Effect of genetic origin, diet and weaning weight on carcass composition, muscle physicochemical and histochemical traits in the rabbit

Fifty rabbits originating from the crossing of one dam strain with three sire strains, Hy+, INRA 9077 and INRA 3889, were studied. The adult body weights of the sire strains were 5·1, 4·1 and 3·1 kg, respectively. After weaning, the Hy+ and the INRA 9077 rabbits were fed either an H (11·99 MJ DE kg DM⁻¹) or L diet (9·67 MJ DE kg DM⁻¹). The INRA 3889 rabbits were fed only the H diet. In each of these five blocks, two weaning weights were studied and the rabbits were slaughtered when the average body weight of each block reached 2·5 kg. Slaughter yield, carcass fatness and hindleg meat to bone ratio were determined. Muscular tissue was described using (1) physicochemical criteria (ultimate pH, L^*a^*b^* colour) of the biceps femoris (BFE), tensor fasciae latae (TFL) and semimembranosus accessorius (SMA) muscles and (2) histochemical characteristics of the longissimus lumborum muscle (LL) through computerised image analysis (fibre type composition, cross-sectional area). At slaughter, the rabbits of INRA 3889 sire origin, which had the highest degree of maturity (72%), gave the best slaughter yield (p<0·01), the heaviest reference carcass weight (p<0·01), and highest LL proportion (p<0·01), hindleg meat to bone ratio (p<0·05) and fatness (p<0·01); their LL muscle showed the lowest percentage of βR fibres, while the cross-sectional area of their muscular fibres was the highest (p<0·05). When all sire × diet combinations were put together, the heavier the weaning weight, the lower the daily gain (p<0·01) and the lightness (L*) of thigh muscles (p<0·05). The lower the DE content of the diet, the lower the growth rate, the slaughter yield, the reference carcass weight (p<0·01) and the cross-sectional area of all types of muscle fibres of the rabbits of both Hy+ and INRA 9077 sire origin.     

Effect of muscular hypertrophy on physico-chemical, biochemical and texture traits of meat from yearling bulls

The effect of the presence of the double-muscling gene either homozygous (mh/mh) or heterozygous (mh/+) on the physico-chemical, biochemical and texture traits of Longissimus thoracis muscle of yearling bulls of the Asturiana de los Valles (AV) breed was studied. Meat of mh/mh bulls had lower amount of intramuscular fat (p<0.001) and also lower total (p<0.01) and insoluble collagen (p<0.05), although the double-muscling genotype did not affect collagen solubility. Homozygous animals had lower pigment content (p<0.05) and a lighter meat, showing lower water holding capacity, estimated as expressible juice under pressure (p<0.001). Genotype affected significantly the metabolic traits of muscle, with mh/mh animals having higher muscle glycolytic metabolism, assessed by a higher (p<0.001) lactate dehydrogenase (LDH) activity and lower (p<0.001) oxidative activity of the isocitrate dehydrogenase (ICDH). The percentage of myosin heavy chain I in muscle was lower, although not significantly, for mh/mh bulls compared to mh/+ bulls. Texture measurements performed on raw material showed that meat of mh/mh bulls had lower resistance to total and 80% compression, which means lower background or collagen toughness. However, there were no differences between genotypes on shear force of cooked meat. Therefore, the physico-chemical, biochemical and texture traits of meat from mh/mh and mh/+ bull are in general significantly different, which could affect the sensorial quality of meat and hence the consumer acceptance.     

Influence of ultimate pH on bovine meat tenderness during ageing

The aim of this work was to evaluate the influence of ultimate pH and ageing at 2±2°C on the tenderness of beef. The m.longissimus thoracis et lumborum from 23 young bulls excised at 28 h post mortem were grouped into: Normal (pH 5.5 to 5.8) moderate DFD (mod DFD) (5.8p<0.05) lower in the DFD group than in the Normal one and a significant (p<0.001) linear relationship was found between ultimate pH and tenderness as evaluated by both methods. The myofibrillar protein solubility (MPS) at pH 7.0 was significantly higher in the DFD group at all post mortem times whereas for myofibrillar fragmentation index (MFI) higher values (p<0.05) were only found in the DFD group at day 1. In all three groups toughness decreased (p<0.05) from 1 to 6 days, with no further decrease to 13 days. This decrease in toughness was associated with an increase of MFI in all pH groups. Collagen solubility in all three groups was not affected by ageing. No significant (p>0.05) differences in soluble collagen and myofibrillar protein solubility (MPS) at pH 5.5 were found between the pH groups at any time. The tenderness evaluated by both methods was significantly (p<0.05) related to MFI, MPS at pH 7.0, cooking loss and juiciness. Total and soluble collagen, sarcomere length, intramuscular fat and MPS at pH 5.5 were not significantly (p>0.05) related with tenderness.     

Post-natal changes in the biological characteristics of Semitendinosus muscle in male Limousin cattle

Samples of semitendinosus muscle from 45 male Limousin cattle reared under similar conditions were taken at 1, 6 and 12 months of age (biopsy) and at 16 months (at slaughter). The development of biochemical (DNA, protein/DNA), enzymic (lactic dehydrogenase, isocitric dehydrogenase), and histochemical (ATPase, succunic dehydrogenase) characteristics was studied. Muscle fibres were classified according to their contractile and metabolic properties (SO = slow oxidative; FOG = fast oxidative glycolytic; FG = fast glycolytic). DNA accumulation or hyperplasia was observed up to the age of 16 months. The period of growth and development, between 1 and 12 months of age, was characterized by increased glycolytic metabolism, as evidenced by the conversion of FOG fibres into FG fibres, a decrease in ICDH activity and a rise in LDH activity. The period between 12 and 16 months, was characterized by a slowing down of the conversion of FOG fibres into FG fibres and an increase in ICDH activity. The presence of type IIC fibres at the four ages studied is discussed. Of the muscle characteristics studied, LDH activity seemed to be a discriminating factor between animals from an early age. It could thus be used as to predict animal muscle characteristics at birth.     

Compositional and enzymatic characteristics of the Longissimus Dorsi muscle from large white, halothane-positive and halothane-negative pietrain, and hampshire pigs

One-hundred-and-twenty-nine pigs from four genetic types—Large Whites, halothane-negative (HN) and halothane-positive (HP) Pietrains and Hampshires—were used to study some compositional and enzymatic muscle traits. Water, nitrogen, hydroxyproline and lipid contents, as well as lactate dehydrogenase and citrate synthase activities, were measured on all pigs, whereas glycogen phosphorylases (a and a + b), glycogen synthetase I + D and myosin isozyme pattern were determined on only fifty-six pigs. Hampshires were markedly different from the other genetic types with respect to the characteristics studied. Their Longissimus dorsi muscle contained less nitrogen (P < 0·0) and more lipid (P < 0·01) and presented higher hydroxyproline to nitrogen (P < 0·001) and water to nitrogen (P < 0·001) ratios, as well as noticeably higher citrate synthase (P < 0·01) and glycogen synthetase     

Thermophysical properties of silver hake and mackerel surimi at cooking temperatures

Thermal diffusivity values obtained using a transient method both from heating and cooling information and apparent specific heat of surimi made from silver hake and mackerel as a function of temperature (60–110 °C) and added potato starch content (3% and 7%, w/w) were determined. The water content of all samples was kept constant at about 77% (w/w) in order to determine the effect of starch. Thermal diffusivity and apparent specific heat of all samples increased with temperature. The effect of temperature on diffusivity was found significant (p=0.001) in all samples at temperatures above 85 °C. This effect may be caused by structural changes as temperature is raised. Thermal diffusivity increased with temperature more rapidly in samples with high levels of starch than in those with no starch. However, thermal diffusivity of silver hake surimi preset at 40 °C for 30 min did not show a significant increase (p<0.05) over the temperature range studied. Thermal diffusivities calculated from cooling and heating data were significantly different (p<0.05).

The differential scanning calorimetry (DSC) thermograms of silver hake and mackerel surimi showed three endothermic peaks. When starch was added to surimi samples an endothermic peak having a large area was observed, which overlapped the third highest temperature peak of surimi samples. No significant shifts in the endothermic peaks of myofibrillar proteins were detected with increasing starch content. Transition temperatures for starch–surimi system were higher than those for starch–water system. There were deviations in the apparent heat capacity function calculated from DSC measurements in surimi samples containing starch. These are attributed to gelatinization of starch and modification of water structure.     

Effects of hot water and lactic acid treatment of beef trimmings prior to grinding on microbial, instrumental color and sensory properties of ground beef during display

The impact of 82°C hot water (HW) or 5% lactic acid (LA) applied aerobically or by vacuum to beef trimmings prior to grinding on Salmonella Typhimurium (ATCC 1769NR; ST), Escherichia coli (ATCC 11775; EC), coliform (CO), aerobic plate count (APC), instrumental color and sensory characteristics of ground beef through simulated retail display was investigated. For this, beef trimmings were inoculated with a mixture (7 log CFU/ml each) of ST and EC, and treated either aerobically or under vacuum in a tumbler with HW or LA antimicrobials. Trimmings were ground, packaged and sampled on days 0, 1, 2, 3 and 7 of display for ST, EC, CO, APC, sensory and instrumental color characteristics. Vacuum HW or LA application had no additive effect (P>0.05) when compared with aerobic application for reducing EC, ST, CO or APC. However, lactic acid was effective for reducing (P<0.05) EC, CO and APC, but reduced ground beef redness.     

Textural assessment of clenbuterol treatment in beef

Eight Charolais heifers (ca. 300 kg) were fed a diet containing either 0 (control) or 1 ppm clenbuterol during 5 weeks. Daily live weight gain was higher (p<0.01), by about 34%, in treated animals. They were slaughtered after a week of withdrawal. Activity of μ-calpain of meat from clenbuterol-fed heifers was lower (p<0.01) immediately post mortem, while activity of calpastatin was higher (p<0.05) than in meat from controls. According to sensory and instrumental data, meat from clenbuterol-fed heifers did not tenderise during aging, and was tougher (p<0.05) than control meat at 8th day post mortem. Both principal component analysis and multivariate discriminant analysis of a pool of data of the textural profile showed differences due to clenbuterol treatment at 24 h. The slope after yield (calculated from the Warner–Bratzler shearing force–deformation curve), was the only textural parameter affected (p<0.05) at 24 h by the treatment.     

Assessment of breed type and ageing time effects on beef meat quality using two different texture devices

Forty-two male yearlings were used to assess the influence of breed type and ageing time on beef texture. Samples of the M. longissimus dorsi of four breed types [double muscled (DM), dual purpose (Brown Swiss, BS), fast growth (FG) and unimproved type (UT)] were aged for 1, 3, 7, 10, 14 or 21 days at 4°C and frozen at −18°C until analysed. Cooked samples (to end-point of 70°C) were assessed using a Warner–Bratzler (WB) device. Raw samples were assessed using a compression device in which transverse elongation was prevented. There were no significant differences in WB values of cooked meat due to breed type, but ageing had a significant (P<0.05) on maximum load. Ageing, but not breed type, had a significant effect on the compression values of raw meat at low compression rates (P<0.001). Compression values, of raw samples, at 80% compression differed significantly (P<0.001) between breed types, but were not affected by ageing. Compression values of raw samples, at 80% compression, were affected by breed type, probably because of genotype differences in the contribution of connective tissue.     

Residence time distribution of carrot cubes in starch solutions in a pilot scale aseptic processing system

Residence time distribution (RTD) of carrot cubes flowing in starch solutions was evaluated in a commercial pilot-scale aseptic processing system using a full factorial design of experiments employing flow rate (15 and 20 kg/min), temperature (80 and 100°C), holding tube length (0, 60 and 100%), particle size (6 and 13 mm) and starch concentration (3 and 5% w/w) as factors. All factors were found to be significant (p<0·05) in influencing the fastest particle residence time (FPRT), mean particle residence time (MPRT), particle residence time variance (PRTV) and their normalized versions. While particle size, holding tube length and starch concentration increased the FPRT, fluid flow rate and temperature had the opposite effect. The FPRT was lower than the average fluid retention time under all testing conditions.     

Muscle composition and fatty acid profile in lambs fattened in drylot or pasture

The effects of two fattening systems on muscle composition and fatty acid profile were determined in an experiment using samples of the longissimus dorsi (LD) muscle of 24 ram lambs (slaughter weight 29–31 kg). The fattening systems were: (i) drylot (a mixture of maize, soybean, wheat and minerals) and (ii) grazing (Cynodon dactylon). The lambs fattened in the drylot system presented higher fat levels (p<0.01), but lower concentrations of moisture (p<0.01) and cholesterol (p<0.05). The lipid content presented a negative correlation with moisture and protein. In lambs fattened in the drylot system increasing levels of fatness of LD muscle were associated with a decrease (p<0.05) in myristic and palmitic acids, but myristic, palmitic and linoleic acids increased (p<0.05) as the cholesterol levels of the muscles increased.     

Cattle at risk for dark-cutting beef have a higher proportion of oxidative muscle fibres

The aim of this investigation was to compare muscle fibre type characteristics in dark-cutting (DFD) and normal beef animals. Three categories of animal were used in this investigation: 9 DFD bulls, 10 DFD steers and 10 normal bulls. For each animal, frozen sections of longissimus dorsi muscle were stained histochemically. The results showed that there were proportionately more slow, oxidative (SO) fibres in DFD bulls and DFD steers than in normal bulls. As far as fast, glycolytic (FG) fibres were concerned DFD bulls contained fewer of this type than DFD steers and normal bulls. When the results on fibre proportions were combined with those on mean fibre cross-sectional areas it was found that both DFD groups contained a smaller proportion of muscle exhibiting FG characteristics than normal bulls. Furthermore, the combination of all oxidative fibres, i.e. SO and fast, oxidative, glycolytic (FOG) fibres, showed that, both by numbers and relative areas, the two DFD groups (especially DFD bulls) exhibited significantly more oxidative metabolism in the longissimus dorsi muscle than the normal animals.     

Carcass and meat quality of finishing Friesian steers fed the β-adrenergic agonist L-644,969

The effect of the β-adrenergic agonist L-644,969 on selected parameters of carcass and meat quality was examined in Friesian steers. Four groups of 18 steers were individually offered ad libitum a pelleted diet that contained 0, 0·25, 1·0, or 4·0 ppm L-644,969 for 12 weeks prior to slaughter. L-644,969 quadratically increased carcass weight (3·7, 9·3, and 8·5%, P < 0·001) and altered the distribution of lean meat such that a greater (0·3–5%; P < 0·01) proportion was in the more valuable cuts. There were no effects of L-644,969 on carcass-chill loss and on the water-holding capacity of the longissimus thoracis et lumborum (LTL) muscle. The intramuscular-fat concentration of the LTL was decreased (27–50%; P < 0·01) and the effects on muscle ultimate pH were small and commercially unimportant. Fibre-optic-probe measurements of the LTL indicated darker (P < 0·01) meat due to β-agonist treatment. L-644,969 increased the shear force required to cut through cooked muscle from the LTL (159%, 209%, and 217%, P < 0·001). It is concluded that L-644,969 treatment improved the quantity and distribution of lean in the carcass but impaired meat quality, primarily through a reduction in tenderness.     

The effect of ractopamine on myofibre distribution and morphology and their relation to meat quality in swine

One hundred and twenty-eight purebred Lacombe pigs (equal number of barrows and gilts) were assigned to one of four treatments at 64 kg and fed a commercial grower-finisher diet ad libitum to which ractopamine (RAC) was incorporated (0, 10, 15 or 20 mg kg⁻¹). Pigs were slaughtered at 100 kg. Histological samples were collected from the semimembranosus (SM) and the psoas major (PM) muscles from the 0 and 20 mg kg⁻¹ RAC groups. Meat quality and muscle composition data were collected for all pigs. A significant 3-way interaction for muscle weight involving treatment, muscle and gender (P = 0·01) indicated that for the SM, gilts appeared to respond to RAC at a lower level of incorporation (10 mg kg⁻¹) than barrows. Despite these differences in response at the gross muscle level, responses were similar at the cellular level for both muscles. The proportion of red fibres did not change (P = 0·21), the proportion of intermediate fibres decreased (P = 0·01) and the proportion of white muscle fibres increased (P = 0·02) in the mg kg⁻¹ RAC group compared to the controls. In addition, when compared to controls, average fibre diameters in the 20 mg kg⁻¹ RAC group remained constant in the red fibres, and increased significantly in both the intermediate and white fibres (P = 0·01 and 0·02, respectively). Over both muscles Kramer Press values were significantly higher (P = 0·030 in the RAC-fed pigs than in the controls. Incorporation of RAC into the diet did not result in any changes to crude protein or total and soluble hydroxyproline levels. Crude fat tended to increase in the 15 mg kg⁻¹ RAC treatment in the SM and decreased in the 20 mg kg⁻¹ RAC treatment in the PM. The shift in fibre type, and the associated changes in fibre size, may contribute to the increased shear values found in RAC-fed pigs.     

Effects of porcine somatotropin (PST) administration on the fat/lean content and processing properties of pork bellies

Porcine somatotropin (PST)-supplemented pigs were slaughtered at 109 or 131·8 kg; bellies were analyzed for compositional and bacon processing characteristics and compared with bellies from controls (slaughtered at 109 kg). Bellies from control and 109 kg, PST-treated pigs were significantly lighter (P < 0·01) in weight whereas the PST-treated bellies were significantly (P < 0·01) leaner than controls regardless of slaughter weight. The leaner bellies resulted in greater (P < 0·01) brine pickup, reduced smokehouse yields and bacon with less fat regardless of slaughter weight. Frying yield for the bacon from PST-treated pigs was significantly (P < 0·01) higher than that of the controls probably because of the fat/lean difference. The changes observed in bacon from PST-supplemented pigs appear to be due to the compositional change induced by PST administration.     

Effect of season on color of Hanwoo (Korean native cattle) beef

A total of 1278 head of Hanwoo (Korean native cattle) slaughtered over four seasons were used to evaluate the effect of season on color characteristics of beef longissimus dorsi (LD) muscle. CIE L^*, a^*, b^*, C^* values and hue angle were significantly lower (P<0.05) in cattle slaughtered in the winter season. Meat color was darker in the winter than in the spring and autumn seasons. The L^* values among three average daily temperature (T_a) categories were different (P<0.05) in order of: [5 °CT_a<25 °C] > [T_a25 °C] > [T_a<5 °C], indicating that the meat color of cattle slaughtered at T_a<5 °C was darker. The a^*, b^*, C^* values and hue angle were significantly lower (P<0.05) in cattle slaughtered at T_a<5 °C. Season at slaughter is of great importance for meat color. Namely, meat color of Hanwoo beef was influenced by environmental temperature. Overall, cattle slaughtered in the winter season of T_a<5 °C produced beef with more undesirable meat color properties.     

The effects of electrical stimulation and ageing on beef tenderness

Seventeen beef carcasses from cattle with a range of breeds, ages and body conditions were used in this trial. The four treatments applied to each carcass were control (C), electrical stimulation (ES), ageing for 28 days (A) and electrical stimulation plus ageing for 28 days (ES + A). Post-mortem muscle pH was measured at 0, 0·5, 4 and 24h post-stimulation. Significantly lower muscle pH values (P < 0·01) were achieved by the stimulated carcass side sompared to the unstimulated side at 0·5 (pH 6·47 vs. 6·91) and 4 h (pH 5·96 vs. 6·44) post-stimulation.

Warner-Bratzler shear and taste panel methods were used to assess the tenderness of Longissimus dorsi muscle samples from each of the four treatments. The ES, A and ES + A treatments were significantly more tender (P < 0·01) than the control treatment. The ES and the A treatments resulted in a similar improvement in tenderness compared to the control. The ES + A treatment was significantly more tender (P < 0·01) than the ES treatment alone, but there was no significant difference in tenderness between the A and the ES + A treatments.     

Lipid and protein oxidation, release of iron from heme molecule and colour deterioration during refrigerated storage of liver pâté

In the present work, lipid and protein oxidation, increase of non-heme iron (NHI) content and colour changes occurring during refrigerated storage (90 days/4 °C) of liver pâtés from Iberian and white pigs were studied. Iberian pigs were reared outdoors and fed on natural resources (grass, acorns) while white pigs were intensively reared and fed on a mixed diet. Lipid and protein oxidation were, respectively, measured by determining TBA reactive substances (TBARS) and protein carbonyl groups. Pâtés from Iberian pigs had better oxidative stability at all stages of storage, having lower amounts of TBARS and carbonyls compared to those from white pigs (p<0.05). NHI increased during refrigerated storage of liver pâtés, with those from white pigs having a higher amount of NHI at all stages of storage (p<0.05). During refrigerated storage, L^*-values tended to increase while the evolution of a^* and b^* depended on the group and did not seem to be related to the oxidative processes.