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.     

Droplet Size and Emulsifier Type Affect Crystallization and Melting of Hydrocarbon-in-Water Emulsions

Differential scanning calorimetry was used to monitor crystallization and melting of 20 wt% n-hexadecane oil-in-water emulsions. The temperature at which droplet crystallization occurred depended on type of emulsifier used to stabilize the droplets: sodium caseinate, whey protein isolate, Tween 20. 40. 60 and 80 or sodium dodecyl sulfate. Emulsifiers with hydrocarbon; ails close in structure to n-hexadecane promdted crystallization at higher temperatures, which suggested that emulsifier molecules at the interface acted as nucleation sites for oil. Smaller droplets crystallized at a slower rate than larger droplets. Droplet size and emulsifier type had no appreciable effect on melting behavior of the droplets.     

Preparation and impact of multiple (water-in-oil-in-water) emulsions in meat systems

The aim of this paper was to prepare and characterise multiple emulsions and assess their utility as pork backfat replacers in meat gel/emulsion model systems. In order to improve the fat content (in quantitative and qualitative terms) pork backfat was replaced by a water-in-oil-in-water emulsion (W₁/O/W₂) prepared with olive oil (as lipid phase), polyglycerol ester of polyricinoleic acid (PGPR) as a lipophilic emulsifier, and sodium caseinate (SC) and whey protein concentrate (WP) as hydrophilic emulsifiers. The emulsion properties (particle size and distribution, stability, microstructure) and meat model system characteristics (composition, texture, fat and water binding properties, and colour) of the W₁/O/W₂, as affected by reformulation, were evaluated. Multiple emulsions showed a well-defined monomodal distribution. Freshly prepared multiple emulsions showed good thermal stability (better using SC) with no creaming. The meat systems had good water and fat binding properties irrespective of formulation. The effect on texture by replacement of pork backfat by W₁/O/W₂ emulsions generally depends on the type of double emulsion (associated with the hydrophilic emulsifier used in its formulation) and the fat level in the meat system.     

Influence of emulsion composition on lubrication capacity and texture perception

The role of fat content and type of surfactant for oral friction processes and texture perception of oil-in-water emulsions was assessed. Emulsions at 22% and 33% fat content containing either sodium caseinate or a sucrose ester as emulsifier were compared with viscosity-adapted aqueous solutions of dextran using both sensory evaluation and friction coefficient measurements on a tongue-palate contact model. The impact of saliva on the emulsion droplet size distribution was studied using tribology, differential interference contrast microscopy and light diffraction measurements. Emulsions at 33% and the corresponding iso-viscous aqueous solutions were discriminated in the sensory experiment whereas emulsions at 22% were not. Friction was significantly different for emulsions at 33% and the corresponding iso-viscous aqueous solutions. The difference was not significant for emulsions with 22% fat level when compared with the iso-viscous aqueous solutions. Saliva significantly decreased the friction coefficient of emulsions depending on the surfactant and amount of fat used.     

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 emulsifier type on freeze-thaw stability of hydrogenated palm oil-in-water emulsions

The influence of emulsifier type (Tween 20, whey protein isolate, casein) on the physical properties of 20 wt% hydrogenated palm oil-in-water emulsions after crystallization of (i) the oil phase only or (ii) both the oil and water phases has been examined. Emulsion stability was assessed by differential scanning calorimetry measurements of fat destabilization after cool–heat cycles, and by measurements of mean particle size, oiling off, and gravitational separation after isothermal storage (−20 to 37 °C). Tween 20-stabilized emulsions showed appreciable fat destabilization at temperatures where the oil phase was partially crystalline, which was attributed to partial coalescence. Protein-stabilized emulsions were stable under these conditions, which was mainly attributed to the relatively thick interfacial membranes surrounding the droplets. When both oil and water phases crystallized, there was complete destabilization of Tween 20- and casein-stabilized emulsions, and extensive destabilization of whey protein-stabilized emulsions, which was attributed to ice crystallization. The results of this study could facilitate the development of frozen food products with improved properties.     

单、双脂肪酸甘油酯(亚麻酸)乳液的制备及特性研究

针对单、双脂肪酸甘油酯（亚麻酸）极易氧化的特点,该研究以乳清浓缩蛋白（WPC）、大豆分离蛋白（SPI）、酪蛋白酸钠（SC）和吐温80（T80）为乳化剂制备乳液,考察乳化剂类型对乳液的理化性质、氧化稳定性和消化特性的影响。结果表明,乳液均具有较小的粒径（131.97~224.87 nm）,且在两周贮藏期内保持稳定。乳液包载能够提高单、双脂肪酸甘油酯（亚麻酸）的氧化稳定性,相比T80（过氧化值为377.40 mmol/kg）,蛋白质对油脂的氧化保护效果更好,其中SPI稳定的乳液过氧化值最低为197.73 mmol/kg。体外模拟消化试验表明,乳化剂类型对游离脂肪酸的释放影响较小,但蛋白稳定的乳液在胃消化阶段更容易发生液滴聚集;亚麻籽油的脂质水解程度最低为23.93%,而单、双脂肪酸甘油酯（亚麻酸）的初始消化速度更快,最终脂解程度更高（46.33%）。因此,蛋白质乳液能有效提高单、双脂肪酸甘油酯（亚麻酸）的氧化稳定性,且单、双脂肪酸甘油酯（亚麻酸）相比亚麻籽油具有更好的消化效率,有望替代亚麻籽油作为人体亚麻酸的食物来源。     

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.     

Role of emulsifier layer,antioxidants and radical initiators in the oxidation of olive oil-in-water emulsions

Lipid oxidation in oil-in-water (O/W) emulsions is largely affected by the properties of the interfacial layer surrounding the oil droplets. In this work, the effect of the emulsifier layer structure, presence of both hydrophilic and lipophilic antioxidants and radical initiators on the development of lipid oxidation in olive oil-in-water emulsions was investigated. The olive oil-in-water emulsion is a suitable model of low fat food emulsions. The rationale of the work was to study the role of the interfacial layer when both the antioxidants and the radical initiators came from the two different emulsion compartments. Emulsions were prepared by using food grade emulsifiers of the Tween series (polyoxyethylene sorbitan esters) in the water phase and Span 80 (sorbitan monoleate) in the oil phase. The properties of the interfacial layer were changed by using Tween 20, Tween 60, Tween 80, which have different hydrophobic tails. These systems were oxidized by means of both hydrophilic (AAPH (2,2′-azobis,2-methyl-propanimidamide dihydrochloride), AIPH (2,2′-azobis[2-(2-imidazolin-2-yl) propane] dihydrochloride) and lipophilic (AMVN (2,2′-azobis(2,4-dimethylvaleronitrile)) radical initiators at 40 °C. A continuous fluorescent method based on the front face technique allowed us to follow directly the development of oxidation in the whole emulsion. The combination Tween 80/Span 80 produced an interfacial layer more resistant to radical attack. Moreover, a polar paradox was verified also for radical initiators, while the results suggest that the best way to protect emulsions is to use a combination of antioxidants in both phases, to promote a synergy and the regeneration of antioxidants mediated by the interfacial layer.     

The choice of homogenisation equipment affects lipid oxidation in emulsions

Milk proteins are often used by the food industry because of their good emulsifying properties. In addition, they can also provide oxidative stability to foods. However, different milk proteins or protein components have been shown to differ in their antioxidative properties, and their localisation in emulsions has been shown to be affected by the emulsification conditions. The objective of this study was to investigate the influence of homogenisation equipment (microfluidizer vs. two-stage valve homogeniser) on lipid oxidation in 10% fish oil-in-water emulsions prepared with two different milk proteins. Emulsions were prepared at pH 7 with similar droplet sizes. Results showed that the oxidative stability of emulsions prepared with sodium caseinate was not influenced by the type of homogeniser used. In contrast, the type of homogenisation equipment significantly influenced lipid oxidation when whey protein was used as emulsifier, with the microfluidizer resulting in lower levels of oxidation.     

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.     

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.     

复配乳化剂HLB值对稀奶油脂肪聚结及结晶的影响

将单,双甘油脂肪酸酯与蔗糖酯按一定比例复配成不同亲水亲油平衡（hydrophile lipophilic balance,HLB）值的乳化剂,研究复配乳化剂HLB值对稀奶油脂肪聚结及结晶影响,并对其乳液性质及打发性质进行表征。结果表明,随着复配乳化剂HLB值的增大,乳液粒径增大且表观黏度升高进而使搅打时间延长;热力学及Avrami等温结晶动力学结果表明,复配乳化剂HLB值为10时,高熔点乳脂熔融温度改善显著,并且结晶速率最快;HLB值为8～10时打发性较好,乳清泄漏率较低,涂抹性较佳。因此,复配乳化剂HLB值应控制在8～10,此时更适用于高品质裱花稀奶油的工业生产。     

Effects of emulsifier type on physical and oxidative stabilities of algae oil-in-water emulsions

Algae oil-in-water emulsions were prepared using sodium caseinate (SC, 0.5%), whey protein concentrate (WPC, 0.5%), and a mixture of TWEEN80 (T80, 0.5%), and SPAN80 (SP80, 0.6%), and their emulsification and oxidative stabilities during storage were compared. Oil droplet sizes of SC- and T80+SP80-emulsions were smaller than that of WPC-emulsion. Serum layer appeared in all emulsions from day 15, and serum layer thicknesses were higher in WPC-emulsion than SC- and T80+SP80-emulsions, but an excess layer oil was observed only at the top of T80+SP80-emulsion until day 36. According to conjugated dienes, aldehydes, hydroperoxide and TBARS values, the oxidative stability of SC-emulsion was better than those of WPC- and T80+SP80-emulsions. This trend was also observed in fatty acid profiles of the emulsions showing the largest DHA reduction and palmitic acid increase in T80+SP80-emulsion, followed by WPC- and SC-emulsions. In present study, sodium caseinate formed stable algae oil-in-water emulsions with excellent antioxidative activity.     

Iron‐mediated lipid oxidation in 70% fish oil‐in‐water emulsions: effect of emulsifier type and pH

The objective of this study was to investigate the protective effect of five different emulsifiers on iron‐mediated lipid oxidation in 70% fish oil‐in‐water emulsions. The emulsifiers were either based on protein (whey protein isolate and sodium caseinate) or based on phospholipid (soy lecithin and two milk phospholipids with different phospholipid contents, MPL20 and MPL75). Lipid oxidation was studied at pH 4.5 and 7.0, and results were compared to lipid oxidation in neat fish oil. Results showed that all emulsions oxidised more than neat oil. Furthermore, emulsions prepared with proteins oxidised more at low pH than at high pH, and casein emulsions oxidised the least (Peroxide value (PV) at day 7 was 0.5–0.7 meq kg^?1). Among emulsions prepared with phospholipids, emulsions with MPL75 were the most oxidised followed by emulsions prepared with lecithin and MPL20. Thus, PV in MPL75 emulsions was 5.0–5.5 meq kg^?1 at day 7 compared with 0.9–1.9 meq kg^?1 in MPL20 emulsions.     

Fortification of cheese with vitamin D(3) using dairy protein emulsions as delivery systems

Vitamin D is an essential vitamin that is synthesized when the body is exposed to sunlight or after the consumption of fortified foods and supplements. The purpose of this research was to increase the retention of vitamin D(3) in Cheddar cheese by incorporating it as part of an oil-in-water emulsion using a milk protein emulsifier to obtain a fortification level of 280 IU/serving. Four oil-in-water vitamin D emulsions were made using sodium caseinate, calcium caseinate, nonfat dry milk (NDM), or whey protein. These emulsions were used to fortify milk, and the retention of vitamin D(3) in cheese curd in a model cheesemaking system was calculated. A nonemulsified vitamin D(3) oil was used as a control to fortify milk. Significantly more vitamin D(3) was retained in the curd when using the emulsified vitamin D(3) than the nonemulsified vitamin D(3) oil (control). No significant differences were observed in the retention of vitamin D(3) when emulsions were formulated with different emulsifiers. Mean vitamin D(3) retention in the model system cheese curd was 96% when the emulsions were added to either whole or skim milk compared with using the nonemulsified oil, which gave mean retentions of only 71% and 64% when added to whole and skim milk, respectively. A similar improvement in retention was achieved when cheese was made from whole and reduced-fat milk using standard manufacturing procedures on a small scale. When sufficient vitamin D(3) was added to produce cheese containing a target level of approximately 280 IU per 28-g serving, retention was greater when the vitamin D(3) was emulsified with NDM than when using nonemulsified vitamin D(3) oil. Only 58±3% of the nonemulsified vitamin D(3) oil was retained in full-fat Cheddar cheese, whereas 78±8% and 74±1% were retained when using the vitamin D(3) emulsion in full-fat and reduced-fat Cheddar cheese, respectively.     

Monitoring air/liquid partition of mastic gum oil volatiles in model alcoholic beverage emulsions: Effect of emulsion composition and oil droplet size

The purpose of this work was to study the impact of the structure and composition of hydroalcoholic emulsions on the air–liquid partition of aroma compounds of the essential oil of Pistacia lentiscus var. chia, commonly known as mastic gum oil (mainly consists of terpenes). Oil-in-water emulsions (φ = 0.17), containing 15% (v/v) ethanol, stabilized by three different emulsifiers (sodium caseinate, whey protein isolate and Tween 40), were prepared by using two different lipid phases (sunflower oil and anhydrous butter fat). The homogenization conditions were varied to obtain emulsions with different volume–surface mean diameters. The partition of the volatile compounds between air phase and emulsions at three different temperatures (25, 37 and 50 °C) was monitored by applying the Headspace Solid Phase Microextraction technique, followed by gas chromatography–mass spectrometry (GC–MS) analysis. In general, the results obtained showed that sodium caseinate was the most effective in retaining mastic aroma compounds, while WPI was the least effective. This could partly be explained by the different structure of the two proteins which, when adsorbed at the interface, form a membrane that acts as a barrier and influences the partition of the aroma compounds between the air and the liquid. At the same time interactions of aroma compounds with the two proteins in the bulk phase may also play a role. The retention of the aroma compounds depended on the oil droplet size only in the case of sodium caseinate containing emulsions at 37 and 50 °C. This behaviour could be due to the substantial increase in the thickness of the adsorbed casein layer when moving from a fine sized emulsion to one with a much larger size as well as to differences in the ratio of free to adsorbed emulsifier. The composition of the lipid phase also appeared to have a significant impact on the concentration of volatile compounds in the headspace of mastic gum oil containing emulsions stabilized by proteins. This was lower in the case of butter fat probably due to differences in composition with regard to fatty acid degree of saturation as well as to volatile absorption by the liquid lipid at 40 °C and subsequent entrapment in the semisolid fat at 25 °C.     

Vanillin Interaction with Milk Protein Isolates in Sweetened Drinks

The impact of heat processing and emulsifier addition on the interaction of vanillin and sodium caseinate and whey protein isolate was examined in a model system. Free vanillin in the protein drink was evaluated by a sensory panel and HPLC. Sensory analysis indicated that emulsifier, heat × protein, and heat × emulsifier affected perception of vanillin flavor. Analysis of free vanillin by HPLC indicated only a significant protein effect, with sodium caseinate interacting more with vanillin than did whey protein isolate. No correlation was found between sensory and HPLC results.     

EFFECT OF MILK PROTEINS AND STABILIZER ON ICE MILK QUALITY

Ice milk mixes were made with and without stabilizer/emulsifier as well as with and without milk protein isolate (sodium caseinate or whey protein isolate). The mixes were evaluated for rheological, freezing, melting, and sensory properties. Adding a stabilizer/emulsifier blend to ice milk changed its physical properties more than adding milk protein isolates. The mixes with stabilizer/emulsifier exhibited increased viscosity and chewiness and decreased drainage rate, iciness, and vanilla flavor intensity. The mixes with added caseinate exhibited increased viscosity compared with those with added whey protein isolate. Overall, the quality of ice milk mix was more dependent on stabilizer/emulsifier addition than on milk protein isolate addition.     

Interfacial and emulsifying properties of sucrose ester in coconut milk emulsions in comparison with Tween

In this study, sucrose esters were presented as a promising alternative to petrochemically synthesized Tweens for application in coconut milk emulsions. The interfacial and emulsifier properties of sucrose ester (SE), mainly sucrose monostearate, had been investigated in comparison with Tween 60 (TW), an ethoxylate surfactant. The interfacial tension measurement showed that SE had a slightly better ability to lower the interfacial tension at coconut oil–water interface. These surfactants (0.25 wt%) were applied in coconut milk emulsions with 5 wt% fat content. The effects of changes in pH, salt concentration, and temperature on emulsion stability were analyzed from visual appearance, optical micrograph, droplet charges, particle size distributions, and creaming index. Oil droplets in both SE and TW coconut milk emulsions extensively flocculated at pH 4, or around the pI of the coconut proteins. Salt addition induced flocculation in both emulsions. The pH and salt dependence indicated polyelectrolyte nature of proteins, suggesting that the proteins on the surface of oil droplets were not completely displaced by either added nonionic SE or TW. TW coconut milk emulsions appeared to be thermally unstable with some coalesced oil drops after heating and some oil layers separated on top after freeze thawing. The change in temperature had much lesser influence on stability of SE coconut milk emulsions and, especially, it was found that SE emulsions were remarkably stable after the freeze thawing.