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.     

Compositional Factors That Affect the Emulsifying and Foaming Properties of Whey Protein Concentrates

An emulsion containing 30% fat was used to study emulsifying and foaming properties of commercial whey protein concentrates. Residual lipids, both total and phospholipids, inhibited foaming of dilute aqueous solutions of whey protein concentrates, whereas in aerated emulsions residual lipids were positively correlated with foaming. Under both test conditions the ash content was positively correlated with good and moderate foaming properties. Among the compositional factors which best predicted foaming of emulsions were sulfhydryls. Emulsions which contained insoluble whey proteins were highly stable but air incorporation was poor. When soluble whey proteins were utilized to stabilize emulsions, serum separation occurred more readily but did not correlate with good foaming properties.     

不同结晶态脂肪比例对乳液奶油感感知的影响

通过调配无水乳脂肪的脂肪酸组成，构建含不同结晶态比例的乳脂肪模型和与牛奶脂肪含量和粒径匹配的乳液体系，进而模拟口腔加工，测定含不同结晶态脂肪比例乳液的口腔聚合性和摩擦学特性，并评价其奶油感。成功构建了含不同结晶态比例（10%～85%）的乳脂肪模型（F10～F85），所构建乳液（E10～E85）中脂肪球平均粒径为4 μm，在模拟口腔加工后，乳液粒径显著增大，其中E40样品增大程度最大。随着结晶态脂肪比例的增加，乳液口腔摩擦系数（μ20）先减小后增加，其中E40样品μ20最小，为（0.04±0.01）。描述性感官评价结果显示，随着结晶态脂肪比例的增加，乳液样品的整体奶油感先增大后减小，其中E40样品得分最高，为8.06±0.73。主成分分析结果显示，乳液的口腔光滑感和糊口感与整体奶油感相关性最强，其中E40样品与整体奶油感相关性最强。暂时性感官支配评价结果显示，口腔加工中后期，乳液在口腔感知中最显著的优势感官属性为口腔光滑感和糊口感，其中E40样品的口腔光滑感和糊口感优势率最高。本研究明确了结晶态脂肪比例对乳液奶油感感知的影响，为开发低脂但具备全脂口感的乳制品提供理论依据。     

Enhancing sweetness using double emulsion technology to reduce sugar content in food formulations

In this study, water-in-oil-in-water double emulsions containing saccharose at the outer aqueous phase were formulated and characterised to investigate the potential of double emulsion to enhance the perception of sweetness. We hypothesised that double emulsions containing saccharose at the outer aqueous phase will be detected immediately by taste receptors and evaluated as sweeter than single emulsions containing the same amount of saccharose. Emulsions were prepared with three dispersed phase:continuous phase ratios. The results of the analyses suggested that the phase ratio affected the particle size and rheological behaviour of the emulsions. However, no differences were observed in lipid digestion behaviour. The sensory analysis revealed that the formulation containing double emulsion was sweeter than the formulation containing oil-in-water single emulsion by approximately 75%. Therefore, the development of food products with reduced sugar content may be possible using double emulsions with enhanced sweetness.Industrial relevanceExcessive sugar consumption is an unhealthy diet associated with an increased risk of non-alcoholic fatty liver disease, obesity, diabetes, chronic diseases such as cardiovascular disease, certain types of cancer, and cognitive decline. Therefore, one of the responsibilities of the food industry is to reduce the sugar content of foods. Many food companies have significantly reduced the sugar levels of many products with the policies they have carried out and continue to do so. However, products produced with industrial solutions (especially using artificial sweeteners) to reduce sugar create sensory dissatisfaction in the consumers. Also, the body reacts to artificial sweeteners differently than it does to sugar. The double emulsion technology offers the opportunity to the food industry to reduce the sugar content of foods without causing any sensory loss in food and without the need for the use of an artificial sweetener.     

Fat-crystal stabilised w/o emulsions for controlled salt release

The potential of fat-crystal stabilised w/o emulsions to control the release of salt contained within their aqueous phase has been investigated. A mixture of mono- and triglyceride crystals was used to obtain Pickering-stabilised 60:40 w/o emulsions. Salt release was monitored by placing small amounts of these emulsions into a bulk aqueous phase (this was either pure water or glucose aqueous solutions in order to vary osmotic pressure gradients) and measuring changes in conductivity over time. Less than 5% of total salt was released after 1 month in emulsions containing a mixture of mono- and triglycerides. Emulsions containing only monoglycerides released more than 40% salt in this period. SEM pictures showed that crystals have sintered at the interface to give total surface coverage with no or very few defects. Stability measurements at varying temperatures and Differential Scanning Calorimetry (DSC) indicate that any release is the result of partial melting of the crystals. Finally, varying the osmotic pressure gradient has no impact on salt release.     

Effects of processing conditions on structural and functional parameters of whipped dairy emulsions containing various fatty acid compositions

An understanding of the effects of processing parameters can be applied to formulate emulsions with higher unsaturated fatty acid content. Emulsions using the typical ice cream formulation were produced by anhydrous milk fat alone or in a mixture with either olein or stearin at a 2:1 weight ratio. Effects of both pasteurization holding time (40 or 120 s at 80°C) and aging time (ranging from 2 to 24 h) on the structural and whipping properties of the emulsions were studied. Effects of these processing conditions on emulsion structural characteristics were determined using laser light-scattering measurements, rheological properties, microscopic observations, and image analyses of the whipped emulsions. Furthermore, foaming properties of these emulsions were compared and discussed with regard to effects of both processing and composition on properties of the emulsions, such as thixotropy and sensitivity to shearing. We observed changes in fat globules when different pasteurization holding times were applied, but no changes in either apparent viscosity values or sensitivity to shearing were traceable. However, enrichment of milk fat with the olein fraction increased the whipping ability of the emulsions, as evaluated in terms of overrun and the homogeneity of air bubbles, whatever the aging time. The lowest monodispersity of air bubbles was observed in the formulation rich in stearin. After 24 h of aging, this formulation showed the same overrun as the emulsion made with anhydrous milk fat. Increasing the aging time decreased the overrun by approximately 30%, and increasing the pasteurization holding times decreased it by approximately 20%. In general, in our conditions, increasing the aging time and unsaturated fatty acid content reduced changes in the dynamic rheological and structural properties observed just after production of the emulsions, whatever the pasteurization holding time or fat composition applied.     

Lubrication of Oral Surfaces by Food Emulsions: the Importance of Surface Characteristics

ABSTRACT:  The friction between surfaces in relative motion lubricated by food emulsions has been measured. Different types of surfaces were tested, including metal, glass, rubber, and mucosal surfaces (pig tongue and pig esophagus). We demonstrate that the load-dependent behavior of the coefficient of kinetic friction was different for various types of surfaces used; it decreased with increasing load for the mucosal surfaces, but was constant for glass-metal surfaces. We show that this difference is an effect of the roughness and the deformability of the surfaces. For mucosal surfaces, the friction force did not depend on the oil fraction in the measured range of 10% to 40% (w/w). Furthermore, 3 commercial dairy products were tested between these surfaces. The lubrication properties of the low-fat (1.5% fat content) and high-fat (3.5% fat content) milk were comparable to those of the model emulsions. However, the friction force of the commercial cream (35% fat content) was found to be much lower.     

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%.     

The interactions between oil droplets and gel matrix affect the lubrication properties of sheared emulsion-filled gels

In this work the lubrication behaviour of emulsions, gels, and emulsion-filled gels was studied in relation to their composition and structure. It was found that emulsions had much lower friction coefficients than their continuous phases. Emulsions with 40 wt% oil had the same friction coefficient as the pure oil. The lubrication properties of the gels, sheared by pressing them through a syringe, strongly depended on the molecular properties of the gelling agent and on the breakdown behaviour of the gel matrix. For each type of emulsion-filled gel, the lubrication behaviour was affected by the interactions between oil droplets and matrix. For gels containing oil droplets bound to the matrix, the friction coefficient gradually decreased with increasing oil concentration. For gels containing oil droplets non-bound to the matrix, the friction coefficient of the filled gels was lower than that of the same gel matrix without oil. However, no effect of the oil concentration on friction was observed. The different effects of the oil concentration on the lubrication behaviour of the various gels were explained by the relation between droplet–matrix interactions and the ‘apparent viscosity’ of the sheared gels. For gels with bound droplets, increasing the oil concentration resulted in an increase of the ‘apparent viscosity’ of the sheared gel. For gels with unbound droplets, the oil concentration did not affect the ‘apparent viscosity’. Confocal laser scanning microscopy (CLSM) observations of both emulsions and filled gels did not reveal coalescence of the oil droplets as a result of the shear treatment inherent to friction measurements.     

Beverage emulsions: Comparison among nanoparticle stabilized emulsion with starch and surfactant stabilized emulsions

Emulsions are widely used in beverages to impart desired appearance and flavor to the products. Ring formation in beverages with emulsions during thermal processing and storage is one of the key challenges. This study was aimed at comparing the relative effectiveness of silica nanoparticle based emulsifiers with surfactant and biopolymer based emulsifier (modified starch) in influencing physical stability of emulsions in a model juice. The stability of emulsions was measured by characterizing changes in emulsion droplet size, zeta potential, UV–vis absorbance and visual evaluation of phase separation or ring formation in both primary emulsions and beverage emulsions as a function of storage time. The influence of thermal processing on stability of emulsions both immediately after processing and upon storage was evaluated. The thermal processing conditions simulated both high temperature short time and low temperature long time pasteurization conditions. The results demonstrate that the mean droplet diameter of primary emulsions stabilized by selected emulsifiers was stable during storage for 21 days with and without pasteurization. Based on measurements of mean droplet diameter and visible ring formation, polyoxyethylene sorbitan monolaurate (tween-20) stabilized emulsion was not stable in a model juice and the stability of this emulsion was further reduced with thermal processing. In contrast, starch and silica stabilized emulsions in a model juice did not show significant changes in particle diameter or visible ring formation during storage with and without prior thermal processing, although starch stabilized emulsion did show a decrease in absorbance during storage. Zeta potential measurements in a model juice indicate that the surface properties of emulsions were significantly distinct from those of primary emulsion, indicating interaction of juice components with the emulsion interface influencing the surface charge at the interface. These changes in zeta potential of emulsion droplets did not correlate with reduced stability of the emulsions. Overall, the results demonstrate that nanoparticle stabilized emulsions can improve stability of emulsion in beverages as compared to surfactant and biopolymer stabilized emulsions and provides a comprehensive matrix to evaluate stability of emulsions in beverages.     

Rheological properties of emulsions containing milk proteins mixed with xanthan gum

Oil in water emulsions (30% w/w) containing mixtures of milk proteins with xanthan gum were rheologically characterized at ambient temperature and the evolution of their properties was measured during a month under cold storage. The milk proteins used were sodium caseinate and whey concentrate at 2% mixed with xanthan gum at 0.3% or 0.5%. Emulsions properties were compared to those of respective aqueous systems and in general showed same rheological behaviour as their respective aqueous system, however, emulsions presented higher consistency index, due to oil droplets concentration. The flow behaviour index showed a small variation, increasing its value slightly. The consistency of emulsions with xanthan was similar, independently of the milk protein used, confirming that xanthan rheology predominates on emulsion rheology.     

Effect of oil content and processing conditions on the thermal behaviour and physicochemical stability of oil-in-water emulsions

The destabilisation mechanism of oil-in-water (o/w) emulsions was studied as a function of oil content (20% and 40% o/w), homogenisation conditions and crystallisation temperatures (10, 5, 0, −5 and −10 °C). A mixture of anhydrous milk fat and soya bean oil was used as the lipid phase and whey protein isolate (2 wt%) as emulsifier. Crystallisation and melting behaviours were analysed using differential scanning calorimetry. Physicochemical stability was measured with a vertical scan macroscopic analyser. Emulsions with 20% oil were found to be less stable than those with 40% oil. For 20% o/w emulsions, the crystallisation was delayed and inhibited in emulsions with smaller droplets and promoted in emulsions with larger droplets when compared with 40% o/w emulsions. Depending on the droplet sizes in the emulsion, the formation of lipid crystals (in combination with the emulsifier) either stabilises (small droplets) or destabilises (big droplets) the emulsion.     

Phase separation in optically opaque emulsions

Creaming of the dispersed oil phase in opaque oil-in-water emulsions was followed as a function of time and position using proton magnetic resonance. Measurements of T₁ along a vertical slice were used to quantify the oil-phase concentration. Emulsions were also described by laser-diffraction particle-size analysis to compare particle-size analysis with creaming behavior as determined by T₁ measurements in model triolein-in-water emulsions and more complex milk fat-in-water emulsions. Particle-size distributions failed to accurately predict the measured creaming behavior in the emulsions studied. Measurements of component nuclear relaxation were shown to be useful for characterizing oil-phase migration as a function of surfactant level, dispersed phase volume, and crystallization behavior of the lipid phase in emulsions.     

Emulsifying power of mannan and glucomannan produced by yeasts

Subject of study was the colloid chemical properties of the biopolymers mannan, synthesized from strain Rhodotorula acheniorum MC, and glucomannan, synthesized from strain Sporobolomyces salmonicolor AL(1). Their emulsifying capacity was studied in model systems of aqueous solutions in concentrations from 0.5% to 2.5% with regard to the aqueous phase. Emulsions of the direct type (oil/water) with 50% oil content were obtained. A disperse system with 2.5% glucomannan had 100% intact emulsion in the centrifugation test, while for the system with mannan, this indicator was 72%. Lab cream emulsions were obtained with glucomannan and with the emulsifiers Rofetan N/NS and Arlacel 165 used in the cosmetics industry. It has been established that under standard testing conditions, cream-like emulsions with 2.0% glucomannan have stability indicators comparable to these of 5.0% rofetan N/NS and 5.0% Arlacel 165. The samples with different concentrations of glucomannan showed a pseudo-plastic behaviour, as the highest viscosity was shown by the emulsion with 2.0% stored at 45 degrees C. The newly synthesized exopolysaccharides had a distinct emulsifying power and can be applied in the cosmetic and food industries.     

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.     

Improved oxidative barrier properties of emulsions stabilized by silica–polymer microparticles for enhanced stability of encapsulants

The materials encapsulated within oil-in-water emulsions are prone to oxidation due to the permeation of oxidative species across the oil–water interface and into the lipid phase. Thus, the oxidative barrier properties of the interfacial layer are pivotal in reducing oxidation within emulsified oils. To enhance these barrier properties, we explored an approach of stabilizing emulsions using ‘silica–polymer microparticles’. We hypothesize that these microparticles will enhance the barrier properties of emulsion interfaces by mechanisms such as higher interfacial thickness and quenching of oxidative species before they permeate into the emulsions. Silica–ε-polylysine (Si–EPL) microparticles were synthesized by electrostatic aggregation of anionic silica nanoparticles and cationic ε-polylysine in the aqueous phase. Formation of Si–EPL microparticles was validated using particle size, ζ-potential and scanning electron microscopy measurements. These microparticles were subsequently used for emulsion stabilization. Emulsions stabilized by silica nanoparticles alone were used as control. Oxidative barrier properties were determined by measuring the rate of permeation of peroxyl radicals from the aqueous to the oil phase of the emulsion using fluorescence based methods. The rate of permeation of peroxyl radicals was significantly lower in emulsions stabilized by Si–EPL microparticles compared to that stabilized by silica nanoparticles. One of the mechanisms responsible for the observed effect was enhanced quenching of peroxyl radical by Si–EPL microparticles before they can permeate inside the oil phase. To further validate the results, stability of a model bioactive compound, retinol, encapsulated in these emulsions was compared. Consistent with peroxyl radical permeation measurements, emulsion stabilized by Si–EPL microparticles significantly improved the oxidative stability of retinol compared to that stabilized by silica nanoparticles alone. Thus, by engineering the physical properties of the interfacial layers, the oxidation of the encapsulants in emulsions can be controlled.     

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.     

Textural perception of liquid emulsions: Role of oil content,oil viscosity and emulsion viscosity

This work describes a study on the in-mouth textural perception of thickened liquid oil-in-water emulsions. The variables studied are oil content, oil viscosity, and the concentration of polysaccharide thickener. Gum arabic was chosen as the thickener because of the nearly Newtonian behavior of its solutions and special care was taken to suppress aroma clues. Based on the experimental results and findings from previous studies, this work shows that the emulsion droplets influence textural sensory perception of liquid emulsions by three main mechanisms, each of which relate to changes in specific sensory attributes, and none of which were found to be significantly dependent on the viscosity of the oil: 1) by increasing the viscosity, 2) by becoming incorporated in the mucous oral coating, and 3) by spreading oil at the oral surfaces. Based on these results, the possibility for replacement of emulsified fat by a polysaccharide thickener is evaluated.     

Modulating the fat globules of plant-based cream emulsion: Influence of the source of plant proteins

In this study the physical properties of plant-based cream emulsion using various plant-proteins and homogenisation pressures were investigated. Three plant proteins (soy protein isolate-SPI, faba protein isolate-FBI, and pea protein isolate-PPI) at 2, 3 and 4% (w/w) concentrations were emulsified with 36% plant-fat (a mixture of palm oil, sunflower oil and monodiglyceride) and passed through two-stage homogenisation pressures at 25/5, 10/4, and 7/3 MPa. Increasing homogenisation pressure and protein content reduced the fat globule size as observed in microstructure images but increased the particles size (D[4,3]) in emulsion. All emulsions had high zeta potential values (−25 to −49 mV) suggesting stable emulsions with a firm and thick consistency. The friction coefficient of creams with PPI was significantly lower than SPI and FBI, indicating better lubrication properties. The results obtained suggests the ability to produce stable plant-based cream from plant-based proteins and fat that can replace the dairy cream.