Impact of Phytic Acid on the Physical and Oxidative Stability of Protein-Stabilized Oil-in-Water Emulsions

The effects of phytic acid on the physical and oxidative stability of flaxseed oil-in-water emulsions containing whey protein-coated lipid droplets were investigated. The surface potential, particle size, microstructure, appearance, and oxidation of these emulsions were monitored when they were stored at pH 3.5 and 7.0 for 25 days in the dark (37 °C). The phytic acid and protein-coated lipid droplets had similar charges (both negative) at pH 7.0, but had opposite charges (negative and positive) at pH 3.5. At pH 7.0, the addition of phytic acid had no impact on the physical stability of the emulsions but significantly improved their oxidative stability, which was attributed to its ability to sequester pro-oxidant transition metals (iron ions). At pH 3.5, extensive droplet aggregation and creaming occurred in the emulsions containing phytic acid, which was ascribed to charge neutralization and ion bridging. The oxidative stability of the acidified emulsions, however, still increased after addition of phytic acid, which was again attributed to its ability to chelate iron ions. Interestingly, the antioxidant activity of phytic acid decreased as its level was increased. Our results suggest that phytic acid may be used as a natural antioxidant to improve the oxidative stability of food emulsions containing polyunsaturated fatty acids, but its level must be carefully controlled.

     

Effect of Tween Emulsifiers on the Shear Stability of Partially Crystalline Oil-in-Water Emulsions Stabilized By Sodium Caseinate

We investigated the effects of Tween emulsifier fatty acid chain length on the shear stability and crystallization behavior of 35 wt% partially crystalline oil-in-water emulsions prepared with and without 1 wt% sodium caseinate. Emulsions containing sodium caseinate and Tween 20, 40, 60 or 80 varied in shear stability, degree of supercooling and crystallization behavior depending on the type and concentration of Tween as well as the presence of protein. Generally, emulsions containing the unsaturated emulsifier Tween 80 were the most shear sensitive followed by the saturated emulsifiers Tween 20, 40 and 60 in order of increasing fatty acid chain length. Long chain saturated Tween emulsifiers (40 and 60) improved shear stability regardless of whether sodium caseinate was present indicating that alone, these emulsifiers form more robust interfacial films compared to the saturated short chain length Tween 20 and Tween 80. In emulsions prepared with sodium caseinate, the degree of supercooling decreased and the crystallization rate diminished with increasing saturated fatty acid chain length but only negligible changes were found without sodium caseinate. Together, these findings indicate that long chain saturated Tween emulsifiers provide better emulsion stability regardless of the presence of sodium caseinate but with sodium caseinate, stability may also be affected by changes to fat crystallization. These novel findings provide guidance on how combinations of proteins and emulsifiers can be used to modify and control the stability of partially crystalline oil-in-water emulsions through their combined effects on the properties of the interfacial film and fat crystallization.     

Effect of Processing and Storage Parameters on the Oxidative Deterioration of Oil-in-Water Emulsions

The effect of storage temperature, pH, and homogenization pressure on the oxidative deterioration of Tween 20 and sodium caseinate sunflower oil-in-water emulsions was studied by monitoring conjugated dienes (CD), lipid hydroperoxides (LH), and thiobarbituric acid reactive substances (TBARs). CD increased linearly with storage time, and the rate constant was temperature dependent according to the Arrhenius equation with an activation energy equal to 37.5 kJ mol⁻¹. The increase in LH and TBARs with temperature (5–60°C) was in good agreement with CD variation. Tween-stabilized emulsions oxidized faster as pH increased from 3 to 7, whereas a different behavior was observed in emulsions stabilized with sodium caseinate or a mixture of both emulsifiers. A change of homogenization pressure (30–900 bars), reflecting variation of emulsion average droplet size, had no effect on the oxidative stability of the emulsions.     

In Vitro Digestion of caseinate and Tween 20 Emulsions

Food Biophysics - In vitro digestion experiments are set-up with emulsions stabilized either with sodium caseinate and/or Tween 20, in the presence of mucin in the simulated GI fluids. The progress...     

Formation of Fine Oil-in-Water Emulsions by the Gel Emulsification Method with Saccharide and Protein

An emulsification method using a gel-like phase of a saccharide and protein mixture has been developed. In the method, which is called a gel emulsification method, an oil is added to the highly concentrated saccharide solution containing protein to form a clear gel-like phase, which followed by dilution with water to form a fine oil-in-water emulsion. This emulsion was investigated as to its emulsifying activity and emulsion stability as compared with that obtained by high-shear equipment, which was called a homomixer method. The emulsifying activity of the emulsions prepared by the gel emulsification method was much higher than that of the emulsions prepared by the homomixer method.

The emulsions prepared by both methods were highly stable in terms of the stability against coalescence. On the other hand, the stability against creaming of the emulsions prepared by the gel emulsification method was much higher than that of the emulsions prepared by the homomixer method.

The surface hydrophobicity of the protein and the unfreezable water content in the highly concentrated saccharide solution containing protein were not correlated to the emulsifying properties of the emulsions prepared by the gel emulsification method, which appeared to be dependent on the viscosity of the highly concentrated saccharide solution containing protein.     

Impact of Heat and Laccase on the pH and Freeze-Thaw Stability of Oil-in-Water Emulsions Stabilized by Adsorbed Biopolymer Nanoparticles

The enzymatic cross-linking of adsorbed biopolymer nanoparticles formed between whey protein isolate (WPI) and sugar beet pectin using the complex coacervation method was investigated. A sequential electrostatic depositioning process was used to prepare emulsions containing oil droplets stabilized by WPI – nanoparticle – membranes. Firstly, a finely dispersed primary emulsion (10 % w/w miglyol oil, 1 % w/w WPI, 10 mM acetate buffer at pH 4) was produced using a high-pressure homogenizer. Secondly, a series of biopolymer particles were formed by mixing WPI (0.5 % w/w) and pectin (0.25 % w/w) solutions with subsequent heating above the thermal denaturation temperature (85 °C, 20 min) to prepare dispersions containing particles in the submicron range. Thirdly, nanoparticle-covered emulsions were formed by diluting the primary emulsion into coacervate solutions (0–0.675 % w/w) to coat the droplets. Oil droplets of stable emulsions with different interfacial membrane compositions were subjected to enzymatic cross-linking. We used cross-linked multilayered emulsions as a comparison. The pH stability of primary emulsions, biopolymer complexes and nanoparticle-coated base emulsions, as well as multilayered emulsions, was determined before and after enzyme addition. Freeze-thaw stability (?9 °C for 22 h, 25 °C for 2 h) of nanoparticle-coated emulsions was not affected by laccase. Results indicated that cross-linking occurred exclusively in the multilamellar layers and not between adsorbed biopolymer nanoparticles. Results suggest that the accessibility of distinct structures may play a key role for biopolymer-cross-linking enzymes.     

Effect of Soy Soluble Polysaccharide on the Stability of Soy-Stabilised Emulsions During In Vitro Protein Digestion

This study investigated physicochemical properties of soy soluble polysaccharide (SSP) and pectinase-hydrolysed soy soluble polysaccharide (PH-SSP) from okara, the residue from soy milk production, and their influences when used as a fibre source in oil-in-water (o/w) emulsions. Although pectinase hydrolysed only the carbohydrate fraction in SSP, it resulted in the self-association of PH-SSP to the large-size aggregates. When PH-SSP was added to liquid emulsion containing 3.33% (w/v) rice bran oil and 3.75% (w/v) heated soy protein, it regulated the contents of protein in serum phase, sediment phase and at oil–water interface. The types and contents of soy proteins in the serum phase and sediment phase could be manipulated by pre-heating of soy proteins at 80 °C for 30 min and the addition of PH-SSP. The presence of PH-SSP (0–6% w/v) induced different distribution of proteins to the sediment phase and subsequent in vitro protein digestion in the emulsion. Overall, this study proposed the means to design the distributions of proteins in different phases of o/w emulsion for different degrees of oil release, emulsion stability and protein-polysaccharide coacervation during the course of in vitro peptic and tryptic digestion.     

油相的极性对乳剂稳定性的影响

乳剂是热力学不稳定体系,其不稳定性是由在分散相和分散介质之间形成最小界面区域的趋势造成的.最小界面区域主要由絮凝和Ostwald ripening决定的.絮凝通常被认为是导致乳剂破坏的最主要原因,但是絮凝可以通过选择适宜的稳定剂来避免.而另一方面,只要有弯曲界面的存在,就会发生Ostwald ripening.这种分散相的传递既有胶束传递又有分子传递,而分子传递不仅与乳滴曲率的不同有关,还与乳滴的组成有关.乳滴组成的不同主要是油相的不同,可以通过油相极性的知识来预测,通常来讲,随着油相极性的增大,乳剂的稳定性降低.     

Effect of Gum Arabic,Gum Ghatti and Sugar Beet Pectin as Interfacial Layer on Lipid Digestibility in Oil-in-Water Emulsions

The impact of gum arabic (GA), ghatti gum (GG), and sugar beet pectin (SBP) on the digestion rate of emulsified lipids is investigated in vitro under model duodenal digestion condition. The aim was to understand the role of the interfacial layer surrounding the lipid droplets on lipid hydrolysis in order to control lipid digestion. The emulsifier concentration required to provide the same emulsion droplet size decreased in the order: GA > GG > SBP, demonstrating the best emulsifying activity of SBP. The rate and extent of free fatty acid release during lipid digestion did not differ significantly among the three types of gums in emulsions with D[2,3] < 2 μm. However, considerable difference was observed in emulsions with D[2,3] > 2 μm, and the digestive rate decreased in the order: GA > SBP > GG. The difference in digestion rate was attributed to the stability of the emulsified lipid droplets in the stimulated intestinal juice and the resistance of interfacial layer against displacement by bile salts. The difference of resisting against displacement by bile salts for the interfacial layers was detected with bile salts concentration of 0.025 mg/mL, and all of the pre-adsorbed emulsifiers could be completely displaced from interface by bile salts at 5 mg/mL. Emulsions with SBP were susceptible to Ca²⁺ and Na⁺ in simulated intestinal juice, resulting in the flocculation and coalescence of emulsion droplets. A reduction of the surface area of lipids would contribute to a slow digestion. Emulsion stabilized by GG was very effective at retarding lipolysis mainly due to the affinity of linked protein moieties of GG and its hydrophobic binding with bile salts. The knowledge gained in the study has important implications in designing proper emulsion-based systems for controlling lipid digestibility at specific sites within the gastrointestinal tract.     

Effect of Compositional Factors against the Thermal Oxidative Deterioration of Novel Food Emulsions

This work attempts to determine any relationship between certain endogenous parameters and the oxidative deterioration of protein-stabilized oil-in-water emulsions. The contribution of compositional factors (e.g., type and amount of emulsifier, fat phase, etc.) is further elucidated. Among 10% cottonseed o/w emulsions prepared by 1% emulsifier (Tween, sodium caseinate, or whey protein), lipid autoxidation (at 40°C) was much faster in the Tween emulsion than in the protein ones, with whey protein presenting a clear antioxidant effect. Increase in protein concentration (0.5–2% w/w) led to a decrease in droplet size but an increase in oxidative stability, in terms of conjugated diene hydroperoxides formation at 232 nm. The type of lipid phase significantly affected the rate of thermal oxidation at 60°C. In the most oxidatively vulnerable sunflower-oil-based emulsions, an increase in fat content (10–40%) resulted in a reduction of oxidative deterioration. By selecting a more concentrated emulsion (20% o/w, 2% emulsifier), in order to structurally approach real novel food products, any influence of the composition of the emulsifier (combination of Tween and sodium caseinate preparation) was subsequently tested. An increase in protein proportion in the emulsifier was found to inhibit proportionally the oxidative instability of the emulsions, as evaluated by the determination of both primary (conjugated diene and lipid hydroperoxides) and secondary [thiobarbituric acid-reactive substances (TBARS)] oxidation products.     

Specific Ions Effect on Emulsions, Foams, and Gels of a Seed Protein

A protein concentrate was prepared from the seeds of jack bean (Canavalia ensiformis), and the influence of selected Hofmeister salts on functional properties of the protein concentrate was investigated. Results indicated that kosmotropic salts (Na₂SO₄, NaCl, NaBr) improved water absorption capacity and least gelation concentration of the proteins more than chaotropic salts (NaI, NaClO₄, NaSCN) did. The reduction in water absorption capacity followed the Hofmeister trend (Na₂SO₄ > NaCl > NaBr > NaI > NaClO₄ > NaSCN). However, a reverse trend was observed with the foaming and emulsifying properties. These findings are insightful in understanding the structure–property relations of the concentrate.     

Influence of Nanoemulsion Addition on the Stability of Conventional Emulsions

Interest in using nanoemulsions as delivery systems for lipophilic food ingredients is growing due to their high optical clarity, good physical stability, and ability to increase bioavailability. Nanoemulsion-based delivery systems may need to be incorporated into food matrices that also contain conventional emulsions. The aim of this work was to evaluate the effect of adding nanoemulsions (d?<?200 nm) to conventional emulsions (d?>?200 nm) on the creaming stability and microstructure of the mixed systems. Droplet flocculation and rapid creaming was observed when the nanoemulsion concentration exceeded a particular level: the critical flocculation concentration (CFC) was 3.75 % and 0.25 % (v/v) for conventional emulsions with average droplet diameters of 350 and 250 nm, respectively. Confocal microscopy indicated that there was appreciable droplet flocculation, and the fraction of individual droplets with diameters?<?100 nm decreased after 14 days storage, which was probably due to Ostwald ripening and/or coalescence. The results of the present study might have important implications for the incorporation of nanoemulsion-based delivery systems into food products containing larger fat droplets, such as dressings, sauces, or beverages.     

Effects of Addition of a Palmitic Sucrose Ester on Low-Trans-Fat Blends Crystallization in Bulk and in Oil-in-Water Emulsions

The effect of addition of a highly hydrophobic emulsifier, the palmitic sucrose ester P-170, on isothermal crystallization behavior of a high-melting fraction of milk fat (HMF) and its mixtures with 20% or 40% sunflower oil (SFO), both in bulk and in emulsion systems, were studied by nuclear magnetic resonance (NMR) and by time-resolved in situ small-angle synchrotron X-ray scattering (SAXS). NMR studies showed that the effect of P-170 on the overall isothermal crystallization kinetics in bulk phase could be either acceleration or delay. The effect was strongly dependent on supercooling. For HMF, P-170 retarded crystallization at temperatures above 29.0 ± 0.2 °C, while below that temperature, it accelerated the process. For the blends of HMF with 20% or 40% SFO, the temperature at which the behavior changed was 27.0 ± 0.2 or 26.0 ± 0.2 °C, respectively. In emulsion systems, however, the effect was always acceleration for all temperatures selected. With the aid of SAXS, it was possible to study early stage of crystallization during real time and therefore to improve our understanding of the mechanism of P-170 action. The different effects caused by P-170, as described by SFC curves, were strongly related to the effects of P-170 on fat polymorphism, specially to the value of the time interval of coexistence of the α and β′ forms. These events took place at the very beginning of crystallization and thus could not be described by the traditional X-ray techniques used in previous studies of similar systems.     

Effect of Sorbed Water on the Thermal Stability of Soybean Protein

A soybean protein isolate (SPI), and its β-conglycinin and glycinin componets were obtained from defatted soybean flour by applying dissolution and precipitation based on the difference in their solubility depending on each isoelectric point. The purity evaluated by SDS–PAGE of the β-conglycinin and glycinin preparations was about 84% and 80%, respectively, resulting in a clear difference in the pH dependence on solubility. A BET plot derived from the water sorption isotherm at 25 °C showed that the amount of the monolayer adsorption of these preparations was about 6–9%, the value for the β-conglycinin preparation being about 1.5 times higher than that for the glycinin preparation. The β-conglycinin and glycinin preparations were respectively denatured at around 75 °C and 86 °C in the presence of excess water, whereas the denaturation temperature of both preparations was markedly increased by decreasing sorbed water content below 40%, corresponding well with the unfrozen water content.     

Linoleic Acid and Protein Thiol Changes Suggestive of Oxidative Damage in the Plasma of Patients with Adult Respiratory Distress Syndrome

Patients with the acute lung injury syndrome ARDS are under oxidative stress from the disease and from treatment with high inspired oxygen concentrations. Oxidative stress can lead to molecular damage by a variety of reactive oxygen intermediates generated in the lung. In the present study we sequentially monitor changes in plasma total lipid linoleic acid fatty acid levels, using GC-MS, and express these as a function of changes in plasma protein thiol values. In nine out of eleven ARDS patients there was a relationship between loss of protein thiols and loss of total lipid linoleic acid. In three patients changes in protein thiols preceded changes in total lipid linoleic acid by several days. Parallel decreases in plasma total lipid fatty acid esters of linoleic acid and protein thiols are suggestive of oxidative stress leading to molecular damage.     

限制性液体复苏对失血性休克复苏患者血浆TNF-alpha、IL-6 水平的影响

目的：探究限制性液体复苏对失血性休克复苏患者血浆肿瘤坏死因子（TNF-alpha）、白细胞介素-6（IL-6）水平的影响,为临床治 疗失血性休克选择液体复苏方式提供依据。方法：选择2010 年1 月~2015 年6 月期间,我院收治出血性休克患者63例为研究对 象;采用随机数字法将其分为观察组（32 例）和对照组（31 例）,观察组患者给予限制性液体复苏,对照组患者给予传统充分复苏; 观察并比较两组患者治疗前后血浆TNF-alpha、IL-6 水平的变化。结果：观察组患者给予复苏液体的输入量为（1.95± 0.35）L,对照组 患者给予输液量为（3.61± 0.56）L,观察组患者给予的复苏液输入量显著低于对照组,差异具有统计学意义（P<0.05）;治疗前两组 患者血浆TNF-alpha及IL-6 水平不存在显著差异（P>0.05）;治疗后两组患者血浆TNF-alpha及IL-6 水平均显著上升,且观察组患者血浆 TNF-alpha及IL-6水平均显著低于对照组,差异具有统计学意义（P<0.05）。结论：限制性液体复苏能够明显降低失血性休克患者的出 血量,稳定机体血流动力学,保证机体重要脏器的血流灌注,有利于改善患者血浆TNF-琢和IL-6 水平,提高治疗效果,改善预后。     

Disruption of Myxoviruses with Tween 20 and Isolation of Biologically Active Hemagglutinin and Neuraminidase Subunits

Myxoviruses were disrupted with Tween 20 at high pH, and the major surface antigens were separated in biologically active form. The neuraminidase had a sedimentation coefficient of 10.8S, and the hemagglutinin had a sedimentation coefficient of 8.1S. Electron microscopic examination of negatively stained preparations revealed structures identical in size and morphology to the neuraminidase and hemagglutinin subunits described by others. Inhibition of neuraminidase activity by antibody to the hemagglutinin which occurred with intact viruses (probably for "steric" reasons) did not occur after the viruses were disrupted with Tween 20. Serological assays for neuraminidase were possible in the presence of the mild surfactant, whereas serological assays for hemagglutinin were possible after removal of the reagent. Disruption of myxoviruses with Tween 20 therefore provides a method for the independent study of these antigens during antigenic drift.     

Preparation of Pickering Flaxseed Oil-in-Water Emulsion Stabilized by Chitosan-Myristic Acid Nanogels and Investigation of Its Oxidative Stability in Presence of Clove Essential Oil as Antioxidant

Food Biophysics - The aim of this study was to obtain a stable flaxseed oil (FSO)-in-water Pickering emulsion (PE) stabilized by chitosan (CS)-myristic acid (MA) nanogels and to investigate the...