Effect of Aqueous Phase Composition on Stability of Sodium Caseinate/Sunflower oil Emulsions

The aim of the present work was to investigate the effect of aqueous phase composition on the stability of emulsions formulated with 10 wt% sunflower oil as fat phase. Aqueous phase was formulated with 0.5, 2, or 5 wt% sodium caseinate, or sodium caseinate with the addition of two different hydrocolloids, xanthan gum or locust bean gum, both at 0.3 or 0.5 wt% level or sodium caseinate or with addition of 20 wt% sucrose. Emulsions were processed by Ultra-Turrax and then further homogenized by ultrasound. Creaming and flocculation kinetics were quantified by analyzing the samples with a Turbiscan MA 2000. Emulsions were also analyzed for particle size distribution, microstructure, viscosity, and dynamic surface properties. The most stable systems of all selected in the present work were the 0.3 or 0.5 wt% XG or 0.5 wt% LBG/0.5 wt% NaCas coarse emulsion and the 20 wt% sucrose/5 wt% NaCas fine emulsion. Surprisingly, coarse emulsions with the lower concentration of NaCas, which had greater D _4,3, were more stable than fine emulsions when the aqueous phase contained XG or LBG. In these conditions, the overall effect was less negative bulk interactions between hydrocolloids and sodium caseinate, which led to stability. Sugar interacted in a positive way, both in bulk and at the interface sites, producing more stable systems for small-droplet high-protein-concentration emulsions. This study shows the relevance of components interactions in microstructure and stability of caseinate emulsions.     

Effect of a new emulsifier containing sodium stearoyl-2-lactylate and carrageenan on the functionality of meat emulsion systems

The emulsion capacity and stability of a new emulsifier containing sodium stearoyl lactylate plus iota carrageenan (SSL/iC) in comparison to caseinate and soy isolate was analysed. The emulsion capacity and stability of SSL/iC in oil/water (O/W) model system emulsions was higher than shown by caseinate and soy isolate. However, the O/W emulsion stability was negatively affected by sodium chloride addition, but positively affected by an increase in temperature. Meat batters were made with caseinate, soy isolate, and SSL/iC at the minimum concentration that showed a good performance (>75% stability) in the O/W emulsions. The emulsifier SSL/iC produced high cook yields and good stability when used in meat batters. However, the cooked meat batters containing SSL/iC showed texture characteristics highly detrimental to the sensory analysis. On the other hand, the addition of 2% potato starch reduced the differences in texture parameters among the samples made with the different emulsifiers.     

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.     

Cross-linking proteins by laccase: Effects on the droplet size and rheology of emulsions stabilized by sodium caseinate

The aim of this work was to evaluate the influence of laccase and ferulic acid on the characteristics of oil-in-water emulsions stabilized by sodium caseinate at different pH (3, 5 and 7). Emulsions were prepared by high pressure homogenization of soybean oil with sodium caseinate solution containing varied concentrations of laccase (0, 1 and 5 mg/mL) and ferulic acid (5 and 10 mM). Laccase treatment and pH exerted a strong influence on the properties with a consequent effect on stability, structure and rheology of emulsions stabilized by Na-caseinate. At pH 7, O/W emulsions were kinetically stable due to the negative protein charge which enabled electrostatic repulsion between oil droplets resulting in an emulsion with small droplet size, low viscosity, pseudoplasticity and viscoelastic properties. The laccase treatment led to emulsions showing shear-thinning behavior as a result of a more structured system. O/W emulsions at pH 5 and 3 showed phase separation due to the proximity to protein pI, but the laccase treatment improved their stability of emulsions especially at pH 3. At pH 3, the addition of ferulic acid and laccase produced emulsions with larger droplet size but with narrower droplet size distribution, increased viscosity, pseudoplasticity and viscoelastic properties (gel-like behavior). Comparing laccase treatments, the combined addition of laccase and ferulic acid generally produced emulsions with lower stability (pH 5), larger droplet size (pH 3, 5 and 7) and higher pseudoplasticity (pH 5 and 7) than emulsion with only ferulic acid. The results suggested that the cross-linking of proteins by laccase and ferulic acid improved protein emulsifying properties by changing functional mechanisms of the protein on emulsion structure and rheology, showing that sodium caseinate can be successfully used in acid products when treated with laccase.     

Lipid and water crystallization in protein-stabilised oil-in-water emulsions

Phase and state transitions occurring during freezing and thawing of oil-in-water emulsions with different water phase formulations, interfacial compositions and two lipid types were studied as crucial factors affecting emulsion stability. Emulsions containing 0–40% (w/w) sucrose in the water phase at pH 7, and 10, 20, 30, 40% (w/w) dispersed lipid phase (sunflower oil, SO or hydrogenated palm kernel oil, HPKO) with whey protein isolate, WPI, or sodium caseinate, NaCAS, (protein:lipid = 1:10 and 2:10) as emulsifier were prepared. Phase/state behaviour of the continuous and dispersed phases was determined by differential scanning calorimetry (DSC). Emulsion stability and morphology were derived from DSC data, gravitational separation and particle size analysis during 4 freeze-thaw cycles. Systems were stable when only lipid crystallization occurred. DSC data showed that lipid crystallization prior to water crystallization (i.e. emulsions containing HPKO) caused destabilisation at low sucrose concentrations (0, 2.5 and 5% w/w). Emulsions were stable if the dispersed oil phase crystallized after the dispersing water phase (i.e. emulsions containing SO). A concentration of sucrose ≥10% (w/w) in the aqueous phase gave stable emulsions. At 10:1 lipid to protein ratio, WPI showed better stabilising properties than NaCAS at 2.5 and 5% (w/w) sucrose. Double concentration of WPI (lipid:protein = 10:2) at 0% (w/w) sucrose significantly improved systems stability, whereas no positive effect was observed when the concentration of NaCAS was increased. From morphology study, in addition to lipid destabilisation, thickening and flocculation caused instability of the systems. These were extensive in systems containing WPI and were ascribed to interactions between whey proteins during thermal cycling.     

Physical Characteristics and Microstructure of Reduced-fat Frankfurters as Affected by Salt and Emulsified Fats Stabilized with Nonmeat Proteins

Functional properties and microstructure of frankfurters containing 1.5% or 2.5% salt and 15% pre-emulsified fat (PEF) stabilized with 2% pea protein, soy protein, or sodium caseinate were studied. With the exception of frankfurters with pea protein and 1.5% NaCl, all the others made with PEF" had greater (p < 0.01) thermal stability than all-meat frankfurters. Frankfurters containing soy protein or sodium caseinate had greater (p < 0.01) shear force than those with pea protein. Reducing NaCl in the frankfurters containing PEF did not influence the shear force. Microstructure examination revealed that many fat globules were entrapped physically within soy protein or sodium caseinate, which stabilized the meat emulsions and contributed to a firmer texture. Key Words: emulsified fat, reduced-fat, low-salt, microstructure, frankfurters     

Emulsifying Effects of Food Macromolecules In Presence of Ethanol

The influence on droplet size of ethanol present during homogenization was investigated for emulsions stabilized by macromolecular emulsifiers: sodium caseinate, whey protein isolate, gelatin and gum arabic. Emulsions produced with polysaccharide gum arabic had increasing droplet size as ethanol concentration increased, in contrast to the protein-stabilized emulsions which had decreasing droplet size (up to 20 % ethanol for gelatin and 30 % ethanol for the milk proteins), followed by increasing droplet size with increasing ethanol concentration. Interfacial tension measurements indicated that the emulsifying property of the macromolecules depended on adsorption at the oil-water/alcohol interface during emulsification.     

酒精对酪蛋白酸钠溶液及O/W乳状液的影响

介绍了酒精对酪蛋白酸钠溶液及酪蛋白稳定的O/W乳状液性质的影响 .试验表明酒精在一定程度上可以降低酪蛋白酸钠的溶解度 .界面张力的测定则表明酒精的存在在很大程度上可以降低油—水界面和油—酪蛋白溶液界面的界面张力 .含酒精的乳状液体系的粘度会由于酒精的存在而提高 ,在酒精体积分数达 3 0 %时 ,乳状液体系的粘度会突然大幅度升高 .通过O/W乳状液的分层稳定性测定可发现 ,低浓度的酒精可以提高酪蛋白稳定的乳状液的分层稳定性 ,但酒精质体积分数超过 3 2 %时 ,乳状液的分层稳定性会受到破坏 .含酒精的O/W乳状液体系中油相含量的提高在一定范围内可以提高乳状液的稳定性 ,但高分散相浓度的含酒精的乳状液体系中由于连续相中酒精浓度的提高使乳状液体系稳定性下降 .     

Utilization of layer-by-layer interfacial deposition technique to improve freeze–thaw stability of oil-in-water emulsions

The freeze–thaw stability of 5 wt% hydrogenated palm oil-in-water emulsions (pH 3) containing droplets stabilized by sodium dodecyl sulfate (SDS)–chitosan–pectin membranes was studied. The multilayered interfacial membranes were created using an electrostatic layer-by-layer deposition method. The ζ-potential, mean particle diameter, fat destabilization, apparent viscosity and microstructure of the emulsions were used to examine the influence of freezing on their stability. Emulsions containing oil droplets stabilized only by SDS were highly unstable to droplet coalescence when either the oil phase became partially crystallized or the water phase crystallized. Emulsions containing oil droplets stabilized by SDS–chitosan membranes were stable to droplet coalescence, but unstable to droplet flocculation. Emulsions containing droplets stabilized by SDS–chitosan–pectin membranes were stable to both droplet coalescence and flocculation. The interfacial engineering technology utilized in this study could lead to the creation of food emulsions with improved stability to freeze–thaw cycling.     

Comparison of the Emulsifying Properties of Fish Gelatin and Commercial Milk Proteins

ABSTRACT: We have compared the flocculation, coalescence, and creaming properties of oil-in-water emulsions prepared with fish gelatin as sole emulsifying agent with those of emulsions prepared with sodium caseinate and whey protein. Two milk protein samples were selected from 9 commercial protein samples screened in a preliminary study. Emulsions of 20 vol% n -tetradecane or triglyceride oil were made at pH 6.8 and at different protein/oil ratios. Changes in droplet-size distribution were determined after storage and centrifugation and after treatment with excess surfactant. We have demonstrated the superior emulsifying properties of sodium caseinate, the susceptibility of whey protein emulsions to increasing flocculation on storage, and the coalescence of gelatin emulsions following centrifugation.     

Influence of xanthan gum on the formation and stability of sodium caseinate oil-in-water emulsions

Studies have been made of the changes in droplet sizes, surface coverage and creaming stability of emulsions formed with 30% (w/w) soya oil, and aqueous solution containing 1 or 3% (w/w) sodium caseinate and varying concentrations of xanthan gum. Addition of xanthan prior to homogenization had no significant effect on average emulsion droplet size and surface protein concentration in all emulsions studied. However, addition of low levels of xanthan (≤0.2 wt%) caused flocculation of droplets that resulted in a large decrease in creaming stability and visual phase separation. At higher xanthan concentrations, the creaming stability improved, apparently due to the formation of network of flocculated droplets. It was found that emulsions formed with 3% sodium caseinate in the absence of xanthan showed extensive flocculation that resulted in very low creaming stability. The presence of xanthan in these emulsions increased the creaming stability, although the emulsion droplets were still flocculated. It appears that creaming stability of emulsions made with mixtures of sodium caseinate and xanthan was more closely related to the structure and rheology of the emulsion itself rather than to the rheology of the aqueous phase.     

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.     

Influence of Emulsification Technique and Wall Composition on Physicochemical Properties and Oxidative Stability of Fish Oil Microcapsules Produced by Spray Drying

Encapsulation of fish oil is an effective way to protect it against oxidation and masking its fishy odor. One of the possible ways to produce fish oil microcapsules is to produce an oil-in-water (O/W) emulsion followed by spray drying. This study compares the production of the O/W emulsion by mechanical homogenization (rotor–stator) with membrane emulsification and examines the effect of the type and amount of wall material added before drying. The membrane emulsification process selected for the emulsion production is premix membrane emulsification (ME), which consists of the production of a coarse emulsion by mechanical means followed by droplet breakup when the coarse emulsion is forced through a membrane. The emulsions produced had an oil load of 10 and 20 % and were stabilized using whey protein (isolate and hydrolyzate at 1 or 10 %) and sodium caseinate with concentrations of 2 and 10 %. Regarding the material used to build the microcapsule wall, whey protein, maltodextrin, or combinations of them were used at three different oil/wall ratios (1:1, 1:2, 1:3). The results clearly show that premix ME is a suitable technology for producing O/W emulsions stabilized with proteins, which have a smaller droplet size and are more monodisperse than those produced by rotor–stator emulsification. However, protein concentrations of 10 % are required to reduce the droplet size down to 2–3 μm. Small and monodisperse emulsions have been found to produce microcapsules with lower surface oil content, which increases oil encapsulation efficiency and presents lower levels of oxidation during storage at 30 °C. Of all the possible combinations studied, the one with the highest oil encapsulation efficiency is the production of a 20 % O/W emulsion stabilized with 10 % sodium caseinate followed by the addition of 50 % maltodextrin and drying.     

Ability of whey protein isolate and/or fish gelatin to inhibit physical separation and lipid oxidation in fish oil-in-water beverage emulsion

The effect of pH on the capability of whey protein isolate (WPI) and fish gelatin (FG), alone and in conjugation, to form and stabilize fish oil-in-water emulsions was examined. Using layer-by-layer interfacial deposition technique for WPI–FG conjugate, a total of 1% protein was used to prepare 10% fish oil emulsions. The droplets size distributions and electrical charge, surface protein concentration, flow and dynamic rheological properties and physiochemical stability of emulsions were characterize at two different pH of 3.4 and 6.8 which were selected based on the ranges of citrus and milk beverages pHs, respectively. Emulsions prepared with WPI–FG conjugate had superior physiochemical stability compare to the emulsions prepared with individual proteins. Higher rate of coalescence was associated with reduction in net charge and consequent decrease of the repulsion between coated oil droplets due to the proximity of pH to the isoelectric point of proteins. The noteworthy shear thinning viscosity, as an indication of flocculation onset, was associated with whey protein stabilized fish oil emulsion prepared at pH of 3.4 and gelatin stabilized fish oil emulsion made at pH of 6.8. At pH 3.4, it appeared that lower surface charge and higher surface area of WPI stabilized emulsions promoted lipid oxidation and production of hexanal.     

Synergistic effects of polyglycerol ester of polyricinoleic acid and sodium caseinate on the stabilisation of water–oil–water emulsions

The inherent thermodynamic instability of water–oil–water (W/O/W) emulsions has restrictions for their application in food systems. The objective of this study was to develop a food grade W/O/W emulsions with high yield and stability using minimal concentrations of surfactants. Emulsions were prepared using soybean oil, polyglycerol ester of polyricinoleic acid (PGPR) alone or in combination with sodium caseinate (NaCN) as emulsifier(s) for primary water-in-oil (W/O) emulsions and NaCN as the sole emulsifier for secondary W/O/W emulsions. Increasing the concentration of PGPR (0.5–8%w/v) had no effect on the droplet sizes of the resulting W/O/W emulsions. However, significant increases in droplet sizes of W/O/W emulsions were observed when the concentration of NaCN in external phase was reduced from 0.5 to 0.03% (w/v) (p<0.05). Percentage yields of emulsions (using a water-soluble dye) improved when PGPR concentration in the inner phase was increased from 0.5 to 8% (w/v). A stable W/O/W emulsion with a yield >90% could be prepared with 4% (w/v) PGPR alone as primary hydrophobic emulsifier and 0.5% (w/v) NaCN as external hydrophilic emulsifier. The concentration of PGPR in the inner phase could be reduced to 2% (w/v) without affecting the yield and stability of the W/O/W emulsion by partially replacing PGPR with 0.5% (w/v) NaCN, which was added to the aqueous phase of the primary W/O emulsion. The results indicate that a possible synergistic effect may exist between PGPR and NaCN, thus allowing formulation of double emulsions with reduced surfactant concentration.     

Oil-in-Water Emulsions Stabilized by Sodium Caseinate or Whey Protein Isolate as influenced by Glycerol Monostearate

Competitive adsorption between glycerol monostearate (GMS) and whey protein isolate (WPI) or sodium caseinate was studied in oil-in-water emulsions (20 wt % soya oil, deionized water, pH 7). Addition of GMS resulted in partial displacement of WPI or sodium caseinate from the emulsion interface. SDS-PAGE showed that GMS altered the adsorbed layer composition in sodium caseinate stabilized emulsions containing < 1.0 wt % protein. Predominance of β-casein at the interface in the absence of surfactant was reduced in the presence of GMS. The distribution of α-lactalbumin and β-lactoglobulin between the aqueous bulk phase and the fat surface in emulsions stabilized with WPI was independent of the concentration of added protein or surfactant.     

一种水包油包胶型乳液的制备及其在乳化肠中的应用

以结冷胶和无水氯化钙为内水相凝固剂,酪蛋白酸钠为外水相乳化剂,制备一种水包油包胶（S/O/W）型 乳液。以多重乳液粒径和分布为指标,研究酪蛋白酸钠添加量对S/O/W型多重乳液加工适应性的影响。结果表明： 正交试验得到S/O型单重乳液最佳制备条件为：内水相中结冷胶添加量0.2%、无水氯化钙添加量0.5%;内水相乳化 剂聚甘油蓖麻醇酯添加量2.5%;油相为精炼猪油,油水体积比3∶2;剪切速率17 500 r/min,剪切时间1.5 min。将制 得的S/O型单重乳液与不同添加量酪蛋白酸钠混合制得S/O/W型多重乳液。当酪蛋白酸钠添加量0.1%时,S/O/W型 多重乳液粒径符合加工要求,且贮藏、热处理、剪切稳定性较好。以多重乳液替代猪脂肪制备的低脂乳化肠与高脂 （精炼猪油含量20%）乳化肠外观不存在明显差异;微观结构观察结果表明,多重乳液在乳化肠中包裹良好、分布 均匀。     

STABILITY OF OIL-IN-WATER EMULSIONS. 1. Effects of Surface Tension, Level of Oil, Viscosity and Type of Meat Protein

SUMMARY– Surface tension responses for solutions of salt-soluble protein from cow meat, beef hearts, beef cheek meat, pork trim and pork cheek meat were found to follow the Type III curves assigned to surface-active agents. The stability of emulsions prepared utilizing salt-soluble protein of the meats was significantly affected by concentration of protein and level of oil. As either concentration of protein or of oil was increased, higher and more significant stability of the emulsions was observed. Emulsions prepared from protein of each type of meat had similar responses for stability. High and significant correlation was found between protein surface activity and emulsion stability. Little change in emulsion viscosity was found except at the upper protein and oil levels tested.     

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.     

Effect of heat treatment on the properties of soy protein‐stabilised emulsions

The effect of heat treatment on the properties of soy protein‐stabilised emulsions was investigated. Emulsions were prepared with unheated and heat‐treated soy protein (NSP and HSP) dispersions. Heating on soy protein dispersions at 95 °C for 30 min resulted in smaller average oil droplet size, lower tendency for oil droplet flocculation, higher protein adsorption and lower viscosity. The properties of emulsions were significantly influenced by the protein concentration. The sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) profiles showed that the heat treatment on soy protein dispersions increased the protein adsorption at O/W interface. The viscosity of all samples at low shear rate was inversely proportional to the d₃₂, suggesting a positive relation to the total interfacial area per unit volume. Emulsions showed shear‐thinning behaviour. The relaxation time was found to increase with aqueous phase viscosity determined by the Cross viscosity model.