Effects of Selected Inorganic Phosphates, Phosphate Levels and Reduced Sodium Chloride Levels on Protein Solubility, Stability and pH of Meat Emulsions

The effects were determined of four selected inorganic phosphates at two levels combined with two reduced levels of sodium chloride on the stability, pH, solubilized protein and water-holding capacity of raw meat emulsions. Tetrasodium and tetrapotassium pyrophosphates resulted in higher raw pH, greater protein solubility and improved emulsion stability and water-holding capacity than sodium or potassium tripolyphosphate. Increasing the sodium chloride level from 0.75% to 1.50% decreased the relative effects of phosphate type and level on emulsion stability. The effect of doubling phosphate level on emulsion stability was much less than the effect of doubling the sodium chloride level; however, doubling phosphate level was more effective in increasing pH and soluble protein level of raw emulsions.     

钠盐替代物对全蛋液功能特性的影响

为探究氯化钾和氯化镁替代氯化钠改善全蛋液功能特性的可行性,评估不同浓度的氯化钠（0.2、0.4、0.8 mol/L和1.6 mol/L）、氯化钾（0.2、0.4、0.8 mol/L和1.6 mol/L）和氯化镁（5、10、20 mmol/L和40 mmol/L）对全蛋液理化和功能特性的影响。结果表明：盐的加入显著影响了全蛋液的功能特性。添加0.8 mol/L和1.6 mol/L的氯化钾后,泡沫稳定性分别提高了21.4%和21.6%。添加20 mmol/L和40 mmol/L的氯化镁后,乳化稳定性分别提高了14.7%和24.1%,同时蛋白质的溶解性也提高了12.7%和13.8%。此外,添加40 mmol/L的氯化镁后,全蛋液的凝胶持水性和弹性均未被破坏,硬度显著增高,同时全蛋液的颜色变化程度较低且不会引起全蛋液的pH值出现显著变化。综合来看,氯化镁更具有替代氯化钠改善全蛋液功能特性的潜力。研究结果将为钠盐替代物加入全蛋液中提供理论依据。     

Timed Emulsification Studies with Chicken Breast Muscle: Whole Muscle, Low-Salt Washed Muscle and Low-Salt Soluble Proteins

Emulsion formation with chicken breast muscle was investigated using timed emulsification. Emulsions were made at a fixed oil/water ratio of 2:1 by Omni-mixing for various lengths of time between 0 and 5 min; then the emulsions were centrifuged and the aqueous layer analyzed for protein. Emulsions formed using whole muscle or muscle washed with low molarity salt solution and suspended in buffered (10 mM sodium phosphate, pH 7.0) 0.6M NaCl were superior in stability upon centrifugation to those made with muscle in distilled water, buffered 0.025M NaCl or buffered 0.05M NaCl. Size of insoluble protein pellets from the centrifuged emulsions decreased as emulsification time increased. Little emulsifying effect of the low-salt soluble (sarcoplasmic) protein, defined as those proteins extracted with buffered 0.05M NaCl, was observed in the presence or absence of high-salt solubilized protein.     

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.     

FISH PROTEIN CONCENTRATE AS AN EMULSIFIER

The emulsifying property of solubilized 10% fish protein concentrate (FPC) adjusted to pH 4, 6 or 8 was tested by substituting it for log liquid whole egg in a mayonnaise-type formula. Adjusting the pH to either 6 or 8 favored firmness and fineness and stability of emulsions. Regardless of pH, the emulsions made with 20g of solubilized 10% FPC were significantly (P < 0.05) more stable than those made with 10 or with 30g.     

Some Physical Parameters Involved in the Addition of Inorganic Phosphates to Reduced-Sodium Meat Emulsions

The effects of preblending, order of addition and the physical state of alkaline phosphates on the stability of reduced sodium chloride (0.75%) meat emulsions were determined. Preblending meat batches with reduced sodium chloride for 16 hr resulted in no significant effect upon the stability of meat emulsions, with or without the presence of alkaline phosphates. However, the addition of sodium tripolyphosphate (STPP) and tetrasodium pyrophosphate (TSPP) significantly improved emulsion stability. Neither the order of TSPP addition in relation to that of sodium chloride nor the physical state of its addition (dry or in solution) affected emulsion stability or the soluble protein level.     

Effects of Inorganic Phosphates and Sodium Hydroxide on the Cooked Cured Color, pH and Emulsion Stability of Reduced-Sodium and Conventional Meat Emulsions

Phosphates that increased meat emulsion stability the most also caused the highest decrease in cured color development. The addition of 0.125% sodium hydroxide also reduced cured color development. Holding uncooked emulsions, containing either sodium tripolyphosphate or tetrasodium pyrophosphate, up to 60 min after emulsion preparation plus adding tetrasodium pyrophosphate later in the emulsification procedure improved cured color development upon cooking. In both cases, cooked pH increased as cured color improved, and emulsion stability declined. This suggested that phosphate effects other than, or in addition to, pH were involved in cured color development and emulsion stability.     

Interfacial composition and stability of emulsions made with mixtures of commercial sodium caseinate and whey protein concentrate

The interfacial composition and the stability of oil-in-water emulsion droplets (30% soya oil, pH 7.0) made with mixtures of sodium caseinate and whey protein concentrate (WPC) (1:1 by protein weight) at various total protein concentrations were examined. The average volume-surface diameter (d₃₂) and the total surface protein concentration of emulsion droplets were similar to those of emulsions made with both sodium caseinate alone and WPC alone. Whey proteins were adsorbed in preference to caseins at low protein concentrations (<3%), whereas caseins were adsorbed in preference to whey proteins at high protein concentrations. The creaming stability of the emulsions decreased markedly as the total protein concentration of the system was increased above 2% (sodium caseinate >1%). This was attributed to depletion flocculation caused by the sodium caseinate in these emulsions. Whey proteins did not retard this instability in the emulsions made with mixtures of sodium caseinate and WPC.     

Improvement of stability of oil-in-water emulsions containing caseinate-coated droplets by addition of sodium alginate

ABSTRACT:  The potential of sodium alginate for improving the stability of emulsions containing caseinate-coated droplets was investigated. One wt% corn oil-in-water emulsions containing anionic caseinate-coated droplets (0.15 wt% sodium caseinate) and anionic sodium alginate (0 to 1 wt%) were prepared at pH 7. The pH of these emulsions was then adjusted to 3.5, so that the anionic alginate molecules adsorbed to the cationic caseinate-coated droplets. Extensive droplet aggregation occurred when there was insufficient alginate to completely saturate the droplet surfaces due to bridging flocculation, and when the nonadsorbed alginate concentration was high enough to induce depletion flocculation. Emulsions with relatively small particle sizes could be formed over a range of alginate concentrations (0.1 to 0.4 wt%). The influence of pHs (3 to 7) and sodium chloride (0 to 500 mM) on the properties of primary (0 wt% alginate) and secondary (0.15 wt% alginate) emulsions was studied. Alginate adsorbed to the droplet surfaces at pHs 3, 4, and 5, but not at pHs 6 and 7, due to electrostatic attraction between anionic groups on the alginate and cationic groups on the adsorbed caseinate. Secondary emulsions had better stability than primary emulsions at pH values near caseinate's isoelectric point (pHs 4 and 5). In addition, secondary emulsions were stable up to higher ionic strengths (< 300 mM) than primary emulsions (<50 mM). The controlled electrostatic deposition method utilized in this study could be used to extend the range of application of dairy protein emulsifiers in the food industry.     

Formation and Coalescence Stability of Emulsions Stabilized by Different Milk Proteins

The volume fraction of oil emulsified, surface area, droplet diameter, and coalescence rates of emulsions stabilized by different milk proteins were studied at protein concentrations of 0.25, 0.5, 1.0, and 2.0% (w/w); pH 4, 5, and 7; and ionic strengths 0.1 and 0.2. The emulsion activity index (EAI) and coalescence stability generally increased with increasing protein solubility and hydrophobicity. The volume fraction of oil emulsified decreased with increasing ionic strength. Coalescence stability correlated with droplet diameter for emulsions stabilized by α-lactalbumin, β-lactoglobulin, and sodium caseinate (r²=0.96). With the exception of β-lactoglobulin-stabilized emulsions, coalescence stability was largely unaffected by pH.     

Calcium-Induced Destabilization of Oil-in-Water Emulsions Stabilized by Caseinate or by β-Lactoglobulin

The stability to aggregation of 20% soya oil-in-water emulsions stabilized by 0.3 to 2% sodium caseinate or β-lactoglobulin in the presence of calcium chloride solutions was studied using light scattering and electron microscopy. Stability increased with the amount of protein in the emulsion, and decreased with the concentration of added calcium. Growth of particle size with concentration of Ca²⁺ was more in emulsions containing lower concentrations of protein. Sodium chloride at 50 and 100 mM stabilized both systems to the presence of calcium ions. Microstructure and light scattering showed caseinate emulsions formed clusters even at low concentrations of Ca²⁺ while β-lactoglobulin emulsions formed extensive strands.     

The effects of salt concentration and pH upon water-binding, water-holding and protein extractability of turkey meat

The effects of salt concentration and pH upon protein extractability and water-binding by homogenates of turkey breast, thigh and drumstick meat, and also the effect of salt concentration and centrifugal force upon water-binding of raw meat and water-holding of cooked meat from breast and thigh were studied. Concentrations of sodium chloride above 0.3 M caused swelling of meat homogenates. With the pH value adjusted to 6.0 and with sodium chloride concentrations greater than 0.6 M, breast meat was able to swell more than leg meat. Water-binding increased with increasing pH value. Breast meat homogenates had more extractable protein than leg meat homogenates and protein extraction was increased by increasing both salt concentration and pH. Cooked breast meat retained more water than leg meat with or without salt. At low concentrations of salt, cooked breast meat retained more water than raw meats, but this was reversed at higher salt concentrations.     

Physico-chemical and sensory properties of reduced-fat mortadella prepared with blends of calcium, magnesium and potassium chloride as partial substitutes for sodium chloride

Blends of calcium, magnesium and potassium chloride were used to partially replace sodium chloride (50-75%) in reduced-fat mortadella formulations. The presence of calcium chloride reduced the emulsion stability, cooking yield, elasticity and cohesiveness and increased hardness; however, it yielded the best sensory acceptance when 50% NaCl was replaced by 25% CaCl(2) and 25% KCl. There was no effect of the salt substitutes on mortadella color, appearance and aroma. All salt combinations studied showed stable lipid oxidation during its shelf life. The use of a blend with 1% NaCl, 0.5% KCl and 0.5% MgCl(2) resulted in the best emulsion stability, but the worst scores for flavor. This study suggests that it is possible to reduce the sodium chloride concentration by 50% in reduced-fat mortadella using the studied salt combinations with necessary adjustments to optimize the sensory properties (MgCl(2) 25%; KCl 25%) or emulsion stability (CaCl(2) 25%; KCl 25%).     

Composition, Solubility and Emulsifying Properties of Granules and Plasma of Egg Yolk

Yolk was fractionated by a low speed centrifugation into granules and plasma. The composition, solubility and emulsifying properties of granules and plasma were compared to those of industrial spray-dried yolk. Granules contained about half the lipids and cholesterol and about double the proteins of yolk and plasma. Yolk and granules required an ionic strength ≥ 0.3M sodium chloride to become solubilized at pH 7.0, whereas plasma was solubilized at any ionic strength. At about 80% solubility, yolk, granules and plasma had similar emulsifying activities and granules had the best emulsion stabilization. Results suggest that granules could be used as stabilizers in food emulsions.     

Encapsulation of emulsified tuna oil in two-layered interfacial membranes prepared using electrostatic layer-by-layer deposition

Tuna oil-in-water emulsions (5 wt% tuna oil, 100 mM acetate buffer, pH 3.0) containing droplets stabilized either by lecithin membranes (primary emulsions) or by lecithin–chitosan membranes (secondary emulsions) were produced. The secondary emulsions were prepared using a layer-by-layer electrostatic deposition method that involved adsorbing cationic chitosan onto the surface of anionic lecithin-stabilized droplets. Primary and secondary emulsions were prepared in the absence and presence of corn syrup solids (a carbohydrate widely used in the micro-encapsulation of oils) and then their stability to environmental stresses was monitored. The secondary emulsions had better stability to droplet aggregation than primary emulsions exposed to thermal processing (30–90 °C for 30 min), freeze-thaw cycling (−18 °C for 22 h/30 °C for 2 h), high sodium chloride contents (200 mM NaCl) and freeze-drying. The addition of corn syrup solids decreased the stability of primary emulsions, but increased the stability of secondary emulsions. The interfacial engineering technology used in this study could lead to the creation of food emulsions with novel properties or improved stability to environmental stresses.     

Preparation and functional properties of protein coprecipitate from sheep milk

The optimum conditions for the production of coprecipitate from sheep milk were studied. The best percentage of calcium chloride added to milk was 0.2%, which resulted in a recovery of 97.5% of milk proteins. At low pH (4.5–5), the recovery of protein was low, but it increased at higher pH values (5.5–6.5); recovery was greatest at pH 6.5. The optimum heating temperature to obtain coprecipitate from sheep milk was 85–95°C. The functional properties of the sheep milk coprecipitate were studied. At pH values higher than 6, there were no differences between the solubility of sheep milk coprecipitate and sheep milk sodium caseinate, but the solubility of coprecipitate at pH values lower than 5 was relatively higher than those of the caseinate. At pH ≥6, the emulsion activity index (EAI) for emulsions of sheep milk coprecipitate and caseinate increased as pH increased; at all pH values, the EAI of the coprecipitate was higher than that of the caseinate. Sheep milk coprecipitate showed higher foaming ability and stability than sheep milk sodium caseinate.     

双蛋白纳米颗粒Pickering乳液的构建及稳定性研究

为获得稳定性较好的蛋白基Pickering乳液,实验采用pH循环法以绿豆蛋白和乳清蛋白为原料制备双蛋白纳米颗粒并进行表征,进一步以此为基质制备Pickering乳液,并对Pickering乳液微观结构、粒径及流变学等进行表征,同时探讨了乳液的加工稳定性。结果：获得了粒径为100~250 nm的蛋白纳米颗粒;其制备的Pickering乳液为水包油型,且具有良好稳定性;与单一蛋白纳米颗粒乳液比较,双蛋白纳米颗粒乳液的乳化特性及其本身的稳定性有所提高。乳液的流变学说明乳液出现了剪切稀化现象,形成了凝胶网络结构。随着双蛋白中乳清蛋白比例的增加,乳液粒径减小,稳定性增加。因此,双蛋白制备的纳米颗粒Pickering乳液理化性质得到改善。研究结果可为混合蛋白构建稳定的乳液体系及活性成分的递送提供参考。     

UTILIZATION OF MINCED SUCKER FLESH

Freshwater suckers (Catostamidae family) were obtained from Lake Huron to study the possibility of developing new products utilizing its flesh and the influences of additives on the functionality of sucker muscle proteins. Results showed that sodium chloride increased protein solubility, but also decreased swelling, gel forming and pH. In comparison, sodium tripolyphosphate increased protein solubility, pH, swelling and gel formation. Fish sausages and canned products showed low binding characteristics. However, adding corn meal and soy protein in combination with sodium chloride and sodium tripolyphosphate improved their water holding capacity, texture and cook yield. It was concluded that sodium tripolyphosphate, corn meal and fat should be used in manufacturing minced sucker products.     

去骨凤爪凝胶特性影响因素的研究

以市售凤爪为原料,建立凤爪凝胶特性的综合评价指标,研究压力、pH、氯化钠添加量和柠檬酸钙添加量对去骨凤爪凝胶强度、弹性、脆度和持水率的影响。试验结果表明：四个单因素均能显著提高凤爪的凝胶性能。各因素对去骨凤爪凝胶特性综合指标影响的主次顺序为：氯化钠添加量〉柠檬酸钙添加量〉压力〉pH。由正交试验结果表明去骨凤爪凝胶特性最佳的组合为：500MPa压力下保压25min、pH4.0、氯化钠添加量为1.0%,柠檬酸钙添加量为0.04%。在此组合下,去骨凤爪凝胶特性最好,综合指标为94.765。     

玉米醇溶蛋白/乳清蛋白纤维核复合纳米粒稳定 Pickering乳液的制备与性质

以玉米醇溶蛋白和乳清蛋白为原料,利用反溶剂共沉淀法制备玉米醇溶蛋白/乳清蛋白纤维核复合纳米粒,并与玉米油高速剪切制备Pickering乳液。探究了复合纳米粒在不同pH下的乳化性,以及复合纳米粒添加量对Pickering乳液粒径、微观形貌、储藏稳定性及流变学特性的影响。结果表明：玉米醇溶蛋白与乳清蛋白纤维核复合后乳化性显著提高,制备的Pickering乳液类型为水包油型;随着复合纳米粒添加量的增加,Pickering乳液粒径先减小后稍增大,添加量大于3 g（100 mL玉米油）后无显著性差异;在复合纳米粒添加量为4 g（100 mL玉米油）时,Pickering乳液油滴大小均一,储藏稳定性最好;Pickering乳液为假塑性流体,随复合纳米粒添加量的增加,表观黏度先减小后增大。