Physicochemical and Gelation Properties of Pre- and Postrigor Chicken Salt-soluble Proteins

The physicochemical and gelation properties of salt-soluble proteins (SSP) extracted from chicken muscles were studied at 0.6M NaCl, pH 6.00. Thermally induced protein unfolding and protein-protein interaction were determined by 8-anilino-1-naphthalene sulfonate (ANS) fluorescence and turbidity. Breast and leg SSP showed similar changes in protein unfolding, but differed in protein-protein interactions. Post-rigor breast SSP formed stronger and more elastic gels than prerigor breast and pre and postrigor leg SSP. Leg SSP gelation was less affected by muscle rigor state than breast SSP. Protein conformational changes were concluded to precede SSP association, which was a prerequisite for gel formation.     

A COMPARISON OF THE RHEOLOGICAL CHARACTERISTICS OF DIFFERENT FRACTIONS OF CHICKEN MYOFIBRILLAR PROTEINS1

ABSTRACT Suspensions of myofibrils and salt-soluble (SSP) or insoluble (SIP) proteins of chicken breast muscle in 0.6 M NaCl at pH 6.0 were heated to induce gels. Dynamic oscillating measurements showed multiple transitions in the shear storage modulus and loss modulus for all three protein fractions in the temperature range of 40–65C. However, changes in these viscoelasticities were most pronounced for SSP and least appreciable for SIP. Gel penetration test also revealed a descending order of SSP < myofibrils < SIP in gel strength. The three fractions of myofibrillar proteins appeared to follow a similar gelation mechanism but vary in the density of the gel networks.     

Protein Extractability and Thermally Induced Gelation Properties of Myofibrils Isolated from Pre- and Postrigor Chicken Muscles

Purified chicken myofibrils were suspended in 0.6M NaCl at various pH values to study gelation properties of the myofibrils. Postrigor breast myofibrils showed a greater protein extractability and gel strength than prerigor breast myofibrils, but the reverse was found for leg myofibrils. Salt-soluble protein was least extractable at pH 5.50 for both breast and leg myofibrils. The pH for optimum gelation, indicated by increased penetration force, was 6.00 for breast and 5.50 for leg myofibrils. Heating at 1°C/min from 20 to 70°C produced stronger breast but weaker leg myofibril gels than isothermal heating at 70°C for 20 min. Muscle rigor state showed a greater effect on protein extractability and gel strength for breast myofibrils than for leg myofibrils.     

Chicken muscle homogenate gelation properties: effect of pH and muscle fiber type

Gelation properties of chicken breast and thigh muscle homogenates at a protein concentration of 4.5% under different pH conditions (5.80–6.60) and those of myofibrillar proteins at a protein concentration of 2% were compared to determine the influence of muscle fibre types on gelation. The optimal gelling pH for breast muscle homogenates (pH 6.30) was slightly higher than that for thigh muscle homogenates (pH 5.80–6.30), a similar trend was found for the isolated chicken myofibrillar proteins (pH 6.00 for breast and 5.50 for leg). Similarly, the pH values at which breast muscle homogenate gels were weaker (pH<6.20) or stronger (pH6.20) than thigh muscle homogenate gels were higher when compared with chicken breast and leg myofibrillar protein gels (pH<5.80 and pH>5.90, respectively).     

THERMAL GELATION OF DUCK BREAST AND LEG MUSCLE PROTEINS

Gels were made by heating duck breast and leg myofibrillar protein suspensions (20 mg/ml; pH 5.50, 5.75 and 6.00) at a constant rate of 1C/min from 18C to 70C. After heating the suspensions to 70C at pH 5.50, breast proteins formed gels which were not different (p > 0.05) in strength from leg proteins. At pH 5.75 and 6.00, however, breast proteins formed significantly stronger gels than leg proteins. Increasing the protein suspension pH from 5.50 to 5.75 had no significant effect on the strength of leg protein gels, whereas the strength of breast protein gels more than doubled. A further increase in pH from 5.75 to 6.00 resulted in a three-fold decrease in the strength of leg protein gels; no significant difference was observed for breast gels. Overall, pH 5.75 was suitable for forming strong breast and leg protein gels, whereas pH 5.50 and 6.00 were detrimental for gel formation of breast and leg proteins, respectively. Variations in the gelation behavior of duck breast versus leg protein gelation are characteristic of differences in fiber composition of the muscle types.     

Storage Stability of Antioxidant-Washed Myofibrils From Chicken White and Red Muscle

Oxidation and gel-forming ability of chicken white (breast) and red (leg) muscle myofibrillar proteins during storage at 0°C were examined. Breast myofibril gels exhibited greater shear moduli than leg myofibril gels throughout 8 days storage. Shear moduli of both breast and leg gels in the intermediate temperature zone (45–55°C) decreased during storage, but at >55°C, they either increased or remained unchanged. Lipid oxidation was inhibited by washing myofibrils with antioxidants propyl gal-late, ascorbate, and tripolyphosphate. However, these antioxidants did not affect the content of protein carbonyls, and only slightly decreased the amine content during storage. Storage affected the kinetic process of myofibril gelation independently of antioxidant treatments.     

Changes in Protein Solubility and Gelation Properties of Chicken Myofibrils during Storage

The effect of storage on protein solubility and heat-induced gelation properties of chicken hen breast and leg myofibrils was investigated. Myofibrils suspended in 0.6M NaCl, pH 6.0, showed increasing protein solubility, viscosity, gel strength and water holding capacity with storage at 4°C. However, the effect of storage was most dramatic only during the initial 10 hr for all of the parameters studied. The relative distribution of the proteins comprising the salt soluble protein (SSP) extract changed during storage. Although storage had little effect on breast SSP, it was detrimental to leg SSP gelation. Breast myofibril suspensions, for all storage times, contained a greater amount of SSP and had better gelation properties than leg myofibril suspensions.     

Thermal Aggregation Properties of Duck Salt-Soluble Proteins at Selected pH Values

Thermal aggregation properties of duck breast and leg salt-soluble proteins (SSP) were studied at pH 5.50, 5.75 and 6.00. At pH 5.50, a major transition for breast was observed at 60.3°C and for leg at 41.8°C. At pH 5.75, major transitions at 44.6 and 43.2°C were obtained, respectively, for the breast and leg SSP. Three transitions at 46.0, 53.0 and 59.0°C were exhibited by breast SSP at pH 6.00, whereas only two major transitions at 47.4 and 54.0°C were identified in leg SSP. Changes in transition peak heights and shifts in transition temperatures as a result of pH changes indicated that, depending on fiber type, pH may enhance or suppress the aggregation behavior of specific constituents of the myosin/actomyosin complex, thereby altering the overall aggregation pattern of the protein preparation.     

Insolubilized Whey Protein Concentrate and/or Chicken Salt-Soluble Protein Gel Properties

Properties of gels prepared from five whey protein concentrates (WPC) with protein solubilities ranging from 27.5% to 98.1% in 0.1M NaCl, pH 7.0, chicken breast salt-soluble protein (SSP), or a combination of SSP and WPC at pH 6.0, 7.0 or 8.0 were compared. WPC did not form gels when heated to 65°C. SSP gels heated to 65°C were harder than those heated to 90°C at all pHs and hardness decreased as pH was increased. Hardness of combination gels heated to 65°C increased as WPC solubility decreased at all pHs; however, the opposite trend was observed at 90°C. Combination gels of the same WPC solubility at 65°C were more deformable than those heated to 90°C.     

Viscoelastic Properties of Myofibrillar Protein-Polysaccharide Composite Gels

The influence of polysaccharide gums on thermal gelation of chicken salt-soluble protein (SSP) was studied by determining changes in dynamic: viscoelasticity and aggregation of the protein-gum composites in 0.6M NaCl at pH 6.0. Xanthan gum increased the storage modulus (G') of SSP up to 45°C, but decreased Cl'and inhibited the sol – gel transition at > 45°C. Alginate generally hindered SSP gelation. SSP-gum composite gels cooled to 23°C were weaker but held more water than gels made from SSP alone. Neither gum altered the SSP aggregation pattern, nor the SSP absorption spectra. The inhibition of SSP gelation by both gums appeared mainly due to physical entanglement rather than chemical interactions.     

Gelation of Crude Myofibrillar Protein Isolated From Beef Heart Under Antioxidative Conditions

Oxidation inhibition during washing, as it affects gelling properties and binding strength of beef heart myofibrillar protein, was investigated. Crude myofibrils isolated by repeated washing in the presence of propyl gallate, ascorbate and tripolyphosphate had a lower TBA value and formed stronger gels (puncture and compression strengths) in the pH range 5.8–7.0 and in 0.6M NaCl than the control myofibrils. Inhibition of oxidation increased tensile stress of myofibrillar gels and enhanced bind strength in restructured meat. Functionality of myofibrillar protein could be protected by antioxidants used in the washing process.     

Thermal Transitions of Salt-soluble Proteins from Pre- and Postrigor Chicken Muscles

Salt-soluble protein (SSP) was extracted from pre- and postrigor chicken muscles at various pH values, and protein thermal denaturation was studied using several techniques. Heating at 1°C/min from 20 to 70°C induced a three- to fourfold increase in breast and leg hydrophobicity. Differential scanning calorimetry of breast and leg SSP showed a major transition occurring within the range 55 to 64°C, with the value dependent on rigor state and pH. Protein-protein association, as measured by turbidity change upon heating, underwent two transitions for leg SSP and two or three for breast SSP. The specific transition temperature and rate were dependent on pH, muscle type and rigor state. However, muscle type and pH had a greater effect than muscle rigor state on SSP denaturation.     

Gelation of chicken breast and thigh muscle homogenates: effect of pH and time of aging

Gelation properties of chicken breast and thigh muscle homogenates were studied at various pH values. Breast muscle homogenates showed a greater protein extractability at pH 5.8-6.6 and gel strength at pH 6.3-6.6 than thigh muscle homogenates. At pH 5.8-6.0 breast muscle homogenate gels were weaker than thigh muscle homogenate. The pH for optimum gelation, indicated by the highest stress at failure was 6.3 for breast and 6.0 for thigh muscle homogenates. The pH dependence of chicken breast and thigh muscle homogenate gel strengths, influenced by the muscle fibre type, probably was due to altered protein-protein and other meat component interactions and changes in protein extractability.     

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.     

猪腿纤维蛋白的热致胶凝与功能性质(英文)

本实验探讨了蛋白浓度和 pH 值对猪腿纤维蛋白的溶解度、凝胶强度、蒸煮失重以及热致胶凝性质的影响。在 0.6mol/L、pH6.0 的 NaCl 溶液中,纤维蛋白的胶凝性最强,凝胶强度随着蛋白浓度的增加而增加。然而,蛋白浓度的增加对蒸煮失重和蛋白质溶解度产生不利影响。猪腿纤维蛋白在 4℃贮存一段时间后,其溶解度有所增加。实验结果表明:pH 值对猪腿纤维蛋白的溶解度、凝胶强度、蒸煮失重和粘弹性都有一定的影响。在 pH6.0 时,蛋白的凝胶强度最大,而在 pH7.0 时,蛋白溶解度最大,蒸煮失重最小。     

Functional Properties of Turkey Salt-Soluble Proteins

The functional properties of salt-soluble proteins (SSP) extracted from turkey breast and thigh were determined. Breast and thigh SSP extracts were comprised of similar proteins and there was no difference in the effect of pH and NaCl concentration on solubility. Gels formed in a pH 6.0, 0.5M NaCl phosphate buffer were stable to centrifugation and had the greatest rigidity. Gels formed at pH 7.0 with breast SSP were stable to centrifugation, whereas pH 7.0 thigh SSP gels were not consistently stable. Uniaxial compression was used to determine failure shear stress, failure shear strain and hardness of gels. Breast SSP at 25 mg/mL and 35 mg/mL formed gels suitable for compression analysis, whereas thigh SSP gels of similar concentration were too frail for analysis. Breast SSP had more favorable gelation properties than thigh SSP.     

Thermal Gelation of Brown Trout Myofibrils: Effect of Muscle Type, Heating Rate and Protein Concentration

The thermal gelation properties of myofibril solutions (KCl 0.6M; pH 6.0) from reared brown trout white and red muscles were analyzed by thermal scanning rheometry. With a heating rate of 1°C/min, red muscle myofibrils exhibited a lower gelation capacity than white muscle myofibrils at low temperatures. No difference was observed above 60°C where solid gels were formed from the two myofibril types. Increasing protein concentration or reducing heating rate increased the values of the rheological parameters at 80°C for the two muscle type myofibrils. With a low heating rate (0.25°C/min), white muscle myofibrils formed stronger gels whatever the temperature.     

Myofibrillar Protein Gelation: Viscoelastic Changes Related to Heating Procedures

Dynamic Theological properties were investigated during gelation of chicken myofibrillar protein as influenced by heating procedures, Thermal scan (1°C/min) of myofibril suspensions in 0.6M NaCl (pH 6.0) induced a major transition in storage modulus (G′, peak 48°C), preceded by a transition in protein-protein aggregation (46°C) and accompanied by a marked reduction in actomyosin solubility. Preheating at 50°C diminished the transition and resulted in increased final G′value. Isothermal heating produced complex, temperature-dependent Theological changes (G′and phase angles), particularly within 43–58°C. The rheological transitions of myofibrillar protein were probably related to kinetic changes during formation of elastic gel networks. Such Theological data on gel formation can help predict and control muscle food responses to specific thermal processes.     

不同质量比鸡胸肉、鸡腿肉混合肌原纤维蛋白的热诱导凝胶特性

以鸡胸肉和鸡腿肉为材料,研究鸡胸、鸡腿肉混合肌原纤维蛋白不同质量比(9:1、3:1、1:1、1:3、1:9)热变性温度、质构特性、流变特性和保水性的差异。结果表明：鸡胸肉肌原纤维蛋白的凝胶特性显著优于鸡腿肉,鸡胸肉与鸡腿肉的混合可以显著提升鸡腿肉蛋白的硬度、保水性;混合蛋白中,m鸡胸肉蛋白:m鸡腿肉蛋白为9:1的蛋白硬度、保水性最大,分别达到167.64g和83.6%,其凝胶特性和纯鸡胸肉差异不大;m鸡胸肉蛋白:m鸡腿肉蛋白为1:9的混合蛋白硬度、保水性和贮能模量终值均为最小,分别为110.82g、48.75%和297Pa,其凝胶特性优于纯鸡腿肉肌原纤维蛋白。     

Apparent viscosity of chicken muscle homogenates. Influence of pH and muscle type

The effect of pH and type of muscle on apparent viscosity of chicken breast, thigh and combined B/T muscles was investigated. The apparent viscosity of thigh muscle homogenate at pH from 5.8 to 6.6, and combined B/T muscle homogenate at pH from 5.8 to 6.3 was increasing. The apparent viscosity of breast muscle homogenate increased with pH increase, reaching a maximum at pH 6.3 and then decreased. When pH raised from 5.8 to 6.3, breast muscle homogenate apparent viscosity increased 3.5-6.0 times more than apparent viscosity of thigh muscle homogenate. An increase of combined B/T muscle homogenate apparent viscosity under shear rate 0.3333-48.6 (s-1) was approximately an average of increases for its individual muscles. At pH 5.8 and 6.0, apparent viscosity of thigh muscle homogenate was approximately two times higher than that of breast muscle homogenate, and reversibly, at pH 6.3, breast muscle homogenate apparent viscosity was about 20% higher than that of thigh muscle homogenate. The apparent viscosity of combined B/T muscle homogenate at pH 5.8 and 6.0, was greater than apparent viscosity of breast muscle homogenate, and at pH 6.3, was greater than apparent viscosity of thigh muscle homogenate. The present data extend the results reported by other researches that there are remarkable differences not only in functional and rheological properties of myofibrillar proteins (SSP, myosin) but also in those of homogenates from chicken white and red muscles.