Technical note: Sampling methodology for relating sarcomere length,collagen concentration,and the extent of postmortem proteolysis to beef and pork longissimus tenderness

The objective of this study was to determine the effect of sampling methodology on the relationship between longissimus tenderness and measures of biochemical meat traits. Sampling methodology included measurements of sarcomere length, collagen concentration, and postmortem desmin proteolysis on raw samples and measurements of these same traits on the same cooked meat used for shear force measurement. Twenty crossbred steers and 20 crossbred barrows were used for these studies. The beef longissimus thoracis were vacuum-packaged, stored at 2 degrees C until 14 d postmortem, then frozen and stored at -30 degrees C. The pork longissimus thoracis et lumborum were vacuum-packaged, stored at 2 degrees C until 7 d postmortem, then frozen and stored at -30 degrees C. Trained sensory panel tenderness rating ranged from 3.1 to 7.6 for beef and 4.1 to 7.4 for pork. The coefficient of variation was lower for sarcomere length than for all other traits. Simple correlation coefficients between measurements on raw and cooked samples were 0.58 (beef) and 0.11 (pork) for sarcomere length, 0.66 (beef) and 0.59 (pork) for collagen, and 0.74 (beef) and 0.76 (pork) for desmin degradation. Simple correlation coefficients between biochemical traits and measures of tenderness (Warner-Bratzler shear force and trained sensory tenderness rating) were higher or not different for cooked compared to raw samples. Correlation coefficients between biochemical traits and tenderness rating were 0.38 (raw) and 0.22 (cooked) for sarcomere length, -0.12 (raw) and -0.45 (cooked) for collagen, and 0.48 (raw) and 0.80 (cooked) for desmin degradation in beef longissimus and 0.14 (raw) and 0.15 (cooked) for sarcomere length, -0.38 (raw) and -0.33 (cooked) for collagen, and 0.53 (raw) and 0.67 (cooked) for desmin degradation in pork longissimus. The coefficients of determination for explaining variation in tenderness rating using sarcomere length, collagen concentration, and desmin degradation for raw and cooked samples were 0.43 and 0.73 (beef) and 0.48 and 0.57 (pork), respectively. This study indicates that measurements of biochemical traits on the same cooked meat as used for shear force determination account for more of the variation in measures of tenderness than biochemical measurements made on a separate raw sample.     

The extent of proteolysis is independent of sarcomere length in lamb longissimus and psoas major.

The objective of this experiment was to determine the effect of sarcomere length on postmortem proteolysis and meat tenderness. Eighteen Dorset market-weight sheep were slaughtered conventionally. The longissimus thoracis et lumborum and psoas major from each carcass were either left intact on the carcass (control), which was chilled at 0 degrees C, or excised from the carcass and chilled in an ice slurry (0 degrees C). At 24 h, control muscles were excised, and all muscles were cut into sections and assigned to 1 or 10 d of postmortem storage at 2 degrees C. Sarcomere length was shorter (P < .01), as intended, in the shortened relative to the control treatment and in longissimus relative to psoas major (1.36 vs 1.69 microm, raw longissimus; 1.45 vs 3.03 microm, raw psoas major). Sarcomere length was not affected (P > .05) by aging time. Western blot analysis of troponin-T and desmin indicated no effect (P > .05) of the shortened treatment compared to the control on the extent of proteolysis. Regardless of aging time or treatment, troponin-T was more degraded (P < .01) in longissimus than in psoas major (38.1 vs 23.5%) and desmin tended to be more degraded (P = .08) in longissimus than in psoas major (50.4 vs 35.1%). Regardless of muscle or treatment, aging 10 d compared to 1 d increased degradation of troponin-T (46.3 vs 15.3%) and desmin (69.3 vs 16.1%). Warner-Bratzler shear force was greater (P < .01) in the shortened treatment than in control (6.9 vs 3.8 kg), greater (P < .01) in longissimus than in the psoas major (6.5 vs 4.2 kg), and greater (P < .01) with 1 d than with 10 d of aging time (6.1 vs 4.6 kg). A muscle x aging time interaction (P < .05) indicated shear force declined more in longissimus than in psoas major during aging. We conclude that sarcomere length did not affect the extent of proteolysis. However, sarcomere length may have an indirect effect on tenderization during aging due to its effect on initial tenderness.     

Postmortem titin proteolysis is influenced by sarcomere length in bovine muscle

The calpain protease system, in particular, μ-calpain is involved in the disassembly of specific myofibrillar proteins, resulting in tenderization of meat postmortem. Given the size, complexity, and integral nature of titin to the structure of the sarcomere, it is plausible that the length of a sarcomere may alter the susceptibility of various domains of titin to cleavage by the calpains. Therefore, we hypothesized titin degradation differs in a sarcomere-length-dependent manner in beef. After slaughter, beef carcasses were split and sides were either suspended by the Achilles tendon (normal suspension, NS) or by the aitchbone (hip suspension, HS). Immediately after suspension, samples were dissected from the LM, psoas major (PM), and semitendinosus (STN) muscles to serve as 0-d controls. After 24 h, 4 steaks were removed from each muscle and randomly assigned to 1-, 4-, 7-, or 10-d aging treatments. After the assigned aging period, myofibrils were purified for determination of sarcomere length. Warner-Bratzler shear force analysis was also performed to evaluate differences in tenderness. Muscle proteins were solubilized and subjected to SDS-VAGE (vertical agarose gel electrophoresis) to evaluate titin degradation. Sarcomere lengths differed (P < 0.0001) between contralateral muscles of NS and HS carcasses. Quantification of SDS-VAGE gels revealed less (P < 0.05) intact titin in the PM muscle of NS carcasses at each aging period compared with the PM of HS carcasses. No significant differences (P > 0.05) were detected in the disappearance of intact titin among suspension methods in the LM or STN. These data demonstrate that suspension method alters proteolysis of titin and suggest an increase in sarcomere length may contribute to the susceptibility of titin to postmortem proteolysis in beef.     

Modified-atmosphere storage under subatmospheric pressure and beef quality: II. Color, drip, cooking loss, sarcomere length, and tenderness

Beef has a requirement for refrigerated storage up to 14 d to achieve adequate aging and a tender product. To achieve this aging with little spoilage and no surface drying, vacuum packaging is attractive, because it is inherently simple and offers a clear indication to the packer when the process has failed or there is risk of spoilage. However, there is increasing pressure on the meat industry to limit the use of packaging materials in view of their cost and the cost involved in their recovery and recycling. The purpose of this report was to evaluate an alternative storage system in containers using modified atmospheres at reduced pressure (approximately 25 kPa). The quality of the meat for both container- and vacuum-packed treatments was measured during chilled storage for up to 3 wk. Storage time had the most significant effect on quality characteristics, irrespective of the packaging method. Storage in containers under a 70%N2:30%CO2 gas mixture gave characteristics similar to beef stored under vacuum. Storage in containers under 100% CO2 produced less drip loss than under 70%N2:30%CO2, but generally container storage produced 3 times as much drip loss as vacuum packaging. Shear force of the LM was unaffected by the type of packaging, and at d 2 after slaughter (i.e., before the storage trial was begun), sarcomere lengths of muscles intended for container storage were similar to those destined for vacuum storage. During the packaging treatment, the comparison between the storage systems was always done within 1 animal using one carcass-half for container storage and the other half for vacuum packaging; all bulls were shackled from the left hindleg during bleeding. The majority of the muscles from the left sides had lower shear force values than those from the right sides at the earlier storage times (2 and 9 d after slaughter) but had similar values after longer storage (16 and 23 d after slaughter). This is the first report that shackling beef carcasses from the left side can result in more tender meat in the LM from that side. The increased tenderness in the LM from the shackled side probably resulted from an early decrease in pH and an increase in calpain activity after mechanical strain of the muscles on the shackled side. This effect of shackling should be taken into account when designing systematic comparisons of tenderness in beef.     

Mapping intramuscular tenderness variation in four major muscles of the beef round

The objective of this study was to quantify intramuscular tenderness variation within four muscles from the beef round: biceps femoris (BF), semitendinosus (ST), semimembranosus (SM), and adductor (AD). At 48 h postmortem, the BF, ST, SM, and AD were dissected from either the left or right side of ten carcasses, vacuum packaged, and aged for an additional 8 d. Each muscle was then frozen and cut into 2.54-cm-thick steaks perpendicular to the long axis of the muscle. Steaks were broiled on electric broilers to an internal temperature of 71 degrees C. Location-specific cores were obtained from each cooked steak, and Warner-Bratzler shear force was evaluated. Definable intramuscular shear force variation (SD = 0.56 kg) was almost twice as large as between-animal shear force variation (SD = 0.29 kg) and 2.8 times as large as between-muscle variation (SD = 0.20 kg). The ranking of muscles from greatest to least definable intramuscular shear force variation was BF, SM, ST, and AD (SD = 1.09, 0.72, 0.29, and 0.15 kg, respectively). The BF had its lowest shear force values at the origin (sirloin end), intermediate shear force values at the insertion, and its highest shear force values in a middle region 7 to 10 cm posterior to the sirloin-round break point (P < 0.05). The BF had lower shear force values toward the ST side than toward the vastus lateralis side (P < 0.05). The ST had its lowest shear force values in a 10-cm region in the middle, and its highest shear force values toward each end (P < 0.05). The SM had its lowest shear force values in the first 10-cm from the ischial end (origin), and its highest shear force values in a 13-cm region at the insertion end (P < 0.05). Generally, shear force was lower toward the superficial (medial) side than toward the deep side of the SM (P < 0.05). There were no intramuscular differences in shear force values within the AD (P > 0.05). These data indicate that definable intramuscular tenderness variation is substantial and could be used to develop alternative fabrication and(or) merchandising methods for beef round muscles.     

The influence of ultimate pH and intramuscular fat content on pork tenderness and tenderization

Intramuscular fat (IMF) and ultimate pH (pHu) influence tenderness, but their roles have not been conclusively determined. Length of storage also affects tenderness and may interact with IMF and pHu. We evaluated the effects of pHu, IMF, and storage time on the tenderness of pork longissimus muscle and determined whether the contribution of the various factors was dependent on genetic line. To obtain variation in IMF, Berkshire (B), Duroc (D) and Hampshire (H) boars were crossed with Yorkshire-Landrace sows. In four trials, a total of 176 pigs were used. To obtain a range in pHu, half of the pigs were deprived of feed before slaughter. Warner-Bratzler shear force (WBS) of each loin was assessed after 2, 7, and 14 d of storage at 0 to 2 degrees C. Warner-Bratzler shear force decreased (P < 0.05) from 4.89 kg at d 2 to 4.16 kg at d 7 to 3.52 kg at d 14. The H pork (n = 62) had a lower (P < 0.05) WBS than the other pork at d 2. After 7 d of storage, this difference had disappeared. Based on glycolytic potential, 30 of the H pigs were carriers of the Rendement Napole (RN) gene. When these pigs were excluded from the analysis, there was no difference in tenderness or tenderization of H, D, and B pork. The correlation between IMF and WBS was -0.11 at d 2, -0.21 at d 7, and -0.19 at d 14. In D pork, the relationship between IMF and WBS was linear, and IMF accounted for 47% of the differences in WBS. In H and B pork, the relationship between IMF and WBS was not significant. For each cross, the relationship between pHu and WBS was different; in D pork it was quadratic, in H pork WBS increased linearly, and in B pork there was no significant relationship between WBS and pHu. The 30 kDa/actin ratio, a measure of myofibrillar degradation, increased (P < 0.05) during storage. Differences in 30 kDa/actin ratio did not explain differences in pork tenderness or tenderization. Further research on determinants and mechanisms of pork tenderness and pork tenderization is needed before production of consistently tender pork will be possible.     

Comparison of collagen content, distribution and architecture among the pectoralis, iliotibialis lateralis and puboischiofemoralis muscles with different myofiber composition in Silky cocks

The total amount of collagen, the relative distributions of types I and III collagens in perimysium and endomysium, and the collagen fiber architecture were compared among the pectoralis (PT), iliotibialis lateralis (ITL) and puboischiofemoralis (PIF) muscles in Silky cocks. All of the myofibers in the PT muscle were type IIB, the myofibers in the ITL muscle were divided into type IIA, 41.7% and IIB, 58.3%, and the PIF muscle was composed of type I, 24.6%; IIA, 64.6%; and transitional, 10.8%. The total amount of collagen differed significantly among the PT (2.92 mg/g), PIF (4.20 mg/g) and ITL (8.06 mg/g) material, where only the PIF was a whole muscle with epimysium. On the image analysis of the immunohistochemical preparations, the percentage area of perimysial collagen to the total area in each type differed significantly among the PIF, PT and ITL muscles, where it was 26.8, 50.0 and 74.4% for the type I collagen and 27.4, 32.9 and 61.7% for the type III collagen, respectively. In the scanning electron micrography of the perimysium in macerated preparations, thick bundles of collagen fibers were observed in the ITL muscle, thinner but broad platelets in the PT muscle, and a coarse tissue of thinner collagen fibers in the PIF muscle. However, the endomysial fabric of collagen fibrils was similar among the muscles. Small, transverse collagen fibers, which branched off from the thicker perimysia, occupied narrow interendomysial spaces and separated the primary myofiber fasciculi. The results indicate that the ITL muscle, localized in the distorted and overextended part of the leg and subject to strong external forces, had highly developed perimysial collagen fiber bundles, but the ITL endomysial collagen architecture was similar to that of the PT and PIF muscles.     

Postmortem proteolysis in longissimus muscle from beef, lamb and pork carcasses

Postmortem proteolysis in skeletal muscle and factors affecting this process were examined in pork, lamb and beef longissimus muscles (LM) to determine the cause of differences in meat tenderness among these species. Fat thickness differed among species in the following order: pork greater than beef greater than lamb. The following patterns were observed for rate of temperature and pH decline: lamb greater than pork greater than beef and pork greater than beef greater than lamb, respectively. At 1 d postmortem, pork was the most tender, followed by beef and lamb, respectively. Between 1 and 14 d of postmortem storage, lamb LM was the most improved in tenderness, followed by beef and pork, respectively. Species did not differ (P greater than .05) in LM collagen solubility. Pork LM from fed pigs had the highest (P less than .05) level of cathepsins B + L and cystatin(s) activities, whereas no differences (P greater than .05) were observed among the species for cathepsin B activity. The lowest (P less than .01) Ca2(+)-dependent protease (CDP)-II and CDP inhibitor activities were observed in pork LM. Beef LM had the highest CDP inhibitor activity (P less than .05) but was intermediate in CDP-II activity. No differences were observed among species for CDP-I activity. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of myofibrils isolated at 0, 1 and 14 d postmortem indicated that by d 1, desmin hydrolysis was most extensive in pork muscle, followed by lamb and beef.(ABSTRACT TRUNCATED AT 250 WORDS)     

Variation in palatability and biochemical traits within and among eleven beef muscles

The objective of this study was to determine the extent of variation in, and relationships among, biochemical and palatability traits within and among 11 major beef muscles. Longissimus thoracis et lumborum (LD), psoas major (PM), gluteus medius (GM), semimembranosus (SM), adductor (AD), biceps femoris (BF), semitendinosus (ST), rectus femoris (RF), triceps brachii (TB), infraspinatus (IS), and supraspinatus (SS) from one side of 31 Charolais x MARC III steer carcasses were vacuum-packaged, stored at 2 degrees C until 14 d postmortem, and then frozen at -30 degrees C. The 2.54-cm-thick steaks were obtained from two or three locations within muscles in order to assess biochemical traits and Warner-Bratzler shear force, and from near the center for sensory trait evaluation. The PM was most tender and was followed by IS in both shear force and tenderness rating (P < 0.05). The other muscles were not ranked the same by shear force and tenderness rating. The BF had the lowest (P < 0.05) tenderness rating. The PM, GM, and LD had lower (P < 0.05) collagen concentration (2.7 to 4.5 mg/g muscle) than muscles from the chuck and round (5.9 to 9.0 mg/g), except for the AD (4.9 mg/g). Desmin proteolysis was highest (P < 0.05) for BF and LD (60.7 and 60.1% degraded), and was lowest (P < 0.05) for PM (20.2%). The PM, TB, IS, RF, and ST had relatively long sarcomere lengths (> 2.1 microm), whereas the GM had the shortest (P < 0.05) sarcomere length (1.7 microm). Cooking loss was lowest (P < 0.05) for BF (18.7%) and was followed by LD and IS (20.7%); it was highest (P < 0.05) for ST (27.4%). Across all muscles, tenderness rating was highly correlated (r > 0.60) with shear force, connective tissue rating, sarcomere length, and collagen content. Within a muscle, correlations among all traits were generally highest in LD and lowest in AD. Within muscle, location effects were detected (P < 0.05) for shear force (PM, ST, BF, SM, and RF), sarcomere length (PM, ST, BF, LD, SS, IS, SM, and RF), collagen concentration (PM, BF, SS, IS, SM. AD, TB, and RF), desmin degradation (PM, GM, BF, SM, AD, and, RF), and cooking loss (all muscles except SS and AD). There is a large amount of variation within and among muscles for tenderness traits and tenderness-related biochemical traits. These results increase our understanding of the sources of variation in tenderness in different muscles and provide a basis for the development of muscle-specific strategies for improving the quality and value of muscles.     

Calpain activation and proteolysis in postmortem goose muscles

Meat tenderness is considered as the most important criterion for meat quality by consumers and can be improved by the actions of endogenous proteases, mainly calpains, during postmortem storage at 0–5°C. The purpose of this study, therefore, was to examine the postmortem calpain activation and proteolysis in breast (BM) and leg and thigh (LM) muscles of White Roman goose. BM and LM were taken from goose carcasses (n = 15) at 0 (10–15 min postmortem), 1, 3, and 7 days of storage at 5°C. The decrease in postmortem pH, calpain‐1 and ‐11 activities, and contents of the calpain‐1 80 kDa subunit and desmin was more rapid (p < .05) in BM than in LM. Our results show that postmortem proteolysis was more extensive in BM than in LM of White Roman goose, not only because the difference in fiber type composition between two muscles, but because the rate and extent of calpain activation were greater in BM as well. These results may provide useful information to optimize meat processing for different muscles in goose industry.     

The influence of crossbreeding on collagen solubility and tenderness of Infraspinatus and Semimembranosus muscles of semi‐intensively reared young bulls

The aim of the present study was to investigate the effects of crossbreeding on collagen content and solubility, shear force (WBSF) and the eating quality of Infraspinatus (INF) and Semimembranosus (SM) muscles of young bulls and the relationships between collagen content and solubility, shear force and the eating quality of beef. The experimental material comprised muscles of crossbred young bulls (about 600 days old) of Polish Holstein‐Friesian (PHF) × Limousine (LM) (n = 10), PHF × Charolaise (CH) (n = 9), PHF × Hereford (HER) (n = 9) breeds. The crossbreeding influenced WBSF, aroma and taste, total, water‐soluble, acid‐soluble, total soluble and insoluble collagen content, as well as the acid‐soluble, total soluble and insoluble collagen proportions. WBSF was significantly negatively correlated with sensorial tenderness and water‐soluble collagen content. The eating quality of beef obtained from different crossbreds was similar; however, the meat from PHF × LM and PHF × HER bulls had lower WBSF values than PHF × CH bulls. © 2016 Japanese Society of Animal Science     

Growth changes of the collagen content and architecture in the pectoralis and iliotibialis lateralis muscles of cockerels

1. Growth changes of the collagen content and architecture in the pectoralis (PT) and iliotibialis lateralis (ITL) muscles were examined using cockerels from 1 to 14 weeks of age. 2. Total collagen content in PT muscle showed little change, but in ITL muscle reached a maximum at 5 weeks and thereafter decreased slightly until 14 weeks. The collagen content was markedly larger in ITL muscle after 5 weeks. Pyridinoline content of collagen increased abruptly from 5 to 14 weeks in both muscles, but no difference between muscle types was detected. 3. The cell size of the endomysial honeycombs increased with the development of myofibres, and the mesh size of the perimysium around the honeycombs enlarged. 4. In both muscles endomysia were an incomplete network of collagen fibrils with many foramina at one week, became a very thin membrane of felt-like fabric in 2 to 5 weeks and thereafter increased in thickness until 11 to 14 weeks. 5. Perimysial width around the secondary fasciculus differed between the muscle types after 5 weeks. In the wider perimysium of ITL muscle, the collagen fibres increased in number and size to make a stack of collagen bands around the fasciculus. In the narrower perimysium of PT muscle, a few platelets of collagen fibres also developed. 6. The perimysial collagen fibre at 1 to 2 weeks had a smooth surface and appeared to be composed of fine collagen fibrils. The fibre at 11 to 14 weeks showed a rugged surface and was composed of coarser collagen bundles that combined with each other into a net-like configuration with very slim meshes. 7. Our results showed that the collagenous components of chicken intramuscular connective tissue changed markedly during the early period of muscle growth in distribution, architecture and quality but with little difference in quantity.     

Development of components of the extracellular matrix, basal lamina and sarcomere in chick quadriceps and pectoralis muscles

1. The purpose of this study was to investigate differences in the development of components of the cell/matrix linkage in two functionally different muscle types: the pectoralis muscle, a major locomotory muscle in birds but not particularly functional in chickens, and the quadriceps muscle, a smaller and more functionally active muscle in the chicken. 2. The development of the extracellular matrix, basal lamina and sarcomere in the pectoralis and quadriceps muscles in chick embryos was examined biochemically to determine differences in the rate of development between these two muscles. Samples of these muscle types were dissected out from chick embryos from embryonic day 10 until 8 weeks post hatch. 3. Using SDS-PAGE electrophoresis and western blotting with antibodies against sarcomeric actin, laminin and collagens I, III and IV, it was apparent that muscle development begins earlier in the quadriceps muscle than in the pectoralis, and that late in the developmental process (d 18) both muscle types were well differentiated. The final concentration of collagens in the mature muscle remained higher in the quadriceps than in the pectoralis muscle. 4. The onset of development of the extracellular matrix, basal lamina and sarcomere was earlier in the quadriceps than the pectoralis, which could have functional implications for these muscles as a whole.     

Impact of the hydrodyne process on tenderness, microbial load, and sensory characteristics of pork longissimus muscle.

Paired, boneless pork loin muscles were obtained from 76 market hogs to evaluate tenderness, meat quality characteristics, sensory attributes, and microbial characterization of pork muscle exposed to the Hydrodyne Process (H) compared with untreated control (C) loin. A subset of 16 paired loins was randomly selected for use in sensory evaluation and microbial characterization. Loins were vacuum packaged and immersed in a heat shrink tank prior to the H treatment. The Hydrodyne treatment exposed the loin to the pressure equivalent of a 150-g explosive, generating a pressure distribution of approximately 703 kg/cm2 at the surface of the samples. Meat quality assessments taken following treatment included subjective color, firmness/wetness, marbling scores (1 to 5 scale), Minolta reflectance and color readings, drip loss, and lipid content. The P-value for statistical significance for main effects and interactions was set at <.05 in all analyses. Administration of H resulted in a 17% improvement in Warner-Bratzler shear force (2.69 vs. 3.24 kg), with the shear force similar at two end-point cooking times (11 and 16 min) corresponding to approximately 75 and 83 degrees C, respectively. No differences between H and C were observed for color score, firmness score, Minolta L, Minolta Y, or drip loss on uncooked samples. The H loins had lower marbling scores (P<.05) and intramuscular lipid (P<.05) content than the paired C loin. Sensory evaluation on the randomly selected (n = 16) paired loins samples showed no improvement in Warner-Bratzler shear force. Sensory panelists were also unable to detect a difference between H and C loins for both initial and sustained tenderness scores. No differences between H and C loins were found for pork flavor, off-flavor, cohesiveness, or number of chews before swallowing, but H loins had a significantly lower juiciness score and more cooking loss than C loins. Microbial analysis results showed no differences in coliform bacteria counts, aerobic plate counts, and no detectable levels of Escherichia coli bacteria in any loins. The findings support the ability of the Hydrodyne procedure to improve tenderness without impacting other muscle quality attributes of pork.     

Influence of ultimate pH,sarcomere length and cooking loss on the textural variability of cooked M. pectoralis major from free range and standard broilers

1. An experiment was conducted to quantify the extent of variability in the texture of cooked poultry breast meat and to attempt to identify which intrinsic and extrinsic factors contribute to this.

2. Free range (FR) and standard (STD) broilers were killed and processed under commercial conditions and the M. pectoralis major muscle assessed for ultimate pH (pH_u), sarcomere length, cooking loss and texture 24 h and 7 d after slaughter.

3. Although FR broilers were females with an average age of 60 d, whereas the STD broilers were 45 d old and predominantly male, there were no significant differences in mean values obtained for pH_u, sarcomere length, cooking loss and shear force results between the two bird types.

4. While aging for 7 d increased the pH_u and cooking loss means, sarcomere length means remained unchanged and shear force values decreased by 6% and 9% for FR and STD birds respectively.

5. Variability in shear force values also decreased on aging for 7 d, no birds having values above 4 kg/cm² on day 7 whereas 16% were above this value on day 1.

6. There were significant correlations between the results for shear force, pH_u and sarcomere length, indicating that increased shear force values were associated with a decrease in both pH_u and sarcomere length.

7. These correlations suggest that variability in the texture of cooked M. pectoralis major from FR and STD chickens is strongly influenced by those post‐mortem biochemical changes which lead to the development of rigor during the early stages of processing.     

胶原蛋白交联的研究进展及其对肉的纹理和嫩度的影响

胶原蛋白是肌间结缔组织的主要成分 ,它在肌肉中的含量和质量对肌肉纹理性状的影响实际上是取决于胶原蛋白分子间交联的水平、方式和成熟程度。影响胶原蛋白分子间交联的因素很多 ,包括动物的品种、年龄、性别和肌肉的来源以及其它一些与生长有关的环境因素。本文着重对由一系列酶介导的胶原蛋白分子间的共价交联、胶原蛋白在细胞外的被动修饰、胶原蛋白对烤制后肌肉纹理的影响、胶原蛋白分子间交联及其影响因素和调控机制进行综述和探讨     

Effects of pre-slaughter nutritional condition on intramuscular collagen solubility, pyridinoline cross-links and meat tenderness in aged goats

Effects of preslaughter nutritional condition on intramuscular collagen characteristics were studied, in order to clarify the potential of intensive feeding to aged animals in improving meat tenderness. Ten castrated male goats were assigned into one of two groups: one group was allowed ad libitum access to a concentrate diet (total digestible nutrients 70%, crude protein 15%) and Italian ryegrass hay (ADLIB‐group), and the other group was fed a restricted amount of their diet (concentrate diet 0.5% of bodyweight/day; hay 1.5% of bodyweight/day) to maintain their bodyweight (MAIN‐group). After 3 months of the experimental period, goats were slaughtered and meat samples were obtained immediately. Goats in ADLIB‐group had lower total and insoluble collagen concentrations, higher fat concentrations and collagen solubility than those in MAIN‐group, but soluble collagen concentrations of muscles were similar for both groups. Goats in ADLIB‐group had lower pyridinoline concentrations than those in MAIN‐group, in all muscles, but the differences of pyridinoline concentration between the groups were not statistically significant. Warner‐Bratzler shear force values of Longissimus and Biceps femoris muscles were lower in ADLIB‐group than in MAIN‐group. The increase of meat tenderness by preslaughter intensive feeding seemed to be associated with the increase in intramuscular fat deposition and high collagen solubility, and pyridinoline cross‐link appeared to be one of the factors related to collagen solubility.     

Effect of litter size and birth weight on growth, carcass and pork quality, and their relationship to postmortem proteolysis

The objective of the study was to test the hypothesis that birth weight (BtW) influences growth, carcass characteristics, meat quality, and postmortem (pm) proteolysis differently when pigs originate from small (S) or large (L) litters. Swiss Large White barrows (60) used in this study originated from 20 litters with either less than 10 (S) or more than 14 (L) piglets born per litter. Within each of the S and L litters, 3 barrows were selected at birth: the lightest (L-BtW), the heaviest (H-BtW), and the one with a BtW nearest to the average BtW of the litter (M-BtW). The BW and total feed intake of the individually penned pigs were determined weekly. At slaughter, carcass characteristics were assessed. Meat quality traits were determined in the LM and dark portion of semitendinosus muscle. Titin, nebulin, desmin, and integrin proteolysis were evaluated by SDS-PAGE and Western blot technique, and mu - and m-calpain activities were monitored using casein zymography. Litter size affected BtW of L-BtW and M-BtW but not of H-BtW barrows (BtW x litter size interaction; P = 0.07). From weaning to slaughter, L-BtW barrows grew slower (P < 0.01), ingested less feed (P < 0.01), and were less efficient (P < 0.01) than H-BtW and M-BtW barrows. The carcass yields were greater (P < 0.01), and livers and kidneys were lighter (P 相似文献