2002). Briefly, samples (app. 50 g) were partly thawed and finely chopped using a food processor. The chopped meat samples (6 g) were mixed with 20 mL of 0.9% NaCl and heat-treated for 2 h at 90 °C
Frozen samples were thawed overnight and equilibrated to room temperature (25 °C) prior to texture analysis. Warner–Bratzler shear force was measured on raw and cooked meat after 10 days of ageing post-mortem. Slices were cooked in a water bath at 80 °C until a 75 °C internal temperature was reached, cooled for 45 min in running tap water and stored at 4 °C until analysis. For each animal, shear force measurements of raw and cooked samples were performed on 10 blocks (2 cm in length and 1 cm by 1 cm of cross section), and cut perpendicular to the fibre direction. The maximum force required to shear through the sample using a triangular-shaped Warner–Bratzler shear blade was determined. The blade was mounted on a 1011 Instron machine, running at a crosshead speed of 100 mm/min. The compression test was carried out on raw meat aged 10 days as described by Campo et al. (2000). Samples, 1 cm2 in cross section, were cut with muscle fibres parallel to the longitudinal axis of the sample and were analysed using a modified compression device that avoids transversal elongation of the sample. Stress at 80% of maximum compression was assessed using an Instron 4301 machine with a probe speed of 150 mm/min. Compression of raw meat at high strain values can be used to measure the strength of the connective tissue in raw meat (Lepetit & Culioli, 1994). 2.7. Determination of sarcomere length Meat pieces of 4× 4 mm cross section and 8 mm long, obtained from slices of meat collected at 48 h post-mortem, were transferred to a test tube and fixed for 1 h in 2.5% phosphate-buffered glutaraldehyde. Muscle fibres were carefully separated and mounted on a slide. Measurement of sarcomere length was performed using light microscopy with an oilimmersion objective (Nikon model L-kc, Nippon Kogaku, Japan) on ten different fibres isolated from the same muscle preparation. 2.8. Statistical analysis Differences between breeds for all traits were analysed by the method of least squares means using the mixed procedure in SAS
M. Christensen et al. / Meat Science 87 (2011) 61–65 Table 1 Descriptive statistics for pH 24 h post-mortem (pH24), sarcomere length (SL), collagen characteristics, total lipid content, compression to 80% and Warner–Bratzler shear force either raw or after heat-treatment of bulls from 15 different European cattle breeds. Trait pH24 SL (μm) Total collagen (mg/g wet tissue) Insoluble collagen (mg/g wet tissue) Soluble collagen (%) Lipid (mg/g wet tissue) Compression, raw (N/cm2) Shear force, raw (N/cm2) Shear force, cooked (N/cm2)
N
Mean
SD
Minimum
Maximum
423 435 435 435 435 436 432 434 432
5.65 2.08 3.45 2.60 24.4 29.4 38.7 44.6 53.8
0.15 0.22 0.62 0.45 3.48 18.4 9.28 9.95 12.3
5.32 1.48 2.02 1.54 15.0 7.26 16.9 21.7 27.7
6.25 3.00 5.33 3.99 39.8 144 69.1 69.8 91.1
Software (SAS Institute Inc., Cary, NC, USA). The statistical model included the fixed effect of breed. Significant differences between least squares means were evaluated using the option Pdiff, with no corrections due to multiple comparisons. From Proc GLM (SAS), the Manova statement with the Printe option was used to calculate Partial Correlation Coefficients (ρ) from the error SSCP Matrix (error sum of squares and cross-products matrix). Data were considered significantly different if P b 0.05. 3. Results All traits measured showed a large amount of variation within and between breeds (Table 1). However, the variation in total lipid content was especially large in Aberdeen Angus, Holstein and Danish Red Cattle; 20.8–87.0 mg/g wet tissue, 27.3–114.0 mg/g wet tissue and 32.2–143.5 mg/g wet tissue respectively. Significant breed effects were found for pH24, sarcomere length, collagen characteristics (total collagen, insoluble collagen and percentage of heat-soluble collagen), and total lipid content (P b 0.001). Mean values of the above variables for each breed are shown in Table 2. Mean pH24 ranged from 5.57 (Charolais and Pirenaica) to 5.82 (Casina). The shortest sarcomere length was found in Jersey, followed by Danish Red Cattle, and the longest in Highland, followed by South Devon. Piemontese, Limousin and Asturiana de los Valles contained the lowest amount of insoluble collagen while the dairy breeds Jersey, Holstein and Danish Red Cattle had significantly more insoluble collagen than all other breeds. Percentage of heat-soluble collagen was lowest in Holstein and Danish Red Cattle and highest in Jersey and Aberdeen Angus. Total collagen content was calculated from sum of insoluble and heat-soluble collagen. Total collagen content ranged from 2.72 (Piemontese) to 4.07 mg/g wet tissue (Jersey). Danish Red Cattle and Holstein had
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significantly higher total lipid content than any of the other breeds, whereas Piemontese, Limousin and Asturiana de los Valles contained the lowest amount of total lipid content. Collagen characteristics and total lipid content were partially correlated for all animals (Table 3). Total lipid content correlated positively with total and insoluble collagen content but only explained about 4–5% of their variability. A strong positive correlation (r = 0.95, P b 0.001) was found between the amount of insoluble collagen and the amount of total collagen and a weaker positive correlation was found between percentage heat-soluble collagen and total collagen (Table 3). The variation in texture parameters between the fifteen European cattle breeds is shown in Table 4. Compression and shear force measured on raw meat samples were lowest in Piemontese and highest in Danish Red Cattle and Holstein. However, in cooked meat samples, shear force was lowest in Avileña-Negra Ibérica followed by Charolais, Casina and Pirenaica and highest in Simmental followed by Highland and Marchigiana. In raw meat samples, positive (P b 0.01) correlations were found between compression analysis and total collagen and insoluble collagen (Table 5). No correlation between collagen characteristics and raw and cooked meat texture measured by shear force was observed. Total lipid content showed a small negative correlation to meat toughness. A positive partial correlation (r = 0.18, P b 0.001) between compression and shear force measured in raw meat was observed, whereas compression analysis of raw meat correlated negatively (r = −0.26, P b 0.001) with shear force on cooked samples. Shear force performed on raw samples correlated positively (r = 0.19, P b 0.001) to shear force determined in cooked meat samples. 4. Discussion A Warner–Bratzler shear value for cooked beef of about 60 N/cm2 has been suggested as the threshold separating tender and tough meat (Shackelford et al., 1997). In the present study shear force of cooked samples varied from 43.8 N/cm2 (Avileña-Negra Ibérica) to 67.4 N/cm2 (Simmental) in the LT muscle after ageing for 10 days. Therefore, LT from 11 out of 15 European breeds in the present study may be considered tender after 10 days of ageing using this criterion and average breed values. Of the 432 animals included in the study only 12 young bulls had shear force values above 80 N/cm2 and hence could be considered extremely tough. Within breed a maximum of three animals had shear force values above 80 N/cm2 and this was only seen for Jersey cattle. In six other breeds 1 or 2 animals had a shear force value above 80 N/cm2. In all other breeds evaluated shear force did not exceed 80 N/cm2. The 15 cattle breeds were reared in 5
Table 2 Differences in pH 24 h post-mortem (pH24), sarcomere length (SL), collagen characteristics (total, insoluble and heat-soluble collagen) and total lipid content in 15 different European cattle breeds. Values are expressed as lsmeans ± standard error. Breed
pH24
SL (μm)
Total collagen (mg/g wet tissue)
Insoluble collagen (mg/g wet tissue)
Soluble collagen (%)
Total lipid (mg/g wet tissue)
Jersey Holstein Danish Red Cattle Aberdeen Angus Charolais Casina Marchigiana Highland Avileña-Negra Ibérica Simmental Pirenaica South Devon Asturiana de los Valles Limousin Piemontese
5.67 ± 0.02cde 5.65 ± 0.02def 5.62 ± 0.02efg 5.59 ± 0.02fg 5.57 ± 0.02g 5.82 ± 0.02a 5.58 ± 0.02g 5.68 ± 0.02cde 5.68 ± 0.02cde 5.70 ± 0.03cd 5.57 ± 0.02g 5.62 ± 0.03efg 5.73 ± 0.02bc 5.79 ± 0.03ab 5.58 ± 0.02g
1.89 ± 0.04e 2.04 ± 0.04 cd 1.98 ± 0.04de 2.09 ± 0.04bc 2.10 ± 0.04bc 2.08 ± 0.04bcd 2.05 ± 0.04bcd 2.27 ± 0.04a 2.08 ± 0.04bcd 2.04 ± 0.05bcd 2.11 ± 0.04bc 2.15 ± 0.04b 2.04 ± 0.04cd 2.10 ± 0.04bc 2.09 ± 0.04bc
4.07 ± 0.09a 3.86 ± 0.09ab 3.83 ± 0.09bc 3.76 ± 0.09bcd 3.68 ± 0.09bcd 3.61 ± 0.09bcde 3.59 ± 0.09cde 3.55 ± 0.09de 3.51 ± 0.09de 3.35 ± 0.11ef 3.18 ± 0.09fg 3.12 ± 0.09fg 2.96 ± 0.09gh 2.87 ± 0.09h 2.72 ± 0.09h
2.96 ± 0.06a 3.02 ± 0.06a 2.98 ± 0.06a 2.74 ± 0.06b 2.78 ± 0.06b 2.68 ± 0.06bc 2.73 ± 0.06b 2.69 ± 0.06bc 2.65 ± 0.06bc 2.49 ± 0.08cd 2.43 ± 0.06 2.31 ± 0.07 2.24 ± 0.06ef 2.15 ± 0.06ef 2.07 ± 0.06f
27.3 ± 0.58a 21.7 ± 0.59g 22.0 ± 0.60fg 26.7 ± 0.59ab 24.2 ± 0.58de 25.5 ± 0.57bcd 23.9 ± 0.60e 24.1 ± 0.60de 24.3 ± 0.58de 25.2 ± 0.72bcde 23.4 ± 0.57ef 26.0 ± 0.61abc 24.4 ± 0.58cde 24.8 ± 0.58cde 23.4 ± 0.58ef
37.8 ± 2.08b 57.2 ± 2.15a 61.8 ± 2.15a 39.6 ± 2.11b 23.4 ± 2.08ef 31.3 ± 2.08cd 17.6 ± 2.18fg 36.4 ± 2.18bc 26.1 ± 2.11de 22.1 ± 2.58efg 21.4 ± 2.08efg 22.8 ± 2.22ef 16.4 ± 2.11gh 16.0 ± 2.08gh 10.9 ± 2.11h
a–h
Within column, values with the same letter are not significantly different (P N 0.05).
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Table 3 Partial correlations between collagen characteristics (insoluble, total and soluble collagen) and intramuscular lipid content in 15 European cattle breeds. Level of significance: *** (P b 0.001).
Total collagen Insoluble collagen Soluble collagen
Insoluble collagen
Soluble collagen
Lipid
0.95***
0.35*** 0.05
0.20*** 0.22*** −0.04
different countries; however, all animals were raised under standardised management system and fed a standardized diet, to minimize the effect of location. Sarcomere length (Ahnström, Enfält, Hansson, & Lundström, 2006; Davey, Niederer, & Graafhuis, 1976; Olsson, Hertzman, & Tornberg, 1994) and ultimate pH (Silva, Patarata, & Martins, 1999) have previously been reported to affect shear force of cooked meat. In the present study, sarcomere length varied from 1.89 μm in Jersey to 2.27 μm in Highland and a negative correlation between sarcomere length and shear force of cooked LT was found, however differences in sarcomere length only accounted for 7% of the total variation in shear force. pH24 varied from 5.57 in Charolais and Pirenaica to 5.79 in Limousin, however the variation in pH24 only explained 4% of the variation in shear force of cooked meat. Total and insoluble collagen content was highest in the dairy breeds Jersey, Holstein and Danish Red Cattle and lowest in the meat breeds Piemontese, Limousin and Asturiana de los Valles. The Piemontese and Asturiana de los Valles used in the study had the double muscling phenotype (Albertí et al., 2008) indeed the Piemontese breed is fixed for this trait. Previous studies have also reported low total and insoluble collagen content in double muscled breeds (De Smet, Claeys, Buysse, Lenaerts, & Demeyer, 1998; Monsón et al., 2004; Oliván et al., 2004; Sañudo et al., 2004). The Piemontese, Asturiana de los Valles, Pirenaica, Limousin, South Devon, Charolais and Aberdeen Angus breeds could be characterized as specialized beef breeds with high muscularity and low to medium level of fat (Albertí et al., 2008), whereas Jersey, Casina, Highland, Holstein and Danish Red Cattle could be characterized as local and dairy breeds, small in size with high to medium fat level. Percentage heat-soluble collagen was highest in Jersey followed by Aberdeen Angus and South Devon, whereas the lowest soluble collagen was found in Danish Red Cattle and Holstein. According to Campo et al. (2000), earlier maturing breeds tend to deposit more collagen with a greater proportion of insoluble material, whereas late maturing breeds that exhibit rapid growth during the fattening period have been reported to have higher
Table 4 Differences between fifteen European cattle breeds in meat texture (N/cm2) measured after 10 days of storage on raw meat samples using compression to 80% and Warner– Bratzler shear force either on raw or cooked meat samples. Values are expressed as lsmeans ± standard error. Traits
Compression, raw Shear force, raw Shear force, cooked
Simmental Highland Marchigiana South Devon Jersey Piemontese Asturiana de los Valles Aberdeen Angus Limousin Danish Red Cattle Holstein Pirenaica Casina Charolais Avileña-Negra Ibérica
40.0 ± 1.64bcd 36.5 ± 1.36de 41.8 ± 1.39bc 35.2 ± 1.41ef 38.9 ± 1.34cde 27.8 ± 1.34h 32.6 ± 1.34fg 39.9 ± 1.34bcd 31.2 ± 1.32gh 50.6 ± 1.41a 48.5 ± 1.39a 36.4 ± 1.32de 39.0 ± 1.32cd 43.0 ± 1.32b 41.3 ± 1.36bc
a–j
44.2 ± 1.99 cd 50.0 ± 1.64ab 46.3 ± 1.64bc 42.5 ± 1.67 cd 46.5 ± 1.56bc 33.4 ± 1.58f 40.8 ± 1.58de 46.3 ± 1.58bc 37.9 ± 1.56e 52.5 ± 1.61a 52.6 ± 1.64a 39.7 ± 1.56de 45.4 ± 1.56c 45.7 ± 1.56bc 46.8 ± 1.58bc
67.4 ±2.50a 63.3 ± 2.10ab 61.8 ± 2.06abc 60.3 ± 2.10bcd 56.3 ± 2.03cde 54.7 ± 1.99def 54.6 ± 1.99ef 53.5 ± 1.99efg 53.1 ± 1.96efgh 52.8 ± 2.03efgh 50.4 ± 2.03fghi 48.3 ± 1.96ghij 47.7 ± 1.96hij 47.1 ± 1.96ij 43.8 ± 1.99j
Within column, values with the same letter are not significantly different (P N 0.05).
Table 5 Partial correlations between the different measured traits (collagen characteristics, lipid, pH 24 h post-mortem (pH24) and sarcomere length (SL)) and Warner–Bratzler shear force performed on 10 day aged samples either raw or after heat-treatment and compression to 80%. Level of significance: *** (P b 0.001), ** (P b 0.01), * (P b 0.05).
Total collagen Insoluble collagen Soluble collagen Lipid pH24 SL
Compression, raw
Shear force, raw
Shear force, cooked
0.222*** 0.246*** −0.027 0.082 −0.161** 0.120*
0.085 0.090 0.007 −0.008 −0.024 −0.012
−0.081 −0.075 −0.046 −0.176*** 0.202*** −0.267***
soluble collagen than earlier maturing breeds (Monsón et al., 2004). According to Albertí et al. (2008), it is likely that Aberdeen Angus and South Devon exhibited compensatory growth between 9 and 12 months since the two breeds exhibited an unexpectedly high live weight gain during this period. This later increased growth rate may have affected the percentage heat-soluble collagen; it has been found that compensatory growth resulted in increased solubility of collagen in pigs (Therkildsen et al., 2002) and beef (Damergi, Picard, Geay, & Robins, 1996). Collagen content is believed to greatly influence beef toughness of different muscles and is believed to constitute the “background” toughness of meat after prolonged storage (Purslow, 2005). A high correlation between collagen content and meat toughness after cooking has been reported in studies where samples had large variation in the amount of collagen e.g. inter-muscle comparisons (Dransfield, 1977), however, in other studies lower correlations have also been observed (Dransfield et al., 2003; McKeith, De Vol, Miles, Bechtel, & Carr, 1985; Ngapo et al., 2002). No correlation between cooked meat toughness and collagen characteristics was found in the present study. Low correlations within muscles have been reported between texture and collagen content (Ngapo et al., 2002; Renand, Picard, Touraille, Berge, & Lepetit, 2001) and tenderness and heatsoluble collagen (Berge et al., 2001; Chambaz, Scheeder, Kreuzer, & Dufey, 2003; Renand et al., 2001). According to Lepetit (2007), in general none of the individual collagen characteristics are closely linked to meat tenderness. An explanation for the lack of significant correlations between collagen characteristics and toughness in cooked meat seen in the present and other studies might be that shear force variations above 60 °C mainly reflect the contribution from the myofibrils (Christensen, Purslow, & Larsen, 2000). Furthermore, it is important to note that LT contains a relatively low amount of total collagen compared to other muscles which may induce a lower technical precision in the measurement of total and insoluble collagen amounts (Listrat & Hocquette, 2004). It therefore seems reasonable that the correlation between texture and collagen characteristics would be weak after cooking. In raw meat, connective tissue strength can be analysed by either compression at high strains (Lepetit & Culioli, 1994) or shear force (De Smet et al., 1998). The insoluble collagen and total collagen content correlated positively to compression to 80% (Table 5). Torrescano, Sánchez-Escalante, Giménez, Roncalés, and Beltrán (2003), found a positive relationship between shear force of raw samples and total collagen content (r = 0.72) and insoluble collagen (r = 0.66) of beef, and Nishimura, Fang, Wakamatsu, and Takahashi (2009) found a positive correlation (r = 0.72) between total collagen and shear force of raw pork. However, in the present study partial correlations did not reveal any significant correlations between total and insoluble collagen and shear force of raw samples. Lipid content correlated negatively to shear force of cooked meat (Table 5). Shackelford et al. (1994) likewise found a correlation between shear force of cooked meat and intramuscular fat content (r = −0.27) and Dikeman et al. (2005) reported r = −0.21 between sensory evaluation of degree of marbling and shear force of cooked meat.
M. Christensen et al. / Meat Science 87 (2011) 61–65
The present study suggests that cooked meat toughness of European cattle breeds of similar age cannot be explained by the connective tissue but may be due to factors mainly influencing the myofibril integrity such as differences in proteolytic enzyme activity and fibre type characteristics. 5. Conclusions Ten day aged Longissimus thoracis from 11 of 15 European cattle breeds had average shear force values of cooked meat below 60 N/ cm2, a value suggested as a cut-off between acceptably tender and tough beef. Variation in collagen characteristics could not explain the differences in cooked meat toughness. However, differences in total and insoluble collagen showed positive correlations with compression values of raw meat. Acknowledgements This work was funded by the EU Commission Sixth Framework Programme Project “GemQual” (QLK5-CT-2000-00147). 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Meat Science j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / m e a t s c i
Relationship between collagen characteristics, lipid content and raw and cooked texture of meat from young bulls of fifteen European breeds Mette Christensen a,⁎, Per Ertbjerg a, Sebastiana Failla b, Carlos Sañudo c, R. Ian Richardson d, Geoff R. Nute d, José L. Olleta c, Begoña Panea e, Pere Albertí e, Manuel Juárez b, Jean-François Hocquette f, John L. Williams g,1 a
Department of Food Science, University of Copenhagen, DK-1958 Frederiksberg C, Denmark CRA-PCM, Via Salaria 31, 00016 Monterotondo, Italy Departamento de Producción Animal y Ciencia de los Alimentos, Universidad de Zaragoza, 50013 Zaragoza, Spain d Division of Farm Animal Science, University of Bristol, Langford, Bristol, BS40 5DU, United Kingdom e Centro de Investigación y Tecnología Agroalimentaria, Gobierno de Aragón, 50059 Zaragoza, Spain f INRA, UR1213, Unité de Recherches sur les Herbivores, Equipe Croissance et Métabolisme du Muscle, INRA-Theix, 63122 Saint-Genes Champanelle, France g Roslin Institute (Edinburgh), EH25 9PS, United Kingdom b c
a r t i c l e
i n f o
Article history: Received 2 July 2010 Received in revised form 31 August 2010 Accepted 1 September 2010 Keywords: Cattle M. longissimus thoracis Sarcomere length Intramuscular fat Shear force Compression
a b s t r a c t Variations in texture were determined for 10 day aged raw and cooked Longissimus thoracis (LT) muscle from 436 bulls of 15 European cattle breeds slaughtered at an age of 13–16 months. Variations in texture were related to differences in pH 24 h post-mortem, sarcomere length, collagen characteristics and lipid content. The shear force of cooked meat samples varied from 43.8 to 67.4 N/cm2. Simmental, Highland and Marchigiana cattle had the highest shear force values and Avileña-Negra Ibérica, Charolais, Casina and Pirenaica cattle had the lowest values. Cooked meat toughness showed a weak negative correlation to lipid content (P b 0.001) but no correlation to collagen characteristics. Raw meat texture measured by compression correlated positively (P b 0.001) with total and insoluble collagen. In conclusion, collagen characteristics showed correlation to raw meat texture but not to cooked meat toughness of LT muscle in European young bulls. © 2010 The American Meat Science Association. Published by Elsevier Ltd. All rights reserved.
1. Introduction To produce high quality meat, it is necessary to evaluate variables related to animal production, such as genetics and management which regulate muscle gene expression (Hocquette, Lehnert, Barendse, CassarMalek, & Picard, 2007), as well as variables associated with the processing of meat (Short et al., 1999). Breed is an important factor that can influence the characteristics of the raw muscle tissue (Cuvelier et al., 2006) and hence of the finished product (Vieira, Cerdeño, Seffano, Lavín, & Mantecón, 2007). A large number of genetically distinct cattle breeds exist in Western Europe, and this genetic diversity could produce meat with many different qualities (Albertí et al., 2008). Meat quality of different beef breeds has been evaluated in several studies (Barkhouse et al., 1996; Mandell, Gullett, Wilton, Kemp, & Allen, 1997; Seideman, Koohmaraie, & Crouse, 1987; Sherbeck, Tatum, Field, Morgan, & Smith, 1995; Vieira et al., 2007). However to date, variation in meat quality
⁎ Corresponding author. Tel.: +45 35 33 32 02; fax: +45 35 33 33 41. E-mail address: [email protected] (M. Christensen). 1 Present address: Parco Tecnologico Padano, via Einstein, 26900, Lodi, Italy.
among the main Western European beef, dairy or dual purpose breeds has not been compared within the same study. Tenderness is one of the most important quality attributes of beef and depends on many physical, chemical and biochemical factors. Inconsistency in beef tenderness is one of the major factors affecting consumer satisfaction and has been identified as one of the major problems facing the beef industry (Koohmaraie, 1994). Two of the main components contributing to meat toughness are the myofibrils and connective tissue (Maltin, Balcerzak, Tilley, & Delbay, 2003). The total amount and chemical composition of collagen is believed to contribute to the background toughness reached after optimal ageing time (Purslow, 2005). Differences in toughness can be caused by a variety of factors such as differences in fibre type proportions (Geay, Bauchart, Hocquette, & Culioli, 2001; Gil et al., 2001), sarcomere length, pH, marbling (Barker, Mies, Turner, Lunt, & Smith, 1995), connective tissue characteristics (Campo et al., 2000) and rate of tenderisation (Campo, Sañudo, Panea, Albertí, & Santolaria, 1999; Monsón, Sañudo, & Sierra, 2004; Shackelford, Wheeler, & Koohmaraie, 1997). The aim of the present study was to determine the variation in beef texture parameters of Longissimus thoracis muscle within and among 15 European cattle breeds reared under comparable management conditions. Furthermore, the effect of lipid content and collagen characteristics on texture was investigated.
0309-1740/$ – see front matter © 2010 The American Meat Science Association. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2010.09.003
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M. Christensen et al. / Meat Science 87 (2011) 61–65
2. Materials and methods 2.1. Animals and rearing conditions The study used 436 young bulls obtained from 15 different European cattle breeds. Bulls from Jersey, South Devon, Aberdeen Angus and Highland were raised in the United Kingdom; Holstein, Danish Red Cattle and Simmental in Denmark; Asturiana de los Valles, Casina, AvileñaNegra Ibérica and Pirenaica in Spain; Piemontese and Marchigiana in Italy and Limousin and Charolais in France. The number of animals per breed varied from 20 for Simmental to 31 for Jersey, Casina, Pirenaica and Limousine (Albertí et al., 2008). Animals were reared under intensive conditions with ad libitum access to concentrate. Feed composition and management details are described in Albertí et al. (2008). At approximately 15 months of age, when the breed had reached about 75% of the mature bull weight, animals were slaughtered in either commercial or experimental abattoirs, depending on the experimental facilities of each country. All animals were without feed before slaughter for less than 24 h and had free access to water; transportation of animals did not exceed 8 h. Mixing of unfamiliar animals was avoided during lairage. During lairage, animals were kept in groups of 6 to 8 for less than 12 h. Stunning of animals was performed using captive bolt pistol and no electrical stimulation of carcasses was performed. Live weight, body size and carcass characteristics of the fifteen different breeds were reported by Albertí et al. (2008).
in a water bath. The tube was cooled to 40 °C and homogenised for 1 min using an Ultra Turrax Mixer T25 at 9500 rpm (IKA-WERKE, Stanfen, Germany). Distilled water (10 mL) was used to flush the homogeniser and then added to the tube. The homogenate was centrifuged for 15 min at 4000 ×g. The supernatant was filtered through paper into a second glass centrifuge tube and the filter was added to the pellet. Thirty mL of 6.0 M HCl was added to the supernatant and 50 mL of 6.0 M HCl was added to the pellet. Both were then hydrolyzed overnight in a sand bath at 110 °C (Harry Gestigkeit GmbH type ST32, Düsseldorf, Germany). The concentration of hydroxyproline was determined according to the NMKL method described by Kolar (1990). The amount of heat-soluble collagen was calculated from the hydroxyproline concentration using a conversion factor of 7.14. The total collagen content was calculated from the sum of the hydroxyproline concentration in the pellet (insoluble collagen) and in the supernatant (soluble collagen) and expressed in mg per gram wet tissue (Kolar, 1990). The collagen in the supernatant was expressed as the percentage of the total collagen content. 2.5. Determination of total lipid content Fat was extracted by the method of Folch, Lees, and Stanley (1957) separated into neutral lipid and phospholipid, methylated, separated by GLC and the individual peaks identified and quantified as described in detail by Scollan et al. (2001). Total lipid content, was taken as the sum of the neutral lipid and phospholipid fractions.
2.2. Sampling 2.6. Texture measurements After slaughter carcasses were chilled at +4 °C for 24 h. At 24 h postmortem the Longissimus thoracis (LT) muscle was excised from the left side of the carcass between the 6th and the 13th rib and a sample taken immediately and frozen for chemical analysis including fat concentration. The remainder was stored at +2 °C ± 1 °C until 48 h post-mortem. A section was then subdivided into slices, a sample taken for collagen analysis, vacuum packed, and frozen at −18 °C. The remaining section was aged to 10 days post-mortem before being subdivided, vacuum packed and frozen. Samples were taken from the 48 h post-mortem section to determine collagen characteristics and total lipid content. Samples were taken from the 10 day aged section for Warner–Bratzler shear force and compression analysis of instrumental texture. Samples for the individual analysis were taken from the same position on LT from all animals. Samples were vacuum packed and frozen and transported on dry ice to the CRA-PCM (Italy) for shear force determination, to the Universidad de Zaragoza (Spain) for compression test and sarcomere length measurement, to the Department of Food Science, University of Copenhagen (Denmark) to test collagen characteristics and to the Division of Farm Animal Science, University of Bristol (United Kingdom) to determine total lipid content. 2.3. pH and temperature determination pH was determined 24 h post-mortem (pH24) in LT between the 9th and 10th rib using a Radiometer pHM201 pH meter with a insertion-electrode ME 6.0226.100 (Metrohm, Herisau, Switzerland). Temperature was measured at the same location using a Testo 110 digital thermometer. Calibration of the pH meter was performed at the same temperature as the internal temperature of LT at 24 h postmortem (Karlsson & Rosenvold, 2002). 2.4. Determination of total, heat-insoluble and heat-soluble collagen content Heat-insoluble and heat-soluble collagen was determined using a slight modification of the method described by Kristensen et al. (2002). Briefly, samples (app. 50 g) were partly thawed and finely chopped using a food processor. The chopped meat samples (6 g) were mixed with 20 mL of 0.9% NaCl and heat-treated for 2 h at 90 °C
Frozen samples were thawed overnight and equilibrated to room temperature (25 °C) prior to texture analysis. Warner–Bratzler shear force was measured on raw and cooked meat after 10 days of ageing post-mortem. Slices were cooked in a water bath at 80 °C until a 75 °C internal temperature was reached, cooled for 45 min in running tap water and stored at 4 °C until analysis. For each animal, shear force measurements of raw and cooked samples were performed on 10 blocks (2 cm in length and 1 cm by 1 cm of cross section), and cut perpendicular to the fibre direction. The maximum force required to shear through the sample using a triangular-shaped Warner–Bratzler shear blade was determined. The blade was mounted on a 1011 Instron machine, running at a crosshead speed of 100 mm/min. The compression test was carried out on raw meat aged 10 days as described by Campo et al. (2000). Samples, 1 cm2 in cross section, were cut with muscle fibres parallel to the longitudinal axis of the sample and were analysed using a modified compression device that avoids transversal elongation of the sample. Stress at 80% of maximum compression was assessed using an Instron 4301 machine with a probe speed of 150 mm/min. Compression of raw meat at high strain values can be used to measure the strength of the connective tissue in raw meat (Lepetit & Culioli, 1994). 2.7. Determination of sarcomere length Meat pieces of 4× 4 mm cross section and 8 mm long, obtained from slices of meat collected at 48 h post-mortem, were transferred to a test tube and fixed for 1 h in 2.5% phosphate-buffered glutaraldehyde. Muscle fibres were carefully separated and mounted on a slide. Measurement of sarcomere length was performed using light microscopy with an oilimmersion objective (Nikon model L-kc, Nippon Kogaku, Japan) on ten different fibres isolated from the same muscle preparation. 2.8. Statistical analysis Differences between breeds for all traits were analysed by the method of least squares means using the mixed procedure in SAS
M. Christensen et al. / Meat Science 87 (2011) 61–65 Table 1 Descriptive statistics for pH 24 h post-mortem (pH24), sarcomere length (SL), collagen characteristics, total lipid content, compression to 80% and Warner–Bratzler shear force either raw or after heat-treatment of bulls from 15 different European cattle breeds. Trait pH24 SL (μm) Total collagen (mg/g wet tissue) Insoluble collagen (mg/g wet tissue) Soluble collagen (%) Lipid (mg/g wet tissue) Compression, raw (N/cm2) Shear force, raw (N/cm2) Shear force, cooked (N/cm2)
N
Mean
SD
Minimum
Maximum
423 435 435 435 435 436 432 434 432
5.65 2.08 3.45 2.60 24.4 29.4 38.7 44.6 53.8
0.15 0.22 0.62 0.45 3.48 18.4 9.28 9.95 12.3
5.32 1.48 2.02 1.54 15.0 7.26 16.9 21.7 27.7
6.25 3.00 5.33 3.99 39.8 144 69.1 69.8 91.1
Software (SAS Institute Inc., Cary, NC, USA). The statistical model included the fixed effect of breed. Significant differences between least squares means were evaluated using the option Pdiff, with no corrections due to multiple comparisons. From Proc GLM (SAS), the Manova statement with the Printe option was used to calculate Partial Correlation Coefficients (ρ) from the error SSCP Matrix (error sum of squares and cross-products matrix). Data were considered significantly different if P b 0.05. 3. Results All traits measured showed a large amount of variation within and between breeds (Table 1). However, the variation in total lipid content was especially large in Aberdeen Angus, Holstein and Danish Red Cattle; 20.8–87.0 mg/g wet tissue, 27.3–114.0 mg/g wet tissue and 32.2–143.5 mg/g wet tissue respectively. Significant breed effects were found for pH24, sarcomere length, collagen characteristics (total collagen, insoluble collagen and percentage of heat-soluble collagen), and total lipid content (P b 0.001). Mean values of the above variables for each breed are shown in Table 2. Mean pH24 ranged from 5.57 (Charolais and Pirenaica) to 5.82 (Casina). The shortest sarcomere length was found in Jersey, followed by Danish Red Cattle, and the longest in Highland, followed by South Devon. Piemontese, Limousin and Asturiana de los Valles contained the lowest amount of insoluble collagen while the dairy breeds Jersey, Holstein and Danish Red Cattle had significantly more insoluble collagen than all other breeds. Percentage of heat-soluble collagen was lowest in Holstein and Danish Red Cattle and highest in Jersey and Aberdeen Angus. Total collagen content was calculated from sum of insoluble and heat-soluble collagen. Total collagen content ranged from 2.72 (Piemontese) to 4.07 mg/g wet tissue (Jersey). Danish Red Cattle and Holstein had
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significantly higher total lipid content than any of the other breeds, whereas Piemontese, Limousin and Asturiana de los Valles contained the lowest amount of total lipid content. Collagen characteristics and total lipid content were partially correlated for all animals (Table 3). Total lipid content correlated positively with total and insoluble collagen content but only explained about 4–5% of their variability. A strong positive correlation (r = 0.95, P b 0.001) was found between the amount of insoluble collagen and the amount of total collagen and a weaker positive correlation was found between percentage heat-soluble collagen and total collagen (Table 3). The variation in texture parameters between the fifteen European cattle breeds is shown in Table 4. Compression and shear force measured on raw meat samples were lowest in Piemontese and highest in Danish Red Cattle and Holstein. However, in cooked meat samples, shear force was lowest in Avileña-Negra Ibérica followed by Charolais, Casina and Pirenaica and highest in Simmental followed by Highland and Marchigiana. In raw meat samples, positive (P b 0.01) correlations were found between compression analysis and total collagen and insoluble collagen (Table 5). No correlation between collagen characteristics and raw and cooked meat texture measured by shear force was observed. Total lipid content showed a small negative correlation to meat toughness. A positive partial correlation (r = 0.18, P b 0.001) between compression and shear force measured in raw meat was observed, whereas compression analysis of raw meat correlated negatively (r = −0.26, P b 0.001) with shear force on cooked samples. Shear force performed on raw samples correlated positively (r = 0.19, P b 0.001) to shear force determined in cooked meat samples. 4. Discussion A Warner–Bratzler shear value for cooked beef of about 60 N/cm2 has been suggested as the threshold separating tender and tough meat (Shackelford et al., 1997). In the present study shear force of cooked samples varied from 43.8 N/cm2 (Avileña-Negra Ibérica) to 67.4 N/cm2 (Simmental) in the LT muscle after ageing for 10 days. Therefore, LT from 11 out of 15 European breeds in the present study may be considered tender after 10 days of ageing using this criterion and average breed values. Of the 432 animals included in the study only 12 young bulls had shear force values above 80 N/cm2 and hence could be considered extremely tough. Within breed a maximum of three animals had shear force values above 80 N/cm2 and this was only seen for Jersey cattle. In six other breeds 1 or 2 animals had a shear force value above 80 N/cm2. In all other breeds evaluated shear force did not exceed 80 N/cm2. The 15 cattle breeds were reared in 5
Table 2 Differences in pH 24 h post-mortem (pH24), sarcomere length (SL), collagen characteristics (total, insoluble and heat-soluble collagen) and total lipid content in 15 different European cattle breeds. Values are expressed as lsmeans ± standard error. Breed
pH24
SL (μm)
Total collagen (mg/g wet tissue)
Insoluble collagen (mg/g wet tissue)
Soluble collagen (%)
Total lipid (mg/g wet tissue)
Jersey Holstein Danish Red Cattle Aberdeen Angus Charolais Casina Marchigiana Highland Avileña-Negra Ibérica Simmental Pirenaica South Devon Asturiana de los Valles Limousin Piemontese
5.67 ± 0.02cde 5.65 ± 0.02def 5.62 ± 0.02efg 5.59 ± 0.02fg 5.57 ± 0.02g 5.82 ± 0.02a 5.58 ± 0.02g 5.68 ± 0.02cde 5.68 ± 0.02cde 5.70 ± 0.03cd 5.57 ± 0.02g 5.62 ± 0.03efg 5.73 ± 0.02bc 5.79 ± 0.03ab 5.58 ± 0.02g
1.89 ± 0.04e 2.04 ± 0.04 cd 1.98 ± 0.04de 2.09 ± 0.04bc 2.10 ± 0.04bc 2.08 ± 0.04bcd 2.05 ± 0.04bcd 2.27 ± 0.04a 2.08 ± 0.04bcd 2.04 ± 0.05bcd 2.11 ± 0.04bc 2.15 ± 0.04b 2.04 ± 0.04cd 2.10 ± 0.04bc 2.09 ± 0.04bc
4.07 ± 0.09a 3.86 ± 0.09ab 3.83 ± 0.09bc 3.76 ± 0.09bcd 3.68 ± 0.09bcd 3.61 ± 0.09bcde 3.59 ± 0.09cde 3.55 ± 0.09de 3.51 ± 0.09de 3.35 ± 0.11ef 3.18 ± 0.09fg 3.12 ± 0.09fg 2.96 ± 0.09gh 2.87 ± 0.09h 2.72 ± 0.09h
2.96 ± 0.06a 3.02 ± 0.06a 2.98 ± 0.06a 2.74 ± 0.06b 2.78 ± 0.06b 2.68 ± 0.06bc 2.73 ± 0.06b 2.69 ± 0.06bc 2.65 ± 0.06bc 2.49 ± 0.08cd 2.43 ± 0.06 2.31 ± 0.07 2.24 ± 0.06ef 2.15 ± 0.06ef 2.07 ± 0.06f
27.3 ± 0.58a 21.7 ± 0.59g 22.0 ± 0.60fg 26.7 ± 0.59ab 24.2 ± 0.58de 25.5 ± 0.57bcd 23.9 ± 0.60e 24.1 ± 0.60de 24.3 ± 0.58de 25.2 ± 0.72bcde 23.4 ± 0.57ef 26.0 ± 0.61abc 24.4 ± 0.58cde 24.8 ± 0.58cde 23.4 ± 0.58ef
37.8 ± 2.08b 57.2 ± 2.15a 61.8 ± 2.15a 39.6 ± 2.11b 23.4 ± 2.08ef 31.3 ± 2.08cd 17.6 ± 2.18fg 36.4 ± 2.18bc 26.1 ± 2.11de 22.1 ± 2.58efg 21.4 ± 2.08efg 22.8 ± 2.22ef 16.4 ± 2.11gh 16.0 ± 2.08gh 10.9 ± 2.11h
a–h
Within column, values with the same letter are not significantly different (P N 0.05).
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M. Christensen et al. / Meat Science 87 (2011) 61–65
Table 3 Partial correlations between collagen characteristics (insoluble, total and soluble collagen) and intramuscular lipid content in 15 European cattle breeds. Level of significance: *** (P b 0.001).
Total collagen Insoluble collagen Soluble collagen
Insoluble collagen
Soluble collagen
Lipid
0.95***
0.35*** 0.05
0.20*** 0.22*** −0.04
different countries; however, all animals were raised under standardised management system and fed a standardized diet, to minimize the effect of location. Sarcomere length (Ahnström, Enfält, Hansson, & Lundström, 2006; Davey, Niederer, & Graafhuis, 1976; Olsson, Hertzman, & Tornberg, 1994) and ultimate pH (Silva, Patarata, & Martins, 1999) have previously been reported to affect shear force of cooked meat. In the present study, sarcomere length varied from 1.89 μm in Jersey to 2.27 μm in Highland and a negative correlation between sarcomere length and shear force of cooked LT was found, however differences in sarcomere length only accounted for 7% of the total variation in shear force. pH24 varied from 5.57 in Charolais and Pirenaica to 5.79 in Limousin, however the variation in pH24 only explained 4% of the variation in shear force of cooked meat. Total and insoluble collagen content was highest in the dairy breeds Jersey, Holstein and Danish Red Cattle and lowest in the meat breeds Piemontese, Limousin and Asturiana de los Valles. The Piemontese and Asturiana de los Valles used in the study had the double muscling phenotype (Albertí et al., 2008) indeed the Piemontese breed is fixed for this trait. Previous studies have also reported low total and insoluble collagen content in double muscled breeds (De Smet, Claeys, Buysse, Lenaerts, & Demeyer, 1998; Monsón et al., 2004; Oliván et al., 2004; Sañudo et al., 2004). The Piemontese, Asturiana de los Valles, Pirenaica, Limousin, South Devon, Charolais and Aberdeen Angus breeds could be characterized as specialized beef breeds with high muscularity and low to medium level of fat (Albertí et al., 2008), whereas Jersey, Casina, Highland, Holstein and Danish Red Cattle could be characterized as local and dairy breeds, small in size with high to medium fat level. Percentage heat-soluble collagen was highest in Jersey followed by Aberdeen Angus and South Devon, whereas the lowest soluble collagen was found in Danish Red Cattle and Holstein. According to Campo et al. (2000), earlier maturing breeds tend to deposit more collagen with a greater proportion of insoluble material, whereas late maturing breeds that exhibit rapid growth during the fattening period have been reported to have higher
Table 4 Differences between fifteen European cattle breeds in meat texture (N/cm2) measured after 10 days of storage on raw meat samples using compression to 80% and Warner– Bratzler shear force either on raw or cooked meat samples. Values are expressed as lsmeans ± standard error. Traits
Compression, raw Shear force, raw Shear force, cooked
Simmental Highland Marchigiana South Devon Jersey Piemontese Asturiana de los Valles Aberdeen Angus Limousin Danish Red Cattle Holstein Pirenaica Casina Charolais Avileña-Negra Ibérica
40.0 ± 1.64bcd 36.5 ± 1.36de 41.8 ± 1.39bc 35.2 ± 1.41ef 38.9 ± 1.34cde 27.8 ± 1.34h 32.6 ± 1.34fg 39.9 ± 1.34bcd 31.2 ± 1.32gh 50.6 ± 1.41a 48.5 ± 1.39a 36.4 ± 1.32de 39.0 ± 1.32cd 43.0 ± 1.32b 41.3 ± 1.36bc
a–j
44.2 ± 1.99 cd 50.0 ± 1.64ab 46.3 ± 1.64bc 42.5 ± 1.67 cd 46.5 ± 1.56bc 33.4 ± 1.58f 40.8 ± 1.58de 46.3 ± 1.58bc 37.9 ± 1.56e 52.5 ± 1.61a 52.6 ± 1.64a 39.7 ± 1.56de 45.4 ± 1.56c 45.7 ± 1.56bc 46.8 ± 1.58bc
67.4 ±2.50a 63.3 ± 2.10ab 61.8 ± 2.06abc 60.3 ± 2.10bcd 56.3 ± 2.03cde 54.7 ± 1.99def 54.6 ± 1.99ef 53.5 ± 1.99efg 53.1 ± 1.96efgh 52.8 ± 2.03efgh 50.4 ± 2.03fghi 48.3 ± 1.96ghij 47.7 ± 1.96hij 47.1 ± 1.96ij 43.8 ± 1.99j
Within column, values with the same letter are not significantly different (P N 0.05).
Table 5 Partial correlations between the different measured traits (collagen characteristics, lipid, pH 24 h post-mortem (pH24) and sarcomere length (SL)) and Warner–Bratzler shear force performed on 10 day aged samples either raw or after heat-treatment and compression to 80%. Level of significance: *** (P b 0.001), ** (P b 0.01), * (P b 0.05).
Total collagen Insoluble collagen Soluble collagen Lipid pH24 SL
Compression, raw
Shear force, raw
Shear force, cooked
0.222*** 0.246*** −0.027 0.082 −0.161** 0.120*
0.085 0.090 0.007 −0.008 −0.024 −0.012
−0.081 −0.075 −0.046 −0.176*** 0.202*** −0.267***
soluble collagen than earlier maturing breeds (Monsón et al., 2004). According to Albertí et al. (2008), it is likely that Aberdeen Angus and South Devon exhibited compensatory growth between 9 and 12 months since the two breeds exhibited an unexpectedly high live weight gain during this period. This later increased growth rate may have affected the percentage heat-soluble collagen; it has been found that compensatory growth resulted in increased solubility of collagen in pigs (Therkildsen et al., 2002) and beef (Damergi, Picard, Geay, & Robins, 1996). Collagen content is believed to greatly influence beef toughness of different muscles and is believed to constitute the “background” toughness of meat after prolonged storage (Purslow, 2005). A high correlation between collagen content and meat toughness after cooking has been reported in studies where samples had large variation in the amount of collagen e.g. inter-muscle comparisons (Dransfield, 1977), however, in other studies lower correlations have also been observed (Dransfield et al., 2003; McKeith, De Vol, Miles, Bechtel, & Carr, 1985; Ngapo et al., 2002). No correlation between cooked meat toughness and collagen characteristics was found in the present study. Low correlations within muscles have been reported between texture and collagen content (Ngapo et al., 2002; Renand, Picard, Touraille, Berge, & Lepetit, 2001) and tenderness and heatsoluble collagen (Berge et al., 2001; Chambaz, Scheeder, Kreuzer, & Dufey, 2003; Renand et al., 2001). According to Lepetit (2007), in general none of the individual collagen characteristics are closely linked to meat tenderness. An explanation for the lack of significant correlations between collagen characteristics and toughness in cooked meat seen in the present and other studies might be that shear force variations above 60 °C mainly reflect the contribution from the myofibrils (Christensen, Purslow, & Larsen, 2000). Furthermore, it is important to note that LT contains a relatively low amount of total collagen compared to other muscles which may induce a lower technical precision in the measurement of total and insoluble collagen amounts (Listrat & Hocquette, 2004). It therefore seems reasonable that the correlation between texture and collagen characteristics would be weak after cooking. In raw meat, connective tissue strength can be analysed by either compression at high strains (Lepetit & Culioli, 1994) or shear force (De Smet et al., 1998). The insoluble collagen and total collagen content correlated positively to compression to 80% (Table 5). Torrescano, Sánchez-Escalante, Giménez, Roncalés, and Beltrán (2003), found a positive relationship between shear force of raw samples and total collagen content (r = 0.72) and insoluble collagen (r = 0.66) of beef, and Nishimura, Fang, Wakamatsu, and Takahashi (2009) found a positive correlation (r = 0.72) between total collagen and shear force of raw pork. However, in the present study partial correlations did not reveal any significant correlations between total and insoluble collagen and shear force of raw samples. Lipid content correlated negatively to shear force of cooked meat (Table 5). Shackelford et al. (1994) likewise found a correlation between shear force of cooked meat and intramuscular fat content (r = −0.27) and Dikeman et al. (2005) reported r = −0.21 between sensory evaluation of degree of marbling and shear force of cooked meat.
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The present study suggests that cooked meat toughness of European cattle breeds of similar age cannot be explained by the connective tissue but may be due to factors mainly influencing the myofibril integrity such as differences in proteolytic enzyme activity and fibre type characteristics. 5. Conclusions Ten day aged Longissimus thoracis from 11 of 15 European cattle breeds had average shear force values of cooked meat below 60 N/ cm2, a value suggested as a cut-off between acceptably tender and tough beef. Variation in collagen characteristics could not explain the differences in cooked meat toughness. However, differences in total and insoluble collagen showed positive correlations with compression values of raw meat. Acknowledgements This work was funded by the EU Commission Sixth Framework Programme Project “GemQual” (QLK5-CT-2000-00147). 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