Solubility of Salmon Myosin as Affected by Conformational Changes at Various Ionic Strengths and pH

The relationship between solubility and conformational changes of salmon ( Oncorhynchus tshawytscha ) myofibrillar proteins at various ionic strengths and pH was investigated using myosin as a model system. Solubility of myosin increased with increased KCl concentration up to 0.5M. Further increasing salt concentration resulted in a gradually reduced solubility. In the absence of salt, myosin was slightly soluble at pH>7 or <4. The increased solubility correlated with the increased surface hydrophobicity and relative sulfhydryl content as well as the decreased α-helicity. At KCl >1.0M, myosin regained its helix structure with a concomitant loss of solubility due to the dominant hydrophobic interaction among nonpolar amino acid residues.     

Thermal Stability and Gel-Forming Ability of Shark Muscle as Related to Ionic Strength

Thermal stability and gel-forming ability of silvertip, hammer-head and thresher shark as affected by ionic strength were investigated. Low temperature endothermic peaks (LTEP, between 30 and 44°C) were observed in differential scanning calorimetric (DSC) thermograms of the shark muscles and surimi samples. Increases in ionic strength reduced the thermal stability of surimi as shown by depression of transition temperature, denaturation enthalpies and LTEP. Although gel strength of heat-treated surimi increased with increasing NaCl concentration, the three species had different sensitivities to ionic strength. The highest NaCl-induced gel-forming ability of surimi was achieved at 0.5M salt concentration for silvertip and thresher; at 1.0M for hammer-head shark.     

Effects of Chloride Salts on Appearance, Palatability, and Storage Traits of Flaked and Formed Beef Bullock Restructured Steaks

Restructured steaks made with 0.5 or 1.0% KCl, 0.5% MgCl₂ and 0.5% CaCl₂ were more desirable and darker red in raw color than blends formulated with 0.5 or 1.0% NaCl. Visual properties of raw steaks containing 0.5 or 1.0% chloride salt were scored higher than the control (no salt added) in 14 of 16 orthogonal contrast mean comparisons. Steaks made with 1.0% CaCl₂ or MgCl₂ were rated lower than the control in flavor desirability and overall satisfaction ratings. Control, 0.5 or 1.0% NaCl or 0.5 and 1.0% KCl steaks were not different in juiciness, tenderness, flavor desirability or overall satisfaction ratings. Steaks made with chloride salts were rancid after 70 days frozen storage. Results showed steaks made with KCl were superior to steaks formulated with CaCl₂ or MgCl₂.     

Sodium Chloride (0.8 M) as a Better Protein Extractant for Fish Meat Quality Assessments

The extractability of proteins by NaCl, KCl, and LiCl as affected by different ionic strengths and pH was compared to determine the best protein extractant. The individual proteins in the extracts were identified by electro‐phoresis. The optimum ionic strength (IS) at pH 7.0 for the protein extractability (PE) of NaCl, KCl, and LiCl were 0.8, 0.9, and 1.0, respectively. The PE of NaCl and KCl declined as pH changed from 6.0 to 8.0, whereas an opposite effect was observed for the LiCl. The NaCl had the highest PE, followed by LiCl and KCl. The maximum number of proteins (15 bands) was found at the optimum IS of each salt. However, the resolution and clarity of the protein bands were better in the NaCl extracts.     

The effects of high salt and low pH on the water-holding of meat

The study investigated the water-holding (WH) in meat in the pH–NaCl (ionic strength) combinations that prevail in dry sausages during fermentation and drying. WH in raw beef homogenates, with 230% added water, was determined by centrifugation at pH values of 5.47–4.60, and ionic strengths (μ) 0.50–1.50. The minimum WH in relation to pH was at pH 4.8, but at higher pH values, the WH optimum was at 1.0–1.5 μ; at lower pH-values (< 5.0) the optimum was more pronounced at 1.0 μ. The WH reducing effect by pH decrease was stronger than the effect of μ. At lower pH values, the relative effect of μ on WH was higher compared to that of pH than at higher pH values. The pH–salt combinations prevailing in fermented sausage in the beginning of the ripening produced a high WH, which decreased, first with pH decrease and then in the last period of ripening mainly due to the increase of ionic strength.     

Comparison between reconstituted and fresh skim milk chemical and electrochemical acidifications

The aim of this study was to compare the electrochemical and chemical acidification of reconstituted and fresh skim milk in terms of electrodialytic parameters, precipitation kinetics, chemical composition and physicochemical and functional properties of isolates produced by bipolar membrane electro acidification (BMEA). The electrodialytic parameters were not influenced by the type of milk when both milks were compared at a similar protein and salt content. The difference in precipitation kinetics observed between the two milks, whatever the acidification procedure, can be explained mainly by a difference in salt content. Isolates produced by BMEA showed similar physicochemical and functional properties (except for foaming capacity) to isolates produced chemically. The main factor affecting the composition and the physicochemical and functional properties was the pre‐treatment of milk prior to acidification: it had a higher impact on the functional properties than the acidification treatment itself. Copyright © 2002 Crown in the right of Canada. Published for SCI by John Wiley & Sons, Ltd     

Binding of Meat Pieces: Influence of Some Processing Factors on Binding Strength and Cooking Losses

Evacuation of the chamber of the press used to form flaked beef into a restructured meat product (patty) did not affect the binding strength of the cooked patty but under some conditions decreased the cooking loss. In studies using patty mixes containing 0–1.0% added sodium chloride, meat binding strength increased with decrease in the temperature of the mix when formed into patties over the temperature range - 1° to -5°C. The largest effect generally occurred between - 1° and -2°C. However, the effect was only noted in patties that were frozen (-30°C) before being cooked for assessment. With decrease below - 1°C of the temperature of patties when pressed, cooking losses increased for the patties without added salt but decreased for those with added salt (0.5% or 1%). Change in the pressure applied to form the patty (in the range 1.4–13.7 MPa) can affect binding strength.     

Thermal gelation of brown trout myofibrils from white and red muscles: effect of pH and ionic strength

The effects of pH and ionic strength on the thermal gelation of brown trout myofibrils from white and red muscles were analysed by thermal scanning rheometry. The highest gelation ability was obtained at low pH (around 5.6) whatever the ionic strength. No effect of ionic strength was observed at pH 5.6; however, at pH 6.0, lowering the salt (KCl) concentration to 0.3 M or less improved the characteristics of the gels formed. The effects of pH and ionic strength on myofibrils from both muscle types appeared to be similar, but red muscle proteins were less sensitive to changes in their physicochemical environment. Consequently, the differences between muscle types appeared to be dependent on pH and ionic strength. Solubility measurements revealed large differences between muscle types and between different pH values. Ultrastructural observations confirmed that different kinds of gels were formed depending on the physicochemical conditions and muscle type origin. © 2002 Society of Chemical Industry     

Ionic Strength Effects on Heat-induced Gelation of Myofibrils and Myosin from Fast- and Slow-twitch Rabbit Muscles

The effects of ionic strength on myofibrils and myosin from rabbit fast-twitch Psoas major (PM) and slow-twitch Semimembranosus proprius (SMp) muscles before and after heating were studied by electron microscopy and thermal scanning rheometry. The direct suspension of proteins in low ionic strength (0.2M KCl; pH 6.0) led to very weak gels, whereas a gradual lowering of the ionic strength (by dialysis against 0.2M KCl; pH 6.0) of 0.6M KCl protein solutions induced strand-type networks at low temperature and strong heat-induced gels. As shown by transmission and scanning electron micrographs, in low ionic strength, SMp myosins formed shorter filaments before heating and thinner and shorter structures in heat-induced gels, as well as a lower gel porosity than PM myosins.     

Dynamic rheological behaviour and biochemical properties of rabbit skeletal actomyosin during storage at 0° C

The relationship between the dynamic rheological properties of heat induced gels of actomyosin (natural actomyosin) and the denaturation of actin in actomyosin during storage without ATP at pH 6.0 and 0°C was investigated using biochemical and dynamic rheological measurements. The complex modulus of gels after heating actomyosin containing 0.5 or 1.5 M KCl (pH 6.0) at 80°C increased with increasing storage time. The dynamic rheological behaviour during heat gelation of actomyosin in 1.5 M KCl indicated that the first rheological transition peak in the 50–53°C range induced by the presence of F-actin gradually disappeared with increasing storage time. However, in 0.5 M KCl, this transition peak clearly remained even after 15 days. The time course of denaturation of actin in actomyosin treated with 1.5 M KCl at pH 6.0 showed an increase in the percent denaturation after the storage was started, and about 100% of the actin became denatured after 21 days. In the case of 0.5 M KCl, unlike 1.5 M, the denaturation of actin occurred quickly within the first 5 days and then did not proceed. A sigmoidal relationship was found between the percent denaturation of actin and the KCl concentration added, the greatest change occurring at KCl concentrations between 0.5 and 1.0 M. The data indicated that the change in the property of actin in actomyosin during storage at low temperature exerts a great influence on the viscoelasticity of heat-induced gels of actomyosin.     

Ionic strength-induced formation of smectite quasicrystals enhances nitroaromatic compound sorption

Sorption of organic contaminants by soils is a determinant controlling their transport and fate in the environment. The influence of ionic strength on nitroaromatic compound sorption by K+- and Ca2+ -saturated smectite was examined. Sorption of 1,3-dinitrobenzene by K-smectite increased as KCl ionic strength increased from 0.01 to 0.30 M. In contrast, sorption by Ca-smectite at CaCl2 ionic strengths of 0.015 and 0.15 M remained essentially the same. The "salting-out" effect on the decrease of 1,3-dinitrobenzene aqueous solubility within this ionic strength range was <1.5% relative to the solubility in pure water. This decrease of solubility is insufficient to account for the observed increase of sorption by K-smectite with increasing KCl ionic strength. X-ray diffraction patterns and light absorbance of K-clay suspensions indicated the aggregation of clay particles and the formation of quasicrystal structures as KCI ionic strength increased. Sorption enhancement is attributed to the formation of better-ordered K-clay quasicrystals with reduced interlayer distances rather than to the salting-out effect. Dehydration of 1,3-dinitrobenzene is apparently a significant driving force for sorption, and we show for the first time that sorption of small, planar, neutral organic molecules, namely, 1,3-dinitrobenzene, causes previously expanded clay interlayers to dehydrate and collapse in aqueous suspension.     

KCl复配5’-肌苷酸二钠替代钠盐对鱼糜凝胶特性的影响

为研制低盐鱼糜,探究食盐替代物KCl和5’-肌苷酸二钠（inosine 5’-monophosphate disodium salt,IMP）对鱼糜凝胶品质的影响,以鲢鱼鱼糜为研究对象,设计3 组实验,A组添加2.0% NaCl,B组添加0.8% KCl和1.2% NaCl,C组添加0.7% KCl、0.1% IMP和1.2% NaCl,通过测定鱼糜凝胶的白度、持水性、强度、质构、水分分布与组成以及微观结构变化,探究NaCl的最佳替代方案。结果表明：相比于A组,B组鱼糜凝胶白度、持水性、强度变低,硬度、胶着性、咀嚼性、内聚性显著降低,弹性无显著变化,不易流动水含量减小、自由水含量升高,凝胶网络空间结构形成不完全;C组鱼糜凝胶除咀嚼性显著下降外,其余指标未发生显著劣变,说明KCl和IMP复配是一种理想的NaCl替代方案。     

Heat-induced Gelation of Chicken Gizzard Myosin

Chicken gizzard myosin solution formed a gel when heated above 40°C. The rigidity of the gel was constant above 65°C. Maximum pH for gel formation was 5.9 at 0.6M and 5.7 at 0.15M KCl. Higher rigidity of the myosin gel was observed at low ionic strength than at high ionic strength. Rigidities of myosin at 0.6M KCl increased by (mg/mL)^2.5 and at 0.15M (mg/mL)^{1, 4} myosin concentration. The strength of gizzard myosin gels was comparable to that of myosin gels from chicken breast muscle under similar conditions.     

组氨酸与氯化钾混合液对兔肉肌球蛋白特性的影响

目的：研究组氨酸与氯化钾混合液对肌球蛋白溶出率、聚集特性和热凝胶特性的影响。方法：提取纯化兔腰大肌肌球蛋白,并用含有组氨酸的盐溶液透析处理,测定不同离子强度条件下蛋白溶出率、浊度以及热诱导凝胶的硬度和保水性（water holding capacity,WHC）。结果：经组氨酸处理后,在低离子强度（1 mmol/L KCl）条件下肌球蛋白的溶出率从17.2%提高到64.4%,聚集程度显著下降,热凝胶的硬度和保水性显著提高（P＜0.05）;而在生理离子强度（0.15 mol/L KCl）和高离子强度（0.6 mol/L KCl）条件下肌球蛋白的溶出率和聚集特性均未受组氨酸处理的影响,但其热凝胶硬度值显著降低（P＜0.05）;虽然在高离子强度条件下肌球蛋白热凝胶的保水性显著降低（P＜0.05）,但是在生理离子强度条件下凝胶保水性没有发生变化。结论：组氨酸处理可以显著增强低离子强度条件下肌球蛋白溶出率和其热凝胶形成能力,是低钠凝胶类肉制品生产和研发的一个新思路。     

HEAT-INDUCED GELATION OF MYOSIN IN THE PRESENCE OF ACTIN

ABSTRACT The rabbit muscle contractile proteins, myosin, actin and reconstituted actomyosin were mixed in 0.1–1.0 M KCl, 20 mM buffers, pH 5.0–8.0, and were tested quantitatively for thermally induced gelation properties by measuring the rigidity (shear modulus) of the system at 20–70°. Scanning electronmicroscopy (SEM) was also used to study the structure of the gels formed by gelation of myosin in the presence of F-actin. Under the standard condition, i.e. at 0.6 M KCl, pH 6.0 and 65°, decrease of the myosin/actin mole ratio to about 1.5–2.0 in the reconstituted acto-myosin system resulted in substantial augmentation of the rigidity of the gel formed. Further decreases in the myosin ratio relative to F-actin reduced the rigidity value of the gel to close to the level of myosin alone. Gel-formability of the reconstituted actomyosin was maximal at pH 5.5–6.0 and between 0.5 and 0.8 M KCl and decreased considerably at other pH values and KCl concentrations. The SEM studies revealed progressive changes in three dimensional ordering as actin concentration in the actomyosin varied. These were in concordance with the results of gel strength.     

Gamma-Irradiation of CIostridium botulinum Inoculated Turkey Frankfurters Formulated with Different Chloride Salts and Polyphosphates

The effects of gamma-irradiation doses (0, 0.5, and 1.0 Mrad) on C. botulinum toxin production in turkey frankfurters formulated with three different chloride salts (NaCl, KCl, and MgCl₂) at isoionic strength (equal to 2.5% NaCl) and three types of phosphates added to 2.0% NaCl frankfurters were studied. The use of 2.5% NaCl together with 0.5 or 1.0 Mrad was substantially more effective at inhibitinlg botulinal toxin production when frankfurters were incubated at 27°C than the combination of irradiation with KCl or MgC1₂ (40, 9, and 4 days, respectively, when treated with 1 Mrad). Phosphate addition revealed that 0.4% sodium acid pyrophosphate addition was the most inhibitory for botulinal toxin production followed by hexametaphosphate and tripolyphosphate addition.     

Chloride salt type/ionic strength, muscle site and refrigeration effects on antioxidant enzymes and lipid oxidation in pork

The effects of NaCl and KCl at varying ionic strengths on catalase and glutathione peroxidase (GSH-Px) activities and lipid oxidation in refrigerated ground pork muscles from different anatomical locations were studied. Catalase and GSH-Px activities were higher in boston butt (BB) than in longissimus dorsi (LD), whereas lipid oxidation measured by 2-thiobarbituric acid substances (TBARS) content was higher in LD. Catalase activity was stable in both BB and LD during 4-day storage; GSH-Px activity decreased in LD. GSH-Px activity decreased more with NaCl than KCl, whereas salt type had no consistent effect on catalase activity. TBARS content, however, increased more with NaCl than with KCl. NaCl at the highest ionic strength decreased GSH-Px activity by 19.2 and 18% in LD and BB, respectively, and increased TBARS content by 8- and 3.6-fold. Results indicated that pork samples with higher catalase and GSH-Px activities would undergo less lipid oxidation, and the accelerated lipid oxidation in salted pork may be partly related to a decrease in GSH-Px activity.     

Effect of Salt Reduction on the Yield, Breaking Force, and Sensory Characteristics of Emulsion-Coated Chunked and Formed Ham

The effect of a modified processing procedure (emulsion coating) on the characteristics of ham with reduced sodium chloride (salt) content was investigated. Emulsion coated (EC) and conventionally processed (CP) chunked and formed hams were prepared with 0.5, 1 and 2% added salt. When compared to CP hams, EC hams had increased cooking yield, breaking force, moisture retention, juiciness, texture, tenderness, and taste panel acceptability. The EC 1.0% salt treatment closely resembled the CP 2.0% salt treatment. The EC 0.5% salt product had many similarities to the CP 1.0% salt treatment but was significantly different in many attributes from the CP 2% salt product. Reducing salt in chunked and formed ham from 2.0% added salt addition to levels as low as 1.0% appears possible when combined with emulsion coating to minimize the effects of salt reduction.     

基于人体必需金属盐替代的低钠盐肌原纤维蛋白凝胶特性和作用机理

为降低肌原纤维蛋白凝胶中钠盐的使用量,研究不同氯盐(CaCl₂、MgCl₂、KCl)部分替代NaCl对肌原纤维蛋白凝胶性质包括强度、微观结构、持水力和流变学性质的影响,并通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、内源性荧光光谱、表面疏水性、巯基含量等技术手段阐明其作用机理。结果表明,3种氯盐替代效果排序为KCl>CaCl₂>MgCl₂。0.5%～1.5%质量分数的盐替代范围内,KCl替代组的凝胶强度优于对照组(3%NaCl),持水力与对照组相比无显著差异(P>0.05);Ca Cl₂替代组的凝胶强度在1.5%替代质量分数时显著下降(P<0.05),持水力呈先下降后上升趋势;MgCl₂替代组凝胶强度显著降低(P<0.05),持水力上升。在流变学性质方面,不同质量分数KCl替代组的储能模量明显高于对照组。CaCl₂和MgCl₂的替代使肌原纤维蛋白表面疏水性增大、巯基含量减少,3种氯盐的替代...     

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.