Fatty acid composition and sensory properties of Italian Simmental beef as affected by gene frequency of Montbéliarde origin

Fatty acid composition and sensory properties of Italian Simmental beef as affected by gene frequency of Montbéliarde origin

Meat Science 83 (2009) 543–550 Contents lists available at ScienceDirect Meat Science journal homepage: www.elsevier.com/locate/meatsci Fatty acid ...

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Meat Science 83 (2009) 543–550

Contents lists available at ScienceDirect

Meat Science journal homepage: www.elsevier.com/locate/meatsci

Fatty acid composition and sensory properties of Italian Simmental beef as affected by gene frequency of Montbéliarde origin E. Piasentier a,*, S. Bovolenta a, B. Moioli b, L. Orrù c, R. Valusso a, M. Corazzin a a

Department of Animal Science, University of Udine, via Sondrio 2A, 33100 Udine, Italy CRA-PCM, via Salaria 31, 00015 Monterotondo, Italy c CRA-GPG, via San Protaso 302, 29017 Fiorenzuola d’Arda, Italy b

a r t i c l e

i n f o

Article history: Received 7 April 2009 Received in revised form 28 June 2009 Accepted 5 July 2009

Keywords: Italian Simmental Montbéliarde genes Stearoyl Co-A desaturase Meat quality

a b s t r a c t The aim of this study was to investigate the effect of Montbéliarde (Mb) gene frequency on fatty acid composition and sensory properties of Italian Simmental (IS) steaks (longissimus thoracis m.). Twentyseven bulls belonging to three strains with different percentages of Mb genes: traditional (ISt), without Mb ascendants (ISt = 0% Mb genes), cross-strain (ISmt = 37.5–50% Mb genes), Montbéliarde strain (ISm = 87.5–100% Mb genes) and balanced for stearoyl Co-A desaturase genotype were considered. ISt has the highest C20:4 n 6 (P < 0.01), C22:4 n 6 (P < 0.05) and total PUFA n 3 level (P < 0.01), while ISt and ISmt have higher C18:3 n 3 (P < 0.05) and slightly lower MUFA (P = 0.08) than ISm. Sensory tests indicated that the three experimental groups can be differentiated; moreover, ISmt meat is perceived as less hard (P < 0.01), less chewable (P < 0.01) and less fibrous (P < 0.05) than ISt meat. Ó 2009 Elsevier Ltd. All rights reserved.

1. Introduction The Italian Simmental (IS), with a national herdbook stock of about 50,000 cows, is the most common dual-purpose breed in Italy, and its breeding goal is to obtain the highest income from combined milk and meat production. In the 1990s, with the aim of improving milk production, the best Montbéliarde (Mb) bulls were introduced into the traditional Italian Simmental population (ISt). Among the Red and White Simmental cattle, the Mb represents the most marked dairy type breed; furthermore, cross-breeding takes advantage of the different additive genetic levels of the two breeds, generating offspring with better milking ability. Thirty six percent of the 55 IS bulls admitted to the progeny test in 2006 and 2007 had >50% of Mb genes (ANAPRI, 2008). As reported by Piasentier, Valusso, Volpelli, and Failla (2003), the inclusion of Mb genes in ISt young bulls can modify carcass quality and some meat characteristics such as colour and Warner–Bratzler shear force. However, from the consumer’s point of view, meat quality is receiving more and more attention due to its impact on human health, and it is one of the most important motivators for liking and purchasing (Resurreccion, 2003). Increasing the content of n 3 polyunsaturated fatty acids (PUFAs) and reducing the content of saturated fatty acids (SFAs) with the net effect of increasing the PUFA/SFA ratio and reducing the n 6/n 3 ratio are considered the current priorities (Scollan et al., 2006). Beef * Corresponding author. Tel.: +39 0432558190; fax: +39 0432558199. E-mail address: [email protected] (E. Piasentier). 0309-1740/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.meatsci.2009.07.003

fatty acid (FA) composition might differ between lean and fatter breeds; Wood et al. (2008) showed that lean breeds have a higher proportion of phospholipids and consequently a higher proportion of PUFA in total lipids. De Smet, Raes, and Demeyer (2004) reported that genetic factors are also responsible for the variation in FA beef composition, while Warren et al. (2008) reported that the breed strongly influences beef FA profile. As for the specific genes that are considered responsible for the variation of FA profile in beef, the most studied is stearoyl Co-A desaturase (SCD), which encodes a key enzyme in the cellular biosynthesirs of monounsaturated fatty acids (MUFAs). A non-synonymous mutation within exon 5 of this gene (g.10329C > T; GenBank accession AY241932) codes for a different aminoacid codon: alanine (allele C) or valine (allele T). Taniguchi et al. (2004) found that the valine residue may change the enzyme’s catalytic activity compared to the alanine residue; they showed that, in Japanese Black cattle, allele C was more frequently associated with a higher MUFA content in carcasses. Zhang (2005) tested the effect of the valine/alanine variant on the individual FA composition of fat extracted from loin muscle of 172 bulls and found that the valine allele was more frequent (0.83) in the cattle analysed, but agreed with Taniguchi et al. (2004) that heterozygous valine/alanine animals had higher C16:1/C16:0 in intramuscular fat than the homozygous valine ones. Differences in beef sensory properties are due to several factors (Monson, Sanudo, & Sierra, 2005), such as sex and management; the breed is also an important factor of variation: Olleta et al. (2006) showed that it is possible to differentiate the meat of 11

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different European cattle breeds on the basis of organoleptic properties. Only a few papers have compared FA profile in dual-purpose breeds of Simmental origin (Zapletal, Chládek, & Šubrt, 2008); because meat quality is considered as a very important breeding goal in the IS, and because Mb genes have been introduced in the original IS population, the objective of this paper was to investigate the effect of Mb genes on the FA composition and sensory properties of IS beef.

2. Materials and methods 2.1. Experimental design The experiment was carried out on 27 IS young bulls belonging to three strains with different percentages of genes of Montbéliarde (Mb) origin: traditional strain (ISt), comprising nine young bulls without ascendants of Mb origin (ISt = 0% Mb genes); crossstrain (ISmt), comprising nine crossings of Mb bulls per eight pure ISt cows, and one 75% ISt cow (i.e., a cow with one Mb grand parent) (ISmt = 37.5–50% Mb genes); Montbéliarde strain (ISm), comprising two pure Mb young bulls and seven crossings of Mb bulls per 25% ISt cows (i.e., cows with only one ISt grand parent) (ISm = 87.5–100% Mb genes). These groups were balanced for the frequency of SCD types A and V genes. The experimental animals belonged to a herd of 104 young bulls subjected to performance test at the IS National Association Genetic Centre (Piasentier et al., 2003) and reared in slatted floor multiple pens (six bulls per 20 m2 pen) from the age of 5 months. The animals received a unifeed composed (by weight) of corn silage (45%), meadow hay (17%), maize (23%) and a compound complementary concentrate (15%) based on soybean meal with a mineral and vitamin additive, until the age of 12 months. Afterwards, in the fattening period, they were fed a unifeed composed of corn silage (80%), maize (12%) and the same compound complementary concentrate (8%). In the last month before slaughter all the bulls received 1 kg maize added to the feed mixture. The unifeed was given once a day in the morning. The beef production characteristics such as age at slaughter and live weight were recorded on the slaughter day. The following day the carcasses were weighed and graded according to the (S)EUROP grading system (Anonymous, 1981, 1991); at the same time, samples of the m. longissimus thoracis (LT) were collected from the carcasses’ left side between the 8th and 11th ribs (approximately 11 cm thick), and the pH was measured using a glass piercing electrode (Crison 52-32) connected to a pH meter. The muscle was then divided into five parts. From the caudal end, on the first sample, vacuum-packed and aged at 4 °C for 7 days, cooking loss was measured in a 75 °C water bath for 20 min (ASPA, 1996) and shear force was measured on the cooked sample, using a Warner–Bratzler device (WBSF), with a triangular hole in the shear blade, mounted on an Instron 4301 (Instron Ltd., High Wycombe, United Kingdom) universal testing machine. The measurement was recorded as the peak yield force in N, required to shear, at a 100 mm/min cross-head speed, perpendicular to the direction of the fibres, three cylindrical cross-section replicates, 10 mm diameter  30 mm length, from each sample. The other samples were vacuum packed, rapidly frozen and stored at 20 °C until analysis. Proximate analysis was carried out on the second part (ASPA, 1996), while total and insoluble collagens were analysed (AOAC, 2000) on the third part. The fatty acid assay and SCD analysis were performed on the fourth and fifth portions of the muscle, respectively. The carcasses’ right sides were aged at 4 °C for 7 days post-mortem. Samples of LT were collected between the 8th and 11th ribs,

divided into three steaks for sensory tests (two for triangle test and one for profiling), then vacuum packed and stored at 20 °C until analysis. 2.2. Genotyping of the g.10329C > T mutation of SCD gene DNA was extracted from 0.3 g muscle, using a Genomix kit (Talent), following the manufacturer’s protocols, modified as in Orrù, Napolitano, Catillo, and Moioli (2006). The DNA of all the animals was amplified with primers designed on the cattle sequence (GenBank accession AY241932) in order to produce an amplicon of 212 bp, spanning from 10,232 to 10,443 bp, encoding the portion of exon 5 containing the targeted g.10329C > T mutation. The primers used were: forward: ACCTGGCTGGTGAATAGTGC; reverse: TGACATATGGAGAGGGGTCA. The polymerase chain reaction (PCR) amplification was performed in a final volume of 50 ll, containing 250 ng genomic DNA, 0.2 mM of each dNTP, 40 pmol of each primer, 2 mM MgCl2 and 2.5 U AmpliTaq Gold (Applied Biosystems, Foster City, USA). Thirty-five PCR cycles at Tannealing of 58 °C were performed. Direct sequencing was performed on all samples on a Perkin–Elmer ABI Prism 310 DNA sequencer. The PCR for sequencing was obtained using ABI Prism BigDye Terminator Cycle Sequencing, Ready Reaction Kits (version 1.1 – Applied Biosystems). The protocol for Single- and Double-Stranded DNA was optimized in 20 ll final volume, containing: 4 ll of Terminator Ready Reaction mix, 10–15 ng PCR product and 5 pmol of single primer. The product of sequencing reaction was purified with a Nucleoseq kit (M-Medical). 2.3. Fatty acid analysis The extraction of total lipids was performed according to Folch, Lees, and Stanley (1957). Every meat sample (1.5 g) was minced, nonadecanoic acid (C19:0) was added, and homogenized in 30 ml of chloroform–methanol mixture (2:1 v/v) using a Ultra-Turrax T 25 basic (Ika-Werke); the samples were then filtered by vacuum filtration on Whatman filter paper. The extract was washed with 7.5 ml of 0.88% (w/v) KCl, mixed vigorously for 1 min, and then left overnight. The organic phase was separated and the solvents were evaporated under vacuum at 40 °C. Fatty acid methyl esters were prepared using methanolic HCl (Sukhija, & Palmquist, 1988). The lipid sample was mixed with 2 ml of hexane and 3 ml of methanolic HCl in 20 ml glass tubes with Teflon-lined caps. The mixture was heated at 70 °C for 2 h in a metal block and cooled to room temperature; the methyl esters were then extracted in 2 ml of hexane after addition of 5 ml K2CO3 of 6% (w/v) and Na2SO4. The samples were allowed to stand for 30 min and were centrifuged. The upper hexane layer was removed, concentrated under nitrogen and then diluted in hexane. Methyl ester analysis was performed using Carlo Erba gas chromatograph (HRGC 5300 mega-series) fitted with an automatic sampler (Model A200S) and FID detector; 1 ll of sample was injected into the gas chromatograph in split mode (split ratio 1:30). The conditions used were: SP-2380-fused silica capillary column (60 m  0.25 mm i.d., film thickness 0.20 lm) (Supelco Inc., Bellafonte, PA), programmed temperature from 50 to 200 °C at 20 °C/min and from 200 to 240 °C at 10 °C/min, and then held for 5 min. The carrier gas was helium at a flow rate of 1.0 ml/min. Fatty acid methyl esters were identified using external standards, quantified using C19:0 as an internal standard, and expressed as percentage of the total lipids. 2.4. Sensory analysis Sensory analysis was performed in a laboratory with all requirements according to the international standards (ISO, 1988). Steaks

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(approximately 3.5 cm thick) were thawed at 4 °C overnight 24 h before the test and cooked on a grill at 200 °C until the internal temperature reached 70 °C, and were monitored by an internal thermocouple. All external connective tissues were trimmed from the steaks, which were then cut into 2 cm3 samples, wrapped in codified aluminum paper and stored (for approximately 5 min) in warm pans at 60 °C until they were tasted. Triangle tests and sensory profiling were performed. In every ballot each assessor compared meat samples of different strains but with the same SCD genotype. Three triangle tests (ISO, 1983) were conducted on meats by a panel of 72 judges, scheduled in groups of six to ensure full randomization within the groups, for pair comparisons of the experimental meats. To assure consistency across animals, the difference between each pair of meats was tested using 12 different pairs of bulls (Nute, 2002). The order of sample presentation to assessors was randomized and balanced to minimize carry over effects (MacFie, Bratchell, Greenhoff, & Vallis, 1989). In contrast, sensory profiling was carried out by a panel of nine trained assessors experienced in meat evaluation (ISO, 1985, 1993). During a preliminary phase, consisting of discussions aimed at developing a common sensory vocabulary and avoiding any doubt about the meaning of attributes, the panel developed a profile protocol for a quantitative descriptive method (Stone & Sidel, 1992) containing 15 validated attributes relating to: total odour, beef odour, liver odour, barnyard odour, acid odour, broth odour, acid taste, metallic taste, persistence (expressed as the continuation of taste in the mouth), total flavour, fatness (expressed as the feeling of mouth lining), juiciness (amount of moisture released by the sample during chewing), hardness (the force required to bite the sample with molar), chewiness (number of times it is to be chewed to make the bite-size suitable for ingestion), and fibrousness (size of fibres perceived at the end of chewing). The sensory evaluation was replicated nine times; in each session, every judge assessed three meat samples from different animals of different strains but with the same SCD genotype. The panel rated the intensity of each sensory attribute on a 100 mm unstructured scale, anchored at each end, on which a score of 0 meant low odour and flavour intensity, dry, low fat, low taste of acid or metallic, low persistence, tender, low chewiness and low fibrousness and a score of 100 stood for high odour and flavour intensity, juicy, high fat, high taste of acid or metallic, high persistence, tough, high chewiness and high fibrousness. 2.5. Statistical analyses The statistical analysis was performed using SPSS version 17 software (SPSS Inc., Illinois) if not otherwise specified. Growth rate, carcass characteristics and chemical composition were subjected to one-way analysis of variance with strain as fixed factor. The fatty acid profiles were subjected to analysis of variance using a two-way factorial design with strain and SCD genotype as fixed effects. Interaction between strain and SCD genotype was considered, but the value was not reported in Table 3 because it never reached a level of significance (P > 0.05). The variability of the ‘‘hardness” attribute was examined with a covariance design considering the genotype effect as a factor and the WBSF as a covariate. The probability associated with the observed distribution (number of total answers/number of correct answers) for each triangular test was evaluated to determine whether there were differences between pairs of experimental products, and to determine their level of significance (Schlich, 1993). Every sensory attribute was initially analysed following a twoway factorial design in which the strain and panelist were treated

as fixed effect and random variable, respectively. Using a mixed model allows us to generalize conclusions about strains to the whole population of potential assessors (Lea, Naes, & Rødbotten, 1997). Multivariate procedures were then applied to the sensory data set in order to geometrically represent and explain the actual dimensionality of the IS beef sensory space. Among the multivariate procedures, general procrustes analysis (GPA) was performed, with Senstools version 3.01 (OP&P Product Research BV, NL), in order to consider the possibility that beef attributes were not used in the same way by the assessors (Dijksterhuis, 1996).

3. Results and discussion 3.1. Growth rate, carcass characteristics and chemical composition As reported in Table 1, the three young bull strains were of similar age at slaughter (543.7 days; P > 0.05) and of similar carcass weight (379.3 kg; P > 0.05) with an averaged dressing percentage of 56.3% (P > 0.05). The carcass conformation scores tended to decrease linearly as the frequency of Mb genes increased (P < 0.01), while the fatness scores did not significantly differ between the experimental groups (P > 0.05). These results are in agreement with the findings of Chla˘dek, Zˇizˇlavsky, and Šubrt (2005), which showed worse carcass conformation and similar carcass fatness comparing Montbéliarde bulls with Czech Pied bulls – a breed phylogenetically originated in Simmental cattle that is important for beef production. The pH at 24 h after slaughter was higher in ISmt than in the other groups (P < 0.01), while the pH at 7 days did not vary between strains, and its values fell within the normal pH range accepted for commercial meats (Table 2). No differences were found in meat proximate composition and cooking loss (P > 0.05). The absolute and relative insoluble collagen content tended to increase with the frequency of Mb genes, but this was not statisti-

Table 1 Mean value of live weight, age and carcass quality traits of IS bulls, n = 9 per strain. Strain

Age at slaughter (day) Live weight slaughter (kg) Cold carcass weight (kg) Dressing percentage (%) SEUROP conformationa SEUROP fat gradeb

RMSE

ISt

ISmt

ISm

544 675 387.3 57.4 3.8A 2.6

545 688 386.3 56.1 3.1AB 2.3

542 656 364.4 55.5 2.9B 2.4

28.0 44.8 30.81 2.49 0.55 0.52

RMSE: root mean standard error. A,B Within the same row, means with unlike letters differ significantly at P < 0.01. a S = 5 (superior), E = 4, U = 3,. . ., P = 0 (poor). b Class 5 = 5 (very fat),. . . Class 1 = 1 (very lean).

Table 2 Main characteristics of longissimus thoracis muscle of IS bulls. Strain

pH 24 h pH 7 days Ether extract (g/100 g DM) Warner–Bratzler shear force (N) Cooking losses (%) Total collagen (mg/g DM) Insoluble collagen (mg/g DM)

RMSE

ISt

ISmt

ISm

5.43B 5.54 3.26 42.6B 33.5 4.29 3.46

5.58A 5.64 3.75 54.8A 31.1 4.86 3.89

5.51AB 5.55 3.06 60.3A 31.9 4.95 4.08

0.085 0.147 1.023 9.94 2.17 1.229 0.907

RMSE: root mean standard error. DM: dry matter. A,B Within the same row, means with unlike letters differ significantly at P < 0.01.

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cally significant (P > 0.05). However, in a previous study which considered all the 104 young bulls among which the experimental animals of this trial were chosen, Piasentier et al. (2003) found that the insoluble collagen content, and its insolubility, increased with the frequency of Mb genes. Moreover, in our trial, WBSF was lower in ISt than in the other groups (P < 0.05). In particular, the degree of post-mortem proteolysis is the major determinant of longissimus muscle tenderness (Koohmaraie, Kent, Shackelford, Veiseth, & Wheeler, 2002). Pringle, Williams, Lamb, Johnson, and West (1997) also found different shear force values as the percentage of Brahman breeding increased in crossing with Angus steers, highlighting strong relationships between the calpastatin/calpain activity ratio, percentage of Brahman breeding and WBSF. 3.2. SCD genotype and fatty acid content Table 3 reports the FA composition of the intramuscular fat. The total lipid content of LT was comparable among strains and SCD genotypes. Thus the differences in FA composition between experimental groups can be regarded as generally quantitative rather than only relative, even if expressed as a percentage of total lipids. Regarding the SCD genotype, samples from homozygous alanine animals (AA) and from heterozygous alanine/valine animals (AV) had higher total MUFA than those from homozygous valine ones (VV) (P < 0.01). Genotypes AA and AV also had lower SFA percentage than the other group, but without a significant difference (P > 0.05). Our findings are in agreement with results reported by several authors, in that SCD alanine variant contributes to higher MUFA and lower SFA percentages (Jiang et al., 2008; Taniguchi et al., 2004). From another point of view, the levels of C14:0, C16:0, and C18:0 were similar between experimental groups, C18:1 n 9, C20:1 n 9 were higher in AA and AV (P < 0.05), and the level of C16:1 n 7 was also higher in these groups, but this is without statistical significance (P > 0.05). Moreover there were no differences in total n 6, n 3 series and PUFA level (P > 0.05)

with the sole exception of C18:3 n 3, which is lower in AA group (P < 0.05) although this result is hard to justify, because this enzyme should not be directly involved in the metabolism of this FA. In general, these results highlight a higher SCD activity of genotype AA. SCD activity involves the last step of the conversion of myristic (C14:0) and palmitic acids (C16:0) into the corresponding monounsaturated fatty acids myristoleic (C14:1) and palmitoleic acids (C16:1) (De Smet et al., 2004). Furthermore, it is well known that, in ruminants, oleic acid (C18:1) is largely hydrogenated to stearic acid (C18:0) by ruminal microorganisms, and an important function of SCD enzyme is also to partially re-convert stearic acid to oleic acid and, in general, to catalyze the conversion of SFA to n 9 MUFA (Oka et al., 2002). Chung, Lunt, Kawachi, Yano, and Smith (2007) found a significant relationship between C16:1 n 7/C18:0 ratio and SCD gene expression and between the C16:1 n 7/C18:0 ratio and SCD activity in adipose tissue of Angus and Wagyu corn fed steers. In our trial this ratio is higher in the AA group than in the VV group (0.172 vs. 0.130) but the difference was not significant (P = 0.110). The meat fatty acid profiles of the three experimental groups were different (Table 3). However, the levels of saturated FA C14:0, C16:0 and total SFA are similar between groups (P > 0.05), while the level of C18:0 is slightly higher in ISmt (P = 0.09) meat. Braghieri, Cifuni, Girolami, Riviezzi, and Napolitano (2005) showed differences in C16:0, but not in C14:0, C18:0 and total SFA in meat produced by Podolian bulls and their crosses with Limousin. Zapletal et al. (2008) evaluated FA profiles in meat samples of Montbéliarde and Czech Simmental, and found differences in FA C14:0, C16:0 and C18:0, but not in total SFA. In our trial, the slightly higher ISmt level of C18:0 (P = 0.09) could be due to positive heterosis, expressed as the differences between cross-bred and parental means (Malau-Aduli, Edriss, Siebert, Bottema, & Pitchford, 2000) and could involve the de novo synthesis of C18:0 from C16:0 by chain elongation. This heterosis is not beneficial to human health; in fact it is widely recognized that C18:0 favours cardio-vascular

Table 3 Effect of stearoyl Co-A desaturase (SCD) types A and V gene frequency and different percentages of genes of Montbéliarde origin on beef fatty acid total weight (mg/g muscle) and composition (g/100 g of total lipids). SCD genotype

Total weight C14:0 C16:0 C16:1 n 7 C18:0 C18:1 n 7 C18:1 n 9 C18:2 n 6 C18:3 n 3 C20:1 n 9 C20:2 n 6 C20:3 n 6 C20:4 n 6 C20:5 n 3 C22:4 n 6 C22:5 n 3 SFA1 MUFA2 PUFA3 PUFA n 34 PUFA n 65 PUFA n 6/n 3

Strain

RMSE

AA

AV

VV

ISt

ISmt

ISm

41.1 2.36 26.45 2.92 17.02 2.36 38.45A 6.72 0.30c 0.15a 0.03 0.39 1.98 0.07 0.30 0.36 45.83 43.88A 10.29 0.74 9.41 12.8

42.8 2.25 25.9 2.84 17.26 2.44 38.32A 7.35 0.36b 0.17a 0.10 0.34 1.86 0.09 0.30 0.30 45.40 43.77A 10.83 0.75 9.94 13.2

37.5 2.50 26.18 2.54 19.58 2.16 34.76B 8.77 0.45a 0.12b 0.09 0.34 1.74 0.10 0.27 0.30 48.26 39.57B 12.17 0.85 11.20 13.3

38.1 2.22 26.16 2.98 16.29 2.37 36.28 8.82 0.41a 0.17 0.05 0.51A 2.70A 0.09 0.40a 0.46A 44.67 41.78 13.55 0.96A 12.48 13.5

44.5 2.56 26.38 2.53 19.60 2.19 36.59 6.86 0.41a 0.13 0.08 0.30B 1.59B 0.10 0.26b 0.27B 48.54 41.43 10.03 0.78B 9.10 11.3

38.5 2.32 25.99 2.79 17.97 2.41 38.66 7.15 0.29c 0.15 0.08 0.26B 1.29B 0.07 0.20b 0.23B 46.28 44.01 9.71 0.60C 8.97 14.6

1244 0.349 1.278 0.422 2.691 0.511 2.091 2.787 0.078 0.035 0.072 0.134 0.775 0.055 0.122 0.091 3.307 2.209 3.758 0.149 3.716 3.71

P-value SG

S

ns ns ns ns ns ns  ns   ns ns ns ns ns ns ns  ns ns ns ns

ns ns ns ns 0.09 ns 0.09 ns  ns ns   ns   ns 0.08 ns  ns ns

RMSE: root mean standard error; SG: effect of SCD genotype; S: effect of strain; **,A,B,CWithin the same row, means with unlike letters differ significantly at P < 0.01; Within the same row, means with unlike letters differ significantly at P < 0.05; ns: not significant. 1 SFA (saturated fatty acids) = C14:0 + C16:0 + C18:0. 2 MUFAs (monounsaturated fatty acids) = C16:1 n7 + C18:1 n7 + C18:1 n9 + C20:1 n9. 3 PUFAs (polyunsaturated fatty acids) = PUFA n 3 + PUFA n 6. 4 PUFA n 6 = C18:2 n6 + C20:2 n6 + C20:3 n6 + C20:4 n6 + C22:4 n6. 5 PUFA n 3 = C18:3 n3 + C20:5 n3 + C22:5 n3.

*,a,b,c

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diseases. In our trial, the level of total SFA seems to be lower than ˇ , Zahrádková, Teslík, and Krejcˇová that reported by Bureš, Barton (2006) in Aberdeen Angus, Charolais, Simmental and Hereford bulls. The level of monounsaturated FA C18:1 n 9 tends to be higher in ISm (P = 0.086). This result can be explained by a different hydrogenation of C18:1 in the rumen or by genetic differences in de novo fatty acid synthesis, as supposed by Bureš et al. (2006) who also found that the breed influences the level of C18:1 n 9. Total MUFA content is slightly higher in ISm (P = 0.08); however, Zapletal et al. (2008) did not find any difference in total MUFA of meat from two breeds of the same phylogenetic origin. An increased C18:1 in meat is considered highly desirable, because of its hypocholesterolaemic properties (Bonamone & Grundy, 1988), while MUFA have neutral effects on human cholesterol levels (Scientific Review Committee, 1990). Considering the n 6 FA series, the differences involve single FA as C20:4 n 6 and C22:4 n 6, both of which are higher in ISt (P < 0.05); also total n 6 FA was higher in ISt, but this has no statistical significance (P = 0.15). For ISt group, these results apparently suggest an increase in the activity of D6 desaturase, elongase and D5 desaturase, involved in the conversion of C18:2 n 6, to C20:4 n 6 and to C22:4 n 6 as the last step. Moreover, Warren et al. (2008) suggest the existence of differences in D6 and D5 desaturase enzyme activity between Holstein Friesian and Aberdeen Angus. This hypothesis is supported by the results of our trial, when considering the n 3 series, in which D6 and D5 desaturases allow the conversion of C18:3 n 3 to C22:5 n 3. In fact we found that C18:3 n 3 level is higher in ISt and ISmt than in ISm (P < 0.05) and C22:5 n 3 is also higher in ISt. These results also seem to confirm that a high availability of C18:3 enhances the synthesis of long chain PUFA n 3 (Nuernberg et al., 2005). Considering the single PUFA, Bureš et al. (2006) found differences only in C18:3 n 3 levels between the meat of Simmental and Aberdeen Angus, but did not find any differences between Simmental and Hereford beef. In our trial, total PUFA n 3 level was also higher in ISt (P < 0.05) in agreement with previous studies, which found a breed effect on total PUFA n 3, but not in total PUFA n 6 (Laborde, Mandell, Tosh, Wilton, & Buchanan-Smith, 2001; Raes et al., 2003). From a nutritional point of view the higher C18:3 n 3, C20:4 n 6 and total n 3 FA levels in ISt are relatively important. In fact, human beings are able to synthesize C20 PUFA and 22:6 n 3 from 18:3 n 3 (Scollan et al., 2001) and these FAs, together with C20:4 n 6, play various essential metabolic roles such as in eicosanoid production (Wood et al., 2008). However the mean n 6/n 3 ratio found in this experiment was about 13.2, a value that is much higher than the maximum range (4.0) recommended by the Department of Health (1994), because this ratio expresses a risk factor for cancer and coronary heart disease. Total PUFA was slightly higher in ISt meat but this had no statistical significance (P = 0.121), in agreement with the findings of Zapletal et al. (2008) and Bureš et al. (2006) whereas the breed seems not to influence total PUFA level. Moreover, the proportions of PUFA were higher in this study than those reported by Mahecha et al. (2009) in German Simmental bulls fed maize and grass silage, 1 kg of molasses and 3 kg of concentrate. In our trial the PUFA/SFA ratio was very low, about 0.26, which is below the minimum recommended value of 0.45 (Department of Health, 1994) for human consumption, but quite normal in ruminant beef because of the hydrogenation of dietary unsaturated fatty acids by rumen microorganisms. 3.3. Sensory properties To understand if the beef of the different experimental groups could be differentiated by consumers, three triangle tests were car-

ried out (Table 4). In this analysis, based on overall impression, more than 40% of the panellists correctly selected the odd sample among the triplet presented, thus demonstrating that a sensory difference exists (P 6 0.05). In addition, Wheeler, Cundiff, Shackelford, and Koohmaraie (2004) suggested that there are differences among and within cattle sire breeds in meat palatability traits; in general, European breeds produce meat that can be differentiated by their organoleptic properties (Olleta et al., 2006). Bureš et al. (2006) showed that assessors were able to recognize different meat samples from late maturing Charolais steers and fatter Aberdeen Angus steers. With the aim of a deeper understanding of why the strain groups could be distinguished by the consumer, a Quantitative Descriptive Analysis was performed. The total flavour was easily perceivable in experimental meat (an average score of about 43 on a 100 point scale, Table 5) and there were only slight differences between ISt and ISmt (P > 0.05). On the contrary, Raes et al. (2003) suggest that beef can be differentiated on the basis of flavour intensity, but these authors evaluated animals of very different origin (Belgium, Argentina and Ireland) and production system (intensive and extensive). On the other hand, our results are in agreement with Braghieri, Carlucci, Girolami, and Napolitano (2008), which found no differences in the perception of overall flavour of meat from Podolian young bulls and their crosses with Limousin sires. These results could be explained by the recent findings of Koutsidis et al. (2008) in which the breed had only a small effect on meat concen-

Table 4 Triangle tests used to evaluate the sensory differences between IS beef types.

Pair comparison Total responses (no.) Correct selectionsa (no.) P for ‘‘no differences hypothesis”b (%)

ISm vs. ISt

ISmt vs. ISt

ISmt vs. ISm

72 32 0.05

72 33 <0.05

72 32 0.05

a Refers to the number of occasions the odd sample in triangle tests was correctly identified by a 72-member consumer taste panel. b Probability of significant differences determinate using tabulated critical number (minimum) of correct answers.

Table 5 Mean intensity scores for IS beef types; anchors on a 100 mm unstructured scale. Strain

Attribute1 Total odour Beef odour Liver odour Barnyard odour Acid odour Broth odour Acid taste Metallic taste Persistence Total flavour Fatness Juiciness Hardness Chewiness Fibrousness

RMSE

ISt

ISmt

ISm

50.2 45.2 16.5 22.2 10.7 37.2 13.1 15.6 34.9 44.9 26.7ab 38.5 36.4B 47.2B 42.9b

52.2 47.6 17.8 22.4 12.0 39.9 15.5 17.7 33.8 40.1 28.1b 36.7 27.1A 35.9A 35.5a

49.2 44.3 18.4 22.4 10.2 36.9 16.7 17.4 34.5 43.7 24.4a 34.9 37.8B 45.6B 38.7ab

15.45 15.68 13.00 11.03 11.87 18.05 9.78 9.33 11.85 18.71 8.64 14.53 18.18 14.79 13.43

RMSE: root mean standard error. A,B Within the same row, means with unlike letters differ significantly at P < 0.01. a,b Within the same row, means with unlike letters differ significantly at P < 0.05. 1 See Section 2.4 for attribute description.

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tration of water-soluble flavour precursors, such as ribonucleotides, creatinine, free amino acids and sugars; moreover differences in meat flavour are more evident between the meat of pure breeds than between the meat of their crosses (Sobczak et al., 2005). Considering the fatty acid profile, flavour score could be significantly correlated with C14:1. C18:0, C18:1 and C18:3 of the neutral lipids and with C18:3 of the polar lipids (Melton, Amiri, Davis, & Backus, 1982) or with the fatty acid ratio (Farmer, 1994). In our trial there were no significant differences (P > 0.05) between the experimental groups in these individual fatty acids, except for C18:3n3 (P < 0.05). However, the difficulty of relating fatty acid profile to overall meat flavour has also been mentioned in a recent study by Stelzleni and Johnson (2008). The perception of acid taste was slightly higher in ISm than in ISt, but this does not reach the level of significance (P = 0.09); however, the perception of this attribute, usually associated to non-volatile taste active compounds such as free amino acids, was not very pronounced, as indicated by the modest average scores (15.1 within a scale of up to 100). Fatness attribute was higher in ISmt than in ISm (P < 0.05) and this is probably linked to the higher, but without statistical significance (P > 0.05), ether extract value of this group; however, also in this case, the perception of this attribute was not pronounced, reaching a mean score of about 26 on a scale of up to 100. As reported in Table 5, ISt and ISm meats were perceived to be harder than ISmt meat (P < 0.01). In general, it is well known that beef quality, including tenderness, can be affected by several factors, including breed, solubility and space organization of the collagen, fatness and the ultimate pH of the meat. As shown in Tables 1 and 2, the animals in this study were of almost the same age (P > 0.05) and live weight (P > 0.05) at slaughter. They were produced under the same conditions and their meat was aged for the same period of time. Moreover the total and insoluble collagen content values were similar (P > 0.05), as were collagen insolubility and fat ratio (P > 0.05). The ISmt beef had higher pH at 24 h than the ISt beef (P < 0.01), but was not statistically different from ISm beef (P > 0.05), so these differences could be too small to markedly

affect the perception of hardness. Moreover, Dufey (1987) improved the tenderness of Simmental beef by cross-breeding with Red Holstein, probably because the specialized breeds (beef and dairy breeds) had the highest tenderness values (Olleta et al., 2006). Monson et al. (2005) showed significant differences in meat tenderness from four breeds which represented different biotypes (dairy, dual-purpose, meat and high muscularity types). In general, numerous studies have reported a significant effect of genotype on meat sensory tenderness scores (Braghieri et al., 2008; Campo, Sanudo, Panea, Alberti, & Santolaria, 1999; Chambaz, Scheeder, Kreuzer, & Dufey, 2003). In this regard, Koohmaraie and Geesink (2006) demonstrated that the calpain system plays an important role in the post-mortem proteolysis of myofibrillar proteins and in the resultant meat tenderization, while Casas et al. (2006) found a link between meat tenderness and the polymorphisms of calpastatin (CAST) and l-calpain (CAPN1) genes. When compared with the results using mechanical texture analysis, our results do not correspond exactly. In fact, as shown in Table 2, WBSF is higher in ISmt than in ISt (P < 0.01). However, the covariate analysis demonstrated a significant correlation between WBSF and hardness (0.65; P < 0.05). A common, positive regression coefficient between strains was determined, together with a significant additive effect, expressing a systematic more tender perception of ISmt beef at every level of instrumental shear force. This result reflects the complexity of food disintegration during mastication, where the perception of fibrousness and chewiness, which followed a similar trend, has probably influenced the perception of beef hardness. Chambaz et al. (2003) considered the meat quality of Angus, Simmental, Charolais and Limousin steers, and showed that WBSF followed the same trend, but this was not closely correlated with sensory tenderness for all animals. The range of correlation between these measures is quite wide: Szczesniak (1968), in many experiments, showed correlations between 0.16 and 0.94; more recently Peachey, Purchas, and Duizer (2002) reported a correlation of about 0.7. Difficulty in relating sensory evaluation with instrumental measures is also reported by Raes et al. (2003). In fact, WBSF is an instrumental technique that is used routinely to provide measures of beef hardness; it

ISm Metallic t Acid t Persistence Barnyard o Total o

ISmt

Broth o Acid o Liver o Beef o

Total flavour Juiciness

Fatness

Hardness Chewiness

Fibrousness

ISt

Fig. 1. GPA group average configuration of IS beef types on the basis of 15 sensory descriptors, whose correlations with the space dimensions are reported as vectors (see Section 2.4 for attribute description; o: odour; t: taste).

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gives the maximal force needed to shear a core of meat, but does not satisfactorily mimic the dynamics of biting, mastication rate and salivation. In this trial the perception of fibrousness was higher in ISt meat than in ISmt meat (P < 0.05), while chewiness was higher in ISm and ISt meats (P < 0.05) following the same trend of hardness. It is interesting to note that Peachey et al. (2002) showed a strong correlation between hardness and chewiness detected by a trained sensory panel (r2 = 0.98) and also suggested that the panellists probably could not distinguish these attributes clearly. While Sobczak et al. (2005) did not find difference in the chewiness attribute of meat from Charolais pure breed and Charolais cross with Hereford and Simmental; Campo et al. (1999) did not find differences in the perception of fibrousness of meat from seven European breeds with dual-purpose, fast growth rate and rustic characteristics. Considering all the sensory attributes at the same time using multivariate GPA, the IS strain beef could be clearly discriminated, as summarized in the bi-dimensional group configuration reported in Fig. 1. ISmt beef is clearly separated from both ISm and ISt beef in the first dimension (53.3% of the total variance explained), the main associated attributes of which are the texture ones. Indeed the loadings of chewiness, hardness and fibrousness were, respectively, 0.94, 0.86 and 0.64. On the other hand, ISm and ISt differentiated along the second dimension (40.4%) mainly correlated to flavour profile. A combination of sensory attributes (fatty mouthcoating, metallic and acid taste, total odour) loaded on these dimensions with values comprising 0.25 to 0.40. 4. Conclusions The inclusion of Mb genes decreased the carcass conformation of young bulls and reduced the level of C20:4 n 6, C22:4 n 6, C18:3 n 3 and total n 3 FA of beef, which becomes less beneficial to human nutrition; the FA profile of meats reflects the possible genetic differences in fatty acid metabolism. With triangular test analysis, based on an overall impression, the meat samples produced by the three experimental groups could be differentiated. The taste panel was also able to detect differences in the sensory profile of beef; GPA provided a group configuration that clearly discriminated the strains, mainly for the texture parameters of their meat. In particular, the inclusion of 50% of Mb genes reduces the perception of hardness, chewiness and fibrousness and tends to increase the perception of meat fatness. From the point of view of the IS meat valorization, the inclusion of Mb genes should be taken into account in breeding programmes in order to monitor meat quality while breeding for improved milk production. Acknowledgements The authors wish to thank the director and technicians of the Italian Simmental Breeders’ Association for their co-operation in animal procurement. References ANAPRI (2008). Valutazioni genetiche. In Assemblea nazionale dei soci – Attività anno 2007. Udine, Italy: Associazione Nazionale Bovini di Razza Pezzata Rossa Italiana. (Accessed 18.06.09). Anonymous (1981, 1991). Community scale for the classification of carcasses of adult bovine animals. Council regulation no. 1208/81 and 1026/91. Official Publications of the European Communities. AOAC (2000). AOAC official method 990.26. Hydroxyproline in meat and meat products. 39.1.27. In Official methods of analysis of AOAC international (17th ed.). Arlington, VA: Association of Official Analytical Chemists.

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