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1.
Droplet size distribution and rheological properties of egg yolk-stabilized emulsions were studied before and after storage (25 °C, 30 days). The dispersed phase (70%) of the emulsions was based on soybean oil (SBO) and 10–40% palm kernel olein (PKO) replacements of SBO. Replacement of PKO resulted in a significant increase in droplet mean diameters and a decrease in rheological properties of the emulsions. All emulsion exhibited a gel-like characteristic with storage modulus higher than loss modulus and tan δ greater than 0.3. Significant increase (p < 0.05) was found for droplet mean diameters and rheological properties of the emulsions after storage. Emulsion with fully SBO and the highest PKO replacement (40%) were found to be the most unstable, which was ascribed to a strong flocculation. With 10–30% PKO replacements, the emulsions displayed a better stability after storage, most probably promoted by significant content of short-medium chain fatty acids in PKO.  相似文献   

2.
Thermally-inactivated baker's yeast (Saccharomyces cerevisiae) and lactic acid bacteria (Lactobacillus acidophilus and Streptococcus thermophilus) were used to generate and stabilize model oil-in-water (O/W) emulsions containing up to 80 wt.% dispersed oil. With optimized compositions, cell-covered dispersed oil droplets were stable against droplet coalescence and bulk phase separation for over four months. From a textural perspective, these emulsions were self-supporting and exhibited a mayonnaise-like consistency. The microbial cells acted as Pickering-type stabilizers by residing at the oil–water interface. The three-phase contact angle of the yeast at the oil–water interface measured using confocal microscopy was 30 ± 9°, demonstrating its ability to stabilize O/W emulsions. These microbial cells may be used in the design of processed food emulsions with an ‘all-natural’ designation as well as for the replacement of common synthetic surfactants to permit clean label declarations.  相似文献   

3.
The oxidation kinetics of soybean oil (SBO)/anhydrous milk fat (AMF) blends was studied by differential scanning calorimetry (DSC). Lipid blends containing 0–100% of SBO in AMF at 10% intervals were analyzed. Samples were heated in the DSC at different heating rates (2.5, 5.0, 7.5, 10.0 and 12.5 °C/min) and oxidation kinetics parameters from the Arrhenius equation (activation energy, pre-exponential factor and oxidation rate constant) were calculated using the Ozawa–Flynn–Wall method. Results show a significant increase in the oxidation rate (k) with temperatures for 60–90% SBO blends. The increase in k with SBO addition was only significant for 240 and 250 °C. A significant correlation between the rate constant and the chemical composition of the samples was not observed. This behavior suggests possible interactions among fatty acids present in the blends.  相似文献   

4.
Stability of emulsions formulated with 10 wt.% oil (concentrated fish oil, CFO, sunflower oil, SFO, or olive oil, OO), sodium caseinate concentrations varying from 0.5 to 5 wt.%, giving oil-to-protein ratios of 20–2, and 0, 20, 30 or 40 wt.% aqueous trehalose solution was studied by Turbiscan. Particle size distribution, microstructure, and small angle X-ray scattering (SAXS) patterns were also obtained. The main mechanism of destabilization in a given formulation strongly depended on oil-to-protein ratio. As evidenced by the BS-profile changes with time, emulsions formulated with 0.5 and 1 wt.% NaCas destabilized mainly by creaming while for the 2 wt.% NaCas concentration, both creaming and flocculation mechanisms, were involved. The main destabilization mechanism for the 3, 4 or 5 wt.% NaCas emulsions was flocculation. Stability of emulsions was also affected by the content of trehalose in the aqueous phase. Trehalose diminished the volume-weighted mean diameter (D4,3) and greatly improved stability.  相似文献   

5.
Hazelnuts, sesame seeds and soybeans were selected as three diverse sources of oil bodies. Application of aqueous extraction and centrifugation steps resulted in concentrated oil body creams that were studied for their physical stability after dilution to a series of 5.0 wt.% oil-in-water emulsions incorporating sodium caseinate (1.0 wt.%), Tween 80 (1.0 wt.%) or xanthan gum (0.1 wt.%). In terms of aggregation/coalescence and creaming, the stability of the oil body based emulsions was ruled to a large extent by the initial natural oil droplet size and the presence of co-extracted exogenous proteins and secondarily by the added biopolymers and the surfactant. More specifically, soybean oil bodies exhibited the highest physical stability, even though incorporation of Tween 80 into all three oil body emulsions improved the stability against aggregation/coalescence, while xanthan gum was an effective stabilizer against creaming.  相似文献   

6.
Carotenoid solubilization in the oil phase is a prerequisite for carotenoid bioaccessibility during digestion. However, the level of bioencapsulation and the hydrophobicity of carotenoids were proven to strongly affect their transfer to oil during in vitro digestion. Therefore, thermal processing (95–110 °C) was exploited to favor carotenoid transfer from tomato- and carrot-based fractions to the oil before digestion. Initially, the total (all-trans + cis) carotenoid content in the oil increased quickly, thereafter, depending on the temperature applied, either a drop or a plateau was reached at longer treatment times. Treatment conditions of > 100 °C for 10 min significantly favoured carotenoid transfer to oil (≥ 75%). The rates of transfer to oil were as follows: β-carotene  α-carotene > lycopene. The results revealed that the cell wall hinders carotenoid transfer to oil during thermal processing. Overall, the results indicate that typical high temperature short time thermal processing can be sufficient to achieve maximal carotenoid transfer to oil with minimal degradation in real food systems/food emulsions and this can be crucial to improve the nutritional quality of carrot and tomato based products.  相似文献   

7.
《Food Hydrocolloids》2003,17(1):87-93
The influence of an anionic surfactant (sodium dodecyl sulfate, SDS) on the thermal stability of emulsions stabilized by a globular protein (bovine serum albumin, BSA) was examined. 1 wt% n-hexadecane oil-in-water emulsions (0.5 wt% BSA, 100 mM NaCl, 20 mM imidizole, pH 7.0) were held isothermally at temperatures from 30 to 90 °C for 30 min. Extensive droplet flocculation was only observed in emulsions held at 90 °C, which lead to rapid creaming instability. The thermal stability of emulsions heated at 90 °C could be greatly improved by adding SDS at surfactant-to-protein molar ratios (R) greater than 5 (∼0.01 wt% SDS). On the other hand, adding surfactant (0<R<600) to the emulsions after heating could not prevent extensive droplet aggregation. Adding SDS to emulsions prior to heating may have improved their thermal stability by increasing the electrostatic repulsion between the lipid droplets or by increasing the denaturation temperature of the adsorbed proteins. These results may have important applications in the development of heat-stable emulsions.  相似文献   

8.
Eight oil-in-water emulsions were prepared using melt high-pressure homogenisation (HPH) at 300 or 1200 Bar. The emulsions produced from lipid phase (20%) were composed by palm oil alone or in mixture with α-tocopherol at 4:1 weight ratio, and an aqueous phase containing whey proteins alone or in mixture with phospholipids. The resulting nanoemulsions (fat droplet size ranging from 200-500 nm) presented different stability against aggregation and coalescence, fat crystallinity and polymorphisms in relation to different degrees of α-tocopherol encapsulation and protection against chemical degradation. Protein stabilised emulsions were monomodal, while emulsions stabilised by proteins and lecithins were slightly bimodal. Application of an isothermal treatment (4 °C for 2 hours) to these emulsions showed crystallization peaks located at longer time values in smaller particle size emulsions, while in the presence of added α-tocopherol average particle size values were higher and crystallization was not observed in 2 hours storage. Study of fat polymorphisms performed after 12 hours storage at 4 °C revealed the formation of 2L structures with coexistence of α, β’ and β forms in all of the emulsions. Increasing HPH from 300 to 1200 Bar favoured development of β structure (4.5 A-1) in α-tocopherol added emulsions, with the presence of one extra peak β structure evolved at 3.9 A-1 only in emulsions containing lecithins. α-tocopherol addition decreased in 2L structures (by approx. 40-50%). The formation of lipid nanoparticles with decreasing size values (increasing HPH parameters) was accompanied by increased long-term stability against aggregation and coalescence, but increased vitamin degradation (up to 15 wt% for 1200 bar). Degradation of α-tocopherol after 2 months storage at 4 °C was lower for nanoparticles stabilised by whey proteins alone (21 and 33%, respectively) than for nanoparticles stabilised by whey proteins in mixture with phospholipids and presenting higher size values (44 and 52%, respectively), where β polymorphs were more evolved.  相似文献   

9.
Palm olein-based diacylglycerol (POL-DAG) was blended with palm super olein (POoo) in various concentrations (10–90%), with increments of 10% (wt/wt) POL-DAG. The physical and chemical characteristics, i.e., iodine value, acylglycerol content, fatty acid composition, melting and crystallization profiles and solid fat content, for POL-DAG, POoo and their binary blends were evaluated. The mid-infrared FTIR was used to determine the absorption bands of the different concentrations of the oil blends. Only slight differences of FAC and IV were observed. POL-DAG:POoo blends showed significant changes (p < 0.05) in DAG content and decreases in TAG content with increasing POL-DAG content. The DSC thermograms showed that the addition of different concentrations of POL-DAG changed the melting and crystallization behavior of the oil blends (POL-DAG:POoo). The crystallization onset point increased (p < 0.05) with an increasing POL-DAG concentration (10–90%). POL-DAG has the same absorption bands as POoo, with the exception of several minor peaks that appeared at (I) 2954 cm 1, (II) 1267 cm 1, (III) 1199 cm 1, (IV) 1222 cm 1 and (V) 966 cm 1. This study will provide essential information for the palm oil industry to identify the most suitable POL-DAG blends with desirable physicochemical properties for food application purposes.  相似文献   

10.
11.
The effect of Ultra-High Pressure Homogenization (UHPH, 100–300 MPa) on the physicochemical properties of oil-in-water emulsions prepared with 4.0% (w/v) of soy protein isolate (SPI) and soybean oil (10 and 20%, v/v) was studied and compared to emulsions treated by conventional homogenization (CH, 15 MPa). CH emulsions were prepared with non-heated and heated (95 °C for 15 min) SPI dispersions. Emulsions were characterized by particle size determination with laser diffraction, rheological properties using a rotational rheometer by applying measurements of flow curve and by transmission electron microscopy. The variation on particle size and creaming was assessed by Turbiscan® analysis, and visual observation of the emulsions was also carried out. UHPH emulsions showed much smaller d3.2 values and greater physical stability than CH emulsions. The thermal treatment of SPI prior CH process did not improve physical stability properties. In addition, emulsions containing 20% of oil exhibited greater physical stability compared to emulsions containing 10% of oil. Particularly, UHPH emulsions treated at 100 and 200 MPa with 20% of oil were the most stable due to low particle size values (d3.2 and Span), greater viscosity and partial protein denaturation. These results address the physical stability improvement of protein isolate-stabilized emulsions by using the emerging UHPH technology.  相似文献   

12.
Oil-in-water pre-emulsions (15% sunflower + 5% olive oils) obtained by colloid mill homogenization (CM) at 5000 rpm using whey protein isolate at different levels (1, 2 and 4%) were stabilized by ultra high-pressure homogenization (UHPH, 100 and 200 MPa) and by conventional homogenization (CH, 15 MPa). Emulsions were characterized for their physical properties (droplet size distribution, microstructure, surface protein concentration, emulsifying stability against creaming and coalescence, and viscosity) and oxidative stability (hydroperoxide content and thiobarbituric acid reactive substances, TBARs) under light (2000 lux/m2 for 10 days). UHPH produced emulsions with lipid droplets of small size in the sub-micron range (100–200 nm) and low surface protein with unimodal distribution when produced at 4% whey proteins and 200 MPa. All emulsions exhibited Newtonian behavior (n  1). Long term physical stability against creaming and coalescence was observed in UHPH-emulsions, compared to those obtained by CM and CH. However, CH emulsions were highly stable against creaming (days) in comparison to the CM emulsions (hours). UHPH resulted in emulsions highly stable to oxidation compared to CM and CH treatments, especially when 100 MPa treatment was applied.Industrial relevanceIn the food, cosmetic and pharmaceutical sectors, industrial operators are currently interested in developing encapsulating systems to delivery bioactive compounds, which are generally hydrophobic, unstable and sensitive to light, temperature or/and oxygen. Ultra high-pressure homogenization is capable of producing stable submicron emulsions (< 1 μm) with a narrow size distribution, inducing more significant changes in the interfacial protein layer thus preventing droplet coalescence and also inhibit lipid oxidation. The present study suggests that emulsions produced by whey protein (4%) treated by ultra high-pressure homogenization have a good physical stability to flocculation, coalescence and creaming and also high stability to lipid oxidation, opening a wide range of opportunities in the formulation of emulsions containing bioactive components with lipid nature.  相似文献   

13.
This study investigated the adsorption characteristics of olive leaf water extract and its major phenolic compound, oleuropein, at the triglyceride oil–water interface. We also investigated the preparation characteristics of food-grade triglyceride oil-in-water (O/W) emulsions stabilized by oleuropein using microchannel (MC) emulsification. Refined soybean oil, extra virgin olive oil, refined olive oil, and medium-chain triacylglyceride (MCT) oil were used as triglyceride oils. Both olive leaf extract (OLE) and highly purified oleuropein had a pronounced ability to decrease the interfacial tension at the refined soybean oil–water interface. The packing of oleuropein molecules at the triglyceride oil–water interface was estimated on the basis of their surface excess concentration and area occupied per molecule, determined from the Gibbs adsorption equation. MC emulsification was performed using a silicon grooved MC array plate (model CMS6-2). The continuous aqueous phase contained 0.6 wt.% of oleuropein. Monodisperse, oleuropein-stabilized O/W emulsions with an average droplet diameter of 25 μm and coefficient of variation (CV) of < 5% were produced in all systems, except the MCT oil-containing system, even in the absence of a cross-flowing continuous phase. This successful MC emulsification was observed without droplet coalescence for 15 h of continuous operation. Our findings demonstrate that the use of oleuropein, which has an interfacial activity, is capable of producing monodisperse O/W emulsions using MC emulsification and stabilizing the generated oil droplets when appropriate types of triglyceride oils are used.  相似文献   

14.
Coconut cream protein (CCP) fractions were isolated from coconuts using two different isolation procedures: isoelectric precipitation (CCP1-fraction) and freeze–thaw treatment (CCP2-fraction). The ability of these protein fractions to form and stabilize oil-in-water emulsions was compared with that of whey protein isolate (WPI). Protein solubility was a minimum at ∼pH 4, 4.5 and 5 for CCP1, CCP2, and WPI, respectively, and decreased with increasing salt concentration (0–200 mM NaCl) for the coconut proteins. All of the proteins studied were surface active, but WPI was more surface active than the two coconut cream proteins. The two coconut cream proteins were used to prepare 10 wt% corn oil-in-water emulsions (pH 6.2, 5 mM phosphate buffer). CCP2 emulsions had smaller mean droplet diameters (d32  2 μm) than CCP1 emulsions (d32  5 μm). Corn oil-in-water emulsions (10 wt%) stabilized by 0.2 wt% CCP2 and WPI were prepared with different pH values (3–8), salt concentrations (0–500 mM NaCl) and thermal treatments (50–90 °C for 30 min). Considerable droplet flocculation occurred in the emulsions near the isoelectric point of the proteins: CCP2 (pH  4.3); WPI (pH  4.8). Emulsions with monomodal particle size distributions, small mean droplet diameters, and good creaming stability could be produced at pH 7 for WPI, but CCP2 produced bimodal distributions at this pH. The CCP2 and WPI emulsions remained relatively stable to droplet aggregation and creaming at NaCl concentrations ⩽50 and ⩽100 mM, respectively. In the absence of salt, both CCP2 and WPI emulsions were quite stable to thermal treatments (50–90 °C for 30 min).  相似文献   

15.
《Food Hydrocolloids》2006,20(2-3):269-276
The heat stability of emulsions (4 wt% corn oil) formed with whey protein isolate (WPI) or extensively hydrolysed whey protein (WPH) products and containing xanthan gum or guar gum was examined after a retort treatment at 121 °C for 16 min. At neutral pH and low ionic strength, emulsions stabilized with both 0.5 and 4 wt% WPI (intact whey protein) were stable against retorting. The amount of β-lactoglobulin (β-lg) at the droplet surface increased during retorting, especially in the emulsion containing 4 wt% protein, whereas the amount of adsorbed α-lactalbumin (α-la) decreased markedly. Addition of xanthan gum or guar gum caused depletion flocculation of the emulsion droplets, but this flocculation did not lead to their aggregation during heating. In contrast, the droplet size of emulsions formed with WPH increased during heat treatment, indicating that coalescence had occurred. The coalescence during heating was enhanced considerably with increasing concentration of polysaccharide in the emulsions, up to 0.12% and 0.2% for xanthan gum and guar gum, respectively; whey peptides in the WPH emulsions formed weaker and looser, mobile interfacial structures than those formed with intact whey proteins. Consequently, the lack of electrostatic and steric repulsion resulted in the coalescence of flocculated droplets during retort treatment. At higher levels of xanthan gum or guar gum addition, the extent of coalescence decreased gradually, apparently because of the high viscosity of the aqueous phase.  相似文献   

16.
The influence of calcium ions and chelating agents on the thermal stability of model nutritional beverages was examined. Oil-in-water emulsions (6.94% (w/v) soybean oil, 0.35% (w/v) WPI, 0.02% (w/v) sodium azide, 20 mM Tris buffer, 0–10 mM CaCl2, and 0–40 mM EDTA or citrate, pH 7.0) were stored at temperatures between 30 and 120 °C for 15 min. The particle size, particle charge, creaming stability, rheology, and free-calcium concentration of the emulsions were then measured. In the absence of chelating agents, appreciable droplet aggregation occurred in emulsions held at temperatures from 80 to 120 °C, which led to increased emulsion particle diameter, shear-thinning behavior, apparent viscosity, and creaming instability. Addition of chelating agents to the emulsions prior to heating decreased, but did not prevent, droplet aggregation in the emulsions. EDTA was more effective than citrate in decreasing droplet aggregation. Heat treatment increased the amount of chelating agents required to prevent droplet aggregation in the emulsions. Free-calcium concentration and droplet surface potential was independent of heat-treatment temperature, indicating that the performance of the chelating agents in binding calcium ions was not affected by the heat treatment. It was suggested that increased hydrophobic attractive interactions between the droplets occurred during heating, which induced droplet aggregation.  相似文献   

17.
Probiotics have demonstrated various health benefits but have poor stability to sustain food processing and storage conditions, as well as after ingestion. Biopolymer beads are commonly studied to encapsulate probiotic cells to improve their stability, but the millimeter-dimension of these beads may not meet the quality requirement of food products. The aim of this study was to enhance the viability of Lactobacillus salivarius NRRL B-30514 by encapsulation in emulsion droplets with multiple lipid-protein-pectin layers. Spray-dried L. salivarius was suspended in melted anhydrous milk fat that was then emulsified in a neutral aqueous phase with whey protein isolate or sodium caseinate to prepare primary solid/oil/water (S/O/W) emulsions. Subsequently, pectin was electrostatically deposited onto the droplet surface at pH 3.0 to form secondary emulsions. The encapsulation efficiency was up to 90%. After 20-day storage at 4 °C, the viable cell counts of bacteria in secondary emulsions at pH 3.0 and primary emulsions at 7.0 were 3 log higher than the respective free cell controls. After heating at 63 °C for 30 min, free L. salivarius was inactivated to be undetectable, while about 2.0 log CFU/mL was observed for primary (at pH 7.0) and secondary (at pH 3.0) emulsion treatments. Additionally, a 5 log-CFU/g-powder reduction was observed after spray drying free L. salivarius, while a 2 log CFU/g reduction was observed for emulsion treatments with capsules smaller than 20 μm. Furthermore, cross-linking the secondary emulsion with calcium enhanced the viability of L. salivarius after the simulated gastric and intestinal digestions. Therefore, the studied S/O/W emulsion systems may be used to improve the viability of probiotics during processing, storage, and gastrointestinal digestion.  相似文献   

18.
The experiments evaluated the influence of fish oil quality and cold storage temperature on the oxidative stability of milk emulsions containing 1.0% w/w milk fat and 0.5% w/w of either a pure fish oil or a fish oil:rapeseed oil mixture. The results showed that it was possible to produce a pasteurised milk product enriched with the important n-3 PUFA from fish oil with acceptable sensory characteristics if (1) the emulsions were based on a mixture of fish oil and rapeseed oil and (2) the initial peroxide value (PV) of the added oil blend was below 0.5 meq kg−1. The sensory analysis showed a clear distinction between emulsions based on oil with PV 0.1 and 0.5 meq kg−1, whereas the PV and the gas chromatographic (GC) analysis of volatile oxidation products were not sensitive enough to reveal these differences clearly. The GC analyses showed that the onset of formation of the volatiles was earlier with increased storage temperature in the range of 2–9 °C.  相似文献   

19.
O/W emulsions (6 wt.% olive oil) were prepared at pH 3.3 using different WPI:Tween 20 weight ratios (1:0, 3:1, 1:1, 1:3, 0:1) at 1 wt.% total concentration. The emulsion droplet size was found to decrease with an increase in Tween 20. A minimum droplet size of d3,2 300 nm was found for Tween systems alone, similar to that found (360 nm) for a 1:1 WPI:Tween 20 combination (p < 0.05). This specific composition showed a value for the interfacial tension close to that of Tween 20 alone. However, the emulsions presented low stability regardless of the WPI:Tween 20 ratio. To increase their stability, pectin was added, in various concentrations (0.2, 0.4 and 0.6 wt.%), using the Layer by Layer technique. In the presence of pectin, the ζ-potential of the oil droplets became negative; indicating that negatively charged pectin was absorbed onto the positively-charged droplet surface forming a secondary layer. The additional layer resulted in a wide range of emulsion stability. For all pectin concentrations, the 1:1 ratio of WPI:Tween 20 showed the highest stability. In most emulsions, extensive aggregation of oil droplets was observed, and their viscosity increased. Insufficient amounts of pectin to form the secondary layers led to bridging flocculation phenomena of oppositely charged pectin and proteins, leading to aggregation of the oil droplets. The higher the concentration of pectin, the greater the stability of the emulsion due to higher viscosity. All in all, the addition of a second layer consisting of pectin can be used to increase the stability of an emulsion containing emulsion droplets in the sub-micron range.  相似文献   

20.
The potential of using microparticulated whey protein (MWP) in combination with either modified starch or locust bean gum (LBG) as fat mimetics to fabricate reduced calorie emulsion-based sauces and dressings was studied. The influence of food matrix composition (protein, polysaccharide, and fat content), ionic strength, and pH on the properties of thermally processed model emulsions (90 °C/10 min) was investigated. Increasing protein concentration (2.5–7.5%) increased the mean (d3,2) particle diameter due to the formation of large protein aggregates. All MWP-containing systems had a creamy white appearance with high lightness (L* > 75). Addition of fat droplets (5%) further increased their lightness (L* > 90) due to enhanced light scattering. Addition of starch, LBG, or MWP increased emulsion viscosity due to the increased effective volume fraction of the dispersed phase. Addition of calcium chloride (10 mM) and pH adjustment (2–8) caused little change in the physicochemical properties of the mixed systems. Overall, the appearance and rheological properties of the mixed systems were similar to commercial sauces and dressings. This study demonstrates that reduced calorie food emulsions with appearance and consistency similar to those of full-fat versions can be formulated using protein microparticles and polysaccharides.  相似文献   

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