RELATIONSHIPS BETWEEN BINDING QUALITY OF MEAT AND MYOFIBRILLAR PROTEINS: III: Contribution of Myosin A and Actin to Rheological Properties of Heated Minced-Meat Gel

Myosin A and myosin B gels formed by heating exhibited similar binding abilities as measured by the breaking energy, but different physical properties. At equivalent concentrations, myosin A gels exhibited smaller values for the Young's modulus of elasticity and larger values for strain at the breaking point. It was inferred from the results of a simple model experiment that in sausage manufacture the physical properties of the heat set minced meat gel are of the myosin B type when no pyrophosphate is present, and similar to the myosin A type when pyrophosphate is added. In the latter case, the contribution of actin may be significant. The binding quality of the heat set myosin B gel increased with myosin concentration. Hence, the binding quality of sausage should be influenced by the myosin B content of meat.     

EFFECT OF MgCl2/SODIUM PYROPHOSPHATE ON CHICKEN BREAST MUSCLE MYOSIN SOLUBILIZATION AND GELATION

Sodium chloride (0.29 M) at pH 7 solubilized about 24% of the myosin of washed, minced chicken breast muscle. At a similar pH, 0.2 M sodium chloride in the presence of 10 mM sodiumpyrophosphate and 10 mM magnesium chloride solubilized almost 60% of the myosin. In spite of the greater solubility of myosin under the latter conditions, when gels were prepared with these concentrations of salt at pH 7, the gels without the sodium pyrophosphate and magnesium chloride were slightly superior in both stress (39.3 kPa vs 28.3 kPa) and true strain (2.3 vs 2.0) values. Gels made at a lower pH (6.1–6.5) made much poorer gels. This was true whether the low pH was obtained naturally in the preparation of the sample or re‐adjusted after bringing the mince to a neutral pH. It appears that conditions of pH and salt content that cause solubilization of myosin at more dilute conditions does not contribute to gel quality, but the neutral pH is an important factor for obtaining good gels at ionic strengths <0.3.     

Gel Strength Enhancement by Addition of Microbial Transglutaminase during Onshore Surimi Manufacture

Surimi from Alaska pollock flesh was manufactured onshore with Microbial transglutaminase (MTGase). Effect of MTGase was investigated by evaluating breaking strength and deformation of gels from MTGase-treated surimi with and without setting at 30°C. Quantitative analysis of ε-(γ-glutamyl)lysine (GL) crosslink was also carried out to monitor the MTGase reaction. In set gels, breaking strength and GL crosslink increased, and myosin heavy chain decreased correspondingly with MTGase concentration. These changes were smaller in gels prepared without setting. Results suggest that surimi gel could be improved through the formation of GL crosslinks by added MTGase in surimi.     

Effect of feed texture, meal frequency and pre-slaughter fasting on carcass and meat quality, and urinary cortisol in pigs

The gelation characteristics of myofibrillar proteins are indicative of meat product texture. Defining the performance of myofibrillar proteins during gelation is beneficial in maintaining quality and developing processed meat products and processes. This study investigates the impact of pH on viscoelastic properties of porcine myofibrillar proteins prepared from different muscles (semimembranosus (SM), longissimus dorsi (LD) and psoas major (PM)) during heat-induced gelation. Dynamic rheological properties were measured while heating at 1 °C/min from 20 to 85 °C, followed by a holding phase at 85 °C for 3 min and a cooling phase from 85 to 5 °C at a rate of 5 °C/min. Storage modulus (G′, the elastic response of the gelling material) increased as gel formation occurred, but decreased after reaching the temperature of myosin denaturation (52 °C) until approximately 60 °C when the gel strength increased again. This resulted in a peak and depression in the thermogram. Following 60 °C, the treatments maintained observed trends in gel strength, showing SM myofibrils produced the strongest gels. Myofibrillar protein from SM and PM formed stronger gels at pH 6.0 than at pH 6.5. Differences may be attributed to subtle variations in their protein profile related to muscle type or postmortem metabolism. Significant correlations were determined between G′ at 57, 72, 85 and 5 °C, indicating that changes affecting gel strength took effect prior to 57 °C. Muscle type was found to influence water-holding capacity to a greater degree than pH.     

Dynamic rheological measurements on heat-induced myosin gels: Effect of ionic strength,protein concentration and addition of adenosine triphosphate or pyrophosphate

Myosin solutions and suspensions have been monitored during heating at pH 6.0 by using dynamic rheological measurements. The storage modulus (G′), the loss modulus (G) and the phase angle (δ) all showed a marked dependence on ionic strength in the temperature range 25–75°C. The filamentous gels (ionic strength <0.34) displayed a temporary reduction in G′ at temperatures between 50 and 60°C, presumably due to denaturation in parts of the rod portion of the myosin molecule. In the same temperature region the concentration dependence of G′ changed by a power of 2. The loss modulus also showed a marked concentration dependence, while the phase angle varied with concentration primarily at low (<50°C) temperatures. For the final gels, heated to 75°C, only G′ indicated marked differences due to different protein concentrations and ionic strengths; all gels were almost completely elastic (δ?1°). Adenosine triphosphate was shown to have a pronounced temporary effect on the filamentous gel formed at low temperatures, i.e. on the gel with the highest concentration dependence, while pyrophosphate had no such effect. However, both adenosine triphosphate (or rather its hydrolysis product: adenosine diphosphate) and pyrophosphate appeared to have a small, lasting effect on the heat-gelling ability of myosin: the former a detrimental effect, the latter an improvement.     

RELATIONSHIPS BETWEEN BINDING QUALITY OF MEAT AND MYOFIBRILLAR PROTEINS

The binding quality of the heat set gel increased when F-actin was present in an appropriate ratio to myosin A. It increased further when tropomyosin was added to the myosin A/F-actin model system. The water holding capacity was increased by tropomyosin only. Thus, the contribution of not only myosin A but also of native tropomyosin and actin should be controlled in sausage manufacture. The presence of 0.6 M NaCl or KCl in the sol was necessary to produce high binding quality and high water holding capacity of heated myosin B gels. NaCl is preferred because of the taste effect on the meat product. Heating temperature (65, 80, or 90°CC) affected the physical properties of heated myosin B gels. The water holding capacity and the maximum relaxation time decreased with increasing temperature. In the manufacture of meat products, the heating temperature should be selected in accordance with the desired properties in the finished product.     

Properties of milk protein gels formed by phosphates

We investigated the properties of gels that were formed by adding emulsifying salts, such as tetrasodium pyrophosphate (TSPP), to reconstituted milk protein concentrate solution. The pH of a 51 g/L milk protein concentrate solution was adjusted to 5.8 after adding TSPP. Milk protein concentrate solutions were placed in glass jars and allowed to stand at 25°C for 24 h. Gels with the highest breaking force were formed when TSPP was added at a concentration of 6.7 mM, whereas no gel was formed when TSPP was added at concentrations of ≤2.9 or ≥10.5 mM. Several other phosphate-based emulsifying salts were tested but for these emulsifying salts, gelation only occurred after several days or at greater gelation temperatures. No gelation was observed for trisodium citrate. Gelation induced by TSPP was dependent on pH, and the breaking force of gel was greatest at pH 6.0. Furthermore, when the concentration of milk protein concentrate in solution was increased to 103 g/L, the breaking force of the gel increased, and a clearly defined network between caseins could be observed by using confocal scanning laser microscopy. These results suggest that TSPP-induced gelation occurs when the added TSPP acts with calcium as a cross-linking agent between dispersed caseins and when the balance between (a reduced) electrostatic repulsion and (enhanced) attractive (hydrophobic) interactions becomes suitable for aggregation and eventual gelation of casein molecules.     

Myosins from red and white bovine muscles: Differences measured by turbidimetric,calorimetric and rheological techniques

The aim of this study was to elucidate the functional performance of the most abundant protein component in meat, ie myosin, which is recognised as important for binding in meat products. As several genetic variants of skeletal myosin exist, myosins from two bovine muscles of different fibre type composition, M masseter and M cutaneus trunci were compared with respect to filament forming properties and denaturation characteristics. The principal methods used were turbidimetric measurements, which were used to monitor filament formation, calorimetry and rheology. The myosin systems were examined at two different salt levels (0.2 and 0.6 M NaCl) and at pH 5.5–7.0. The method of preparing myosin suspensions/solutions was also examined. Differences in the filament-forming process for the two myosins were detected. Measurements of turbidity revealed that at conditions of low pH and low ionic strength white myosin had a higher ultimate turbidity compared with red myosin. Early in the transition from low to high turbidity, red myosin had a higher turbidity than white myosin corresponding to reduced solubility. The turbidity increased with time of storing the myosin suspensions/solutions. This change was attributed to formation of filaments and further association of filaments. White myosin had a smaller apparent enthalpy of denaturation than red myosin. The calorimetric measurements recorded in 0.2 M NaCl suggested that the head and the rod of white myosin were less stable than the corresponding parts of red myosin. However, exceptions to this rule were found at pH 6.0. In 0.6 M NaCl the identification of the transitions for red myosin was more difficult. The method of preparing myosin suspensions affected calorimetric and rheological measurements. In 0.6 M NaCl and pH 6.0 calorimetric thermograms of both myosins were affected by the preparation method. At pH 5.5 this change was interpreted as caused by denaturation promoted by the dilution/rapid titration technique compared with dialysing the systems to pH 5.5 from pH 7. Differences in the filaments formed might, however, also contribute to the variations seen in the calorimetric ther-mograms. The gelling properties of white myosin were most sensitive to the preparation method used. Systems prepared by dialysis gave stronger heat-induced gels than those prepared by ‘dilution’. White myosin always produced stronger gels than red myosin independent of the preparation technique. The rheological properties (at 80°C) of red myosin were less affected by the preparation method than were those of white myosin. At lower temperatures, however, there was more variation in the shapes of the rheological thermograms (? versus temperature) for red myosin than in the corresponding thermograms of white myosin.     

Thermal scanning rheology of myofibrillar proteins from muscles of defined fibre type

Emulsion meat products are made with little regard to rheological properties of different muscles. Here the rheology of gels made from three classes of muscle defined by myosin type (fast twitch, slow twitch and heart) are compared. Myofibrillar fractions were prepared from representative bovine muscles-cutaneus trunci, masseter and heart-by a procedure that removed connective tissue, fat and sarcoplasmic proteins. Complicating effects of nongelling agents were thus minimized. Fractions were mixed with NaCl and pyrophosphate at concentrations typical of those used in processed meats. Rigidity and elasticity of the gelling mixtures were monitored during heating from 10 to 84°C over a range of pH values. Several indices of gelation showed that masseter and heart (slow muscle group) gelations were similar to each other but distinct from cutaneus trunci (fast) gelation. Gelation temperature was 10°C lower for fast than slow, perhaps explainable by one of two hypotheses: differential salt extraction or lower thermal stability of fast myosin rod. Cutaneus trunci gels were also more rigid at all pH values. Slow group gels suffered from proteolysis, which was combated with cathepsin inhibitors. For both fast and slow groups, rigidity increased as pH decreased, analogous to results reported for purified myosin in dilute solution. Texture also changed. Below pH 5·7 slow group gels were brittle and granular, with low water-holding capacity. Above that pH, gels were elastic and smooth. The equivalent point for cutaneus trunci gels was pH 5·5. Around pH 7, pyrophosphate had a fluidizing effect at pregelation temperatures, but elasticity data indicated that this ion plays no part in final gelation.     

Continuous Production of Fish Meat Sol using a Twin-Screw Extruder

The washed minced meat of flying fish was extruded at low temperatures with NaCl in a twin-screw extruder while varing screw rotation, feeding rate, feeding of NaCl, and barrel temperature. Extrusion at a higher screw rotation and moderate feeding rate with the residence time of about 1 min, using NaCl in solution and with cooling by ice-water, gave the most adhesive meat sol. Heat-induced gel from this meat sol had a similar textural parameters measured by an instrument to the gel prepared with a conventional stone grinder, however, the toughness score in sensory test of the gel prepared by extrudate was a little smaller than the gel by a conventional method.     

Effects of electrical stimulation and ageing of beef on the gelation properties and protein extractability of isolated myofibrils

The gelation properties of bovine myofibrils, as evaluated by dynamic rheological measurements, were shown to be very sensitive to the variables investigated: stimulation and/or ageing of the meat used, presence of 5 mM pyrophosphate and 5 mM MgCl₂ (PP) and concentration of NaCl (0·3 or 0·M). Statistical evaluation of final gel storage moduli (determined at 70°C) revealed ageing to have a consistent detrimental effect. Fresh, stimulated processing of meat), gave gels of about 40% lower elasticity (storage modulus) than did non-stimulated myofibrils; when PP was included in the gel-forming mixture no effect from electrical stimulation was seen. In spite of the negative effects observed for gel elasticity, the myofibrils in question displayed enhanced protein extractability prior to heating. Electrophoretic results suggest myosin degradation to be partly responsible.     

Antioxidative/Antimicrobial effects of galangal and alpha-tocopherol in minced beef

The antioxidant and microbial stabilities of galangal (Alpinia galanga) extract in raw minced beef were examined at 4 +/- 1 degree C. Raw minced beef containing galangal extracts (0 to 0.10%, wt/wt) were prepared. Lipid oxidation during refrigerated storage was assessed by monitoring malonaldehyde formation, using the thiobarbituric acid reactive substances method. In minced beef, added galangal extract improved oxidative stability. Galangal extract at higher concentrations of 0.05% and 0.10% (wt/wt) were also found to extend the shelf-life of minced beef. Addition of alpha-tocopherol (0.02%, wt/wt) to galangal extract (0.05%, wt/wt) were observed to increase the oxidative but not the microbial stability of minced beef during the storage of 7 days. Galangal extract may prove useful in inhibiting lipid oxidation and increasing microbial stability of minced meat.     

Differential scanning calorimetric study of muscle and its proteins: Myosin and its subfragments

The thermal denaturation of rabbit skeletal muscle myosin and its subfragments was investigated by differential scanning calorimetry. The thermal denaturation of myosin was shown to occur via three (at least) partly independent cooperative endothermic processes. The temperatures at which these processes occurred (312, 317 and 323 K at pH 6.0 and I=1.0) were shown to vary with pH (5.5–8.0) and I (0.05–1.0). The apparent enthalpy of denaturation of myosin was also shown to be dependent on pH and I. By comparing thermograms of myosin with those of the isolated myosin subfragments, the three major processes associated with the thermal denaturation of rabbit myosin could be tentatively assigned to different regions of the myosin molecule, namely, the helical tail, the ‘hinge-region’ and the globular heads. The ‘hinge-region’ thermal denaturation was shown to be reversible at pH 6.0 and I=1.0. Investigations of the effects of ortho-, pyro-, and tripolyphosphate on the thermal denaturation of myosin showed that added pyrophosphate destabilised the myosin molecule by about 9 K compared to the effects of ortho and tripolyphosphate, even though the latter was probably hydrolysed to ortho and diphosphate.     

Formation of two types of gels from bovine myosin

Myosin was isolated from bovine m. semimembranosus and gels were formed by heat treatment at different pH values and ionic strengths. The gels were subjected to rigidity measurements and their microstructure was studied by scanning electron microscopy. This article provides evidence that myosin can form two completely different gel structures in the pH range 5.5–6.0, depending on ionic strength. Fine stranded gel structures were formed at low ionic strength (0.25M KCl), whereas coarsely aggregated gel structures were formed at high ionic strength (0.6M KCl). The fine stranded structure had a higher rigidity than the coarsely aggregated structure. It was found that all fine strand myosin gels were formed from turbid solutions and the aggregate gels from clear solutions. When the pH was lowered to 4 in 0.6M KCl a strand-type gel structure formed spontaneously on dialysis, even without heat treatment. This structure did not change in character on heating. It was concluded that the conditions required for the formation of strand-type myosin gels were already present before the heat treatment and that the strands were made up of myosin filaments at certain pH and ionic strength combinations, which produced a turbid solution. The strand-type structures were considered specific with regard to myosin interactions which was not the case for the aggregated structures. Variation of the heating temperature in the range 55 to 65°C had no major effect on the type of structure formed.     

Gelling properties of white shrimp (Penaeus vannamei) meat as influenced by setting condition and microbial transglutaminase

The properties of white shrimp (Penaeus vannamei) gel added with different levels of microbial transglutaminase (MTGase) and subjected to setting at 25 °C for 2 h or 40 °C for 30 min, prior to heating at 90 °C for 20 min were studied. Breaking force of gels with and without setting increased with increasing MTGase amount added (P<0.05). However, no changes in deformation in all samples were noticeable (P>0.05). Directly heated gels showed the lower breaking force than those with prior setting at all MTGase levels added (P<0.05). Generally, gels prepared by setting at 25 °C exhibited the greater breaking force than those set at 40 °C, possibly associated with the appropriate protein structure for cross-linking at 25 °C and greater degradation at 40 °C as evidenced by a greater trichloroacetic acid soluble peptide content (P<0.05). Sodium dodecyl sulfate polyacrylamide gel electrophoretic study revealed that myosin heavy chain (MHC) underwent polymerization to a higher extent in the presence of MTGase, but the strengthening effect on gel was dependent on setting temperature. Regardless of setting condition, microstructure of gel added with MTGase was finer with a smaller void, compared with those of gel without MTGase. Therefore, setting temperature played an essential role in gel property of white shrimp meat added with MTGase.     

Extraction of sardine myoglobin and its effect on gelation properties of Pacific whiting surimi

ABSTRACT:  Myoglobin (Mb) was extracted from Pacific sardine and added to Pacific whiting surimi to measure its effects on protein gelation. The purity of Mb extract was determined by SDS-PAGE. Mb extract using ethanol showed higher purity than Mb extract using ammonium sulfate. The addition of 0.2% Mb significantly reduced breaking force. However, a synergistic effect of 1.0% Mb was observed with 1.0% beef plasma protein (BPP) to increase surimi gel strength. The highest storage modulus of gels was observed at 1.0% Mb addition, which corresponded with the nonfracture gel and also supported a synergistic interaction between 1.0% Mb and 1.0% BPP. Differential scanning calorimetry showed Mb addition might have affected myosin denaturation and aggregation.     

Improvement of Gelling Properties of Lizardfish Mince as Influenced by Microbial Transglutaminase and Fish Freshness

ABSTRACT:  The effects of microbial transglutaminase (MTGase) at different levels (0 to 0.8 units/g sample) on the properties of gels from lizardfish ( Saurida undosquamis ) mince set at 25 °C for 2 h or 40 °C for 30 min prior to heating at 90 °C for 20 min were studied. Breaking force and deformation of gels increased with increasing MTGase amount added ( P < 0.05). At the same MTGase level used, gels with the prior setting at 40 °C for 30 min showed a higher breaking force compared with those subjected to prior setting at 25 °C for 2 h ( P < 0.05). Sodium dodecyl sulfate-polyacrylamide gel electrophoretic study revealed that myosin heavy chain (MHC) underwent polymerization to a higher extent in the presence of MTGase. Regardless of setting condition, microstructure of gel added with MTGase was finer with a smaller void compared with that of gel without MTGase. Therefore, setting temperature affected the property of gels added with MTGase. Gel properties of mince obtained from lizardfish stored in ice for different times (0 to 10 d) with and without MTGase at a level 0.6 units/g were determined. Irrespective of MTGase addition, breaking force and deformation of all gels decreased as the storage time of lizardfish increased ( P < 0.05). The addition of MTGase was able to increase both breaking force and deformation of the resulting gel produced from lizardfish kept in ice for all storage times used. Therefore, both freshness and MTGase addition had the direct impact on gel properties of lizardfish mince.     

MECHANICAL PROPERTIES OF FISH AND BEEF GELS PREPARED WITH AND WITHOUT WASHING AND SODIUM CHLORIDE

Excellent gels, as measured by fold test, were prepared from three species of fish without first washing the minced tissue. Dependent on species (red hake, cod, or winter flounder), excellent to adequate gels, as determined by the fold test, could be prepared from fish muscle without NaCl provided that the minced tissue was washed prior to gel formation. Postrigor beef formed inadequate gels while excellent to good gels could be produced from prerigor beef although salt was a requirement. The concentration of contractile proteins in fish gels was estimated and they did not appear to be a major factor determining gel quality. Soluble muscle protein did not appear to interfere with gel formation either. Percent expressible moisture, percent recovery, and modulus of deformability did not relate well to fold test scores.     

Thermal Gelation Properties of Protein Fractions from Pork and Chicken Breast Muscles

Thermal gelation properties of myosin, actin, myofibrils (MF), sarcoplasmic protein (SP) and connective tissue (CTS) from pork semimem-branosus and chicken breast (CB) were evaluated. Gels were prepared at pH 6.0, 2% NaCl and cooked to 70°C at 0.7°C/min. Pork myosin had a higher gel strength and a lower cooking loss than CB myosin at 7% protein. Actin from both species did not form a measurable gel. MF gels from pork and CB had the lowest cooking loss while CTS and SP had the highest cooking loss. Difference in gel strength between muscle and MF+SP+CTS at 7% protein was not consistent with that at 10% protein.     

复合卵白蛋白-大豆分离蛋白对肉糜凝胶特性和微观结构的影响

运用卵白蛋白改善大豆蛋白与肉糜凝胶强度。通过在大豆分离蛋白中添加不同比例的卵白蛋白,应用于肉糜制品中,观察肉糜凝胶理化特性和微观结构,综合分析卵白蛋白和大豆分离蛋白复合凝胶在肉糜制品中的应用效果。结果表明：复合组显著改善产品的硬度、弹性、蒸煮损失、保水性（P＜0.05）,复合蛋白质量比为1∶1时,产品的脂肪聚集体达到最小,硬度得到改善,产品的弹性稳定且达到最大值,产品的可接受度最佳。