Bovine muscle 20S proteasome. II: Contribution of the 20S proteasome to meat tenderization as revealed by an ultrastructural approach.

The role of the 20S proteasome proteolytic effects was revisited using an ultrastructural approach with the aim to explain some particular structural changes identified in type I muscles and in high pH meat. In both types of meat, major changes observed after ageing are an increase in the thickness of the Z-line followed by the appearance of an amorphous protein structure spreading out over the I-band. This was followed by a total degradation of this amorphous structure and of the Z-line. Partial transversal fragmentation of the myofibrils within the I-band can also be detected. The data reported clearly demonstrate that the 20S proteasome was able to mimic these sequential structural changes, a feature never obtained with either calpains or cathepsins. It is the first time that a direct implication of this complex in postmortem muscle is postulated.

Pork quality, processing, and sensory characteristics of dry-cured hams as influenced by Duroc crossing and sex.

This study was designed to evaluate Duroc (DU) crossing for Carso dry-cured ham production. One hundred fifty-four pigs (81 females and 73 castrates) of four different genotypes, pure Landrace pigs (LAN), offspring of LAN females crossed with Large White (LW) males (LWxLAN), offspring of LAN females crossed with DU males (DUxLAN), and offspring of LWxLAN females crossed with DU males (DUx[LWxLAN]), were chosen in the weight range of 105 to 120 kg (112.7 +/- 0.4 kg). Raw material quality was evaluated for ham fatness (intra- and intermuscular and subcutaneous) and meat quality (pH, color, water-holding capacity) of longissimus dorsi, biceps femoris, and semimembranosus muscles. Ham weight losses were recorded at different stages of processing. The biceps femoris and semimembranosus muscles were analyzed for chemical composition before (lipid, moisture, total nitrogen, nonprotein nitrogen) and after (moisture, salt, total nitrogen, nonprotein nitrogen) processing. Chemical and sensory analyses were performed on 96 dry hams (12 castrates and 12 females per genotype). Biceps femoris and semimembranosus muscles were evaluated for color, saltiness, aroma, and texture. Pigs of the four genotypes had similar ham fatness as estimated by subcutaneous fat thickness. Duroc crosses exhibited higher intramuscular fat content, marbling, and intermuscular fat. Crossing with DU resulted in lower weight losses during ham processing. Castrates were fatter and had more intra- and intermuscular fat and lower ham processing weight losses than females. A strong negative relationship between ham fatness and ham processing losses was observed. Chemical and sensory traits of dry ham muscles were little affected by DU crossing. Lower salt content of biceps femoris was found in DU crosses. Dry hams from female pigs had higher total and nonprotein nitrogen, but drier, firmer texture and higher resistance to cutting force compared to dry hams from castrated pigs. Crossing with DU demonstrated some disadvantages (more intermuscular fat, more slice visible fat) and advantages (lower weight loss and salt intake) for the quality of dry-cured ham.

Effect of duration of feed withdrawal and transportation time on muscle characteristics and quality in Friesian-Holstein calves.

Twenty-week-old Friesian-Holstein calves were used to assess the influences of the duration of feed withdrawal before transport (1 or 11 h) and of transport time (1 or 11 h) on carcass and muscle characteristics and meat sensory qualities. One hundred twelve calves were used for live weight and carcass measurements, following a 2 x 2 factorial design (28 replicates). Twelve calves were randomly selected in each treatment group to examine muscle characteristics and sensory quality of longissimus lumborum (LL) and semimembranosus (SM). Long transport (11 h) increased loss in live weight (P < .001) and dressing percentage (P < .001). Feed withdrawal for 11 h also increased dressing percentage (P < .001). Long transport resulted in decreased liver weight (P < .05), glycolytic potential (P < .01), and pH at 4 h postmortem (P < .05) in the LL. Drip loss, compositional traits, cooking loss, and sarcomere length in the LL, as well as drip loss, pH values, compositional traits, cooking loss, and sarcomere length in the SM, were unaffected by the treatments. However, long transport decreased tenderness score in the LL (P < .05) and SM (P < .01). It also increased myofibrillar resistance (P < .001) in the latter muscle. The results demonstrate an unfavorable effect of long transport on the sensory quality of veal. This effect cannot be explained on the basis of differences in pH values and(or) compositional characteristics.

Performance, plasma hormones, histochemical and biochemical muscle traits, and meat quality of pigs administered exogenous somatotropin between 30 or 60 kilograms and 100 kilograms body weight.

Forty-five Large White barrows were injected daily i.m. with either excipient from 30 to 100 kg BW (CTRL), excipient from 30 to 60 and porcine somatotropin (pST; 100 micrograms/kg BW) from 60 to 100 kg BW (pST-60), or pST (100 micrograms/kg BW) from 30 to 100 kg BW (pST-30). Somatotropin accelerated overall growth rate (+4 and +9% for pST-60 and pST-30, respectively), increased longissimus (+10.3 and +14.7%) and semitendinosus (+17 and +13%) muscle weights, and decreased backfat (-49 and -58%) and leaf fat (-49 and -53%) weights. The administration of pST resulted in a similar increase in muscle fiber size for all fiber types in both longissimus (LM) and semispinalis (SS) muscles (+21%). Somatotropin had otherwise little effect on muscle fiber types and biochemical traits of LM, whereas dramatic changes were observed in SS. The relative area occupied by Type IIB fibers was increased (+22 and +29%) and that of Type I fibers was decreased (-10 and -15%). In pST-30 animals, myosin ATPase activity (+15%) and native myosin fast isoform proportion (+10%) were augmented, and energy metabolism was more glycolytic (lactate dehydrogenase: +25%) and less oxidative (citrate synthase: -13%; beta-hydroxyacyl-CoA dehydrogenase: -21%). Compared to CTRL animals, administration of pST increased muscle water concentration (LM: +.8 and +1.1%: SS: +3.3 and +3.3%) and decreased intramuscular fat (LM: -29 and -27%; SS: -39 and -50%). The pH measured 45 min and 24 h postmortem, glycogen content, reflectance, and index of light diffusion were mostly not affected by pST treatment. In conclusion, pST had a very favorable effect on growth performance without any important effect on meat quality traits except for the reduction in intramuscular lipid content. The results indicated that the effects of pST on muscular histochemical and biochemical characteristics were different in LM and SS muscles.

Influence of environmental temperature on growth, muscle and adipose tissue metabolism, and meat quality in swine.

An experiment involving 32 individually housed, castrated male pigs was conducted to determine the effects of environmental temperature (12 degrees C = T12 or 28 degrees C = T28) on the performance, carcass characteristics, muscle and adipose tissue metabolism, and meat quality of pigs fed to achieve equal rates of weight gain between 8 and 92 kg live weight. The T12 pigs had less muscle (P less than .01) and more subcutaneous fat (P less than .01) in the ham than did T28 animals. Thyroids and adrenals were heavier (P less than .01) in T12 than in T28 pigs. Percentage of type I muscle fibers was higher (P less than .01) and fiber cross-sectional areas smaller (P less than .01) in semispinalis muscle (SS) of T12 pigs, whereas no effect of temperature was noticed in longissimus muscle (LD). Cold exposure induced a larger increase in oxidative metabolism in SS (+30 to 32%, P less than .001) than in LD (+14 to 17%, P less than .10) and an enhanced glycolytic metabolism in LD (P less than .05). Lipid concentration was higher in SS of T12 than in that of T28 pigs. Lipogenic enzyme activities and unsaturation of backfat were higher in T12 than in T28 pigs, whereas no effect of temperature was noticed in leaf fat. Cold treatment resulted in a faster postmortem pH decline (P less than .01), higher glycolytic potential (P less than .01), and lower ultimate pH (P less than .01) in LD. The results indicate that 12 degrees C vs 28 degrees C induced detrimental effects on growth, ham composition, and muscle and adipose tissue quality.

Effects of the halothane genotype and slaughter weight on texture of pork.

The objective of this study was to investigate the effects of the halothane (HAL) genotype, slaughter weight (SW), and the HAL x SW interaction on compositional and textural traits of raw and cooked pork. Pigs were bred to exhibit one of the three HAL genotypes (NN, Nn, and nn) with otherwise equivalent genomes. The nn halothane reactors are known to typically produce PSE pork, whereas NN pigs do not typically produce PSE pork. Pietrain x Large White gilts and boars, all with verified Nn genotype (by DNA test), were mated to obtain F2 littermates of the three HAL genotypes. These pigs were slaughtered at either 101 +/- 3 ("light") or 127 +/- 3 ("heavy") kg BW and were evaluated for longissimus muscle traits. The pH at .5 h after death (pH1) was 6.35, 6.13, and 5.68 in NN, Nn, and nn pigs, respectively. Sarcomere length was greater in nn than in NN and Nn pigs (1.94 vs 1.83 and 1.85 microm, respectively). Mechanical resistance was higher in nn than in NN pigs for both raw and cooked meat. Meat from nn pigs was judged by a trained panel to be less rough, more cohesive, harder, more fibrous, less granular, more elastic, and less easy to swallow than meat from NN pigs. For most traits under study, the heterozygotes were intermediate between the homozygotes but closer to NN than to nn pigs. Muscle from heavy pigs had longer sarcomeres and less moisture than muscle from light pigs. The n allele of the HAL gene unfavorably affects pork texture, and this effect is maintained throughout the range of 101 to 127 kg BW.

Phenotypic and genetic parameters for longissimus muscle fiber characteristics in relation to growth, carcass, and meat quality traits in large white pigs.

A total of 383 barrows and gilts from a French Large White experimental herd were slaughtered at 100 kg BW. Samples of longissimus muscle were taken to categorize myofibers according to their contractile (I, IIA, and IIB) and metabolic (oxidative and nonoxidative) properties. Myofiber percentages, cross-sectional areas (CSA), and relative areas were measured. Growth rate, carcass composition, muscle chemical composition, metabolic enzyme activities, and meat quality traits were also measured to estimate phenotypic and genetic correlations between these traits and myofiber characteristics. Genetic parameters were estimated using a REML procedure applied to an individual animal model. Heritabilities of fiber traits were moderate to high (h2 = .20 to .59). Highest heritabilities were found for type I fiber percentage (h2 = .46 +/- .11), type IIBw fiber percentage (h2 = .58 +/- .11), and type I fiber cross-sectional area (h2 = .59 +/- .10). For a given fiber type, the relative area was phenotypically and genetically more closely related to the percentage than to the CSA. Phenotypic correlations between fiber type composition and other traits were low. Genetically, growth rate, carcass leanness, and loin eye area were positively related to fiber CSA. Intramuscular fat content was not related to fiber type composition (r(g) = -.05 to .06), whereas it was positively related to fiber CSA (r(g) = .68). Type IIBw fiber percentage was related to pH at 30 min (r(g) = -.46), pH at 24 h (r(g) = -.62), glycolytic potential (r(g) = .31), and lightness of color (r(g) = .55) of longissimus muscle.

Influence of the three RN genotypes on chemical composition, enzyme activities, and myofiber characteristics of porcine skeletal muscle.

An experiment was conducted to evaluate the effects of the RN genotype on skeletal muscle characteristics in pigs sharing otherwise the same polygenic background. Animals were genotyped for RN on the basis of RTN (Rendement Technologique Napole) records using segregation analysis methods. Samples of longissimus (L) and semispinalis capitis (S) muscles were taken from 39 rn+/rn+, 38 RN-/rn+ and 37 RN-/RN- pigs slaughtered at 108 +/- 8.6 kg live weight. Activities of lactate dehydrogenase (LDH), citrate synthase (CS), and beta-hydroxy-acyl-coenzyme A dehydrogenase (HAD) were measured on both muscles to assess glycolytic, oxidative, and lipid beta-oxidation capacities, respectively. Histological examinations and chemical analyses were performed on L muscle. The energetic metabolism of the white L muscle was more oxidative in RN-/RN- than in rn+/rn+ pigs, as shown by increased CS and HAD activities (P < .001), decreased LDH activity (P < .001), larger cross-sectional area of IIA (P < .05) and IIB-red (P < .05) fibers, higher relative area of IIA fibers ( P < .05), and lower relative area of IIB-white fibers (P < .001). No significant difference was found between heterozygous and homozygous carriers of the RN- allele, except for CS activity, which was lower in RN-/rn+ than in RN-/RN- pigs. In L muscle, the RN- allele led to a large increase in glycolytic potential (+3.5 phenotypic SD between homozygotes) and lightness (+.7 SD), and a decrease in ultimate pH, dry matter, and protein contents (-1.7 to -2 phenotypic SD for these three traits), with an almost completely dominant effect. No differences were found between genotypes for intramuscular fat and hydroxyproline contents. In the red S muscle, the presence of RN- had no influence on enzyme activities. These results indicate that the RN genotype greatly influences compositional and histochemical traits and metabolic enzyme activities in a muscle type-dependent manner, with a completely or incompletely dominant effect of the RN- allele.

Recent methods for predicting quality of whole meat.

The world of meat faces a permanent need for new methods of meat quality evaluation. Researchers want improved techniques to deepen their understanding of meat features. Expectations of consumers for meat quality grow constantly, which induces the necessity of quality control at the levels of slaughtering, meat cutting, and distribution. This article is focused on techniques intended to predict technological and sensory qualities from measurements carried out on fresh intact meat. pH has been measured for a long time, but its on-line determination still progresses through automation. In the laboratory, NMR provides new insights on WHC mechanisms. Image processing has considerably improved the assessment of meat appearance. Developments of techniques for prediction of toughness are in progress, either directly, through ultrasonic analysis or NIR reflectance, or indirectly, through determination of connective tissue content by fluorescence probes. Control of authenticity benefits from the last developments of molecular biology and analytical chemistry. However, implementation of methods for meat quality evaluation has been very limited in the industry. The reasons for that situation are analyzed. Among the techniques recently described, the most promising for large-scale meat quality evaluation are considered to be ultrasonic analysis, image processing and NIR spectroscopy.

Pork of low technological quality with a normal rate of muscle pH fall in the immediate post-mortem period: The case of the Hampshire breed.

The aim of the experiment was to determine the technological properties of meat from Hampshire pigs, as compared to good quality meat from Large White pigs and to exudative meat from halothane-positive (HP) Pietrain pigs. All Hampshire and Large White pigs were halothanenegative (HN). In 129 females and castrated males (47 Large White, 20 HN Pietrain, 27 HP Pietrain, 35 Hampshire), several quality characteristics were measured on raw meat and one ham was processed into cooked 'Paris ham'. Although the pH was normal I h post mortem in Hampshire pigs (which, in this respect, did not differ from Large White pigs) pork from Hampshire pigs, especially females, showed a very low ultimate pH and the highest cooking loss in processing. However, meat was much less exudative when fresh and generally darker (reflectance measured at 630 nm or subjective colour score) in Hampshire than in HP Pietrain pigs. A low ultimate pH occurred in muscle from Hampshire pigs owing to a very high 'glycolytic potential' (essentially glycogen content). It is proposed to use the term 'Hampshire type' to denote meat whose qualitative inadequacies basically result from an abnormally lowered ultimate pH, and to keep the term 'PSE' to refer to meat whose exudative state comes from an abnormally rapid pH fall in the immediate postmortem period.

Relation between muscular development and muscle collagen content in pigs.

The relationship between muscle collagen content and muscular development was investigated in the pig using eight Large Whites, eight halothane-negative (HN) and eight halothane-positive (HP) Pietrain pigs. Three muscles varying in the degree of hypertrophy in Pietrain pigs as compared to Large White pigs were studied. Pietrain pigs had higher loin and ham percentages, as well as higher muscle to bone ratio in the ham than Large White pigs. A trend to lower collagen contents in Pietrain pigs as compared to Large White pigs was observed in biceps femoris and longissimus dorsi muscles, although the differences were not significant. On the whole, there does not seem to be any clear relationship between muscle collagen content and muscular development in the porcine species.

Post mortem evolution of myofilament spacing and extracellular space in veal muscle.

The post mortem evolution of water distribution was studied in muscle tissue from veal calves in two experiments. Myofilament spacing, extracellular space and rate and extent of pH fall were determined in Psoas major muscle in Experiment 1. Extracellular space and rate and extent of pH fall were determined in Longissimus dorsi, Psoas major and Trapezius muscles in Experiment 2. In Experiment 2, the variability of ultimate pH was increased by using adrenalin injections. The myofilament spacing decreased after slaughter when pH reached values around 5·9. In both experiments, the extracellular space began to increase soon after slaughter in close relation with the pH changes. The size of the ultimate extracellular space was significantly correlated with the rate of pH fall, but not with the ultimate pH.

Effect of the RN(-) gene on ultrastructure and protein fractions in pig muscle.

The aim of the present experiment was to study the effect of the RN(-) gene on ultrastructure of white fibres and the proportion of the different protein fractions in Longissimus lumborum muscle of RN(-) pigs. The ultrastructure of muscle was observed in 4 RN(-) carrier pigs and 4 rn(+)rn(+) homozygous pigs by mean of electron microscopy. Protein fractionation and quantification were performed on muscle from a second group of 4 RN(-) and 4 rn(+) pigs. No change in the proportions of the different protein compartments was observed. The abnormality of the glycolytic fibres of RN(-) pigs seems to be rather due to an increase of the glucid concentration in the sarcoplasm, perhaps secondarily to a modified osmolarity in the intracellular medium.

Time-related changes in intramuscular lipids of French dry-cured ham.

The aim of this study was to investigate the changes in intramuscular lipids during the processing of French dry-cured hams. In the fresh biceps femoris muscle, the lipid content was on average, 105 mg/g DM with a large individual variation. Glycerides accounted for about 75% of total lipids. During processing for 273 days, phospholipid content decreased markedly whereas free fatty acid content rose from 1·9 mg/g DM to 9·4 mg/g DM. Little change affected the fatty acid composition of both glycerides and phospholipids during processing. After a decrease in the proportion of polyunsaturated fatty acids during the first 2 months, free fatty acid composition remained stable. The results suggest that lipid alteration during dry-curing of hams is due to lipolysis and that lipid oxidation is limited.

Influence of temperature variation on the metabolism of pig muscle in situ and after excision.

The experiment involved six halothane-positive (HP) and six halothane-negative (HN) pigs of about 100 kg liveweight. Under general anaesthesia the tibialis cranialis was exposed. The temperature of the muscle was maintained at either 35 or 40°C (in situ). The muscle was stimulated via the peroneal nerve at 0·1 Hz for 10 min then 1 Hz for 10 further min. Twitch contractions were recorded throughout the stimulation, after which the muscle was excised and split into two parts which were kept in paraffin oil at either 35 or 40°C (post-excision temperature) for 2 h. Samples were taken just before and after the 20 min stimulation period, and at 1 and 2 h after muscle excision for determination of pH and concentrations of PC, ATP, IMP, glycogen, G-6-P and lactate. As soon as one muscle was removed, the operation was repeated on the other leg. Both temperatures (35 and 40°C) were applied to each animal in a balanced design. However data were obtained from only 11 pigs at 40°C as one HP pig died accidentally at the beginning of the 40°C experiment. Halothane sensitivity influenced the pH value and the levels of PC, G-6-P and lactate of the muscle in situ (P < 0·01 in all cases). Temperature affected contrction time (P < 0·01). Both halothane sensitivity and Post-excision temperature affected the pH values and the levels of PC, ATP, IMP, G-6-P and lactate (P < 0·01 in all cases) in the excised muscle. By contrast, the in situ temperature treatments did not affect any of the muscle traits measured after excision. It was concluded that the effects of the various treatments on the rate of metabolism in the excised muscle were wholly explainable in terms of temperature from the time of excision, and that the in situ temperature treatments may not be responsible for the differences after excision.

Eating quality of meat from European × Chinese crossbred pigs.

Meat from half-Chinese crossbred pigs was compared with meat from purebred European pigs for chemical composition and eating quality. In a first experiment, purebred Pietrain pigs were compared to Pietrain × Chinese (Meishan or Jia Xin ) pigs for sensory qualities as assessed by a taste panel. In a second experiment, purebred Large Whites were compared to Large White × Meishan pigs for chemical composition and eating quality as assessed by both taste panel and consumer testing. The lipid and collagen content in the meat were higher in the Large White × Chinese crossbred pigs than in the purebred Large White pigs. In both experiments, meat from half-Chinese cross bred pigs was judged more tender, more juicy and more tasty than meat from purebred European pigs by the taste panel as well as by consumers. However, the latter judged that the overall acceptability of the meat from half-Chinese pigs was not better, probably due to the excessive amount of visible fat.

Paris ham processing: Technological yield as affected by residual glycogen content of muscle.

The aim of the present experiment was to study the relationships between pH, protein and residual glycogen content of pig muscle on the one hand, and technological yield (TY) of Paris ham processing on the other (Paris ham is a type of cured cooked ham). Fifty-two pigs were slaughtered at 100 kg liveweight in a commercial abattoir, in four slaughter series. Ultimate pH, protein and glycogen were determined around 24h post mortem. Two days after slaughter, the right hams were processed to Paris ham. Residual glycogen levels varied from 0 to 78 µmol/g of fresh tissue. All correlations between TY and the other traits under study were significant at the P < 0·05 level. Correlation between glycogen and TY was by far the highest one (r = 0t-0·60, P < 0·01). Protein content and both pH values gave similar but lower correlations with TY (r around 0·4, P < 0·01). It is concluded that the results of the present study agree with the hypothesis that the residual glycogen content of muscle has a direct effect on the technological yield of cooked ham processing.

Nuclear magnetic resonance measurements on pork of various qualities.

Nuclear magnetic resonance measurements were made on pork samples from pigs of various genetic types (Large White, halothane positive and halothane-negative Pietrain) slaughtered either under minimal stress or somewhat stressful conditions. The (1)H spin-lattice (T(1)) and spin-spin (T(2)) relaxation times of water protons were recorded. The observed T(1) was single-exponential but a two-component T(2) relaxation behaviour (components referred to as T(2a) and T(2b)) was observed. Highly significant relationships were found between T(1) and all the meat characteristics studied. T(2a) was related only to ultimate pH and cooking loss, whereas T(2b) was more closely related to the rate of post-mortem pH fall and protein denaturation criteria.

Time-related changes in nitrogen fractions and free amino acids of lean tissue of frech dry-cured ham.

The 80 hams of 40 pig carcasses from one slaughter batch were taken on the day after slaughter. The 40 left hams were dry-cured. Groups of 10 hams were taken for analysis at 74 days (end of rest), 81 days (end of heating), 179 days (mid-seasoning) and 273 days (end of seasoning) after the beginning of processing. A slice of about 150 g was taken in the middle of the Biceps femoris and used for analysis of nitrogen fractions and free amino acids by HPLC. Levels of insoluble nitrogen compounds did not vary significantly, while levels of soluble protein nitrogen decreased strongly from 26 to 16% of total nitrogen, with the fastest decrease observed between days 179 and 273. Levels of non-protein nitrogen increased regularly during the processing from 12 to 23% of total nitrogen. Nitrogen of free amino acids ranged from 3·6% in fresh muscle to 16·6% of total nitrogen at day 179, then decreased to 4·4% of the total nitrogen at the end of the processing. The HPLC method allowed the identification of 29 compounds, among which 27 were amino acids and 2 were dipeptides. The average levels of free amino acids of non-protein origin tended to decrease before day 74, then to increase until day 179 and to decrease again. The levels of compounds of protein origin increased or tended to increase from the beginning until day 179, then decreased.

Effect of temperature on porcine-muscle metabolism studied in isolated muscle-fibre strips.

In the period before and after slaughter, muscle temperature differs between pigs, which is likely to influence muscle metabolism. Muscle-fibre strips were isolated under anaesthesia from six halothane-negative Large White pigs and eight halothane-positive Pietrain pigs and kept in oxygenated Krebs medium at 38, 40, or 42°C, to study the effects of temperature on muscle metabolism. During a period of oxygenation, contraction measurements were carried out to assess the physiological state of the muscle-fibre strips. Aerated Krebs solution was replaced by paraffin oil at the same temperature to simulate post-mortem muscle metabolism. Pietrain muscle-fibre strips were more affected by preparation methods than Large White muscle strips, which led to a higher metabolite breakdown at the time of cessation of the oxygen supply. Pietrain muscle-fibre strips also showed a larger decrease in twitch-force contraction during the period of oxygenation. A moderate effect of temperature on energy metabolism could be seen in muscle-fibre strips of both types of pig, with increasing post-mortem metabolite breakdown at higher temperatures. However, this effect can play only a limited role in the tremendous acceleration of the post-mortem pH fall as observed in PSE muscle (up to five to ten times the normal rate).