Effect of added calcium chloride on the physicochemical and rheological properties of aqueous mixtures of sodium caseinate/sodium alginate and respective oil-in-water emulsions

Changes induced by addition of calcium chloride in particle size distribution and electrokinetic potential were determined in sodium caseinate/sodium alginate mixtures dissolved in water or acetate buffer at ambient temperature. Rheological properties of aqueous mixtures and respective oil-in-water emulsions (30% oil w/w) were evaluated using a low-stress rheometer. Stability and particle diameter of emulsions were measured. Caseinate and alginate solutions were negatively charged and showed negative electrokinetic potential; however values of mixtures were between those of the values for the individual hydrocolloids. When calcium ions were added the electrokinetic potential diminished while the negative charge was preserved. Aqueous mixtures of caseinate and alginate showed average particles size between of those of caseinate or alginate samples. We observed low viscosity values and Newtonian behavior for both caseinate (1 and 2%) and alginate (0.1%). Addition of 5 mM CaCl₂ to alginate solutions induced shear-thinning behavior as well as the development of viscoelasticity. Both the viscosity and the elastic modulus of these polysaccharide solutions were attenuated by the presence of protein or dispersed oil in mixtures or emulsions, respectively. High average particle diameter of emulsions prepared was obtained (close to 10 μm), however, stability of emulsions was possible only with the addition of CaCl₂ to the mixtures, in both water and acetate buffer. In these cases elastic behavior predominated to viscosity in the formation of emulsions, confirming the prevalence of aqueous phase rheology on emulsions.     

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.     

Creaming Stability of Oil-in-Water Emulsions Formed with Sodium and Calcium Caseinates

Creaming stability of emulsions formed with calcium caseinate, determined after storage of emulsions at 20 °C for 24 h, increased gradually with an increase in protein concentration from 0.5% to 2.0%; further increases in caseinate concentration had much less effect. In contrast, the creaming stability of sodium caseinate emulsions showed a decreased with an increase in protein concentration from 0.5% to 3.0%. Confocal laser micrographs of emulsions formed with >2% sodium caseinate showed extensive flocculation of oil droplets with the appearance of a network structure. However, emulsions formed with calcium caseinate or emulsions formed with low concentrations of sodium caseinate (0.5% and 1.0%) were homogenous with no sign of flocculation.     

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 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.     

Oil-in-water emulsions stabilized by sodium caseinate: Influence of pH,high-pressure homogenization and locust bean gum addition

The effect of pH, addition of a thickening agent (locust bean gum) or high-pressure homogenization on the stability of oil-in-water emulsions added by sodium caseinate (Na-CN) was evaluated. For this purpose, emulsions were characterized by visual analysis, microstructure and rheological measurements. Most of the systems were not stable, showing phase separation a few minutes after emulsion preparation. However, creaming behavior was largely affected by the pH, homogenization pressure or locust bean gum (LBG) concentration. The most stable systems were obtained for emulsions homogenized at high pressure, containing an increased amount of LBG or with pH values close to the isoelectric point (pI) of sodium caseinate, which was attributed to the size reduction of the droplets, the higher viscosity of continuous phase and the emulsion gelation (elastic network formation), respectively. All the studied mechanisms were efficient to decrease the molecular mobility, which slowed down the phase separation of the emulsions. In addition, the use of sodium caseinate was also essential to stabilize the emulsions, since it promoted the electrostatic repulsive interactions between droplets.     

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 processing conditions and composition on sodium caseinate emulsions stability

Many food products such as ice cream, yoghurt, and mayonnaise are some examples of emulsion-based food. The physicochemical properties of emulsions play an important role in food systems as they directly contribute to texture, sensory and nutritional properties of food. One of the main properties is stability which refers to the ability of an emulsion to resist physical changes over time. The aim of the present work was to analyze the effect of processing conditions and composition on sodium caseinate (NaCas) emulsions stability. The main destabilization mechanisms were identified and quantified. The relationship between them and the factors that influence them were also investigated. Emulsions stabilized with NaCas were prepared using an ultrasound liquid processor or a high pressure homogenizer. Stability of emulsions was followed by a Turbiscan (TMA 2000) which allows the optical characterization of any type of dispersion. The physical evolution of this process is followed without disturbing the original system and with good accuracy and reproducibility. To further describe systems, droplet size distribution was analyzed with light scattering equipment. The main mechanism of destabilization in a given formulation depended on different factors such as NaCas concentration, droplet size or processing conditions. The rate of destabilization was markedly lower with addition of sugar or a hydrocolloid to the aqueous phase. Xanthan (XG) and locust bean (LBG) gums produced an increase in viscosity of the continuous phase and structural changes in emulsions such as gelation. Sugars interacted with the protein decreasing particle size and increasing emulsion stability. The stability of caseinate emulsions was strongly affected not only by the oil-to-protein ratio but also by processing conditions and composition of aqueous phase. The structure of the protein and the interactions protein–sugar or the presence of a hydrocolloid played a key role in creaming and flocculation processes of these emulsions.     

黄原胶对酪蛋白酸钠乳状液稳定性的影响

研究了一定pH条件下,黄原胶浓度及剪切稀化效应对酪蛋白酸钠乳状液稳定性的影响。结果表明,在酸性条件下,黄原胶无法抑制酪蛋白的变性沉淀,乳液在制备之初,即产生严重絮凝。在中性和弱碱性条件下,黄原胶在一定浓度范围内,诱发了乳状液的排斥絮凝;体系的pH显著影响了乳状液的稳定性,pH6条件下,较低的黄原胶浓度(0.2wt%)便可赋予乳状液良好的稳定性。均质过程大大降低了黄原胶的粘度,导致乳状液的稳定性下降,与添加未经均质处理的黄原胶相比,添加量增大近一倍,才能获得稳定的乳状液。     

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.     

Effects of different dairy ingredients on the rheological behaviour and stability of hot cheese emulsions

The influence of sodium caseinate (SC), butter milk powder (BMP) and their combinations on particle size, rheological properties, emulsion stability and microstructure of hot cheese emulsions made from mixtures of Cheddar and soft white cheese was studied. All emulsions exhibited shear-thinning flow behaviour and increasing SC concentration (1–4%) led to an increase in particle size and a decrease in apparent viscosity. In contrast, increasing BMP concentration caused significant decrease in particle size and slightly reduced the apparent viscosity. Stability against creaming and precipitation increased with increasing concentration of SC, whereas BMP destabilised the emulsions resulting in extensive precipitation. Confocal laser scanning microscopy images showed that SC exerted markedly better emulsification ability than BMP. Emulsions containing equal amounts of SC and BMP presented better stability against creaming and precipitation and this could be developed into a novel strategy to replace emulsifying salts in production of cheese powder.     

Rheology,particle-size distribution,and stability of low-fat mayonnaise produced via double emulsions

In this study, the effects of the double emulsification method on the rheological properties, particle size, and stability of low-fat mayonnaise were studied. Different water-phase-to-oil ratios (2:8 and 4:6) of primary emulsions and different stabilizer types (sodium caseinate, xanthan gum, and lecithin-whey protein concentrate) were used to produce double-emulsified mayonnaise. As a control sample, mayonnaise was prepared conventionally. Sodium caseinate was found to be the most efficient stabilizer. In the presence of sodium caseinate, the stability and apparent viscosity of double-emulsified mayonnaise increased but their particle sizes decreased. It was found that flow behavior of double-emulsified and conventionally prepared mayonnaise could be described by the power law model. The double-emulsified mayonnaise samples were not different from the control samples in terms of stability and particle size. In addition, using the double emulsion method, it was possible to reduce the oil content of mayonnaise to 36.6%.     

Microstructural design to reduce lipid oxidation in oil-inwater emulsions

The influence of emulsifier type (Tween 20 and sodium caseinate (CAS)) and oil phase volume fraction (5% and 30%) on emulsion oxidative stability was investigated. The primary and secondary lipid oxidation products of emulsions stored at 40 °C were measured over 7 days. The results indicated that the oxidative stability of samples stabilised with CAS was significantly higher compared with emulsions stabilised with Tween 20. We propose that this is due to iron binding ability of CAS. Moreover, the impacts of Pickering emulsions (Silica particles) on lipid oxidation were studied and compared with Tween 20 stabilised emulsions. The results showed that silica particles could increase the oxidative stability of 20% sunflower oil-in-water emulsions by acting as a physical barrier between pro-oxidants located in continuous phase and hydroperxide at droplet interface.     

Effect of emulsifier type on sensory properties of oil-in-water emulsions

This work investigates the fundamental properties of emulsifiers that may contribute to the fat-associated sensory attributes of emulsions. Model oil-in-water emulsions were prepared with 0, 12, 24, 36 and 48% oil and emulsified with seven different emulsifiers; two proteins; sodium caseinate and whey protein, and five different sucrose esters. Emulsions were rated for perceived ‘fat content’, ‘creaminess’ and ‘thickness’ on nine-point category scales. Instrumental measurements of particle size, viscosity, thin film drainage, surface dilational modulus and interfacial tension were made. The sensory results indicate significant main and interactive effects of fat level and emulsifier type. At higher fat levels, emulsions prepared with sodium caseinate and whey protein emulsifiers had higher viscosities and higher sensory scores than those prepared with the sucrose esters. Results indicate that emulsifier type has a significant effect on the sensory properties of oil-in-water emulsions, and relationships between instrumental and sensory measures suggest that this may be due to the interfacial properties of emulsifiers at the oil–water interface. © 1998 SCI.     

STABILITY OF OIL-IN-WATER EMULSIONS. 2. Effects of Oil Phase Volume, Stability Test, Viscosity, Type of Oil and Protein Additive

SUMMARY –Stability of oil-in-water emulsions stabilized in sodium caseinate, gelatin and soy sodium proteinate was found to be increased by either an increase in the aqueous phase protein concentration (0.5–2.5%) or oil phase volume (20–50%). Both factors were significantly interrelated. Emulsions stabilized by soy sodium proteinate were generally higher in stability as compared to those stabilized by gelatin or sodium caseinate. With emulsions containing gelatin, greater stability occurred when the stability testing temperature was increased from 37–70°C and when the time interval was decreased from 24 hr to 90 min. Maximum relative viscosities of emulsions stabilized by gelatin and sodium caseinate were 2.0 and 2.5, respectively. Emulsions stabilized by soy sodium proteinate were quite viscous, with relative viscosity from 1.5–30 depending on both protein concentration and oil phase volume. Interchanging the emulsified oil among corn, soybean, safflower and peanut oils did not alter emulsion stability when examined at three concentrations of soy sodium proteinate. Changing the oil to olive oil significantly increased emulsion stability at each soy sodium proteinate level with oil phase volumes of 30, 40 and 50%.     

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 .     

Emulsion stability of clove oil in chitosan and sodium alginate matrix

Clove oil was emulsified in 1% w/w chitosan (CC emulsions) and 2.5% w/w sodium alginate matrix (CA emulsions) containing Tween 80 as the surfactant. Different homogenization speeds (5,000, 10,000, 15,000 and 20,000 rpm) were used to produce the emulsions, and the stability of the emulsions during storage (29 days) was determined. The stability of the emulsions containing clove oil prior to the solidification process was assessed when chitosan and sodium alginate were used as encapsulating materials. Different homogenization speeds resulted in polydisperse emulsions with a size of 2–3 μm and 90% of stability after 29 days of storage. Different homogenization speeds did not significantly affect the concentrations of the active compounds contained in the emulsions. However, these concentrations changed significantly after 29 days of storage when sodium alginate was used to make the emulsions and the homogenization speeds were ≥ 10,000 rpm. High temperature caused by the high viscosity of the solution and high energy dissipation during homogenization suggested that the emulsions composed of sodium alginate were unstable. Chitosan enabled a longer processing time during the clove oil encapsulation process compared to sodium alginate, when emulsification by homogenization was used. The stability of the emulsion of the clove oil-in-chitosan matrix prior to the solidification step was superior.     

Physical stability of emulsion encapsulated in alginate microgel particles by the impinging aerosol technique

Emulsion filled alginate microgel particles can be applied as carrier systems for lipophilic actives in pharmaceutical and food formulations. In this study, the effects of oil concentration, emulsifier type and oil droplet size on the physical stability of emulsions encapsulated in calcium alginate microgel particles (20–80 μm) produced by a continuous impinging aerosol technique were studied. Oil emulsions emulsified by using either sodium caseinate (SCN) or Tween 80 were encapsulated at different oil concentrations (32.55, 66.66 and 76.68% w/w of total solids content). The emulsions were analysed before and after encapsulation for changes in emulsion size distribution during storage, and compared to unencapsulated emulsions. The size distribution of encapsulated fine emulsion (mean size ~ 0.20 μm) shifted to a larger size distribution range during encapsulation possibly due to the contraction effect of the microgel particles. Coarse emulsion droplets (mean size ~ 18 μm) underwent a size reduction during encapsulation due to the shearing effect of the atomizing nozzle. However, no further size changes in the encapsulated emulsion were detected over four weeks. The type of emulsifier used and emulsion concentration did not significantly affect the emulsion stability. The results suggest that the rigid gel matrix is an effective method for stabilising lipid emulsions and can be used as a carrier for functional ingredients.     

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.     

Thermoreversible gelation of caseinate-stabilized emulsions at around body temperature

We have formulated food-grade protein-stabilized emulsions (30 vol% vegetable oil, 4 wt% sodium caseinate) which exhibit heat-induced gelation at around body temperature. Prior to emulsification, these systems have the continuous phase pH adjusted to between 6.8 and 5.3 and various concentrations of calcium chloride added. The minimum CaCl₂ content required to cause gelation on heating decreases with decreasing pH, and the gelation temperature also decreases with decreasing pH. Under certain conditions the small-deformation rheological change associated with the heat-induced gelation has been found to be reversible on back-cooling to ambient. The systems have also been studied with regards to viscometry and phase separation. Emulsion compositions associated with depletion flocculation by excess non-adsorbed protein are shown to be sensitive to both the ionic calcium content and the pH.