RESUMEN
Lung protein isolates after defatting with carbon tetrachloride, chloroform, dichloromethane, iso-propanol, ethanol and methanol, were extruded with and without admixed soya grits. Extrusion of these isolates showed a clear dependence of the process on the lipid content. Extruded products with better characteristics were obtained by defatting the samples. Progressive removal of lipid, as the polarity of the solvent used increased, however, did not promote a corresponding progressive improvement in the textural quality of the extrudates. Protein-protein interaction was assessed by the primary mechanical parameters, hardness, springiness and cohesiveness. It was maximal at intermediate lipid contents. These broadly corresponded to the range of lipid contents where maximum hydration and affinity towards water occurred. It was concluded that residual lipid is necessary in order to maximize protein-protein interactions during extrusion. The effects of lipid-protein interactions on the texturization of offal protein caused a wide variation in the degree of cross-linking between protein molecules during extrusion. The results showed that hydrophobic and electrostatic interactions can play an important rôle in texture formation during thermoplastic extrusion.
RESUMEN
A study was made of thermoplastically extruded products prepared from soy grits incorporating varying percentages of offal. Beyond 35% incorporation no satisfactory extrudate could be prepared. A comparison was therefore made of the expansion ratio, density and hydratability of extrudates prepared from mixes containing 20% and 35% of bovine or porcine offal with those containing soy grit alone. The offal sources consisted of untreated or alkali-extracted bovine and porcine lung and bovine tripe (rumen and reticulum) and bovine tripe extracted by sodium dodecyl sulphate (SDS). Under the determined optimum operating conditions, extrudates from all offal/soy mixtures had lower expansion ratios and rehydratability than those from soy grits alone. Nevertheless, mixtures containing 20% or 35% alkali-extracted offal protein expanded more (greatest expansion at 170°C), had lower density and greater hydratability than those containing these proportions of untreated offal or SDS-extracted offal protein. (The latter expanded most between 175-180°C.) Whereas the incorporation of SDS-extracted bovine or porcine lung protein failed to yield textured extrudates, the incorporation of SDS-extracted bovine tripe protein at the 20% level did so. Effects due to source were otherwise small.
RESUMEN
The effects of electrical stimulation (80-100 V, 15 pps) of hot-deboned, bovine Longissimus dorsi muscles, followed by ageing at 30° or 40°Cfor 5, 7 or 10 h, on the solubility of sarcoplasmic and myofibrillar proteins, soluble non-protein nitrogen, and on the water-holding capacity, colour, tenderness and microbiological status of the meat, was assessed. Comparisons were made with the same traits measured on non-stimulated controls (average muscle temperature, 5°C), which were cold-deboned post rigor, and with hot-deboned, electrically stimulated muscles, subsequently held at 2°C. For each treatment and its corresponding control, six muscles each were studied. Such electrical stimulation produced a typical acceleration of pH fall post mortem and enhanced ageing changes at both 30°C and 40°C. It significantly increased tenderness over non-stimulated, cold-deboned controls. The higher temperature of ageing, however, was significantly associated with adverse colour development, loss of water-holding capacity and increased microbial growth. Electrical stimulation alone would not obviate the need for immediate refrigeration in hot-deboning operations with ambient temperatures of â¼ 40°C.
RESUMEN
The 3-methyl-l-histidine levels were determined in the whole muscles from cheek, flank, round, neck and loin regions of the bovine carcass and in the corresponding myosins prepared from them. Titres were similar between the muscles in the latter three locations, but very low in cheek muscle. This finding was reflected by a very low titre for the myosin prepared from this source.
RESUMEN
The method for the detection and possible quantification of the unusual amino acid 3-methyl-l-histidine has been refined and elucidated. This is an essential prerequisite for the determination of its value as a robust unequivocal index of lean meat protein.
RESUMEN
Mixtures of bovine blood plasma, lung and rumen protein isolates were texturised into a fibrous form containing up to 21% protein. Fibres containing rumen protein in admixture had a greater resistance to shear. The colour of the fibres was dependent upon the proportion of lung in the mixture; reflectance spectra of mixed protein fibres resembled those of cooked meat. Electrophoretograms of the fibres were characterised by the presence of a dense band in close proximity to the origin. Mixing protein species did not produce any electrophoretic component other than those originally present. It would be expected that mixtures of these proteins would produce protein fibres of satisfactory nutritive value.
RESUMEN
An improved method for determining the actin-bound 3-methylhistidine titre of muscle is described. Using this procedure, the titres of actin-bound 3-methylhistidine in bovine muscles Longissimus dorsi (loin), Masseter and Malaris (cheek) and Semimembranosus (round), could be accurately determined and were found to be similar to one another. Actin-bound 3-methylhistidine is thus suggested as an even more consistent index of meat protein than is total protein-bound 3-methylhistidine, since the 3-methylhistidine titre is low in the myosins of ruminant Masseter and Malaris muscles.
RESUMEN
The effect of the composition of the coagulating bath on the formation of spun fibres from blood plasma protein has been investigated. The texture of these fibres is affected by the concentration of the coagulants, especially at low levels. The fibre retained an amount of sodium chloride, proportional to the salt level in the bath, which could be washed free from the fibre without redissolution. As a result a satisfactory level of ash in the textured product could be obtained.
RESUMEN
The proportion of protein recoverable from bovine heart, kidney, liver, lung, rumen and spleen by alkaline extraction, followed by reacidification, was found to be related to the temperature of extraction, the recovery of both lung and rumen protein at 60°C being approximately twice that at 0°C. Extraction for more than 2 h gave increases in protein recovery. The increased protein solubility was partly due to increased solubilisation of collagen and to a reduction in the quantity of protein precipitated by acidification. Alkaline extraction of lung and rumen at 60°C resulted in the formation of the dipeptide lysinoalanine (0·39 and 0·49 g/16gN, respectively), with tracev amounts at 20°C and 40°C. The electrophoretic patterns of raw meat industry by-products are discussed in the light of previous findings.
RESUMEN
The protein-bound 3-methylhistidine content of meat species has been shown to be of value in predicting the meat content of food products. The present paper deals with the development of a rapid method for the detection and estimation of the dinitrophenyl (DNP) derivatives of the methylamino acids and dipeptides, and in particular 3-methylhistidine. The DNP derivatives of methylated and non-methylated basic amino acids and dipeptides were shown to have differing solubilities in diethyl ether and aqueous solution. These differences allowed preliminary purification of hydrolysed meat extracts, thereby allowing rapid determination of 3-methylhistidine using a short ion-exchange resin column.
RESUMEN
Protein-bound 3-methylhistidine, which is present at similar concentrations in various meat species but absent from non-meat proteins, was used to estimate the lean meat content of a range of retailed meat products. The results of the application of this novel method were compared and contrasted with those using standard methods of product analysis. The presence of textured soya protein in products was determined using polyacrylamide gel electrophoresis. Formulae for the calculation of the fat-free lean meat content on the bases of (i) the 3-methylhistidine index for muscle protein and (ii) the connective tissue content, are given. The lean meat contents of products calculated on these bases were found to be of the same order as, but generally lower than, those obtained using standard methods. This was considered to be due to the presence of non-meat proteins, of added connective tissue and/or certain types of offal. These would not be included in the lean meat content, as calculated by the 3-methylhistidine index, but could be legitimately included in the meat content calculated using standard methods according to current practice. A new interpretation of 'meat' in terms of 3-methylhistidine content is given.
RESUMEN
Data concerning the efficiency of protein extraction from meat waste tissues are presented. The tissues investigated were the lungs, stomach and small and large intestines of the ox, sheep and pig. Practically all of the protein, with the exception of connective tissue proteins, was solubilised under optimum extraction conditions both with alkali and anionic detergent. The disadvantages of isoelectric precipitation of alkaline extracted proteins have been investigated in detail using polyacrylamide gel electrophoresis incorporating sodium dodecyl sulphate (SDS). The compositions of the protein isolates from the various tissues studied differed from those of the soluble extracts and supernatants or wheys. However, a component of MW 75,000 daltons was characteristic of the wheys from each tissue. The compositions of both isolates and wheys are discussed in the light of structural and cytoplasmic proteins present in smooth muscle tissues. The usefulness of anionic polysaccharides as a means of whey protein recovery is discussed, together with similar benefits achieved using SDS.
RESUMEN
Thermoplastically extruded products prepared from soy grits alone, and from those containing 20% or 35% of bovine or porcine offal, at various temperatures of extrusion, were subjected to instrumental texture profile analysis (hardness, elasticity, cohesiveness, gumminess, chewiness) and shear force measurements. The offal sources were untreated, or alkali-extracted, protein from bovine and porcine lung and bovine tripe (rumen and reticulum) and protein in extracted by sodium dodecyl sulphate (SDS) from bovine tripe. For products prepared from soy grits alone, hardness, gumminess, chewiness and shear force showed maxima at 170°C, whereas elasticity and cohesiveness increased progressively in the temperature range studied (140-190°C). Products containing SDS-extracted tripe protein required more force to shear, and were more hard, gummy and chewy, than products containing untreated offal, and values for all parameters were greater in the latter than in products containing alkali-extracted offal protein. The effect of extrusion temperature on the textural parameters of the products was less than that due to the mode of offal preparation used (untreated, alkali- or SDS-extracted) or the level of incorporation. Offal source was relatively unimportant. Products containing alkali-extracted offal protein had poor internal structure and were brittle; those containing SDS-extracted protein were tough. The different textural properties of the extracted products might determine their relative suitability for use either alone, as analogues or as extenders.
RESUMEN
Differential scanning calorimetry was performed on protein isolated from bovine lung and rumen. Isolates defatted with solvents of increasing polarities (petroleum ether, carbontetrachloride, chloroform, dichloromethane, isopropanol, ethanol and methanol) presented very similar phase transitions. The thermograms of the original, non-defatted rumen isolates exhibited phase transitions which recovered completely after incubation at 303-313 K. This reversible effect was not noticed after petroleum ether extraction. Mixture and incubation at 313 K of the defatted proteins and the extracted fat fraction failed in reproducing the reversibility observed.
RESUMEN
The neutral salt soluble (NSSC) and acid soluble collagens (ASC) from the intramuscular connective tissue of various species were extracted, purified and studied by optical rotatory dispersion, viscosity and polyacrylamide gel electrophoresis. No significant changes in the quantity of such soluble fractions, in the optical rotatory dispersion or in viscosity of the purified samples were observed during two weeks storage at 1 °C. Electrophoretical analysis suggested a decrease in the relative concentration of the α chains of the ASC. It was concluded that if there are changes in the NSSC or ASC of muscle during ageing these are not detected by the techniques employed.
RESUMEN
'English' type fresh skinless sausages were prepared in which some of the meat (mutton, pork or beef) was replaced on a protein to protein basis by chickpea flour. The acceptability of mutton sausages containing chickpea flour was not affected at levels of substitution up to 40%, whereas pork and beef sausages were significantly less acceptable at substitution levels above 30%. In all the sausages incorporation of chickpea flour led to increased cooking losses and softer textures. Incorporation of chickpea flour caused discoloration of the raw sausages which became more prominent during storage at 0°C.
RESUMEN
Rapid lipid oxidation and metmyoglobin formation in sausages containing up to 30% chickpea flour is due to the presence of lipoxidase in chickpea flour. This enzyme oxidises the unsaturated fats present to peroxides (or related compounds) which then catalyse myoglobin oxidation. Heat treatment of chickpea flour at 80° C for 1 h in water prior to its addition to the batter will prevent both accelerated lipid and myoglobin oxidation in these sausages. An antioxidant containing α-tocopherol and ascorbyl palmitate inhibited the lipid oxidation in these products but had no effect on myoglobin oxidation in sausage batter containing unheated chickpea flour. The relevance of these results to the interdependence of lipid and myoglobin oxidation in meat and meat products is discussed.
RESUMEN
Minced (8 or 18 mm plate) mutton with salt (25%) and sorbate (0·4%) was pressed into cakes about 11 cm in diameter and 3 cm high. The cakes were partially dried in an air oven at 40°C for 48 h to a water activity of about 0·75. The cakes were packed, either in vacuo or in air, and stored at 30 or 2°C for up to 60 days. Objective assessment of quality showed that these dried salted meats can be kept for up to 60 days at 30°C with little loss of textural or nutritional quality although some fading, due to haemoprotein breakdown, occurs. Packaging in vacuum, however, minimises this loss of colour and would be recommended for centralised manufacture prior to distribution in developing, tropical countries.
RESUMEN
Protein isolates extracted from rumen, lung and plasma by alkaline solubilisation were spun into protein fibres and were evaluated for protein quality by rat feeding trials and by amino acid analyses. The net protein utilisation (NPU) of the fibres ranged from 53·0 to 76·9 for plasma and rumen fibres respectively, methionine plus cystine and valine being limiting amino acids. Lysine was not found to be a limiting amino acid in any sample and lysine availability was high in isolates and fell only slightly on spinning. There was a marked discrepancy between chemical score and NPU for rumen isolate and it is postulated that an anti-nutritional factor, possibly a trypsin inhibitor, normally present in bovine organs, could be active in the isolate by lowering methionine availability to the animal and decreasing NPU. Spinning the proteins, however, either destroys the inhibitor or decreases its concentration since NPU and chemical score become equal.
RESUMEN
Non-enzymic browning (NEB) reactions between glycerol and some of the amino acids present in meat have been observed at 38 and 65°C; l-lysine is the most reactive of the amino acids studied and l-cysteine and l-arginine the least. These NEB reactions also occur between glycerol and proteins (gelatin and casein). The reactions are not unique to glycerol as other polyhydric alcohols also form brown pigments with lysine. On prolonged air storage at 65°C glycerol itself undergoes mild oxidation, ultimately yielding a brown solution.