THE EFFECTS OF DELAYED CHILLING AND ALTERED CARCASS SUSPENSION UPON BEEF MUSCLE: I. PHYSICAL AND TEXTURAL PROPERTIES

A total of 60 bovine carcasses from crossbred heifers, 12 to 16 months of age with carcass weights of approximately 260 kg were utilized in two related experiments to evaluate the effects of delayed chilling and altered carcass suspension on certain physical and textural properties of beef muscle. Hip-free suspension (suspension by the os coxae from a hook inserted through the obturator foramen with the limbs hanging free) significantly (P<0.05) reduced the shear force values obtained on samples from the longissimus dorsi (LD) and semimembranosus (SM) muscles but had no effect (P>0.05) on shear force values obtained on samples from the psoas major (PM) muscle. The only other physical property affected by altered carcass suspension was objective measurement of lean color in the SM. Carcasses suspended from the aitchbone had darker SM muscles. Delayed chilling treatments had no effect (P>0.05) on 2-h SM pH values or 144-h pH values for any of the muscles studied. However, carcasses held at either 13°C or 22°C for 24 h had higher (P<0.05) SM pH values. When delayed chilling treatments affected muscle color, treated sides had darker lean than their conventinally chilled counterparts. Textural properties (shear values and taste panel tenderness ratings) and amount of expressible juice generally were unaffected by the delayed chilling treatments evaluated.     

Histological and shear properties of bovine muscle and their alteration during postmortem ageing

A total of 108 longissimus dorsi (LD) and 37 semitendinosus (ST) bovine muscles were utilised to evaluate the cellular changes and interrelationships among histological properties during postmortem ageing. The most important cellular change during postmortem ageing in the LD was an increase in the degree of muscle fibre fragmentation (i.e. reduction in the length of muscle fibre fragments) and in the ST a combination of an increase in degree of muscle fibre fragmentation and a lengthening of the sarcomeres. Degree of muscle fibre fragmentation was the most highly and consistently related histological trait to shear force values and interrelationships of LD histological traits indicated that fibres with larger fibre diameters had shorter sarcomeres and fragmented to a lesser degree. In addition, higher incidences of wavy LD fibres were generally associated with shorter sarcomeres post rigor. In general, histological traits within the ST were interrelated only after 13 days of ageing and histological traits among muscles were generally not significantly interrelated.     

Tenderness of pork muscles as influenced by chilling rate and altered carcass suspension

Tenderness improvements in porcine muscles (M. longissimus dorsi, LD; M. semimembranosus, SM; M. biceps femoris, BF) were evaluated in a total of 72 carcasses by using combinations of three different chilling rates (fast, delayed fast, slow) and two different suspension methods (Achilles tendon, pelvic bone).

Tenderness was improved by fast chilling in LD, SM and BF by the pelvic suspension as compared to conventional suspension in the Achilles tendon (P < 0·05). The lengthening of the sarcomeres in SM and BF as produced by pelvic suspension exceeded those found in LD, without having proportional additional effect on the tenderness. While the pelvic-induced tenderization did not change significantly by delayed fast chilling, additional tenderization in BF and SM was obtained by combining pelvic suspension with slow chilling. In conventionally suspended sides, tenderness was unaffected by delayed fast chilling—with slow chilling, however, improvements were observed in LD and SM to a similar extent as obtained by the pelvic suspension. In the LD muscle, the tenderizing effect produced by treatments was largest in muscles having pH values 45 min post stunning above 6·1 (P < 0·05).     

Interrelationships amongst carcass and meat quality characteristics of sheep

The relationships between various carcass and meat quality characteristics of sheep were studied. Relationships were determined by regression, using data obtained from sheep belonging to a wide range of breeds, sex types and slaughter weight (32-62 kg). The chilling rate of the M. longissimus dorsi (LD) post-mortem was negatively correlated with carcass weight (r=-0.42, P<0.01), back fat thickness (r=-0.54, P<0.001) and the cooking loss of the M. infraspinatus (IS) muscle (r=-0.44, P<0.001). Correlation between chilling rate and shear force of the IS muscle was not significant, which was also the case between chilling rate and the cooking loss and shear force of the LD and M. triceps brachii muscles. A positive relationship was observed between total collagen and cooking loss (r=0.34, P<0.05) and between heat-insoluble collagen and cooking loss of the LD muscle (r=0.37, P<0.01). Generally collagen content was positively correlated with lean content and negatively with fat content. Carcass weight was significantly (P<0.001) correlated with intramuscular fat (r=0.61), moisture (r=-0.76), cooking loss (r=-0.49), shear force (r=-0.41) and hue angle (r=-0.41). Shear force was positively associated with cooking loss (r=0.42, P<0.001), but negatively with intramuscular fat content (r=-0.55, P<0.001). Cooking loss was positively correlated with moisture content (r=0.55, P<0.001).     

The effects of various post-mortem treatments on certain physical and sensory properties of three different bovine muscles

Sixty crossbred steers with chronological ages approximating 15 months, carcass weights approximating 270 kg and subcutaneous fat thickness measurements approximating 1·2 cm, were maintained for approximately 210 days on a constantly increasing concentrate ration (13 to 75%, according to NAS nutrient requirements for beef cattle; NAS, 1976). These animals were utilized to evaluate the effects of delayed chilling, hot-boning and electrical stimulation on certain physical, histological, biochemical and sensory properties of three different muscles (Semimembranosus, SM; Longissimus dorsi, LD; and Triceps brachii, TB). Results indicated that neither delayed chilling nor electrical stimulation produced consistent meaningful alterations in any of the physical, cooking or palatability attributes evaluated. However, early post-mortem excision of muscle (hot-boning) consistently produced toughening in all of the muscles evaluated. This was observed to a much greater degree in the TB than in either the SM or LD. Based upon sarcomere length determinations, such toughening could be attributed to cold shortening only in the TB. Electrical stimulation of excised muscle was ineffective in preventing or offsetting this toughening. The delayed chilling treatment imposed (2 h at 12·5°C) was ineffective in enhancing potential effects of electrical stimulation on tenderness.     

Effects of electrical stimulation, chilling temperature and hot-boning on the tenderness of bovine muscles

The objective of this study was to determine the effects of hot-boning, low voltage electrical stimulation (ES) and chilling temperature on the tenderness of bovine M. longissimus dorsi (LD) and M. semimembranosus (SM) muscles. LD (n=32) and SM (n=32) muscles were subjected to different post-mortem treatments; hot-boning (before 90min post-mortem), cold-boning (at 48h post-mortem), low voltage ES and rapid or slow chilling. Hot-boned muscles which were not electrically stimulated (NES) had higher Warner Bratzler shear force (WBSF) values (P<0.001) and shorter sarcomeres (P<0.001) than cold-boned muscles. Hot-boned muscles subjected to ES had lower pH values (P<0.001) post-stimulation and up to 8h post-mortem than NES muscles. At both chilling temperatures WBSF values were lower in ES hot-boned LD and SM muscles at days 2, 7 and 14 post-mortem than NES muscles. Hot-boned muscles subjected to slow chilling had longer sarcomeres (P<0.001) than those subjected to fast chilling. In hot-boned SM muscles, ES resulted in longer sarcomere lengths (P<0.001). However, ES did not have a significant effect on the sarcomere length of LD muscles. As indicated by WBSF values all muscles tenderised during ageing, including muscles which were 'cold shortened'. Proteolysis was not the main reason for differences in WBSF values between ES and NES muscles as judged by qualitative sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE). A combination of slow chilling and ES had a positive effect on hot-boned muscles with respect to WBSF values.     

Sensory and meat quality traits of pork in relation to post-slaughter treatment and RN genotype

The effects on eating quality and meat quality of two different forms of post-slaughter treatment, performed in an abattoir, were studied in carriers and non-carriers of the RN(-) allele. Carcasses were subjected to rapid and slow chilling, and pelvic and Achilles suspension in a factorial experimental design. A temperature of 10?°C was achieved in the centre of M. longissimus dorsi (LD) within 3.5 h in rapidly chilled carcasses and within 8 h in slowly chilled carcasses. In deep M. semimembranosus (SM) a temperature of 10?°C was achieved within 11.5 h in rapidly chilled carcasses and within 14 h in slowly chilled carcasses. LD from slowly chilled RN(-) carriers suspended by the pelvis exhibited the greatest tenderness, while LD from rapidly chilled non-carriers suspended from the Achilles tendon exhibited the lowest tenderness. Pelvic suspension or slow chilling of non-carriers produced the same improvement in tenderness, and when combined the tenderness increased further. However, the tenderness of the RN(-) carriers was already high, and no significant improvement was seen following any of the studied post-slaughter treatments. Pelvic suspension prevented shortening of muscle fibres, as seen by longer sarcomeres in LD from pelvic-suspended sides. However, longer sarcomeres were associated with greater tenderness only in LD from non-carriers of the RN(-) allele. The presence of the RN(-) allele and a slow chilling regime increased the rate of pH decline in LD. Achilles suspension also increased the rate of pH fall in SM, in addition to the RN(-) allele and slow chilling. The overall tenderness of LD was mainly related to the course of pH decline during rigor; lower pH values between 3 and 7 h post-mortem contributing to greater tenderness. The myofibrillar length was predominantly related to RN genotype and was shorter in RN(-) carriers than in non-carriers. The RN(-) allele and slow chilling contributed to higher evaporation losses and RN(-) carriers exhibited increased frequency of PSE meat in the ham muscles. The use of pelvic suspension appears advantageous over slower chilling, since it improved tenderness without any negative influence on drip loss, evaporation or cooking loss.     

Thermal transition of collagen in ovine connective tissues

The thermal transition temperature (T(m)) of collagen in a range of muscle and non-muscle connective tissues from lambs, hoggets and mature sheep was measured by differential scanning calorimetry. The muscles selected were: semimembranosus (SM), semitendinosus (ST), biceps femoris (BF), Longissimus dorsi (LD) and psoas major (PM). Although the T(m) of intramuscular SM collagen from an aged ewe underwent no significant change with time post mortem, that of a 5-months-old lamb had dropped by 0·9°C after 2 days at 19°C. The epimysium of each muscle exhibited a higher T(m) than the corresponding intramuscular connective tissue. The LD and BF tendons each had a lower T(m) than corresponding intramuscular connective tissue but this was not true for the PM. Furthermore, the PM tendon generated an isometric tension more than five times that of the LD, BF or psoas minor tendons. This indicates that the PM tendon is richer in heatstable crosslinks than any of the other tendons investigated. In all tissues, except the liver capsule, there was an increase in T(m) with animal age. However, the rate of change T(m) varied from one tissue to another. For example, the SM intramuscular collagen matured at an earlier age than that of other muscles, the PM being slowest to mature. In keeping with the changes in T(m) values, the Warner-Bratzler peak force of ST muscles increased markedly in older sheep, but there was no significant difference in peak force of SM muscles between lambs, hoggets and mature sheep.     

新疆褐牛不同部位牛肉肌纤维类型及品质差异研究

为了研究新疆褐牛不同部位牛肉肌纤维类型组成及品质差异,测定了冈上肌、冈下肌、臂三头肌、腰大肌、背最长肌、半腱肌、半膜肌和股二头肌的肌纤维特性和品质特性,并通过相关性分析研究了牛肉品质和肌纤维特性之间的相关性。结果显示腰大肌、背最长肌和股二头肌分别具有最高的Ⅰ型、ⅡA型和ⅡB型肌纤维比例,八个部位肉的肌纤维直径为ⅡB型>ⅡA型>Ⅰ型,且腰大肌三种肌纤维类型直径均小于其他部位。冈上肌具有较低的b^*值,冈下肌具有较低的剪切力、蒸煮损失率;臂三头肌具有较高的剪切力,腰大肌具有较低的剪切力、硬度、胶着性和pH,较高的粘聚性和压力失水率;背最长肌具有较低的咀嚼性、回复性和弹性;半腱肌具有较低的压力失水率、粘聚性和回复性,较高的L^*值;半膜肌具有较低的L^*值和咀嚼性,股二头肌具有较高的弹性、胶着性和咀嚼性。Ⅰ型、ⅡA型和ⅡB型纤维面积、直径与剪切力、硬度和蒸煮损失显著正相关(p<0.05),与压力失水率显著负相关(p<0.01);Ⅰ型肌纤维比例与硬度、剪切力显著负相关(p<0.05),ⅡB型肌纤维比例与剪切力正相关。结果表明,肌肉部位显著影响牛肉品质,特别是嫩度,增加Ⅰ型肌纤维比例、减少ⅡB型肌纤维比例均有利于提高牛肉嫩度。     

VARIATIONS IN THE SENSORY PROPERTIES OF BEEF AS AFFECTED BY SEX CONDITION, MUSCLE AND POSTMORTEM AGING

The longissimus (LD), biceps femoris (BF), psoas major (PM), semitendinosus (ST) and semimembranosus (SM) muscles from 8 bulls and 8 steers were removed from sides at 1 day postmortem and 7 days postmortem. The sensory and textural properties were evaluated and related to meat composition, meat characteristics and mineral content. Muscles were ranked in order of increasing sensory tenderness ratings: PM>ST>LD>BF>SM. The amount of intramuscular fat was found to be positively correlated to sensory panel tenderness ratings. The amount of intramuscular collagen was found to be negatively correlated to sensory panel tenderness ratings. Muscle concentrations of copper, iron and manganese were found to be positively correlated to tenderness ratings.     

Effect of electrical stimulation,delayed chilling and post‐mortem aging on the quality of M. longissimus dorsi and M. biceps femoris of grass‐fed steers

BACKGROUND: Roughage‐based low‐input beef production systems are gaining increasing interest owing to the perceived ecological advantages and potential health benefits associated with the favourable fatty acid composition of such beef. The low plane of nutrition may on the other hand yield less tender beef by affecting growth, carcass weight and fatness and therefore, indirectly, early post‐mortem (p.m.) proteolytic enzyme activity and sarcomere shortening. This study aimed to examine delayed chilling and electrical stimulation as promising techniques to control early p.m. muscle metabolism in a way that improves the tenderness of beef from purely grass‐fed steers in comparison with that from steers receiving a finishing diet with concentrates. RESULTS: Electrical stimulation decreased the pH at 1.5 and 3 h p.m. in the M. longissimus dorsi (LD) and M. biceps femoris (BF) of the treated carcass sides as well as the maximum shear force in the LD, while delayed chilling had no effect on pH or texture. The interactions of carcass fatness with electrical stimulation (P = 0.025) and delayed chilling (P = 0.089) indicated more pronounced effects of the p.m. treatments on beef texture in leaner carcasses. CONCLUSION : Electrical stimulation, but not delayed chilling, could markedly improve pasture beef texture and reduce the aging period needed for proper tenderisation. Copyright © 2008 Society of Chemical Industry     

The relationship between muscle fiber characteristics and meat quality traits of highly marbled Hanwoo (Korean native cattle) steers

To investigate the relationships between muscle fiber characteristics and meat quality traits of Korean native cattle, Hanwoo, Longissimus dorsi (LD), Psoas major (PM) and Semimembranosus (SM) muscles obtained from 18 Hanwoo steers and the muscle fiber characteristics were measured by histochemical analysis. Fiber number, area percentages and density of type IIA and IIB were lower in SM muscle, but higher in PM muscle than other muscles. LD muscle had higher pH_24h, L^? value and fat content whereas SM muscle had lower L^? value and fat content. The lowest WBSF with longer sarcomere length was observed in PM muscle, while SM muscle showed the highest WBSF with shorter sarcomere length. Consequently, the percentage of type I and IIB were highly correlated with meat quality traits and inversely correlated with fat content, L^? value and WBSF. Fiber number and area percentage of type I had a positive correlation with fat content and L^? value and a negative correlation with WBSF. These results suggest that Hanwoo steers had high marbling, more lightness and tenderness when the percentage of type I was high and the percentage of type IIB was low in muscle.     

Muscle fiber properties and thermal stability of intramuscular connective tissue in porcine M. semimembranosus

BACKGROUND: Strips can be easily peeled from raw destructured pork (M. semimembranosus, SM muscle) by hand but in normal meat these strips break. In general, destructured meat is pale in color. Porcine SM muscles have thick muscle fibers which could predispose them to destructuration. This study investigated whether the onset and peak temperatures of thermal shrinkage (T_o and T_p) of intramuscular connective tissue from SM muscles were associated with muscle fiber thickness, capillary density or extracellular space. We also investigated whether these muscle fiber properties of destructured muscles differed from those of normal muscles. RESULTS: The destructured and normal muscles were similar in muscle fiber cross‐sectional area, capillary density, extracellular space and sarcomere length. T_o correlated negatively with sarcomere length. The water content of differential scanning calorimetry samples consisting of intramuscular connective tissue was higher in destructured muscles than in normal muscles. CONCLUSION: Muscle fiber properties (muscle fiber cross‐sectional area and sarcomere length) and capillary density are similar in destructured and normal SM muscles. T_o and T_p of intramuscular connective tissue are similar in destructured and normal muscles. Muscle fiber properties show no association with the thermal shrinkage properties of intramuscular connective tissue. Copyright © 2009 Society of Chemical Industry     

Endurance-exercised growing sheep: I. Post-mortem and histological changes in skeletal muscles

A study was conducted with Suffolk ram lambs to determine whether chronic endurance exercise would affect post-mortem changes in muscle tissue. Muscle fibre diameters, sarcomere lengths, fibre types, and pH and temperature declines were measured in five skeletal muscles (semimembranosus, SM: vastus lateralis, VL; semitendinosus, ST; psoas major, PM; gastrocnemius, G). The exercise had no significant effect on muscle size or muscle fibre diameter in any of the muscles studied. However, endurance-exercised sheep had significantly shorter sarcomeres in all five muscles than their non-exercised counterparts. The pH decline curves differed among muscles; those having the highest proportion of glycolytic fibres had the slowest rates of pH decline. The increased proportion of slow-twitch fibres in the SM, VL, ST and G associated with the exercise regime had little effect on the post-mortem pH decline. However, the ST also had a significant exercise-associated increase in the proportion of oxidative-glycolytic fibres (intermediate) and was the only muscle in which exercise influenced the rate of pH decline significantly.     

THE INFLUENCE OF HOT-BONING AND DELAY CHILLING ON TENDERNESS OF MATURE COW CARCASSES HUNG BY THE OBTURATOR FORAMEN

Carcasses of six mature cows (4 years plus) were investigated to evaluate the effect of hot boning with delay chilling on various muscles. Both sides of the carcasses were suspended by the obturator foramen before the muscle systems were fabricated. One side of each carcass was assigned at random to be delay chilled with hot-boning (experimental treatment). This experimental side was held for 4 hours postmortem at 16°C before various muscle systems were excised and stored at 1 °C for an additional 44 h. The conventionally processed side was held at 1 °C for 48 h before fabrication into muscle systems. Meat tenderness was objectively estimated by the use of the Warner-Bratzler Shear (WB). Subjective evaluation of meat tenderness was by a trained panel. The muscles studied were the longissimus (LD), quadriceps femoris (QF), and psoas major (PM). Shear force values were statistically different (P < 0.01) for the LD and QF and (P < 0.001) for the PM muscles. The taste panel detected variations in tenderness between the two treatments and found steaks from conventional chill muscles to be significantly (P < 0.001) preferred over the delay chilled steaks. Preference and hedonic scale scores all supported findings indicated by WB that delay chill processing for 4 h postmortem with hot-boning did not provide beef of greater tenderness than conventional chill when both sides were suspended through the obturator foramen.     

SOLUBLE INTRAMUSCULAR COLLAGEN CHARACTERISTICS FROM STRETCHED AND AGED MUSCLE

SUMMARY –Changes occurring during stretching and post-mortem aging of intramuscular collagen from bovine muscle were studied. Sucrose density-gradient ultracentrifugation analyses of denatured guanidine hydrochloride-soluble intramuscular collagen (GSIC) indicated stretching and/or aging muscle changes the molecular structure of the collagen. The quantity of aldehyde cross-links in native GSIC supported this finding. The yield of GSIC from stretched muscles was slightly greater than from normal muscles. A high correlation existed between quantity of each collagen chain component and muscle shear value. Stretched muscle had significantly longer sarcomeres than normal muscles, regardless of aging period. Sarcomere length and muscle tenderness were closely associated in unaged muscle.     

Effects of pelvic suspension of beef carcasses on quality and physical traits of five muscles from four gender-age groups

Pelvic and Achilles suspension methods for beef carcasses were compared for four gender-age groups (24 month bulls, 34 month bulls, heifers, and cows) and five muscles [M. longissimus dorsi (LD), M. semimembranosus (SM), M. adductor (AD), M. psoas major (PM), and M. gluteus medius (GM)]. Pelvic suspension increased muscle and sarcomere lengths in the SM, LD, GM, and AD muscles. The following effects were significant (p < 0.05). Peak force was reduced by pelvic suspension in the LD and GM of bulls-24 and bulls-34, but not heifers and cows. Furthermore, peak forces decreased for the SM after pelvic suspension in bulls-24, bulls-34, and heifers. For the AD, the only decrease in peak force was for bulls-34. Water-holding capacity increased and purge in vacuum bags decreased for pelvic suspension of all muscles except the PM. Although the effects of pelvic suspension varied somewhat between gender-age groups and muscles, this method of hanging carcasses merits industrial consideration because it improves muscle yields, tenderness, and reduces variation within muscles.     

Inhibition of the proliferation of myeloma cells by the meat origin strain Enterococcus faecium CH3

Sides of 31 non-stimulated carcasses of young bulls were subjected to the muscle stretching methods Tenderstretch (TS) by pelvic bone suspension or Tendercut (TC) with two skeletal cuts or served as controls by traditional Achilles tendon suspension. The sides were chilled at fast and medium rates, resulting in temperatures of 4-5 and 9°C in the m. longissimus dorsi (LD) at 10 h post mortem. The LDs were examined for sarcomere length, Warner-Bratzler peak shear force and sensory properties after 8 days of ageing at 4°C. At the fast chilling rate, TS and TC increased sarcomere lengths, reduced shear force and improved sensory tenderness of the LDs compared to the controls (P<0.05). At the medium chilling rate, sarcomere lengths increased (P<0.05), but no significant differences were found in shear force or sensory tenderness (P>0.05) of the muscles due to stretching. However, the medium chilling rate was efficient in producing tender LDs without applying muscle stretching methods. TS and TC are feasible alternatives for improving overall tenderness and reducing variation in tenderness of beef LD at cold shortening chilling conditions.     

Maternal dietary protein induces opposite myofiber type transition in Meishan pigs at weaning and finishing stages

To describe the effects of maternal dietary protein level on offspring skeletal muscle fiber plasticity, 14 Meishan sows were fed on either low-protein (LP) or high-protein (HP) diets throughout gestation and lactation, and the myofiber characteristics of the offspring were observed both at weaning and finishing. Body weight, as well as the longissimus dorsi (LD) and psoas major (PM) muscle weights were significantly higher (P<0.05) in HP piglets at weaning with increased myofiber cross-sectional area and higher expression of myosin heavy chain (MyHC) IIb mRNA and MyHC II protein in LD and IIx mRNA in PM. A conversed transition towards higher proportion of type I fibers in LD, together with decreased MyHC II protein and MyHC IIb mRNA in both LD and PM, was observed at finishing stage in HP group. Although the slaughter weight and meat quality were not affected, the fast-to-slow shift in myofiber types was detected at slaughter.     

Occurrence of giant fibers in muscles from wild pigs native to the United States

The semimembranosus (SM) and triceps brachii (TB) muscles from wild pigs native to Florida. USA, were evaluated for histological characteristics. All three fiber types were present in both muscles in varying proportions, reflecting differences between tonic and phasic functioning muscles. Typical fiber arrangements were observed with red fibers grouped in clumps and surrounded by white fibers. The triceps brachii muscle contained a greater percentage of βR and αR fibers and possessed more giant fibers than the SM muscle which contained more αW fibers. The giant fibers observed resembled βR or αR fibers. The presence of hypertrophied fibers in the muscles from these wild pigs suggests that the 'giant fiber syndrome' is an intrinsic susceptibility for muscle fiber enlargement in these animals and not necessarily associated with breeding for muscularity since the carcasses from these pigs contained very small muscles and very little fat.