RELATIONSHIPS BETWEEN BINDING QUALITY OF MEAT AND MYOFIBRILLAR PROTEINS V. Effect of 'Setting' and Pyrophosphate on Rheological Properties of Heated Minced-Meat Gel

‘Setting’ was observed in minced hen meat stored with 3.5% wt/wt added NaCl. When gels were made from the ‘set’ sol the breaking energy was greatly increased and the relaxation modulus was characterized by a wide ‘quasi-equilibrium’ region. The effect of added pyrophosphate on the rheological properties of the gel prepared at pH 6.0 from ground ‘set’ sol was very similar to that previously observed for ATP in gels prepared at pH 6.0 from ‘unset’ sols. When pyrophosphate or ATP were added at pH 7.0 to the ‘unset’ minced meat sol, the strain at the breaking point and the ratio of the equilibrium to the instantaneous modulus of the heated gel were increased. A comparison with previous results from a model system suggests that pyrophosphate brings about a change in gel structure by dissociating ‘myosin B’ into myosin A and F-actin.     

螺杆转速对素肉饼质构特性和结构特性的影响

为了改善素肉饼的质构特性,本研究以大豆分离蛋白和谷朊粉为主要原料,调节不同的螺杆转速,经双螺杆挤压机混合高湿挤压、拆丝混料、调味、煎烤等过程制备植物蛋白基素肉饼,分析不同螺杆转速条件下素肉饼的质构特性、微观结构、二级结构、热转变特性和表面疏水性。结果表明,感官评定人员认为螺杆转速为280r/min的条件制备的素肉饼整体可接受程度最大,硬度为1413.33g,咀嚼性为12.95mJ；从结构特性来看,氢键发生断裂,表面疏水作用增强,素肉饼从有序结构向无序结构发生转变,此条件下素肉饼的纤维结构最为明显。     

螺杆转速对持香型仿肉制品结构及挥发性成分保留率的影响

本研究以大豆分离蛋白及谷朊粉为主要原料,以天然呈味粉末油脂为香气调味料,利用高湿挤压技术制备持香型仿肉制品。通过固相微萃取-气相色谱-质谱联用、扫描电子显微镜、核磁共振及傅里叶变换红外光谱分析,确定螺杆转速对持香型仿肉制品挥发性风味物质保留率、微观结构、水分分布、蛋白结构的影响。结果表明挥发性风味物质保留率总体随螺杆转速的增加有先增多后减少的变化趋势,在300 r/min时最大,且仿肉制品较紧密的微观结构、较小的水分子运动自由度及蛋白质二级结构的展开均有利于风味物质的保持。     

EFFECTS OF SALT REDUCTION ON THE RHEOLOGICAL AND GELATION PROPERTIES OF WHITE AND DARK POULTRY MEAT BATTERS

The rheological and gelation properties of poultry dark and white meat batters prepared with average and reduced NaCl levels (2%, 1% and 0%) and with 0.5% hexametaphosphate (HMP) added to the 1% salt batters were studied. Lowering the salt content decreased the shear stress in both the white and dark meat at the same shear rates. HMP addition to the 1% NaCl treatments increased the shear stress in the dark meat but not in the white meat at the same shear rates using a concentric cylinder viscometer. The relationship between the rotor angular velocity and shear stress of the raw batters was nonlinear and resembled a pseudoplastic behaviour with yield stress in all cases. Plots of the modulus of rigidity (G) versus cooking temperature indicated that white meat always exhibited higher G than that of dark meat. The highest G was observed in the white meat with 2.0% NaCl and the lowest in the dark meat with no salt. The batters with no salt also exhibited gel formation, however with lower G values.     

鱼肉面条挤压成形工艺研究

本文介绍了以新冻鱼糜为原料,添加食盐、淀粉等辅料,经斩拌、挤压成形、加热凝胶等工序制作的鱼面挤压成形工艺。选取淀粉添加量、斩拌时间、螺杆转速、凝胶温度为因素,进行了L93^4正交试验,对鱼面拉伸强度、延伸率、溶出率、膨润度等指标进行模糊综合评价。研究表明,鱼面挤压成形工艺的最佳条件为：淀粉量8％、斩拌时间8min、螺杆转速70r/min、凝胶温度85℃。     

γ-聚谷氨酸对鸡肉糜凝胶特性的影响

以鸡胸肉为原料,制备鸡肉糜凝胶,研究不同添加量的γ-聚谷氨酸(γ-polyglutamic acid,γ-PGA)在不同Na Cl添加量条件下对鸡肉糜凝胶特性的影响。研究结果表明:单独添加0.9‰的γ-PGA可以显著降低鸡肉糜凝胶蒸煮损失率,提高凝胶强度和保水性,明显改善凝胶的硬度、弹性、内聚性和咀嚼性,对鸡肉糜凝胶白度值影响较小。在一定Na Cl添加量条件下,γ-PGA对鸡肉糜凝胶特性的改善作用更为明显,且在Na Cl添加量为3.0%、γ-PGA添加量为0.6‰时,鸡肉糜凝胶蒸煮损失率最小,保水性、凝胶强度、硬度、弹性、内聚性和咀嚼性都达到最大值;在Na Cl添加量为3.0%、γ-PGA添加量为1.2‰时鸡肉糜凝胶白度值最小。流变学曲线变化表明,γ-PGA能够提高凝胶的形成能力。通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳研究发现,γ-PGA与蛋白质分子间有一定的交联作用。     

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.     

Influence of sodium chloride and glucose on acid-induced gelation of heat-denatured ovalbumin

ABSTRACT:  We examined the effects of NaCl and glucose on cold-set ovalbumin gelation. Cold-set gels were prepared by adding glucono-δ-lactone (GDL) to a 2% heated ovalbumin solution. For the gel prepared from ovalbumin heat-denatured with NaCl and glucose, the gel with 10 mM NaCl was most transparent and had high gel strength. Its maximum complex shear modulus ( G *) and turbidity were 2.5 times greater and 3 times lower, respectively, than those of the gel without NaCl. The turbidity of the gel with the higher NaCl content increased steeply after the addition of GDL and did not change during the experimental period. The maximum G * of the gel exhibited positive correlations with the molar mass, radius, and surface hydrophobicity of soluble aggregates and the NaCl content, but the turbidity exhibited negative correlations with these factors. The presence of glucose did not significantly affect the turbidity or rheological properties of the gel. For the gel prepared by adding NaCl and glucose with GDL, the presence of glucose did not affect the turbidity, but the maximum G * decreased in inverse proportion to the glucose content. The turbidity of the gel with higher NaCl content (≥ 50 mM) was the greatest among all samples, and the increased turbidity was maintained throughout the measurements. The gels with 50 and 100 mM NaCl exhibited thixotropy during shearing at a constant shear rate. Therefore, the presence of NaCl and glucose during cold gelation could facilitate the preparation of cold-set gels having various properties for food applications.     

Suppression of Surimi Gel Setting by Transglutaminase Inhibitors

Three types of salted meat paste (3% NaCl, 3% NaCl plus 0.66% NH₄Cl or 3% NaCl plus 0.2% EDTA) were prepared from high and second grade surimi, set at 30°C up to 4 br, and subsequently heated at 85°C for 30 min. The gel strength, crosslinking of myosin heavy chain (MHC) and ?-(γ-glutamyl)lysine (?-(γ-Glu)Lys) content were determined. With extended setting time, gel strength, crosslinking of MHC and the content of a crosslinked product, ?-(γ-Glu)Lys, increased markedly in the gel from the high grade surimi. Such changes were suppressed considerably in the presence of NH₄Cl and EDTA and were not observed in the gel prepared from second grade surimi. These results indicated an active participation of intrinsic transglutaminase in the setting process.     

Solid-Phase Extraction of Florfenicol from Meat Samples by a Newly Synthesized Surface Molecularly Imprinted Sol–Gel Polymer

A new molecularly imprinted polymer (MIP) as a solid-phase sorbent for selective extraction of florfenicol (FF) was prepared by combination of the surface molecular imprinting technique with the sol–gel process. The FF-imprinted silica sorbent was prepared using FF as template, 3-aminopropyltriethoxysilane as functional monomer and tetraethoxysilicate as cross-linker on the silica gel support. The non-imprinted silica (NIP) was synthesized in the same way without addition of FF. The MIP was evaluated as a sorbent in column extraction approach for extraction of FF from aqueous solutions followed by spectrofluorometric determination. The influence of certain variables including the sample pH, the sample volume, the sample flow rate, the type of eluent, and its flow rate on the extraction efficiency of FF was assessed. The prepared FF-MIP silica sorbent showed higher adsorption capacity (64.9 mg g^?1) and significant selectivity than the corresponding NIP (11.5 mg g^?1). The FF-MIP-based solid phase extraction method was successfully applied to the separation and determination of FF from fish and chiken meat samples under the optimized extraction conditions.     

Preparation of Transparent Egg White Gel with Salt by Two-step Heating Method

A heat-induced transparent gel from egg white was prepared at low pH and low ionic strength by a one-step heating method. The addition of NaCl to the egg white formed a turbid gel on heating. Egg white, first diluted with water, gave a transparent solution upon heating of this mixture. The solution formed a transparent gel when heated with NaCl up to a concentration of 0.3M for a second time. The transparent gel obtained at 150 mM NaCl was more firm and less adhesive than the turbid gel prepared by the one-step heating method at the same pH, protein concentration, and NaCl concentration.     

高湿挤压技术制备持香型仿肉制品工艺

以大豆分离蛋白和谷朊粉为挤压原料、天然呈味粉末油脂为香气调味料,利用高湿挤压技术制备持香型仿肉制品。通过固相微萃取-气相色谱-质谱联用技术对仿肉制品挥发性风味化合物进行定性定量分析,确定谷朊粉质量分数、水分质量分数、挤压温度及螺杆转速对挥发性风味物质保留率的影响。在单因素试验结果基础上,采用响应面法对高湿挤压工艺制备持香型仿肉制品进行优化,确定高湿挤压最优工艺参数为谷朊粉质量分数20%、挤压温度150?℃、螺杆转速300?r/min,响应值总挥发性风味物质保留率有最优值,为44.07%。而总挥发性风味物质保留率随水分质量分数的增加而减小,为不影响仿肉制品的咀嚼性,固定原料水分质量分数为60%。     

Effect of Sodium Chloride and Osmotic Dehydration on Viscoelastic Properties and Thermal-Induced Transitions of Duck Egg Yolk

The effects of NaCl and osmotic dehydration on the linear viscoelastic behavior of duck egg yolk were evaluated. An increase in NaCl concentrations from 0% to 3.0% (w/w) resulted in a remarkable change in the linear viscoelastic behavior by inducing a sol–gel transition, specifically. The transition was more pronounced when 1.5% (w/w) NaCl was incorporated. The effect of dehydration on aggregation and network formation was predominant than that of the NaCl addition. Nevertheless, at a lower degree of dehydration, the addition of NaCl could modulate the viscoelastic behavior of duck egg yolk, resulting in a well-developed gel network. Addition of NaCl into duck egg yolk could stabilize the protein molecules as evidenced by an increase in denaturation temperature as well as a delay in gel network formation. As visualized by a scanning electron microscope, the denser network with smaller voids was observed in duck egg yolk gel with increasing NaCl concentration and degree of dehydration.     

Rheological and Gelation Properties of Meat Batters Prepared with Three Chloride Salts

The gelation and rheological properties of poultry meat emulsions prepared with three chloride salts (NaCl, KCl, MgCl₂) and 50/50 mixtures of the above salts at isoionic strength (IS = 0.42) were studied. The relationship between shear rate and shear stress for the different raw meat emulsions was found to be nonlinear and followed Bingham pseudoplastic behavior. The yield stress for the emulsion containing only MgCl₂ was significantly lower as compared to all the other treatments. The highest rigidity modulus values obtained during cooking were observed in the NaCl + MgCl₂ treatment followed by the NaCl + KCl, NaCl and KCl. The emulsion containing MgCl₂ only broke down at the initial stages of cooking, exhibiting the destabilizing effect of the magnesium cation.     

Characteristics of Bovine Plasma Gels as Affected by pH Sodium Chloride, and Sodium Tripolyphosphate

A model system, which simulated the pH, sodium chloride (NaCl), and alkaline phosphate (STP) levels of typical processed meat products, was used to determine the effect of NaCl, STP and pH on firmness and percent cooked yield of bovine plasma gels. Bovine plasma gel firmness increased with increasing plasma pH, whereas percent cooked yield was not affected. In contrast, when the pH, of the plasma solutions, was adjusted to a constant 5.6 to simulate the pH and buffering of meat, percent cooked yield was affected; gel firmness was not affected. With increased levels of NaCl and STP, the percent cooked plasma gel yield increased.     

Rheological changes during isothermal holding of salted beef homogenates

The gelation of lean meat homogenates was examined in a thermal scanning rheology monitor, a device that non-destructively measures rigidity and elasticity, as response to a repetitive small movement. Salted (NaCl and pyrophosphate) homogenates were scanned from 10°C to 85°C at 1°C/min, continuously or with an isothermal hold period at 25, 35, 45, 50 or 55°C. The intention of isothermal holding was to visualize key features of the gelation process. Whatever the thermal path, the final properties of the gel were substantially the same. This indicates that heat-mediated gelation follows only one path and is complete by 85°C. The hold at 55°C yielded the most information on gelation. During the hold, gelation was very nearly complete while rigidity steadily increased. This showed that transition from the sol state to the gel and rigidity development are separate events. Samples held at 25°C underwent pH-dependent transitions in rheological properties but at higher hold temperatures these transitions were often not observed. They were caused by a progressive loss of pyrophosphate due to an endogenous pyrophosphatase. The pH and temperature dependencies of the transitions were easily explained by classic enzymology. The enzyme activity could be inhibited by 10 mm NaF. Under these conditions the onset of final gelation occurred at a slightly, but significantly, lower temperature. Models to explain this and another subtle effect of pyrophosphate are presented. At a given pH, although gelation is subtly affected by pyrophosphate, the final rigidity and elasticity are much the same in its presence or absence. Pyrophosphate is in near universal use in salted meat products. Presumably its reported advantages, better water-holding capacity and greater gel strength, are not revealed by the thermal scanning technique.     

Reducing sodium intake from meat products

Sodium intake exceeds the nutritional recommendations in many industrialized countries. Excessive intake of sodium has been linked to hypertension and consequently to increased risk of stroke and premature death from cardiovascular diseases. The main source of sodium in the diet is sodium chloride. It has been established that the consumption of more than 6g NaCl/day/person is associated with an age-increase in blood pressure. Therefore, it has been recommended that the total amount of dietary salt should be maintained at about 5-6g/day. Genetically salt susceptible individuals and hypertensives would particularly benefit from low-sodium diets, the salt content of which should range between 1 and 3g/day. In industrialized countries, meat products and meat meals at home and in catering comprise one of the major sources of sodium, in the form of sodium chloride. Sodium chloride affects the flavour, texture and shelf life of meat products. The salt intake derived from meat dishes can be lowered by, whenever possible, adding the salt, not during preparation, but at the table. In most cases, salt contents of over 2% can be markedly lowered without substantial sensory deterioration or technological problems causing economical losses. Salt contents down to 1.4% NaCl in cooked sausages and 1.75% in lean meat products are enough to produce a heat stable gel with acceptable perceived saltiness as well as firmness, water-binding and fat retention. A particular problem with low-salt meat products is, however, that not only the perceived saltiness, but also the intensity of the characteristic flavour decreases. Increased meat protein content (i.e. lean meat content) in meat products reduces perceived saltiness. The required salt content for acceptable gel strength depends on the formulation of the product. When phosphates are added or the fat content is high, lower salt additions provide a more stable gel than in non-phosphate and in low-fat products. Small differences in salt content at the 2% level do not have marked effects on shelf life of the products. By using salt mixtures, usually NaCl/KCl, the intake of sodium (NaCl) can be further reduced.     

Development of a Test to Predict Gelation Properties of Raw Turkey Muscle Proteins

A method for extraction and fractionation of muscle proteins into five fractions based on salt (NaCl) solubility was developed. The influence of protein extractability, solubility, muscle pH and total protein on gelation was investigated. Shear stress (gel strength) and shear strain (gel deformability) at failure of cooked (70°C) comminuted turkey breast gels were correlated with the 10 min protein extract and proteins soluble in 0.30–0.35M NaCl. Shear strain was correlated with muscle pH and shear stress was sensitive to total protein. Meat pH and the extraction/fraction method can be used on raw meat to indicate functional properties related to texture of cooked meat.     

Sodium Chloride Effect on Autoxidation of the Lard Component of a Gel

SUMMARY: Stable gels composed of lard, sodium carbomethoxy cellulose and water were used for the examination of factors involved in the pro- and antioxidant activities of sodium chloride, other inorganic salts, heme compounds, meat fractions and other additives. Autoxidation processes were evaluated by peroxide and monocarbonyl determinations. The solid translucent gels, in which additives had been incorporated, were stored frozen, freeze-dried or allowed to oxidize without physical change. The hydrated gels were well aerated in preparation and oxidized in the dark at a convenient pace at 20°C. When the gel was freeze-dried, a sponge-like structure was obtained which, after an induction period, autoxidized rapidly. Freezer-stored gels autoxidized at a rate roughly similar to freezer-stored meat. Sodium chloride had a direct pro-oxidant action on the lard of freezer-stored and dehydrated gels. Hydrated gels containing NaCl when stored at 20°C had an inhibiting autoxidation pattern somewhat similar to the quantitative influence of NaCl on pH. Ethylene-diaminetetraacetate (EDJA) had a powerful antioxidant influence. Sodium chloride accelerated heme catalysis regardless of the presence of antioxidant or chelator. Interesting differences in monocarbonyl patterns and monocarbonyl/peroxide ratios as influenced by additives and moisture content of the gels were observed.     

带鱼纯鱼肉重组工艺以及制品蛋白质体外消化的研究

研究了带鱼纯鱼肉的重组工艺。在单因素试验的基础上,在5℃反应温度下,以谷氨酰胺转胺酶用量、作用时间和NaCl用量3个因素为工艺参数,以鱼肉重组制品的凝胶强度为响应值,通过响应面分析对工艺条件进行优化,优化后的工艺条件为:谷氨酰胺转胺酶用量1.25%,作用时间为2.97 h,NaCl用量为1.01%。在优化工艺条件下,鱼肉重组制品的凝胶强度为2 437.41 g.mm,其蛋白质体外消化率为89.14%,稍高于其他实验组。