首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
The freeze–thaw stability of 5 wt% hydrogenated palm oil-in-water emulsions (pH 3) containing droplets stabilized by sodium dodecyl sulfate (SDS)–chitosan–pectin membranes was studied. The multilayered interfacial membranes were created using an electrostatic layer-by-layer deposition method. The ζ-potential, mean particle diameter, fat destabilization, apparent viscosity and microstructure of the emulsions were used to examine the influence of freezing on their stability. Emulsions containing oil droplets stabilized only by SDS were highly unstable to droplet coalescence when either the oil phase became partially crystallized or the water phase crystallized. Emulsions containing oil droplets stabilized by SDS–chitosan membranes were stable to droplet coalescence, but unstable to droplet flocculation. Emulsions containing droplets stabilized by SDS–chitosan–pectin membranes were stable to both droplet coalescence and flocculation. The interfacial engineering technology utilized in this study could lead to the creation of food emulsions with improved stability to freeze–thaw cycling.  相似文献   

2.
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   

3.
Over the last decade, conscious food consumption has been revolutionizing the food industry. The search for additives that meet concepts of naturalness, healthiness and sustainability represents one of the major challenges in food industry. The development of emulsifiers in the ionic liquid (IL) form using compounds that can be obtained from natural sources to replace conventional ones is a promising approach. In this work, we have reported the application of bio-based ILs derived from fatty acids (FAs) and choline (Ch) as novel emulsifiers to produce potential food-grade oil-in-water emulsions by pre-mixing (PM) or PM followed by high-intensity ultrasound (HIUS)-assisted process (PM + U). The effects of the type of IL, considering molecular structures of FAs (C18OOH or C18:1OOH) and vegetable oil concentration (30:70 or 70:30, oil:water ratio) to form and stabilize emulsions were evaluated. The study was focused on the following aspects: synthesis and characterization of ILs, and kinetic stability, droplet size and size distribution, optical microscopy, viscosity profile and rheological behavior of the emulsions. ILs presented high emulsifier ability, since some emulsions were stable after storage time of at least 30 days, being such stability related to the type of IL, oil concentration and emulsifying process. The observed behavior was associated to lower droplet size and/or emulsion viscosity. [Ch][C18OO] presented higher emulsifier ability than [Ch][C18:1OO], and this behavior was more evident at higher oil concentration. Emulsions obtained by PM presented phase separation after their preparation, whereas most of those prepared by PM + U were visually stable, being those containing higher oil concentration the formulations that presented higher viscoelasticity, with a gel like behavior. Therefore, bio-based ILs have promising application potential as emulsifiers, and their use to obtain high stable emulsions can be enhanced by using the HIUS technique.  相似文献   

4.
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   

5.
Bagasse, a by-product from raw sugar factories, is conventionally burned for energy production. In this study, bagasse extracts from hydrothermal liquefaction (HTL) treatment (160 °C, 1 MPa and 30 min) with a carbohydrate content of 510.3 mg g−1 and 0.5 mg g−1 of total phenols were applied as emulsifiers in oil-in-water (O/W) emulsions. Bagasse extracts from HTL (0.5–4 wt%) lowered the interfacial tension between oil–water interphase from 19.8 to 14.0 mN m−1, owing possibly to the surface-active hydrophilic carbohydrate-hydrophobic lignin complexes in the extracts (lignin content: 7.1% w/w). Emulsions stabilised by bagasse extracts from HTL with average droplet size, dav of 0.79 μm were comparable with gum arabic (GA), dav of 2.24 μm after 11 days at 25 °C. Bagasse extracts containing biopolymers have the potential for industrial applications involving emulsion systems; therefore, HTL treatment of bagasse without any solvents can be regarded as an effective tool for producing natural emulsifiers.  相似文献   

6.
The ability of a modified whey protein concentrate (MWPC), which contains relatively high proportions of phospholipid and high molecular weight protein fractions, to form and stabilize 10 wt% corn oil-in-water emulsions (pH 7.0, 5 mM phosphate buffer) was compared with that of a conventional whey protein concentrate (CWPC). The MWPC stabilized emulsions required less protein to prepare stable emulsions with monomodal particle size distributions and small mean droplet diameters (d43  0.3 μm at [WPC]  0.5 wt%) than CWPC stabilized emulsions (d43  0.4 μm at [WPC]  0.9 wt%) under similar homogenization conditions (5 passes at 5000 psi). In addition, the emulsions stabilized by 0.9 wt% MWPC were more stable to high salt concentration (NaCl  200 mM), thermal processing (30–90 °C for 30 min) and pH (3, 6 and 7) than those stabilized by the same concentration of CWPC, which was attributed to polymeric steric repulsion rather than electrostatic repulsion. This study has important implications for the wide application of WPC as a natural emulsifier in food products.  相似文献   

7.
Food reformulation, either to reduce nutrient content or to enhance satiety, can negatively impact upon sensory characteristics and hedonic appeal, whilst altering satiety expectations. Within numerous food systems, perception of certain sensory attributes, known as satiety-relevant sensory cues, have been shown to play a role in food intake behaviour. Emulsions are a common food structure; their very nature encourages reformulation through structural design approaches. Manipulation of emulsion design has been shown to change perceptions of certain sensory attributes and hedonic appeal, but the role of emulsions in food intake behaviour is less clear. With previous research yet to identify emulsion designs which promote attributes that act as satiety-relevant sensory cues within emulsion based foods, this paper investigates the effect of oil droplet size (d4,3: 0.2–50 μm) and flavour type (Vanilla, Cream and No flavour) on sensory perception, hedonics and expected food intake behaviour. By identifying these attributes, this approach will allow the use of emulsion design approaches to promote the sensory characteristics that act as satiety-relevant sensory cues and/or are related to hedonic appeal. Male participants (n = 24) assessed the emulsions. Oil droplet size resulted in significant differences (P < 0.05) in ratings of Vanilla and Cream flavour intensity, Thickness, Smoothness, Creamy Mouthfeel, Creaminess, Liking, Expected Filling and Expected Hunger in 1 h’s time. Flavour type resulted in significant differences (P < 0.05) in ratings of Vanilla and Cream flavour intensity, Sweetness and Liking. The most substantial finding was that by decreasing oil droplet size, Creaminess perception significantly increased. This significantly increases hedonic appeal, in addition to increasing ratings of Expected Filling and decreased Expected Hunger in 1 h’s time, independently of energy content. If this finding is related to actual eating behaviour, a key target attribute will have been identified which can be manipulated through an emulsions droplet size, allowing the design of hedonically appropriate satiating foods.  相似文献   

8.
Droplet size distribution and thermal behavior of concentrated oil-in-water emulsions based on soybean oil (SBO)/palm kernel olein (PKO) blends were investigated. The emulsions were prepared using 70% (wt./wt.) oil blends of SBO/PKO as dispersed phases and stabilized by egg yolk. An increase in PKO level (0–40% wt./wt.) in the oil dispersed phase volume fraction caused significant increases (p < 0.05) in volume-weighted mean diameter (d4,3). The DSC data suggested that crystallization of the emulsions was induced by a ‘template effect’ of yolk constituents via a surface heterogeneous nucleation. Emulsions with 0–20% (wt./wt.) PKO levels in the dispersed phase demonstrated a good cool–heat stability even after three successive thermal cycles (from 50 °C to ?70 °C at 10 min/°C). After the first thermal cycle, emulsions with 30% and 40% PKO levels in the oil dispersed phase were destabilized due to strong coalescence and crystallized via volume-surface heterogeneous nucleation. The unstable emulsions were attributable to high level of saturated triacylglycerols from PKO, with high droplet size characteristic, causing them to be more prone to partial coalescence.  相似文献   

9.
Oil-in-water emulsions are an important vehicles for the delivery of hydrophobic bioactive compounds into a range of food products. The preparation of very fine emulsions is of increasing interest to the beverage industry, as novel ingredients can be added with negligible impact to solution clarity. In the present study, both a batch and focused flow-through ultrasonic cell were utilized for emulsification with ultrasonic power generation at 20–24 kHz. Emulsions with a mean droplet size as low as 135 ± 5 nm were achieved using a mixture of flaxseed oil and water in the presence of Tween 40 surfactant. Results are comparable to those for emulsions prepared with a microfluidizer operated at 100 MPa. The key to efficient ultrasonic emulsification is to determine an optimum ultrasonic energy intensity input for these systems, as excess energy input may lead to an increase in droplet size.Industrial relevanceThe preparation of oil-in-water emulsions is a common feature of food processing operations. The use of ultrasound for this purpose can be competitive or even superior in terms of droplet size and energy efficiency when compared to classical rotor­stator dispersion. It may also be more practicable with respect to production cost, equipment contamination and aseptic processing than a microfluidisation approach. The present paper shows that ultrasound can be effective in producing nanoemulsions for use in a range of food ingredients.  相似文献   

10.
11.
The effect of heat treatment on the properties of soy protein‐stabilised emulsions was investigated. Emulsions were prepared with unheated and heat‐treated soy protein (NSP and HSP) dispersions. Heating on soy protein dispersions at 95 °C for 30 min resulted in smaller average oil droplet size, lower tendency for oil droplet flocculation, higher protein adsorption and lower viscosity. The properties of emulsions were significantly influenced by the protein concentration. The sodium dodecyl sulphate–polyacrylamide gel electrophoresis (SDS–PAGE) profiles showed that the heat treatment on soy protein dispersions increased the protein adsorption at O/W interface. The viscosity of all samples at low shear rate was inversely proportional to the d32, suggesting a positive relation to the total interfacial area per unit volume. Emulsions showed shear‐thinning behaviour. The relaxation time was found to increase with aqueous phase viscosity determined by the Cross viscosity model.  相似文献   

12.
Oil-in-water emulsions can be considered as an important delivery system for lipophilic food molecules. In this study, pea protein isolate (PPI) was studied for its emulsifying capacity at various pH values and pH 7 was selected to prepare emulsions for the production of dry microcapsules. Emulsions stabilized by PPI just enough to cover oil droplets were mixed with solutions of starch hydrolysates of various dextrose equivalent (DE) and subsequently spray dried to yield powders with 30 wt% oil. Effects of DE (6, 12, 19, and 28) on feed emulsion properties and on the characteristics of the spray-dried powders were examined. Reconstituted emulsion oil droplet size and stability were affected by DE in all cases. Microencapsulation efficiency of dried emulsions increased significantly with increasing DE. The scanning electron microscope results showed that lower maltodextrins DE microcapsules are shallow and presented rough surfaces or invaginations. However, higher carbohydrates DE microcapsules were circular and uniform showing minimum cracks and dents on the surface confirming these DE to be efficient encapsulating materials. The formation of the drying matrix seems control the destabilization of pea protein-coated oil droplets during spray drying. In systems where the matrix is formed in a uniform manner, the interfacial protein film is less affected by the drying process. Thus the functionalities of pea protein can be protected during drying by using high DE carbohydrates.  相似文献   

13.
ABSTRACT: The oxidative stability of polyunsaturated lipids can be improved by incorporating them in oil droplets surrounded by positively charged whey protein isolate (WPI) membranes. This study dealt with the factors that influence the physical properties of WPI-stabilized oil-in-water emulsions at pH 3. Emulsions containing 5 to 50 wt% corn oil and 0.5 to 5.0 wt% WPI (protein-to-oil ratio of 1:10) were prepared at pH 3. The apparent viscosity of the emulsions increased appreciably at oil concentrations ≥ 35 wt%; however, the particle size was relatively independent of oil concentration. The influence of NaCl (0 to 250 m M ) on the physical properties of 28 wt% emulsions was examined. Significant increases in mean particle size, apparent viscosity, and creaming instability occurred at ≥150 m M NaCl, which were attributed to flocculation induced by screening of the electrostatic repulsion between droplets. The influence of heat treatment (30°C to 90°C for 30 min) on 28 wt% emulsions was examined in the absence and presence of salt, respectively. At 0 m M NaCl, heating had little effect on the physical properties of the emulsions, presumably because the electrostatic repulsion between the droplets prevented droplet aggregation. At 150 m M NaCl, the mean particle diameter, apparent viscosity, and creaming instability of the emulsions increased considerably when they were heated above a critical temperature, which was 70°C when salt was added before heating and 90°C when salt was added after heating. These results have important implications for the design of WPI-stabilized emulsions that could be used to incorporate functional lipids that are sensitive to oxidation, for example, ω-3 fatty acids.  相似文献   

14.
Model infant formula emulsions containing 15.5, 35.0 and 70.0 g L−1 protein, soybean oil and maltodextrin (MD), respectively, were prepared. Emulsions were stabilised by whey protein hydrolysate (WPH) + CITREM (9 g L−1), WPH + lecithin (9 g L−1) or WPH conjugated with MD (WPH–MD). All emulsions had mono-modal oil droplet size distributions post-homogenisation with mean oil droplet diameters (D4,3) of <1.0 μm. No changes in the D4,3 were observed after heat treatment (95 °C, 15 min) of the emulsions. Accelerated storage (40 °C, 10 d) of unheated emulsions resulted in an increase in D4,3 for CITREM (2.86 μm) and lecithin (5.36 μm) containing emulsions. Heated emulsions displayed better stability to accelerated storage with no increase in D4,3 for CITREM and an increase in D4,3 for lecithin (2.71 μm) containing emulsions. No increase in D4,3 over storage was observed for unheated or heated WPH–MD emulsion, indicating its superior stability.  相似文献   

15.
High Internal Phase Emulsions (HIPE) were formulated using 1% w/w orange pomace (i.e. uncracked micro-scaled byproduct powder) as sole stabilizer, from a quick and simple process, with 80% of sunflower oil and 20% of water in the liquid phase. Various indicators were monitored over a 2-month storage at Tamb, such as droplet size distribution, flow and viscoelastic properties, multi-scale microstructure (light and confocal microscopy). HIPPEs were stable towards coalescence and drainage, showing the complementarity between the anchoring insoluble fraction acting as Pickering particles at the oil-water interface and the viscosifying/film-forming soluble compounds. The oil droplet size distribution remained the same, and no significant change could be quantified regarding the elastic modulus, the yield stress or the viscosity of the emulsions in 60 days. However, changing the oil source from sunflower to another vegetal or synthetic oil could lead to unstable systems.  相似文献   

16.
The rheological behavior of oil-in-water (O/W) emulsions stabilized by whey protein isolate (WPI) and its relationship with the microstructural changes caused by shearing was studied. O/W emulsions (50, 55, and 60 g oil/100 g) were made using ultrasound and their rheological properties were determined by: flow curve test, constant shear rate test, and hysteresis loop test. Microstructural changes were evaluated in terms of droplet size and droplet size distribution. Emulsions containing 50 and 55 g oil/100 g showed a Newtonian behavior, whereas those with 60 g oil/100 g exhibited shear-thinning behavior. Under constant deformation, the apparent viscosity of the emulsions decreased with time. The hysteresis loop test revealed that increasing oil content increased the degree of thixotropy of the emulsions. Moreover, before and after the constant deformation test droplet size distributions did not show differences, indicating that the decrease in the apparent viscosity may be promoted by breakdown and further deformation and/or reorganization of oil droplets flocs. In turn, experimental data obtained from the constant shear rate test was fitted to a structural kinetic model. The rate constant values showed no particular trend with oil content and shear rate, implying that probably wall slip occurred at high shear rates and high oil contents.  相似文献   

17.
The emulsifying properties of collagen fiber were modified by heat treatment at temperatures ranging from 50 to 85 °C for 20 or 60 min. In addition to heat treatment, the influence of pH (3.5 and 9.2) and the emulsifying process (rotor-stator device and high-pressure homogenizer) were evaluated on oil-in-water emulsions stabilized by collagen fiber through visual analysis (stability), microstructure and rheological measurements. Emulsions homogenized using solely the rotor-stator device showed phase separation and a larger mean droplet size (d32), except for the emulsion composed by non-heated collagen fiber. The alkaline emulsions showed lower kinetic stability, since collagen fibers have a lower net charge (zeta potential) at higher pH values, decreasing the electrostatic stability process. Heat treatment slightly decreased the protein charge and significantly reduced the insoluble protein content, suggesting a decrease in the emulsifying properties of the collagen fiber. The use of high-pressure homogenization (20-100 MPa) made it possible to produce acid emulsions with a reduced droplet size and distribution. At 20 MPa, the emulsions showed a higher d32 value (between 3.17 and 1.18 μm), while at 60 and 100 MPa the emulsions presented lower d32 values (between 0.74 and 0.94 μm) without any significant variation between the different heat-treated collagen fibers, but showing a noticeable decrease in emulsion viscosity and elasticity with increases in the homogenization pressure and heat treatment.  相似文献   

18.
《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   

19.
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   

20.
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   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号