豌豆分离蛋白/卡拉胶复合物乳液的性质研究

为改善豌豆分离蛋白(PPI)在酸性乳液体系中的乳化稳定性,将PPI与阴离子多糖卡拉胶(CG)在酸性条件下混合,制备可溶性静电复合物乳液。通过测定PPI乳液和PPI/CG复合物乳液在不同pH(4～7)下粒径、ζ-电位、显微结构以及乳析指数的变化,判断两种乳液的稳定性。结果表明：pH 4～5时,PPI乳液粒径达到35μm以上,而pH 4～7时PPI/CG复合物乳液粒径均小于18μm;储藏14 d时,PPI乳液和PPI/CG复合物乳液粒径均稍有增加;酸性条件下,PPI乳液的ζ-电位绝对值均小于30 mV,而PPI/CG复合物乳液的ζ-电位绝对值均大于40 mV;酸性条件下,PPI/CG复合物乳液较PPI乳液分散性有明显改善;在储藏14 d过程中,PPI乳液乳析指数随储藏时间的延长而逐渐增大,而PPI/CG复合物乳液乳析指数基本为0。综上,PPI/CG复合物可显著改善PPI在酸性条件下的乳化稳定性。     

蛋黄蛋白-植酸静电复合物对蛋黄乳液物理稳定性的影响

为改善蛋黄（egg yolk，EY）在酸性乳液体系的物理稳定性，采用EY蛋白与植酸（phytic acid，PA）形成静电复合物稳定EY乳液。研究酸性条件下PA质量分数（0%～0.8%）对EY蛋白及EY乳液物理稳定性的影响。结果表明，pH 3.0时，EY与0.012 5%～0.8% PA形成不溶性的静电复合物EY-PA；最优质量分数（0.2%）PA与含1%蛋白的EY形成复合物制备乳液较对照组的乳液黏度升高，粒径及乳析指数显著降低（P＜0.05），界面蛋白质吸附量显著提高（P＜0.05），乳滴分布更均匀，乳液的抗聚结效果提高。因此，EY蛋白与PA形成的静电复合物可调控EY乳液的理化特性，提高EY在酸性乳液体系的物理稳定性。     

玉米醇溶蛋白颗粒和海藻酸丙二醇酯制备的新型双层乳液的理化特性

采用逐层静电沉积技术(LBL)制备了由玉米醇溶蛋白颗粒(ZCP)和海藻酸丙二醇酯(PGA)共稳定的双层乳液,研究了不同浓度的PGA、PGA与ZCP在油滴表面的结合顺序对该双层乳液的表观特性、物理稳定性和微观结构的影响。结果表明:液滴呈均匀球体且在乳液中形成致密网络,PGA的加入改善了双层乳液的物理稳定性,随PGA浓度增加,双层乳液液滴的粒径逐渐减小,并形成网络结构,双层乳液稳定性逐渐增强;就添加顺序而言,PGA具有更好的乳化性,当PGA浓度升高到0.05%时,先加入PGA的双层乳液具有更小的液滴粒径。这种ZCP和PGA协同稳定的新型双层乳液具有良好的稳定性。     

Pickering乳液法制备PPI-TA-MD微胶囊及其对南瓜籽油氧化稳定性的影响

目的:改善南瓜籽油(PSO)的氧化稳定性，促进PSO的开发利用。方法:将豌豆分离蛋白(PPI)—单宁酸(TA)稳定的Pickering乳液在麦芽糊精(MD)作为填充材料存在下，通过喷雾干燥制备南瓜籽油微胶囊，探究PPI-TA-MD包埋体系对PSO氧化稳定性的影响。结果:Pickering乳液经喷雾干燥后，可得到表面光滑的球状微胶囊粉末；随着壁材中TA浓度的增加，微胶囊显示出更小的粒径[(32.00±0.28)μm],相对较低的水分含量[(1.970±0.043)%]和较高的堆积密度[(0.725±0.014) g/cm³];不同TA浓度的PSO微胶囊FFA释放率为39.63%～69.91%,且随着TA浓度增大FFA释放速率减慢；与封装在PPI中的PSO相比，用作外壳材料的PPI-TA复合物提高了PSO的热稳定性、DPPH自由基及ABTS自由基清除能力和氧化稳定性。结论:以PPI-TA-MD为壁材的微胶囊可以改善PSO的抗氧化能力和氧化稳定性。     

植物球蛋白/姜黄素纳米复合物的制备及其对O/W型Pickering乳液氧化稳定性影响

本论文以两类植物球蛋白:豌豆分离蛋白(PPI)和大豆分离蛋白(SPI)为材料制备荷载姜黄素蛋白纳米复合物,并探究荷载前后蛋白所制备乳液的物理和氧化稳定性差异。结果表明:PPI和SPI在pH 3.0和pH 7.0下荷载前后蛋白纳米颗粒粒径没有明显变化。pH 7.0时两蛋白姜黄素荷载量均高于pH 3.0,各pH下SPI荷载量要高于PPI。表面疏水性的显著降低与荧光淬灭现象发生表明形成两种蛋白纳米复合物的主要作用力为疏水相互作用,同时在两pH下,PPI比SPI荧光蓝移趋势更明显且有效淬灭常数也更大,即更易形成复合物。与原蛋白相比,荷载后各蛋白颗粒所制备乳液乳化活性有少许降低,同时pH 3.0时各蛋白颗粒乳化活性要高于pH 7.0。各乳液生成初级氧化产物脂质氢过氧化物浓度的变化趋势与生成次级氧化产物TBARS相类似,均为荷载姜黄素后各乳液氧化水平加速,同时pH 3.0时各类型乳液油滴氧化程度均高于pH 7.0。     

豌豆蛋白对巴旦木饮料贮藏稳定性的影响及其机理探究

该研究制备了不同改性处理的豌豆蛋白(pea protein isolate, PPI),研究其对巴旦木饮料贮藏稳定性的影响，并初步探究了其中的机理。结果显示，与未改性PPI相比，改性PPI对饮料贮藏稳定性改善较为明显，且挤压联合磷酸化处理豌豆蛋白(extruded co-phosphorylated pea protein isolate, EPPPI)对饮料的改善作用接近酪蛋白酸钠(sodium caseinate, SC)。添加EPPPI后，饮料界面蛋白吸附率增加45.80%,液滴间静电排斥力增大8.41%,粒径减小37.13%,离心沉淀率降低22.66%,饮料稳定性改善。贮藏实验和微观形态结果表明，EPPPI制备的饮料粒径分布均匀，在贮藏期间稳定性良好，聚结程度低，与将SC作为乳化剂制备的饮料相似。研究结果表明，EPPPI具有替代SC作为乳化剂应用在市售巴旦木饮料中的可能性。     

豌豆蛋白的功能特性研究

本论文对豌豆球蛋白(7S、11S)和豌豆分离蛋白(PPI)的物化和功能特性进行了分析和比较。结果表明,豌豆球蛋白具有良好的功能特性,其溶解度(PS)、乳化能力、乳化稳定性均显著高于PPI。荧光光谱和表面疏水性(H0)分析表明,PPI是部分变性的蛋白,其制备过程中的酸碱处理导致蛋白分子伸展、H0增加。DSC表明,11S热稳定性比7S要高,豌豆分离蛋白和豌豆7S出现不同程度的蛋白变性。     

绿豆蛋白基乳液的稳定性及胃肠消化行为

为了拓展绿豆蛋白在乳液体系中的应用,该研究以大豆蛋白为对照,系统探究了热处理前后绿豆蛋白结构、表面疏水性、油水界面的吸附行为,以及绿豆蛋白稳定的油水乳液的稳定性和胃肠消化行为的变化。蛋白表面疏水性测定结合表面张力分析发现经湿热处理后（120 ℃,20 min）绿豆蛋白的表面疏水性从4 870.80增加到9 482.50,在油水界面上的扩散速率从0.33 mN·m-1·s-0.5增加到0.45 mN·m-1·s-0.5,热处理的绿豆蛋白在油水界面表现出更高的界面活性。在6%的蛋白浓度条件下,与大豆蛋白相比,热处理的绿豆蛋白稳定的油水乳液呈现出更高的热稳定性及物理稳定性。与大豆蛋白类似,体外模拟胃肠消化发现热处理的绿豆蛋白具有良好的胃肠消化特性,主要表现为蛋白的快速消化,乳液液滴在胃消化过程中呈现一定程度的聚集行为。研究表明热处理的绿豆蛋白具有应用于植物基食品乳液的巨大潜力。     

脱酰胺马铃薯蛋白乳液的制备及其微流变特性

以脱酰胺马铃薯蛋白为原料制备乳液，研究不同脱酰胺时间（0、0.5、3、6、12 h）的马铃薯蛋白乳液的粒径分布、乳化稳定性、微流变特性及微观结构的变化。结果表明，随着脱酰胺时间的延长，乳液粒径（体积平均直径）和稳定性动力学指数值均呈现先减小后增大的趋势；脱酰胺3 h和6 h的马铃薯蛋白乳液粒径分布均匀，乳液较为稳定，可能是因为改性蛋白乳液液滴间静电斥力增大，阻止了液滴的聚集；脱酰胺12 h的马铃薯蛋白乳液粒径增大，乳液稳定性减小，这可能是因为电荷斥力降低使液滴聚集。微流变特性分析表明脱酰胺6 h的马铃薯蛋白乳液的宏观黏度因子值最高，黏度最大，粒子运动速度减慢，乳液液滴间具有强作用力，体系更稳定。本研究为马铃薯蛋白的深入研究及产品开发提供一定参考，提高马铃薯蛋白的利用率，扩大应用范围。     

高强度超声辅助乳化对金鲳鱼蛋白-茶皂苷复合乳液性质的影响

为提升金鲳鱼蛋白乳液的稳定性,改善金鲳鱼蛋白的功能特性,以金鲳鱼蛋白-茶皂苷复合物为乳化剂、大豆油为油相,采用高强度超声(HIUS)辅助乳化制备金鲳鱼蛋白-茶皂苷复合乳液,测定超声处理前后不同乳化剂与油相比例的金鲳鱼蛋白-茶皂苷复合乳液的乳化性、粒径分布、Zeta-电位、流变性、微观形态及贮藏稳定性。结果表明：与未超声处理金鲳鱼蛋白-茶皂苷复合乳液相比,超声处理后乳液的乳化活性指数和乳化稳定性指数总体增高,粒径减小,Zeta-电位的绝对值增加,流动指数升高,黏度系数降低,乳液液滴分布更均匀,乳液液滴更小,贮藏稳定性较好。综上,HIUS处理有助于改善金鲳鱼蛋白-茶皂苷的乳化性能。     

Influence of chitosan on stability and lipase digestibility of lecithin-stabilized tuna oil-in-water emulsions

The influence of chitosan concentration (0–0.3 wt%) and molecular weight (120, 250 and 342.5 kDa) on the physical stability and lipase digestibility of lecithin-stabilized tuna oil-in-water emulsions was studied. The ζ-potential, droplet size, creaming stability, free fatty acids and glucosamine released was measured for the emulsions when they were subjected to an in vitro digestion model. The ζ-potential of the oil droplets in lecithin-chitosan stabilized emulsions changed from positive (≈+53 mV) to negative and the emulsions were unstable to droplet aggregation for all chitosan concentrations and molecular weights used after being subjected to the digestion model. The amount of free fatty acid and glucosamine released per unit amount of emulsion was higher when pancreatic lipase was included in the digestion model. These results suggest that lecithin-chitosan coated droplets can be degraded by lipase under simulated gastrointestinal conditions. Consequently, chitosan coated lipid droplets may serve as useful carriers for the delivery of bioactive lipophilic nutraceuticals.     

Complexation of pea protein isolate with dextran sulphate and interfacial adsorption behaviour and O/W emulsion stability at acidic conditions

This study was aimed at improving the emulsifying property and physical stability of pea protein isolate (PPI) stabilised emulsions at acidic conditions by complexation with dextran sulphate (DS). Soluble and insoluble complexes with different charge and particle size were formed depending on the phase separation behaviour. The surface adsorption of PPI became slower after complexation with DS, but the percentage of adsorbed proteins at the oil–water interface was not affected. The formation of PPI–DS soluble complexes at high content of DS (≥0.4%) significantly improved the negative net charges of PPI, prevented the aggregation of protein, which further improved the emulsifying property of PPI at acidic conditions through the strong electrostatic repulsion and steric hindrance effects. Insoluble complexes with relatively weak net charge and large particles were formed at low DS content (≤0.2%), resulting in the bridging flocculation of oil droplets at pH 5 and 4. Thus, the emulsifying ability of PPI under acidic conditions could be significantly improved by formation of soluble complexes with DS.     

Sodium caseinate/carboxymethylcellulose interactions at oil–water interface: Relationship to emulsion stability

The effect of carboxymethylcellulose (CMC) on the properties of oil-in-water emulsions prepared with sodium caseinate (CN) was studied at different pHs (4–7). At pH 7, the surface protein coverage increased gradually with increasing CMC concentration, followed by a preferential adsorption of β-casein. While at pH 4, a sharp decrease in surface protein coverage was noted between 0 and 0.3 wt.% CMC, and no obvious difference in protein composition was observed. ζ-Potential measurements indicated that CMC adsorbed onto the CN-coated droplets at pH 4–5, but not at pH 6–7. As a result, the excess of non-adsorbed CMC induced depletion flocculation in the neutral emulsions. However, the acidic emulsions containing high levels of CMC (>0.3 wt.%) remained stable after 60 days of storage due to the formation of multilayer structures. At pH 4, CMC desorbed from the droplet surfaces at high NaCl concentrations, leading to lower emulsion stability.     

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.     

阿拉伯树胶-肌原纤维蛋白共建乳状液体系的物理稳定性

研究不同质量分数阿拉伯树胶(arabic gum,AG)对肌原纤维蛋白(myofibrillar protein,MP)为乳化剂的乳化体系稳定性的影响。结果显示,乳化活性和乳化稳定性随着AG质量分数的增加呈先增加后降低的变化趋势。AG质量分数为0.3%时,MP-AG共建乳状液体系表现出最高的物理稳定性,显著地增加了ζ-电势,降低了粒径大小,表现出最低的乳析指数(P0.05)。激光共聚焦显微镜(confocal laser scanning microscopy,CLSM)观察结果表明,与单独以MP为乳化剂的样品相比,添加0.3%AG的乳状液样品液滴颗粒最小,这与粒径大小和分布的结果相一致。通过CLSM进一步观察MP在界面上的吸附行为,结果表明,与未添加AG的乳状液样品相比,添加0.3%AG的MP-AG共建乳状液体系所形成的界面膜更加坚固和致密。总之,AG可以促进蛋白质在油水界面上的吸附作用,提高MP乳化的水包油型乳状液的物理稳定性。     

Influence of molecular weight and degree of substitution of carboxymethylcellulose on the stability of acidified milk drinks

The influence of molecular weight (M_w, 250,000, 700,000) and degree of substitution (DS, 0.7, 0.9 and 1.2) of carboxymethylcellulose (CMC) on the diameter and ζ-potential of casein micelles during acidification in diluted dispersions and on the stability of acidified milk drinks was investigated. The experimental results suggested that CMC with high M_w or low DS would result in thick adsorbed layer onto casein micelles. The ζ-potential of CMC-coated casein micelle increased with increasing the M_w of CMC with the same DS while at a fixed M_w the ζ-potential for CMC with high DS (1.2) increased in comparison with those for CMC with low DS (0.7 and 0.9). Both M_w and DS of CMC influenced the stability of acidified milk drinks. CMC with high M_w increased the viscosity of acidified milk drinks significantly and therefore contributed to the stability. CMC with high DS resulted in high ζ-potential of CMC-coated casein micelles, increasing the electrostatic repulsion between casein particles, which prevented the phase separation in acidified milk drinks. It was also found that the amount of CMC needed for efficient coverage of casein micelles increased with increasing the M_w of CMC. Above the efficient coverage concentration, the long-term stability of acidified milk drinks with high M_w CMC was better than that with low M_w CMC.     

Effect of chitosan on the stability and properties of modified lecithin stabilized oil-in-water monodisperse emulsion prepared by microchannel emulsification

The effect of chitosan (CHI) on the stability of monodisperse modified lecithin (ML) stabilized soybean oil-in-water (O/W) emulsion was investigated. Monodisperse emulsion droplets with particle size of 24.4 ± 0.7 μm and coefficient of variation below 12% were prepared by microchannel (MC) emulsification using a hydrophilic asymmetric straight-through MC silicon 24 × 24 mm microchip consisting of 23,348 microchannels. The stability of the ML stabilized monodisperse emulsion droplets was investigated as a function of CHI addition at various concentration, pH, ionic strength, thermal treatment and freezing-thawing treatment by means of particle size and ζ-potential measurements as well as microscopic observation. The monodisperse O/W emulsions were diluted with CHI solution at various concentrations to a final droplet concentration of 1 wt% soybean oil, 0.25 wt% ML and 0–0.5 wt% CHI at pH 3. Pronounced droplet aggregation was observed when CHI was present at a concentration range of between 0.01 and 0.04 wt%. Above this concentration range, flocculations were less extensive, indicating some restabilization. ML stabilized emulsions were stable at a wide range of NaCl concentrations (0–1000 mM) and pH (3–8). On the contrary, in the presence of CHI, aggregation of the emulsion droplets was observed when NaCl concentration was above 200 mM and when the pH started to approach the pKa of CHI (i.e. ∼6.2–7.0). Emulsions containing CHI were found to have better stability at high temperature (>70 °C) in comparison to the emulsion stabilized only by ML. With sucrose/sorbitol as cryoprotectant aids, emulsions with the addition of CHI were found to be more resistant to droplet coalescence as compared to those without CHI after freezing at −20 °C for 22 h and thawing at 30 °C for 2 h. The use of CHI may potentially destabilize ML-stabilized O/W emulsions but its stability can be enhanced by selectively choosing the appropriate CHI concentrations and conditions of preparation.     

Properties of spray-dried food flavours microencapsulated with two-layered membranes: Roles of interfacial interactions and water

Engineering the interface of oil-in-water emulsion droplets with biopolymers that modify its permeability could provide a novel technique to improve flavour retention in dry powders. The objective of this study was to determine if volatile compounds were more retained in dry emulsions stabilized by pea protein isolate (PPI)/pectin complex than that stabilized by PPI alone. The retention of ethyl esters during spray-drying increased with decreasing volatility of the encapsulated compound and ranged from 28% to 40%. The addition of pectin to feed emulsions was quite effective in markedly improving the retention of the three studied flavour compounds. In our previous work (Gharsallaoui et al., 2010), we showed that pectin was able to improve physical integrity of emulsion oil droplets during spray-drying. However, the pectin positive effect on both the droplet stability and the flavour retention at the time of spray-drying can also be explained by a protein molecular structure protective effect. Indeed, the obtained FTIR results showed that pectin was able to preserve the β-sheet secondary structure of pea protein when pea globulins/pectin complexes are heated. The study of the release characteristics of a flavour compound from dried powders showed that pectin addition did not affect the release profile mainly accomplished by the diffusion mechanism.     

Utilization of layer-by-layer interfacial deposition technique to improve freeze–thaw stability of oil-in-water emulsions

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.     

Pea protein exhibits a novel Pickering stabilization for oil-in-water emulsions at pH 3.0

In this paper we reported that pea protein isolate (PPI) at pH 3.0 exhibits a novel Pickering stabilization for oil-in-water emulsions. At pH 3.0, most of the proteins in PPI were present in the nanoparticle form, with the hydrodynamic diameter of 134–165 nm depending on the concentration (c; 0.25–3.0 g/100 mL). For the emulsions formed at a specific oil fraction of 0.2, increasing the c from 0.25 to 3.0 g/100 mL resulted in a considerable reduction in the emulsion size, while their creaming stability progressively increased, and especially at c values higher than 2 g/100 mL, no creaming occurred even after storage of 20 days. Confocal laser scanning microscopy observations showed that increasing the c resulted in a progressive increase in extent of droplet flocculation, and at higher c values, a network consisting of flocculated droplets could be formed. The emulsions formed at c values above 1.0 g/100 mL exhibited extraordinary stability against coalescence. The flocculated droplet network formation was closely associated with the increased amount of adsorbed proteins at the interface. The results suggest that pea proteins exhibit a good potential to act as a kind of Pickering stabilizers for oil-in-water emulsions at acidic pHs.