Investigation of methods to detect mechanically recovered meat in meat products - I: Chemical composition.

The proximate composition (fat, moisture, nitrogen, ash and collagen) and the calcium, iron and total purine contents of samples of mechanically recovered meat (MRM) derived from beef, lamb, pork, chicken and turkey were analysed. The data obtained illustrate the variability in the composition of mechanically recovered meats derived from different meat species. The effect of including a high proportion of bones containing marrow in the starting material, the effect of recovery machine type (Yieldmaster and Protecon) and the effect of employing different operating conditions, were investigated.

Estimation of lamb carcass composition from measurements of the speed of ultrasound in the soft tissues of live animals and carcasses.

The application of the velocity of sound (VOS) technique to lamb carcasses in a previous study (Fisher & Page, 1986) measured composition at a hind limb and neck site but was not as precise as fat scores in predicting lean proportion. This study examines VOS measurements made at sites in the hind limbs and along the vertebral column in live sheep and carcasses. A group (A) comprising five breeds of males and females (n = 61) and a sub-group (B) of Scottish Blackface castrated males (n = 34) were studied, and the reciprocal velocity of ultrasound (RV) was measured on the live sheep immediately behind the shoulder and over the last rib using a fixed-distance transducer assembly operating at 5 MHz, and in the hind limbs at 2·25 MHz using the apparatus described by Miles et al.

Modelling of the formation of pale, soft and exudative meat: Effects of chilling regime and rate and extent of glycolysis.

The high drip losses and softness of pale, soft and exudative meat are caused by denaturation of myosin before rigor. A simple predictive model is described based on calculations of the time-course of myosin denaturation in carcasses using the known dependence of the rate of denaturation of isolated myosin on temperature and pH (Penny, 1967a). The fraction of myosin denatured increases with the rate of pH fall, then reaches a maximum at a rate of pH fall that depends on the chilling conditions, and finally decreases.

The solubilization of myofibrillar proteins by calcium ions.

The effect of elevated levels (30 mm) of Ca(2+) and other divalent metals ions on rabbit psoas myofibrils was studied to determine whether these caused solubilization of structural proteins and if so whether the effect was due to salting-in or to proteolytic fragmentation resulting from activation of calpains. Incubation of myofibrils in 30 mm CaCl(2) at either pH 5·6 or 7·0 did not cause any apparent solubilization of the major Z-disc proteins, but there was an immediate ( < 1 min) solubilization of C-protein and troponin I together with small amounts of Mr 80 000 protein, troponin T and tropomyosin. Longer incubations with CaCl(2) extracted little additional C-protein but there was a steady increase with time in the solubilization of proteins with Mr values of 45 000 and 42 000, troponin T, tropomyosin and troponin I.

Skip residues correlate with bends in the myosin tail.

Sharp bends have previously been observed in the tail of the skeletal myosin molecule at well-defined positions 44, 75 and 135 nm from the head-tail junction, and in vertebrate smooth myosin at two positions about 45 and 96 nm from this junction. The amino acid sequence of the heavy chain does not straightforwardly account for such bending on the original model of the tail in which an invariant proline residue is present at the head-tail junction and the repeating seven amino acid pattern of hydrophobic residues lies entirely in the tail. Recently, a revised model has been proposed by Rimm et al.

Concentration of solutes during preparation of aqueous suspensions for cryo-electron microscopy.

It is demonstrated that solutes are likely to be significantly concentrated under conditions commonly used to prepare vitrified aqueous suspensions for transmission electron microscopy. Muscle thick filaments in such suspensions were largely dissolved, probably due to an increase in salt concentration caused by evaporation of water immediately prior to freezing. The extent of solubilization indicated that salts had been concentrated by at least 50%.

Review of current techniques for the verification of the species origin of meat.

An overview of developments that have occurred in meat species identification over the last decade is presented. It starts by noting the different requirements for speciation techniques over the period, describes the complex nature of meat in terms of chemical composition and shows how the chain of events from slaughter to retail gives rise to opportunities for deliberate adulteration or innocent contamination. The limitations of techniques such as electrophoresis and isoelectrofocusing are pointed out where the analysis of mixed meats is concerned; attention then focuses on the range of techniques based on antigen-antibody interactions: agar gel immunodiffusion, counter immuno-electrophoresis and enzyme-linked immunosorbent assay (ELISA) in three formats.

The amount and composition of the proteins in drip from stored pig meat.

In order to elucidate the mechanism of drip formation, measurements have been made of the amount of drip, and its protein concentration, from 80 pigs chilled conventionally. The correlation between amount of drip and protein concentration was poor but significant (r = -0·41, P < 0·001). The individual protein components of 20 drip samples were analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE).

An estimate of the incidence of dark cutting beef in the United Kingdom.

Eight slaughterplants with throughputs ranging from 20 to 300 animals per day were examined to estimate the incidence of dark cutting beef in the United Kingdom. Four thousand, eight hundred and sixteen animals were surveyed and information concerning animal category, source, season and preslaughter handling conditions recorded. Muscle samples were removed to estimate glycogen concentration and after incubation, ultimate pH.

Electron microscopy of negatively stained scallop myosin molecules. Effect of regulatory light chain removal on head structure.

The heads of myosin molecules from the striated adductor muscle of scallop have been studied by electron microscopy after negative staining. In common with vertebrate skeletal muscle myosin visualized by this method, the scallop myosin heads were pear-shaped and often showed pronounced curvature. Staining suggestive of two or, more frequently, three domains could often be observed.

Immunodetection of cathepsins B and L present in and secreted from human pre-malignant and malignant colorectal tumour cell lines.

Pre-malignant and malignant human colorectal tumour epithelial cell lines both secreted precursor forms of the 2 cysteine proteinases, cathepsins B and L. The amount of proteinases secreted by these cell lines varied according to the cell density. Comparison at similar cell densities showed that the pre-malignant, adenoma-derived cell line (PC/AA) secreted as much, or more, of both cathepsin B and L precursors as did the malignant, carcinoma-derived cell line (PC/JW/FI).

Differentiation of Staphylococcus aureus from freshly slaughtered poultry and strains 'endemic' to processing plants by biochemical and physiological tests.

A comparison was made of 27 'endemic' strains of Staphylococcus aureus and 35 strains from freshly slaughtered birds, isolated at five commercial slaughterhouses processing chickens or turkeys. Of 112 biochemical and physiological tests used, 74 gave results which differed among the strains. Cluster analysis revealed several distinct groupings which were influenced by strain type, processing plant and bird origin; these included a single group at the 72% level of similarity containing most of the 'endemic' strains.

Transmission densitometry of stained nitrocellulose paper.

We report a simple solution to the problem of quantitative densitometry of stained nitrocellulose paper. By immersing the paper in a household lubricating oil of matching refractive index, the light-scattering properties of the paper are largely eliminated, allowing precise transmission densitometry in any flat bed densitometer. The method was evaluated on immunochemically stained Western blots of the proteinases cathepsins B and L.

Attenuation of ultrasound in homogenates of bovine skeletal muscle and other tissues.

The attenuation of ultrasound in homogenates of bovine skeletal muscle and suspensions of myofibrils was measured over the frequency range 1.5-7 MHz, and found to be proportional to protein concentration in both. In the homogenates it varied with frequency and temperature in a similar way to the attenuation in post rigor muscle tissue; myofibrils showed a higher frequency dependence.

Attenuation of ultrasound in suspensions of bovine muscle myofibrils and myosin.

The attenuation of 1.5-7 MHz ultrasound was measured over the pH range 3-7 in 100 mM KCl suspensions of bovine M. semitendinosus myofibrils, precipitated myosin and the residue of myofibrils after partial extraction of myosin.

Phosphofructokinase: a component of the thick filament?

F-protein, a consistent contaminant of myosin preparations, has been shown to be phosphofructokinase, the key regulatory enzyme of glycolysis. In homogenates of rigor muscle most of the phosphofructokinase sediments with the myofibrils, suggesting that in the living muscle cell phosphofructokinase is not in the soluble fraction as was formerly thought, but bound to the myofibrils. Fluorescent antibody to F-protein labels myofibrils in a zone in each half of the A-band.

Collagenolytic cathepsins of rabbit spleen: a kinetic analysis of collagen degradation and inhibition by chicken cystatin.

We have investigated the steady state kinetics of the degradation of native fibrillar collagen at pH 3.4 by four collagenolytic cathepsins of rabbit spleen. For each enzyme, the dependence of initial velocity on collagen concentration was well described by the Michaelis-Menten mechanism.

The influence of dissolved calcium salts on the degradation of hard-tissue collagens by lysosomal cathepsins.

Bone, calvaria and dentine collagens were incubated with crude preparations of lysosomal cathepsins obtained from liver, spleen and bone cells. Degradation was most rapid near or below pH 4 and the rate of degradation was increased two-to four-fold in the presence of 50-75 mM CaCl2. This concentration of Ca2+ ions was close to the saturating level of ions released from calcium hydroxyapatite in the pH range 3.

Variations in the tensile adhesive strength of meat-myosin junctions due to test configurations.

A model system of two thick slices of beef M. semitendinosus stuck together with a crude myosin preparation and cooked to 80°C for 1 h has been used to show the effects of testing configuration on the tensile adhesive strength (TAS) of the meat-myosin junction. TAS decreased with increasing cross-sectional area in a square cross-sectional geometry, but increasing just one dimension of a rectangular cross-section resulted in smaller, often insignificant, decreases in TAS.

A comparison between tensile and shear adhesive strength of meat-myosin junctions.

A model meat-myosin gel junction was used to compare the adhesive strength of binding junctions when subject to tensile or shear forces. This comparison was made on junctions cooked to 80°C with three different alignments of muscle fibres with respect to the junction plane. Tensile adhesive strength (TAS) and shear adhesive strength (SAS) did not differ significantly when fibres in both of the bound pieces of meat were perpendicular to the plane of the myosin gel function (90°/90° junction).

Degradation of myofibrils from rabbit, chicken and beef by cathepsin l and lysosomal lysates.

The degradation of rabbit, chicken and beef myofibrils by cathepsin L or lysosomal lysates was studied by SDS-polyacrylamide-gel electrophoresis and electron microscopy (EM). Similar degradation patterns were observed for each myofibrillar preparation incubated with cathepsin L, except that myosin heavy chain and tropomyosin of beef were more susceptible than those of rabbit and chicken. Otherwise, troponin T, troponin in I and C-protein were rapidly degraded with slower degradation of titin, nebulin, myosin heavy chain, α-actinin, α-tropomyosin, actin and myosin light chains, LC1 and LC2.