The temperature dependence of anaerobic glycolysis in beef muscle held in a linear temperature gradient

Measurements have been made of the rate of pH fall post-mortem in excised beef sternomandibularis muscles held in a linear temperature gradient. A minimum rate of pH fall was observed between 10 and 12°C and the rate increased as the temperature was further reduced towards 0°C, a phenomenon known to be accompanied by cold-shortening and attributable to increased activity of the contractile actomyosin ATPase which stimulates glycolysis. The increase in rate observed as the temperature was raised above the 10–12°C minimum, had an activation energy of 40kJ/mol, similar to that of the calcium-independent myosin ATPase.     

The tenderising effect of a muscle proteinase on beef

Freeze-dried beef has been reconstituted in a solution of a Ca²⁺ activated muscle proteinase. After storing the reconstituted meat for 5 days, the Z-lines of the myofibrils had disintegrated and the meat, when cooked, became appreciably tender as determined by a tenderometer. Since control samples, without added proteinase, did not become as tender as the enzyme-treated samples it was concluded that this proteinase acts as a meat tenderiser.     

The effect of hot-boning and reduced added phosphate on the processing and sensory properties of cured beef prepared from two forequarter muscles

The functionality of pre-rigor beef was investigated in terms of the effects of phosphate reduction and curing of hot-boned meat on the processing and sensory properties of relatively low-value muscles, M. infraspinatus (IS) and M. pectoralis profundus (PP), from the forequarter. Muscles were excised within 90 min post-mortem (HB) or, from chilled carcasses, 24 h post-mortem (CB), and were injected to 115% of green weight with brine containing phosphate and were vacuum tumbled continuously for 2 h. Hot-boning gave lower total yield of cooked meat for both muscles. Hot-boned PP joints had slightly higher (P < 0.05) cook loss than cold-boned. Reduction of added phosphate (from sodium tri-polyphosphate) from 0.3% to 0.15% of cured meat had detrimental effects on colour; joints containing the conventional 0.3% were lighter (P < 0.001) and redder for both muscles. Hot-boning gave PP joints which were rated less tender by sensory panels, corresponding with higher (P < 0.001) hardness TPA values, higher (P < 0.05) Warner–Bratzler shear force (WBSF) values and shorter (P < 0.05) sarcomere lengths. Effects of phosphate level and boning method were less in IS joints. In these, hot-boning gave products that were rated by sensory panel as slightly more tender but there was no effect on TPA or WBSF values. Furthermore, total yields from hot-boned products did not reflect the expected increase in functionality and reducing added phosphate during processing had a detrimental effect in binding and forming of joints.     

The effect of oestrus behaviour on muscle glycogen concentration and dark-cutting in beef heifers

Preliminary observations at an abattoir showed an association between oestrus behaviour and dark-cutting in beef. Two follow-up experiments examined the relationship between oestrus behaviour and muscle glycogen content, carcass bruising and meat ultimate pH. In the first experiment heifers in oestrus were compared with controls in mid-cycle. Oestrus was associated with a loss of glycogen in M. longissimus dorsi. Also plasma creatine kinase activity increased, reflecting bruising or strenuous muscle activity. In the second experiment heifers were slaughtered during oestrus. On the basis of pre-slaughter behaviour they were assigned to active or inactive groups, which subsequently yielded 39% and zero dark-cutting carcasses, respectively. Loss of muscle glycogen was accounted for by the number of times an animal mounted (r = -0·85). Likewise, variation in meat ultimate pH was associated with mounting activity (P < 0·001). Carcass bruising was higher in the active group (P < 0·0.001) and the main cause of bruising was being mounted (r = 0·74). It was concluded that single penning of oestrus heifers to eliminate mounting activity would reduce the incidence of dark-cutting.     

The effect of marinading on beef

Beef sternomandibularis muscle was tenderised by marinading in 1.5% acetic acid. The effect was marked whatever the cooking temperature, but greatest with mild or severe cooking (60 or 100°C). Addition of 12% sucrose further increased tenderness. Juiciness was not improved, with or without sucrose. Longissimus dorsi steaks when marinaded and grilled showed only a small increase in tenderness. Lengthy soaking of a thick steak is necessary to achieve full penetration of the marinade. Marinading appears to be particularly effective in tenderising muscles containing a large amount of connective tissue, but the benefit is marginal in top quality cuts.     

The effect of family beef taboos on beef consumption on young Taiwanese adults

A family tradition of beef taboos exists in Chinese societies. The marketplace for beef in Taiwan is imported mainly from the U.S., Australia, and New Zealand. For mechanised-farming families or even for those no longer engaged in agriculture, beef consumption is often not encouraged nor allowed by family members. Using quantitative data in the analyses, this study was undertaken to examine whether family beef taboos influenced beef consumption for young adults in Taiwan. Respondents from beef-consuming families consumed more beef (4.34 times/week: average, 150.07 g/week: cooked) than respondents from non-beef-consuming families (1.87 times/week: average, 56.67 g/week: cooked). For the respondents from non-beef-consuming families, spiritual burden was a main factor affecting their own beef consumption. The implications based on this study’s findings are provided.     

A rapid fluorescence assay for danofloxacin in beef muscle: effect of muscle type on limit of quantitation

A simple, rapid fluorescence screening assay was applied to the analysis of beef muscle for danofloxacin at the U.S. tolerance level of 200 ng/g. Muscle samples were homogenized in acetic acid-acetonitrile, the resultant mixture centrifuged, and fluorescence of the supernatants was then measured. The significant difference between the fluorescence of control muscle sample extracts and extracts of samples fortified at 200 ng/g allowed for successful discrimination between the samples. Setting a threshold level at the average 200 ng/g fortified sample extract fluorescence -3sigma allowed for identification of potentially violative samples. Successful analysis of a group of blind fortified samples over a range of concentrations was accomplished in this manner, without any false-negative results. The limits of quantitation for danofloxacin, as well as enrofloxacin, using this assay were determined in three types of beef muscle (hanging tenderloin, neck, and eye round steak), as well as in serum. Significant differences in limits of quantitation were found among the three different muscle types examined, with hanging tenderloin muscle providing the lowest value. This work not only shows the potential for use of the fluorescence screening assay as an alternative to currently used microbial or antibody-based assays for the analysis of danofloxacin in beef muscle, but also suggests that assays using beef muscle may vary in performance depending on the specific muscle selected for analysis.     

Effects of sugars on post-mortem glycolysis in bovine muscle mince

Sternomandibularis muscles from steers were minced, within 75 min of slaughter, with sugars or amylases. The minces were held anoxically at 25°C for at least 7 h. At times samples were removed and chemically analysed. Glucose (1·5%) retarded the post-mortem pH fall, with kinetics similar to those of NaCl (2·0%). Typically, 1·5% glucose maintained the pH at 6·1, whereas control mince attained 5·5. Lesser amounts of glucose had a reduced effect. Other sugars were inactive. The metabolic effects of 1·5% added-glucose were compared with those of an iso-osmotic control, 1·5% added-fructose. For the glucose mince there was no change in glucose concentration over 7 h suggesting that the endogenous hexokinase was inactive. Further, more glycogen remained in the glucose mince that in the control, indicating that glucose inhibited glycolysis. This was confirmed by electron microscopy and was reflected in pH and lactate levels. Hexose monophosphates were strongly affected by glucose. In the control, their concentrations each fell in the first 2 h then increased steadily, as expected. In the presence of glucose, their concentrations were initially lower and decreased steadily with time. Concentrations of adenosine phosphates were little affected by glucose, but downstream products of purine metabolism showed marked differences, probably due to enhanced nucleotidase activity above pH 6. Glucose plus yeast hexokinase produced a mince with a rigor pH close to normal. The data indicated that phosphorylase activity was inhibited by glucose, and suggested that glucose was not phosphorylated because of muscle hexokinase inhibitors such as glucose-1,6-diphosphate.     

The kinetics of rigor onset in beef muscle fibres

Force and stiffness were investigated as beef muscle fibre preparations entered rigor mortis. The results show that single fibres enter rigor rapidly (exhibit a small t_10–90) whilst fibre bundles exhibit a much slower rate of entry into rigor (larger t_10–90). The mean ‘rigor time’ in both cases is, however, similar. The difference in kinetics is probably due to the fact that individual fibres within a bundle enter rigor at different times. Effectively anaerobic fibre bundles treated with iodoacetate exhibit a t_10–90 almost as short as do single fibres when similarly treated, suggesting that much of the inferred heterogeneity of response amongst fibres in a bundle arises from differences between fibres in the ability of glycolysis to sustain ‘relaxing’ concentrations of ATP.

Fibres have been chemically ‘skinned’ after entering the rigor state. Measurements of the relationship between stiffness and tension in the skinned fibres indicate that there are two readily distinguishable rigor ‘states’ depending upon whether rigor is entered from the relaxed of from the contracting state. By contrast, the rigor state achieved by intact fibres is similar to that attained in skinned fibres via the contracted state, suggesting that the ‘natural’ rigor state is preceded by a calcium-activated contraction. Interconversion of the two rigor states generated in vitro requires an intermediary relaxed state.     

The influence of death struggle on the rate of glycolysis in chicken breast muscle

Experiments were conducted to study the effect of killing procedures on the biochemical metabolites of broiler chicken breast muscle. The degree of struggle at death profoundly affected the onset of rigor mortis both in intact carcases and in muscles stored off the bird. Evidence was obtained that the amount of ATP present in the muscle, and hence the time of onset of rigor, could be estimated by measurement of the pH value of the muscle.     

The effect of muscle, cooking method and final internal temperature on quality parameters of beef roast

The aim of the study was to evaluate the influence of cooking conditions (dry air and steam) and final internal temperature (75, 85, 95°C) on the physico-chemical properties of beef infraspinatus (INF) and semimembranosus (SEM) muscles as well as their tenderness and juiciness. Cooking method and temperature influenced moisture, total collagen content in cooked meat and cooking loss, whereas muscle type affected fat, total collagen content and cooking loss. Warner-Bratzler shear force values were affected by cooking method, which also influenced juiciness of roasts. Temperature affected tenderness and juiciness, whereas muscle type influenced juiciness. The most desirable tenderness had INF heated in steam and dry air to 95°C. Processing SEM in dry air to 85 and 95°C lowered the juiciness of the roasts. There were significant correlations between physico-chemical, sensorial and image attributes, however high accuracy of prediction (r(2)>0.8) was achieved only for SEM muscle.     

Comparisons of the effect of electrical stimulation methods on postmortem pH decline in beef muscle

Results of four electrical stimulation (ES) studies were summarized to demonstrate the impact of different ES parameters on pH decline patterns in postmortem M. longissimus thoracis et lumborum. Postmortem pH decline was modeled as a non-linear function of time, and estimates of minimum obtainable pH, pH decline rates, and time to reach pH 6·0 were compared for each study. The decline model for study 4 (AC, 60 Hz, 50 V; 5 min post mortem) had a larger (P < 0·05) estimate for decline rate than that for study 1 (AC, 60 Hz, 400 V; 1 h post mortem) and the control (non-stimulated) data. The model estimate of time to pH 6·0 (0·56 h) for study 4 was the shortest (P < 0·05) for all treatments. Different ES parameters produce different pH decline patterns post mortem and, therefore, may impact product quality and fabrication and chilling protocols adopted in fresh beef processing.     

Elastography of beef muscle

Elastography, a technique that uses ultrasonic pulses to track the internal displacements of small tissue elements in response to an externally applied stress, has been applied to beef muscle. Beef longissimus (1 day post mortem) and semimembranosus (5 days post mortem) muscles were obtained from A maturity beef carcasses. Samples were vacuum-packaged and frozen to -20°C. For elastography measurements, muscles were equilibrated to a constant temperature (30° C± 0·5) in a water tank. Custom transmitters and receivers were used in conjunction with a 2·25 MHz medical transducer. The transducer was driven by a 286 PC, and the radio-frequency echoes digitized at 50 MHz and 8 bits. The pre- and post- compression echo trains (A-lines) were subjected to cross-correlation analysis. Visual interpretation of beef elastograms demonstrate circular areas of relatively inelastic tissues and smaller, banding areas of elastic tissues in the cross-section of beef longissimus muscle. The dark inelastic areas from the elastograms may be related to myofibrilar areas from the same muscle sections; the light, elastic band areas from the elastograms may be related to perimysiaal connective tissue or intramuscular fat. Fatty septa and a calcified abscess could be easily identified on the elastogram. These preliminary results demonstrate that elastography may have potential as a non-intrusive method of visualizing tissue components of beef muscle.     

Transverse anisotropy in beef muscle

In beef sternomandibularis muscles, a variety of treatments—tetanic contraction, cold shortening, cooking shortening and swelling in alkali—caused dimensional changes which differed markedly with the direction chosen within a plane perpendicular to the fibre direction. In all cases a marked increase (up to twice) occurred in the narrow dimension of the muscle, with little change in the wide dimension. In the cooked meat, shear force across the fibre was independent of the transverse direction chosen whether the muscle was relaxed or cold shortened. The effects were also seen in rectus abdominis and psoas, but not in longissimus dorsi muscles. It is suggested that anisotropy is a result of differing organisation of connective tissue in the two directions, although there was little histological evidence. The force to shear parallel to the fibres varied with direction in a manner consistent with this view.     

The influence of temperature on shortening and rigor onset in beef muscle

At sufficient ATP concentration and temperatures below about 15°C, pre-rigor beef muscles (neck muscles) contract; this phenomenon is known as cold shortening. There is also a contracture at higher temperatures occurring just before rigor onset which is called rigor shortening. While rigor shortening starts in neck muscles at pH around 6·3–6·0 and at about 2 μMol ATP/g muscle, cold shortening can begin at pH around 7·0 and the full ATP concentration (4 μMol ATP/g) in the muscle. Shortening can take place as long as there is no irreversible formation of the actomyosin complex in the muscle, i.e. before rigor onset occurs, which can be measured by intermittent loading of the muscle. The degree of extensibility which follows starts to decrease at the moment of rigor onset. This irreversible loss of extensibility at temperatures between the freezing point (?1°C) and physiological temperatures (38°C) starts at various pH values and ATP concentrations in the muscle. At 38°C the rigor onset occurs at pH 6·25 and about 2 μMol ATP/g muscle, dropping at 15°C to pH 5·75 and 1 μMol ATP/g muscle. At 0°C, as at all temperatures below 10°C, the loss of extensibility at medium loads (about 250 g/cm²) begins shortly after cold shortening. This loss of extensibility is reversible by increasing the load or raising the temperature. The irreversible loss, or rigor onset, however, occurs at 0°C with pH of 6·1–6·2 and 1·8–2·0 μMol ATP/g muscle. Thus, the onset of rigor is influenced by more than one factor. Temperature, pH and ATP concentration each play a rôle.Maximum loss of extensibility or completion of rigor is reached between 10°C and 38°C at pH 5·5–5·6 and less than 0·5 μMol ATP/g muscle. At 0°C the completion of rigor takes place at pH 6·0, but still at 0·5 μMol ATP/g muscle. The latter fact shows that the completion of rigor is solely dependent on the ATP concentration in the muscle; nevertheless, the pH of rigor completion is higher in the extreme cold shortening range. This is apparently due to a different pH/ATP relationship in muscles at low temperatures.The results are discussed in terms of changes in the concentration of Ca²⁺ ions and ATP.The results are of particular interest for the handling of hot-boned meat; that is, for both the cooling of pre-rigor muscle and the use of hot-boned meat for processing.     

宰后成熟对牛肉品质的影响

本文通过对牛肉中粗钙激活因子（依钙蛋白酶CAF）的活性及肌原纤维小片化指数、胶原含量的测定,说明牛肉中依钙蛋白酶的活性随宰后时间的延长面下降,直影响到肉嫩度的变化、成熟时间越长,肌原纤维小片化程度越高,肌原纤维结构破坏越来在重,越有利于提高肉的嫩度。