Flaxseed gums and their adsorption on whey protein-stabilized oil-in-water emulsions

The effect of the addition of flaxseed gum on the physicochemical properties of whey protein-stabilized (WPI) oil-in-water emulsions at pH 3.5 was investigated. Two different varieties (Emerson and McDuff) were tested at concentrations ranging from 0% to 0.33% (w/v), by measuring droplet size, ζ-potential, phase separation behavior, microstructure and apparent viscosity. With addition of flaxseed gum the ζ-potential of the droplets decreased from around +30 mV to a negative value (−10 mV) at concentrations >0.2%. These results indicated that the negatively charged polysaccharide fraction from flaxseed interacted with the protein adsorbed at the interface. An increase in apparent particle size was also noted with increasing flaxseed concentration, with destabilization becoming visually evident at concentrations higher than 0.1% (w/v). Microscopy, rheological data and size distribution analysis demonstrated for the first time that flaxseed gum interacts with protein-stabilized oil droplets at low pH, causing bridging flocculation. No significant differences were noted between flaxseed gums extracted from the Emerson and McDuff varieties. This research demonstrated that the electrostatic interactions between flaxseed gums and protein-stabilized emulsions need to be controlled when designing novel acidic beverages containing these polysaccharides.     

Physicochemical properties of whey protein isolate stabilized oil-in-water emulsions when mixed with flaxseed gum at neutral pH

Concentrations ranging from 0% to 0.33% (w/v) of gum (Emerson and McDuff) were added to the emulsions at pH 7. Particle size distribution, viscosity, ζ-potential, microstructure, and phase separation kinetics of the emulsions were observed. Both polysaccharides and protein coated droplets are negatively charged at this pH, as shown by ζ-potential measurements. At all the concentrations tested, the addition of gum did not affect significantly (p < 0.05) the apparent diameter of the emulsion droplets. At low concentrations (gum  0.075% (w/v)), no visual phase separation was observed and the emulsion showed a Newtonian behaviour. However, at concentrations above the critical concentration of gum, depletion flocculation occurred: when 0.1 flaxseed gum was present, there was visual phase separation over time and the emulsion exhibited shear-thinning behaviour. These results demonstrate that flaxseed gum is a non-interacting polysaccharide at neutral pH; it could then be employed to strengthen the nutritional value of some milk-based drinks, but at limited concentrations.     

不同NaCl浓度条件下亚麻籽胶对肌原纤维蛋白凝胶作用力及乳化特性的影响

为改善低盐肉制品凝胶乳化品质的降低,明确亚麻籽胶（flaxseed gum,FG）添加对肉制品品质的影响,以肌原纤维蛋白（myofibrillar protein,MP）为研究对象,通过测定乳析指数、电位值、粒径、显微观察研究不同NaCl浓度条件下FG对MP乳液乳化稳定性的影响,而化学键的测定显示FG对MP凝胶化学作用力的影响。结果表明,形成MP凝胶及FG-MP凝胶体系的关键是二硫键和非二硫共价键的贡献;不同NaCl浓度对FG-MP乳液的乳析指数、ζ-电位、粒径的影响均不显著（P＞0.05）,而MP乳液随着NaCl浓度的提高,乳化稳定性、ζ-电位、粒径均显著变化（P＜0.05）。特别是在低浓度NaCl条件下,FG的加入可以显著提高MP乳液的稳定性（P＜0.05）。显微观察发现加入FG可以改善MP乳液液滴聚集的现象。因此,说明在低浓度NaCl条件下加入FG可以显著提高肌原纤维蛋白乳液的乳化稳定性,提高其抗盐能力,促进亚麻籽在肉制品中的应用。     

Response surface modeling for optimization of formulation variables and physical stability assessment of walnut oil-in-water beverage emulsions

The effect of Arabic gum content (5-10% w/w) and walnut-oil concentration (3-6% w/w) on properties of prepared walnut oil/water emulsion, including turbidity loss rate, density, size index, particle size and stability, was investigated using response surface methodology (RSM). For each response, a second-order polynomial model with high coefficient of determination (R²) values ranging from 0.907 to 0.989 was developed using multiple linear regression analysis. The lack of significant difference between the experimental and predicted values proved the adequacy of response surface equations for describing the physical changes of emulsions. An increase of Arabic gum content in range and initial concentration of walnut oil were associated with high emulsion stability and minimum droplet size. It can be concluded that RSM can determine the most suitable formulation (3% w/w walnut oil and 9.62% w/w Arabic gum) to achieve the highest stability in a developed beverage emulsion based on walnut oil.     

Effect of Lepidium perfoliatum seed gum addition on whey protein concentrate stabilized emulsions stored at cold and ambient temperature

In this study the effect of Lepidium perfoliatum seed gum on the properties of whey protein concentrate (WPC) stabilized corn oil-in-water emulsions at pH 7 was investigated. Various concentrations (0–0.6% w/v) of L. perfoliatum seed gum were used together with 2% (w/v) WPC to emulsify corn oil in water at a ratio of 1:5. Quality attributed such as particle size distribution, creaming profile and coalescence rate during storage at 4 and 25 °C; surface and interfacial tension; zeta potential and viscosity of the emulsions were determined. The results indicated that the addition of L. perfoliatum seed gum had no significant effect on zeta potential but the surface and interfacial tension increased with the rise of gum concentration. It was also found that the addition of L. perfoliatum seed gum to WPC emulsions at a critical concentration of 0.2% (w/v) caused flocculation of oil droplets, which resulted in marked increase in particle size and the creaming rate. However at higher gum concentrations beyond this value, the particle size remained constant, apparently because of the high viscosity of the aqueous phase. At all concentrations tested, emulsions stored at 4 °C were more stable except for those containing 0.2% L. perfoliatum seed gum.     

不同乳化剂对油酸和亚油酸乳状液稳定性的影响

本文以粒径、稳定性和流变为考察指标,利用激光粒度仪、食品稳定性分析仪、流变仪等研究不同种类和添加量的食品乳化剂(阿拉伯胶、酪蛋白酸钠、吐温20)对不饱和脂肪酸(油酸和亚油酸)乳状液的制备及其稳定性的影响。结果表明,三种乳化剂均可制备出稳定性较好的乳状液,不同乳化剂的质量分数不同得到乳状液的稳定性不同。较高质量分数的阿拉伯胶(4%,w/v)乳状液,具有最低的澄清指数并且具有最大粘度(0.30~0.40 Pa·s)。当酪蛋白酸钠的质量分数为2%时,制备出的乳状液较稳定,但粒径较大,贮藏稳定性较差。较低质量分数的吐温20(1%,w/v)的乳状液具有最小粒径(0.20~0.21 μm),经过贮藏后变化程度也最小。本文研究了不同食品乳化剂制备的不饱和脂肪酸乳状液及其稳定性,可为不饱和脂肪酸乳状液的制备和应用提供参考。     

高压均质对大豆分离蛋白-多糖混合体系功能特性的影响

采用亚麻籽胶（FG）、魔芋粉（KGM）、羧甲基纤维素钠（CMC）三种多糖与大豆分离蛋白（SPI）建立SPI-多糖混合体系,研究了不同均质压力（1¹20 MPa）对SPI以及上述三种体系的功能特性的影响。结果表明:亚麻籽胶的添加使SPI的溶解性和乳化性显著（p<0.05）提高,在压力120 MPa时达到最大值,但是其乳化稳定性随压力升高而降低;SPIKGM体系的起泡性和泡沫稳定性在均质压力30 MPa时最佳;均质作用使SPI的持水性下降,添加多糖也没有明显改善SPI的持水性;SPI-FG的持油性在90 MPa时达到最高值。添加CMC的SPI在高压均质作用下各功能性质也有提升,但效果不是十分明显。高压均质对SPI和SPI-多糖体系的功能性质有不同程度的改善。      

Effect of concentrated flaxseed protein on the stability and rheological properties of soybean oil-in-water emulsions

Flaxseed protein concentrate containing-mucilage (FPCCM) was used to stabilize soybean oil-in-water emulsions. The effects of FPCCM concentration (0.5, 1.0, 1.5% w/v) and oil-phase volume fraction (5, 10, 20% v/v) on emulsion stability and rheological properties of the soybean oil-in-water emulsions were investigated. Z-average diameter, zeta-potential, creaming index and rheological properties of emulsions were determined. The result showed that FPCCM concentration significantly affected zeta-potential, creaming rate and emulsion viscosity. The increasing of FPCCM concentration led to a more negative charged droplet and a lower creaming rate. Oil-phase volume fraction significantly affected Z-average diameter, rheological properties, creaming index and creaming rate. With the increase of oil-phase volume fraction, both Z-average diameter and emulsion viscosity increased, while creaming index and creaming rate decreased. The rheological curve suggested that the emulsions were shear-thinning non-Newtonian fluids.     

亚麻籽胶的乳化性质

重点研究了亚麻籽胶的乳化性质，实验结果表明。亚麻籽胶的质量分数、溶解温度、乳化温度、加油量以度贮存温度等对亚麻籽胶的乳化性质都有影响。质量分数增加，亚麻籽胶的乳化稳定性增强；加油量增多。亚麻籽胶的乳化稳定性下降；溶解温度升高能提高亚麻籽胶的乳化稳定性；而乳化温度和贮存温度越高，亚麻籽胶乳状液越不稳定。由于亚麻籽胶与阿拉伯胶在相对分子质量、均方旋转半径、粘度、疏水性氨基酸含量上的差异，导致了亚麻籽胶与阿拉伯胶乳化性质的差异．     

大豆可溶性多糖与Fe2+对O/W乳状液物理稳定性及流变特性的影响

研究大豆可溶性多糖(soybean soluble polysaccharides,SSPS)及不同浓度的Fe2+对大豆分离蛋白(soy isolated protein,SPI)稳定的O/W乳状液的物理稳定性和流变特性的影响。通过测定14 d内添加SSPS和不同浓度的Fe2+的乳状液的稳定动力学指数(turbiscan stability index,TSI)、稳态流变、粒径大小及分布和Zeta-电位,确定其物理稳定性。结果表明,与SPI乳状液相比,添加SSPS后,SSPS-SPI乳状液的TSI显著降低(p<0.05),液滴的表面积平均直径(d_3,2)和体积平均直径(d_4,3)增加,粘度系数增加,Zeta-电位绝对值降低,表明SSPS增加了SPI乳状液的粘度,提高了乳状液的物理稳定性;添加0.1 mmol/L Fe2+后,乳状液的TSI最低,液滴的d_3,2和d_4,3分别为0.686、2.136 μm,为最小粒径,粘度增加,稳定性较好;随着Fe2+浓度的增加,乳状液的TSI显著增加(p<0.05),粒径增大,分布范围变宽,表明0.2~0.5 mmol/L的Fe2+降低了乳状液的物理稳定性。总之,SSPS和0.1 mmol/L Fe2+的添加,提高了SPI稳定的O/W乳状液的物理稳定性。     

Influence of emulsion composition and inlet air temperature on the microencapsulation of flaxseed oil by spray drying

The objective of this work was to study the influence of some process conditions on the microencapsulation of flaxseed oil by spray drying. The process was carried out on a mini spray dryer and gum Arabic was used as wall material. Seventeen tests were made, according to a central composite design. Independent variables were: inlet air temperature (138-202 °C), total solid content (10-30% w/w) and oil concentration with respect to total solids (10-30% w/w). Encapsulation efficiency, lipid oxidation and powder bulk density were analyzed as responses. Powder morphology and particle size distribution were also analyzed. The feed emulsions were characterized with respect to droplet size and viscosity. Higher solid content and lower oil concentration led to higher encapsulation efficiency and lower lipid oxidation, which was related to the higher emulsion viscosity and lower droplets size. Increasing drying temperature resulted in higher lipid oxidation. Bulk density increased when higher solid content and lower inlet air temperature were used. The particles were rounded and shriveled, and their mean diameter was mainly affected by total solid content.     

Particle size distribution and homogenisation efficiency in high-pressure homogenisation of wheat germ oil-water system

Wheat germ oil (WGO) is well-known as a good source of vegetable oil due to its nutrients and health benefits. Emulsification is a process that improves the incorporation of oil into food. High-pressure homogenisation (HPH) is a nonthermal and soft technique with enormous potential in oil-in-water emulsification. This paper focussed on the application of HPH for emulsification of WGO-in-water system. Influences of homogenisation pressure (100–300 bar), oil fraction (10–20% v/v) and lecithin adding (0–0.2% w/v of content) on the homogenisation were evaluated based on distribution of particles diameter and homogenisation efficiency. The increase in operating pressure and lecithin ratio decreased the particle size and increased the emulsion stability, and vice versa for oil fraction. The findings imply that the investigated factors significantly influenced particle size and emulsion system stability. The regression model between mean particle diameter and technical conditions of emulsion was established. With HPH treatment conditions of 300 bar operating pressure, 10% (v/v) oil fraction and 0.2% (w/v) lecithin created an emulsion system with a mean particle size of 3.32 µm, more than 50% of the volume of particles smaller than 1.5 µm of diameter and the homogenisation efficiency of 98.61%. HPH exhibits high efficiency and potential in WGO-in-water emulsification application.     

Mannans as stabilizers of oil-in-water beverage emulsions

The stabilizing effect of spruce galactoglucomannan (GGM) on a model beverage emulsion system was studied and compared to that of guar gum and locust bean gum galactomannans, konjac glucomannan, and corn arabinoxylan. In addition, guar gum was enzymatically modified in order to examine the effect of the degree of polymerization and the degree of substitution of galactomannans on emulsion stability. Use of GGM increased the turbidity of emulsions both immediately after preparation and after storage of up to 14 days at room temperature. GGM emulsions had higher turbidity than the emulsions containing other mannans. The initial turbidity increased with increasing GGM content, but after 14 days storage at room temperature, the turbidity was the highest for GGM/oil ratio of 0.10:1 when ethanol-precipitated GGM was used. Increasing the storage temperature to +45 °C led to rapid emulsion breakdown, but a decrease in storage temperature increased emulsion stability after 14 days. Confocal microscopy showed that the average particle size in the bottom part of GGM emulsions stored for 14 days was smaller than 1 μm. A low degree of polymerization and a high degree of substitution of the modified galactomannans were associated with a decrease in emulsion turbidity.     

Emulsifying Properties of Angum Gum (Amygdalus scoparia Spach) Conjugated to β-Lactoglobulin through Maillard-Type Reaction

In this study, emulsifying properties of Angum gum were improved by covalent bonding with β-lactoglobulin (BLG). Angum gum is a natural gum exudate from mountain almond trees (Amygdalus scoparia Spach). Covalent linkage of β-lactoglobulin-Angum gum conjugate was confirmed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Emulsifying properties of emulsions containing β-lactoglobulin:Angum gum (1:1) conjugates were studied with the advancement of Maillard reaction. Dry-heating time showed no significant (p > 0.05) effect on the emulsion activity index; however, emulsion stability index were significantly increased over time and emulsion stability index of two weeks incubated β-lactoglobulin-Angum gum conjugate was significantly different (p < 0.05) from others (β-lactoglobulin-Angum gum mixture, 0, 2, 6 days, and 2 weeks). Moreover, the creaming index decreased with advancement of Maillard-type conjugation of β-lactoglobulin:Angum gum (1:1). β-lactoglobulin-Angum gum conjugates (1:1, 1:2, and 2:1) exhibited much better emulsification performance than Angum gum and gum Arabic alone at the same emulsifier/oil ratio (1.5 wt. % total biopolymer/ 40% v/v oil). In addition, assessing droplet size distribution during storage and freeze-thaw treatment revealed that β-lactoglobulin:Angum gum (1:1) conjugate had finer droplet size compared to other β-lactoglobulin/Angum gum mixing ratios (1:2 and 2:1), Angum gum and gum Arabic.     

大豆分离蛋白与染料木素共价交联对蛋白表征和结构的影响

探究大豆分离蛋白和染料木素的共价交联对蛋白表征和结构的影响。制备大豆分离蛋白与不同质量浓度染料木素（0、1.2、1.5、2.0 mg/mL）的共价复合物,通过探究粒径、Zeta电位、浊度、表面疏水性分析蛋白体系的表征变化,并采用紫外分光光度计、荧光分光光度计、傅里叶变换红外光谱仪分析蛋白体系的结构变化。结果表明：大豆分离蛋白与染料木素共价复合后,蛋白的中位径由135.6 μm最低减小至98.0 μm,Zeta电位绝对值由15.0 mV最高增大至21.4 mV,表面疏水性由216.0最低减小至115.5,总巯基含量由31.5 μmol/g最低减小至20.4 μmol/g。与对照组相比,共价复合物的浊度增加,并且实验组中SPI-Ge-1.2组低于SPI-Ge-1.5组和SPI-Ge-2.0组。光谱分析表明染料木素对大豆分离蛋白有猝灭效果,二者共价交联后蛋白质的色氨酸与酪氨酸残基所处的微环境疏水性减少,蛋白质二级结构中α-螺旋含量增多、β-折叠含量减少、β-转角含量增多、无规卷曲含量减少,并且加入1.2 mg/mL的染料木素对大豆分离蛋白的表征特征和结构影响效果更好。本研究结果表明在大豆分离蛋白中加入染料木素后,二者的共价交联能够影响蛋白的表征与结构。     

大豆分离蛋白O/W型乳液膜的制备及其性质研究

摘要：为提高大豆分离蛋白膜的性质,制备以大豆分离蛋白（SPI）为原料的O/W乳液膜,采取单因素实验法比较O/W乳液膜与SPI膜的差异性,探究不同SPI质量浓度（20、30、40、50和60 mg/mL）对O/W乳液膜性能及结构的影响。结果表明：O/W乳液膜的遮光性、机械性能、耐水性及热稳定性要优于SPI膜。随着SPI质量浓度的增加,O/W乳液膜的拉伸强度随之增加,断裂伸长率降低。蛋白质量浓度为60 mg/mL时,O/W乳液膜的抗拉强度达到最大值为7.19 MPa,比蛋白膜的抗拉强度高出33%。利用扫描电子显微镜（SEM）、傅里叶红外光谱（FTIR）和差式扫描量热仪（DSC）对O/W乳液膜蛋白分子间的相互作用进行分析,乳液膜的Tg为100 ℃,且红外光谱中酰胺Ⅲ带和1630 cm-1峰值发生了变化,表明共混组分之间的作用力增强,蛋白质形成了致密且稳定的网络结构。     

Physicochemical properties of soy protein isolate gels emulsified with various oils using a microbial transglutaminase

Soy protein isolate (SPI) gels emulsified with oils including soybean, olive, palm, and eicosapentaenoic acid (EPA) were prepared by a microbial transglutaminase (MTGase). The hardness of 10% SPI gel was greatly increased by adding higher amount of oils. The emulsion gels prepared with 10% SPI and 30% olive oil showed the highest hardness of 1,711 g. In the gelation with various oil content (5–30%), the higher concentration of oils indicated the drastic increase of elastic modulus G′ and viscous modulus G″ during initial gelation for 7 min. The G′ value of SPI emulsion gel showed the 150 (soybean oil 30%), 147 (olive oil 30%), 121 (palm oil 30%), and 61 Pa (EPA 25%), respectively. In the color value of SPI emulsion gel, addition of higher concentration of oils resulted in the increase of L value (brightness), indicating 99.14 (L value) at 30% palm oil. The micro-structure of SPI emulsion gel entrapped with various oils showed the homogeneous network with small porosity compared with that of SPI gel without oil. In particular, SPI emulsion gel with 10% palm oil showed the compact structure distributed evenly with small porosity. Conclusively, the functional and rheological properties of SPI emulsion gel produced by catalytic action of MTGase could be modulated by the type and content of oils fortified.     

大豆分离蛋白-黄原胶-茶多酚复合物的制备及其乳液性质表征

以大豆分离蛋白（SPI）、黄原胶（XG）、茶多酚(TP)为原料,改变原料的添加顺序制备三元复合物SPI-XG-TP和SPI-TP-XG,研究了不同复合物的结构与乳化特性的差异。结果表明：蛋白质与多糖、多酚复合之后其结构发生一定程度的改变,且复合物的乳化特性都得到了改善,两种三元复合物中SPI-XG-TP稳定的乳液粒径更小,电位绝对值更大,乳化活性更高,但乳化稳定性略低于SPI-TP-XG稳定的乳液。大分子间能够相互交联形成三元复合物并改变蛋白质的结构,不同原料添加顺序的复合物的结合过程不同     

纳米SiO2改性4 种大分子材料的乳液制备及性质

为提高乳液稳定性,采用纳米SiO2改性明胶（gelatin,GE）、大豆分离蛋白、壳聚糖和阿拉伯胶（gum arabic,GA）制备茶油乳液。以乳化活性、乳化稳定性、离心稳定性、平均粒径、流变特性为考察指标,探究质量分数3.000%的纳米SiO2对4 种大分子材料复合乳液性质的影响,并对乳液的微观结构及油滴分布进行观察。结果表明,纳米SiO2能增强乳液稳定性,其中GE-纳米SiO2复合乳液综合性质最佳。添加纳米SiO2后乳化活性和乳化稳定性显著增加（P＜0.05）,离心稳定性降低68.444%。平均粒径为8.472 μm,乳液粒径最小且分布均匀,表面光滑呈球状。流变表现为典型的弱凝胶特性,稳定性良好。研究结果可为天然高分子和纳米SiO2乳液的制备和应用提供实践基础。     

Assessing the potential of flaxseed protein as an emulsifier combined with whey protein isolate

The potential use of flaxseed protein isolate (FPI) as an emulsifying agent was studied in combination with whey protein isolate (WPI) or alone. All the FPI and WPI–FPI emulsions were kinetically unstable. The increase of FPI concentration (0.7% w/v) led to a higher creaming stability of the FPI emulsions due partly to a reduction in interfacial tension between aqueous and oil phases, but mainly to the gel network formation. However at this same high FPI concentration, WPI–FPI emulsions showed a decrease in droplet size and creaming stability, which could be due to the presence of flaxseed gum in the protein isolate enhancing depletion effects. A protein excess was verified in the mixed systems (0.14 or 0.7% (w/v) FPI) and the increase of FPI concentration led to an even greater surface protein content. Increasing homogenization conditions (pressure and number of passes), the creaming stability of the FPI systems increased, mainly at higher concentration (0.7% w/v). Meanwhile, in the mixed systems, the creaming stability of the emulsions containing 0.7% (w/v) FPI decreased even more, but was improved for the emulsions with 0.14% (w/v) FPI. Thus, it was observed that systems containing only FPI at higher concentration were stabilized by gel formation, while in WPI–FPI systems there was a competition by interface between biopolymers with a consequent depletion process. As a result, more stable systems were obtained with WPI addition at lower FPI concentration (0.14% w/v) and using higher homogenization pressure and number of passes (60 MPa, two passes).