Effect of finishing mode (pasture- or mixed-diet) on lipid composition, colour stability and lipid oxidation in meat from Charolais cattle.

Effects of pasture- or mixed-diet finishing mode on colour and lipid stability were measured in meat from Charolais steers, heifers and cows of different ages after refrigerated storage. Meats from pasture- and mixed-diet finished cattle have more or less significant differences in lipid composition which will influence the colour and lipid stability. The mixed-diet finished cattle have about the same proportions of saturated and monounsaturated lipids as pasture-diet finished animals; on the contrary, cattle fed on grass have higher proportions of n-3 PUFA, and to a less extent, of n-6. Finishing diet had an important effect on lipid stability, meat from pasture-finished animals showing significantly lower TBA-RS level than meat from mixed-diet finished animals. Effect of diet was also significant on myoglobin content with a higher content of haeminic iron in mixed-diet finished animals. Effect of diet on colour stability was slight with a beneficial effect of pasture finishing mode, significant only in heifers, and after a meat storage of six days in air.

Effect of diet finishing mode (pasture or mixed diet) on antioxidant status of Charolais bovine meat.

The aim of this study was to better understand the effect of diet finishing mode (pasture or mixed diet) on the antioxidant status of bovine meat (M. Longissimus dorsi). Effects of sex (cow, heifer and steer) and age (only in cows) were also studied. Vitamin E content of muscle and activity of antioxidant enzymes, such as superoxide dismutase (SOD), catalase (Cat) and glutathione peroxidase (GPx), were measured. Total antioxidant status was also estimated by measuring Trolox equivalent antioxidant capacity (TEAC) and benzoate hydroxylation. Vitamin E content was higher in meat from pasture-finished animals than from mixed diet-finished animals. Diet had also an important effect on antioxidant enzyme activity. Pasture finishing mode increased SOD activity and decreased GPx activity in muscle. Effect of diet on catalase activity was less pronounced. Total antioxidant status measured by benzoate hydroxylation was higher in the mixed diet-group but no effect of diet was observed on TEAC measurement. Effect of sex was observed on SOD and catalase activity and also in benzoate hydroxylation. Effect of age was only noticed on benzoate hydroxylation.

Lipid and protein oxidation in vitro, and antioxidant potential in meat from Charolais cows finished on pasture or mixed diet.

In this work, the effect of finishing diet (pasture- or mixed-diet) on lipid and protein oxidation in beef homogenates was evaluated. Oxidation was chemically induced by ferrous iron and hydrogen peroxide. Lipid and protein oxidation were respectively measured by determining TBA reactive substances (TBA-RS) and protein carbonyl groups (DNPH coupling method). Evaluation of the antioxidant status of meat was also performed by measuring vitamin E concentration and antioxidant enzyme activities: superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase. Pasture-finishing mode of animals significantly protected lipids in meat from oxidation but diet mode did not affect protein oxidation. Concentration of vitamin E was higher in meat from pasture-fed animals. Different diets had opposite effects on SOD and GPx activities, pasture-finishing mode of animals increasing SOD activity but decreasing GPx activity. No significant effect of diet was noted on catalase activity.

Lipid and protein oxidation in microsomal fraction from turkeys: influence of dietary fat and vitamin E supplementation.

The objectives of this study were to investigate the effects of dietary fats (6% soya oil or rapeseed oil or tallow) and α-tocopheryl acetate supplementation (30 ppm for control and 200 ppm for supplemented animals), on lipid and protein oxidation, induced by Fe(3+)/ascorbate, of microsomal fraction in turkey muscles (M. pectoralis major and M. sartorius). Supplementation of turkeys with α-tocopheryl acetate increased the vitamin E content of microsomal membranes. Vitamin E supplementation strongly decreased lipid oxidation in membranal fractions when animals were fed rapeseed oil or tallow; this effect was less pronounced in animals fed soya oil. Vitamin E supplementation induced a slight decrease in protein carbonyl content, especially in animals fed soya oil. Level of protein free thiols was considerably enhanced in diet enriched with soya oil. Vitamin E supplementation had a stabilizing effect on glucose-6-phosphatase activity of microsomes when oxidized by Fe(3+)/ascorbate. No muscle effect was detected on the level of lipid and protein oxidation in membranal fractions even if M. sartorius is known to be more oxidative than M. pectoralis major.

Effect of a dietary vitamin E supplementation on colour stability and lipid oxidation of air- and modified atmosphere-packaged beef.

The effects of dietary vitamin E supplementation on tissue α-tocopherol level and on the susceptibility of fresh and modified atmosphere-packaged beef on myoglobin and lipid oxidation were investigated. Charolais cattle, aged 32-44 months, were fed diets containing 75 (control, n=8) or 1000 mg (supplemented, n=8) α-tocopheryl acetate/kg feed/day for 111 days prior to slaughter. Following vacuum packaging, M. Longissimus lumborum and M. triceps brachii were aerobically packaged and held under refrigerated display (3°C) for 9 days or packaged under modified atmosphere (MAP; 20% CO(2): 80%O(2)) and held under refrigerated display (8°C) for 13 days under fluorescent light. α-tocopherol concentrations were significantly higher (P<0.05) in meat from the supplemented group than from the basal one. Whatever the measured colour characteristics (a*, R(630)-R(580),% MetMb), the vitamin E supplementation had a positive but non-significant effect on the rate of discoloration. But by visual assessment, essentially with MAP, a significant and positive effect of vitamin E supplementation was noted to lower discoloration (P<0.05). TBARS values were significantly lowered (essentially at the end of storage time for the two packaged modes) after an α-tocopheryl acetate-supplementation.

Influence of dietary fat and vitamin E supplementation on free radical production and on lipid and protein oxidation in turkey muscle extracts.

The objectives of this study were to investigate the effects of dietary fat (6% soy oil or rapeseed oil or tallow) and alpha-tocopheryl acetate supplementation at two levels (30 or 200 ppm) on radical production, measured by ESR spectroscopy, and on lipid and protein oxidation in turkey muscle extracts oxidized by an enzymic system (NADPH, ADP, FeSO(4)/cytochrome P450 reductase). Two muscles were tested: pectoralis major (glycolytic) and sartorius (oxidative) muscles. Radical production measured by ESR was higher in pectoralis major muscle than in sartorius muscle, whereas lipid and protein oxidation was more important in sartorius muscle, showing the importance of the pro-/antioxidant ratio in oxidative processes in muscular cells and of the measurement methodology to appreciate the free radical production. Dietary fat had no effect on the level of ESR signals, whereas feeding of animals with soy oil induced higher oxidation of lipids. Protein oxidation was less sensitive to the nature of the dietary fat than lipid oxidation. Vitamin E supplementation significantly decreased radical production, as measured by ESR spectroscopy. Vitamin E also decreased lipid and protein oxidation, but the effect of vitamin E on protein oxidation was less pronounced than on lipid oxidation.

Influence of dietary fat and vitamin E on antioxidant status of muscles of turkey.

The aim of this study was to better understand the effects of more or less unsaturated fat source (tallow/soy oil/rapeseed oil) and/or vitamin E dietary supplementation (200 ppm) on the antioxidant status (at day 1 post-mortem) of turkey muscles [pectoralis major (Pm) and sartorius (S)]. More particularly, when turkeys were fed tallow, supplementation was sufficient to improve significantly the vitamin E status. Feeding rapeseed oil increased the antioxidant enzyme (AOE) activities (catalase, superoxide dismutase, glutathion reductase), glutathione concentration, and value from the benzoic acid test. Dietary soy oil increased glutathione peroxidase activity, compared to other dietary fat sources. With tallow, most of AOE activities were lower than with rapeseed or soy oil. Whatever the feeding mode, vitamin E supplementation did not affect the AOE activities, glutathione concentration, or values from the benzoic acid test. AOE activities were always higher in the oxidative S muscle than in the glycolytic Pm muscle. After feeding tallow, 9 days of storage increased TBA-RS and carbonyl contents, whereas the activity of many antioxidant enzymes and the total antioxidant activity (TEAC test and benzoic acid test) decreased.

Effect of dietary fat and vitamin E on colour stability and on lipid and protein oxidation in Turkey meat during storage.

The objectives of the study were to investigate the effects of dietary fat (6% soya oil or rapeseed oil or tallow), together with tocopheryl acetate at either a basal (30 ppm) or a supplemented (400 ppm) level for 16 weeks on lipid and protein oxidation, including myoglobin, during refrigerated storage of turkey muscles. When turkeys were fed tallow in particular, vitamin E supplementation improved the vitamin E status of the muscles. Vitamin E supplementation significantly delayed lipid oxidation measured by TBARS, whatever the dietary fat. TBARS were highest in meat from animals fed soya oil. Vitamin E supplementation had no positive effect on colour stability of meat during refrigerated storage. Feeding soya oil induced significantly higher oxidation of proteins (carbonyl content) than rapeseed oil or tallow and vitamin E supplementation induced a slight decrease in carbonyl content at day 9 of storage for M. sartorius. SH content was significantly higher in vitamin E supplemented M. sartorius and M. pectoralis than in controls.

Meat quality traits in the emu (Dromaius novaehollandiae) as affected by muscle type and animal age.

Meat quality traits were determined in the major muscles of the emu (Dromaius novaehollandiae) at different slaughter ages (6, 10, 14, 17 or ≥20 months). A mean ultimate pH value of 5.5 was reached within around 3 h post mortem, but this value was 6.1 in animals that had suffered a preslaughter stress (transportation and fasting). The collagen and pigment contents varied widely among the muscles. The protein and pigment contents increased with animal age, but this effect was perceptible only between 6 and 14 months. The other chemical constituents were little affected by muscle type or animal age. The intense red colour of emu meat, due to a high pigment content, was very sensitive to oxidation, thus limiting the storage of fresh meat under aerobic conditions to short periods of time. Despite a rapid post-mortem tenderization (≤24 h), the residual myofibrillar strength obtained after extended ageing remained intermediate between those reported for chicken and beef. The tenderness of meat, cooked to 60 °C, differed between muscles and decreased with increasing age, thus reflecting the changes occuring in the concentration and in the heat stability of the intramuscular connective tissue.

Antioxidant enzyme activities in beef in relation to oxidation of lipid and myoglobin.

Lipid- and oxy-free radical generation has been implicated in oxidative processes which occur during meat maturation but the importance of the antioxidant enzyme (AOE) activity in these processes is not known. It was shown that metmyoglobin (MetMb) % and lipofuscin content were higher in colour-unstable muscles such as psoas major (PM) and diaphragma (D) compared to longissimus lumborum (LL) and tensor fasciae latae (TFL). Although Superoxide dismutase (SOD) activity is higher post mortem in PM and D muscles than in LL and TFL muscles, catalase and glutathione peroxidase (GPx) activities were higher only in D muscle. The higher AOE activity in colour-unstable muscles such as PM and D was not sufficient to prevent increased formation of MetMb and lipofuscin in these muscles compared to LL and TFL muscles.

Relationships between post-mortem pH changes and some traits of sensory quality in veal.

The aim of this study was to evaluate the relationships between the rate and extent of post-mortem pH changes and the colour, the cooking loss and the eating quality of veal. The experiment used 12 calves aged 18 weeks. Variations in ultimate pH were induced by adrenalin administration (0.1-0.4 mg/kg liveweight) to six of the animals. Measurements were made on the Longissimus thoracis muscle. pH and osmotic pressure were measured at 0.5 h, 4 h and 29 h after slaughter. Pigment content, drip loss and cooking loss were measured at 29 h after slaughter, and colour was measured at 2 days and 9 days after slaughter. Cooking loss, tenderness, juiciness and flavour of roasts were assessed at 9 days after slaughter. Correlations between colour traits and pH values were higher with ultimate pH than with pH at 0.5 h or 4 h after slaughter. Lightness, redness and reflectance decreased when the ultimate pH increased. Drip loss was correlated with the rate of pH fall (r = -0.80, P < 0.01 with pH at 4 h), while cooking loss was correlated with ultimate pH (r = -0.94, P < 0.01). Ultimate pH and the sensory quality traits were linearity and positively correlated (r = 0.83) for tenderness, 0.81 for juiciness and 0.71 for flavour, respectively).

A rapid method of oxymyoglobin purification.

Oxymyoglobin was isolated from bovine Longissimus lumborum muscle by precipitation with ammonium sulfate and purification in rapid conditions with only one chromatographic step on Mono-Q HR column with a HPLC system. Purity of oxymyoglobin was controlled by SDS-polyacrylamide gel electrophoresis and isoelectrofocusing.

Effect of feed protein on carcass composition and meat quality in steers.

Forty-five Charolais steers were fed one of four experimental regimes containing maize silage and maize grain supplemented with either protected soyabean-rapessed meal or linseed meal. The first three regimes were formulated to supply the same energy and different protein levels with soyabean-rapessed meal: low (L-SRM), medium (M-SRM) and high (H-SRM). The fourth regime consisted in feeding the same amount (kg/day) of linseed meal as that of soyabean-rapessed meal in the H-SRM regime (LSM). As the protein level increased from L-SRM to H-SRM, the daily weight gain of steers increased and the carcass composition was changed towards higher muscle and lower fat proportions. Though the actual supply of feed protein by regime LSM was close to that achieved with M-SRM, the effect of linseed meal supplementation on weight gain and carcass composition was comparable to that obtained by feeding the high protein level (H-SRM). The dry matter content increased and the heme pigments and lipids contents decreased in longissimus thoracis muscle as the protein supply increased from the low to the high level. Again the amplitude of the differences in meat quality with L-SRM were similar in H-SRM and LSM. Muscle colour, connective tissue and mechanical strength remained practically unaffected by the protein treatments. However, meat was scored less tender in H-SRM and less juicy in treatment LSM than in treatment L-SRM. The results obtained with linseed meal suggest a specific effect of type of feed protein on beef carcass composition and meat quality.

Autoxidation of purified myoglobin from two bovine muscles.

To elucidate the behavioural differences between beef muscles from the viewpoint of colour stability, oxymyoglobin was extracted at 2 h post mortem, purified from two different muscles (longissimus lumborum (LL), stable and psoas major (PM), unstable) and the autoxidation rate was measured. Oxymyoglobin was isolated after separation from metmyoglobin by chromatography on DEAE-Sepharose and TSK SW 2000 columns, and its purity was controlled by electrophoresis and IEF. Over a wide range of pH values (5-9), temperatures (20-50°C) and ionic strength (0-500 mM), no difference was noted between autoxidation rates of LL and PM oxymyoglobin extracted at 2 h post mortem. Conversely, when myoglobin was extracted at 192 h post mortem, the autoxidation rate of PM oxymyoglobin was higher than LL myoglobin, particularly at elevated temperatures. These differences in autoxidation rates after extraction of myoglobin at 2h and 192 h post mortem were not associated with differences in Ea (approximately 23 kcal/mol).

Effects of electrical stimulation, boning-temperature and conditioning mode on display colour of beef meat.

The effects of electrical stimulation of hot-boned (ESHB) bovine longissimus dorsi muscle, followed by vacuum packaging with different temperature/time regimes and storage in aerobic conditions, compared with cold-boned treatment (CB), on colour characteristics was assessed. No significant difference in haeminic iron content was noted between ESHB and CB meat. The opacity was more pronounced in ESHB meat vacuum packaged and incubated at 37°C. This treatment (37° C/4 h) allowed a lighter and brighter red meat colour with a higher level of contamination which was always acceptable. The worst results for colour characteristics were obtained with ESHB meat conditioned rapidly at 2°C. No differences were noted between ESHB meat conditioned at 25°C and CB meat. To explain these discrepancies between treatments about colour characteristics, where muscle translucency is largely involved, differences in enzymic reducing activity and denaturation of sarcoplasmic proteins during glycolysis must be implicated.

Metmyoglobin reductase activity in bovine muscles.

Cow muscles (Longissimus dorsi, Tensor fasciae latae, Psoas major, Diaphragma medialis), with different colour stabilities, were used to measure 'Metmyoglobin reductase activity' in different conditions. The effects of pH and temperature on in vitro metmyoglobin reduction were analysed. The highest metmyoglobin reductase activity was localized in microsomes and in more or less intact mitochondria by means of differential centrifugations. The most unstable muscles, from the colour point of view, presented the highest reducing activities and no differences were noted between activities measured in aerobic or anaerobic conditions.

Influence of straw feeding and growth-implant on veal meat quality.

Trials have been carried out to examine the effects of a food additive supply (Maturex) and/or of anabolic implant (Revalor) on carcass characteristics and on veal meat qualities. Twelve Holstein × Française Frisonne Pie Noire calves acted as controls, twelve calves were implanted with Revalor, approximately 60 days prior to slaughter, twelve others were fed with Maturex, whilst the remaining twelve animals were fed with Maturex and implanted with Revalor. All animals were slaughtered at 4 months. Revalor implantation had a significant effect on carcass weight and conformation. Feeding with Maturex had no significant effect on different carcass characteristics. Neither anabolic treatment nor Maturex supplementation significantly affected pH value, haematocrit, pigment content, FOP, colour characteristics, collagen content and solubility, or dry matter. Although Revalor had a negative effect on weight losses during cooking, Maturex showed no significant effect. While Maturex showed a positive effect on tenderness and no effect on juiciness, Revalor showed a negative effect on tenderness and juiciness. For all sensory characteristics, no effect was noted when both Maturex and Revalor were used together.

Biochemical factors influencing metmyoglobin formation in beef muscles.

To explain the different rates of metmyoglobin accumulation in bovine muscles, biochemical factors such as oxygen consumption rate, cytochrome a(+a(3)) content, myoglobin autoxidation and enzymic ferrimyoglobin reduction were studied. The measurements involved five cows and five bulls. Only six cows were used for Metmyoglobin Reducing Activity (MRA) measurements. Three muscles with different colour stability (Tensor fasciae latae, Psoas major and Diaphragma medialis) were chosen. Meat colour stability, as well as the oxido-reduction potential of myoglobin, were highly related to muscle type. The animal effect was low or non-significant. Muscles with the poorest colour stability, such as Psoas major and Diaphragma medialis had the highest oxidative activities (oxygen consumption rate) and the highest myoglobin autoxidation rates. Enzymic ferrimyoglobin reduction, estimated either by spectrophotometric measurements from muscle homogenates in aerobic conditions ('Metmyoglobin Reductase Activity') or by reflectance measurements in anaerobic conditions (MRA), does not explain the differences observed in muscle colour stability.

[Effects of the nature of energy in food and use of anabolic agents on the quality of veal]. / Influence de la forme d'apport de l'énergie dans la ration et de l'utilisation d'anabolisants sur la qualité de la viande de veau.

The effects of the nature of energy intake, of the slaughter weight and of the use of hormones on the quality of veal meat were studied. Concerning the colour of meat, the use of hormones has no effect either on the pigment content or on the ultimate pH, but the nature of energy intake and the slaughter weight can affect these two parameters. With the increase of the slaughter weight and the substitution of lipids by starch in the diet, the probability to get a redder meat increases. For a given carcass weight, the use of hormones goes with a significant decrease of the tenderness of meat.