大豆分离蛋白乳状液稳定性的几种分析方法比较

用不同质量分数(0.5%、1%、2%、3%)的大豆分离蛋白(SPI)和大豆油制备3%O/W型乳状液,比较不同离心力作用下和添加不同量SPI乳状液稳定性的差异以及添加不同量SPI乳状液黏度的差异,考察贮存期延长过程中的浊度法测定乳状液稳定性以及乳状液粒径和Zeta电位的变化,结合外观和微观观察,寻找一种快速准确测定乳状液稳定性的方法。结果表明:离心法、贮存期浊度法与乳状液外观观察的结论一致,都表明添加3%SPI的乳状液最稳定,并且SPI添加量越高,乳状液黏度越大,稳定性越好。储存期乳状液平均粒径和Zeta电位发生变化,但难以作为乳状液稳定性的判断标准。本实验进一步验证,离心法能够快速、准确地预测乳状液的稳定性,适于产品开发和成品检验的需要。     

温度、pH和盐对乳清蛋白乳状液稳定性的影响

乳清蛋白具有一定的乳化能力,在食品工业中常作为乳化剂使用.以乳清浓缩蛋白(WPC)、乳清水解蛋白(WPH)和乳清分离蛋白(WPI)为乳化剂,经高压均质制备O/W型乳状液,以平均粒径和分层系数为稳定性指标,研究了温度、pH和盐对乳状液稳定性的影响.结果表明:WPI乳状液具有最小的平均粒径.各环境因素对乳状液稳定性的研究表明,pH是影响乳状液稳定性最显著的因素,当pH在蛋白质等电点(4～6)附近时,各乳状液中粒子均发生絮凝或聚合,乳状液发生脱稳,受环境因素影响,WPC乳状液具有最好的稳定性.这些结果为乳清蛋白作为乳化剂用于食品工业提供了重要依据.     

葵花籽蛋白水解物对水包油型乳状液物理和氧化稳定性的影响

利用碱性蛋白酶对葵花籽蛋白进行适度水解后,将葵花籽蛋白水解物(SSH)添加到以单甘酯作为乳化剂制备的乳状液中,通过测定乳状液的乳化活性、乳化稳定性、粒径、絮凝指数、凝结指数以及乳状液贮藏14 d过氧化值和丙二醛含量的变化,评价SSH对乳状液物理和氧化稳定性的影响。结果表明:添加SSH可显著提高乳状液的乳化活性、乳化稳定性、絮凝和凝结稳定性,显著降低乳状液的粒径;SSH添加量为1.0%时,乳状液具有较好的物理稳定性,同时又具有较好的氧化稳定性。     

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。     

不同均质方式对豌豆蛋白水解物乳状液稳定性影响的研究

以豌豆蛋白水解物为原料制备乳状液,研究微流化(50 Mpa)和超声(1、3、5 min)处理2种不同均质方法对乳状液稳定性的影响。测定了乳状液的粒径大小、ζ-电势值、絮凝和凝结稳定性、表面疏水性以及分层指数。结果表明:随着超声时间的增加,乳状液的粒径显著减小、负电荷和表面疏水性显著增加,并能够提升乳状液的絮凝和凝结稳定性;微流化处理的乳状液比超声处理1、3 min的乳化液具有更高的稳定性,但稳定性低于超声处理5 min的乳状液。总体来看,微流化和超声处理均能通过高剪切作用,防止液滴聚集,形成更加均一、稳定的乳状液。     

DHA乳状液制备工艺优化及氧化稳定性的研究

以二十二碳六烯酸(Docose Hexaenoie Acid, DHA)微藻油微胶囊化过程中形成的乳状液为研究对象,研究乳状液制备工艺条件及氧化稳定性。利用透射光浊度法和电导率法测定乳状液的稳定性,研究预乳化时间、乳化温度、均质压力、均质级数对乳状液稳定性的影响。以乳状液稳定性和表面张力为评价指标,在单因素试验基础上采用正交试验对乳状液制备工艺进行优化,制备后进行微胶囊包埋,分析了DHA微藻油微胶囊的氧化稳定性。结果表明,乳状液制备的最佳工艺为乳化温度50℃、均质压力30 MPa、预乳化时间3 min,2级均质,在此条件下,透射光浊度法测定得到乳状液稳定性为8.75%,表面张力为20.5 mN/m。乳状液制备工艺优化后得到的DHA微胶囊氧化稳定性得到显著提高。     

不同植物油水包油型乳状液物理特性及氧化稳定性研究

以紫苏油、橄榄油、棕榈油和葵花籽油为油相,以乳清分离蛋白为乳化剂,制备水包油(O/W)型乳状液,研究其粒径、ζ-电位、絮凝指数等物理特性,比较不同乳状液在贮存期间的氧化稳定性。结果显示,4种乳状液中,紫苏油乳状液体积平均粒径D_(4,3)较小(0.824μm),ζ-电位绝对值较大(37.5mV),呈现良好的物理贮存稳定性;但由于油脂中有较高的多不饱和脂肪酸,体系易被氧化。棕榈油乳状液具有良好的氧化稳定性,体系初级和次级氧化产物浓度均最低;但乳状液粒径较大(D_(4,3)为1.845μm),物理稳定性较差。通过内源性荧光测定发现,乳状液中蛋白质氧化与脂质氧化存在一定关联性。     

不同蛋白对水包油型乳状液稳定性影响

以乳清分离蛋白和大豆分离蛋白为乳化剂,选用紫苏油、橄榄油、玉米油作为油相制备水包油(O/W)型乳状液。研究2种蛋白对不同乳状液的物理特性及稳定性的影响,其物理特性包括粒径、ζ-电势、界面蛋白含量,稳定性则包括储存稳定性和氧化稳定性。结果表明,不同蛋白对乳状液特性的影响较大,以乳清分离蛋白作为乳化剂时,乳状液体积平均粒径(D4,3)较小,ζ-电势绝对值较大(又以紫苏油乳状液最大,其D4,3为1.4μm,ζ-电势为-25.6 m V),界面蛋白含量较高,体系稳定性优于添加大豆分离蛋白的乳状液。在同一乳化剂作用下,橄榄油乳状液的氧化稳定性较其他2种植物油所得体系更好。     

低分子质量大豆种皮果胶对大豆蛋白乳状液贮藏稳定性的影响

利用大豆种皮作为试验原料制备大豆种皮果胶(SHPP),研究添加低分子质量大豆种皮果胶类多糖(SHPP-LMW)对大豆蛋白乳状液稳定性的影响。通过分析添加不同质量分数的多糖乳状液界面张力、粒径分布、流变特性及显微结构的变化,考察SHPP-LMW对大豆蛋白乳状液稳定性的影响。结果表明,添加SHPP-LMW对大豆蛋白乳状液稳定性的影响较大。添加0.5%SHPP-LMW的乳状液其界面张力较低,黏度较大,粒度分布较均匀,且乳状液颗粒较小,D50、D4,3和D3,2均较小。随着贮藏时间的延长,该乳状液变化较小,具有较高的贮藏稳定性。     

苹果提取物对花生蛋白水解物水包油乳状液氧化稳定性的影响

将苹果提取物(apple extract,AE)添加到花生蛋白水解物(peanut protein hydrolysate,PPH)制备的乳状液中,通过测定絮凝稳定性、凝结稳定性、氧化稳定性、色氨酸荧光损失及蛋白分布等指标,探讨PPH与AE对乳状液脂质氧化的联合抑制作用以及乳状液的氧化稳定性。研究结果表明,蛋白质与多酚化合物能够形成共价结合,提高乳状液的稳定性。还能增加PPH在界面上的吸附量,有效的降低PPH制备的乳状液在贮藏期间的过氧化物和丙二醛的生成量。界面膜上的AE和PPH协同作用提供改进的物理屏障,促进乳状液在储存期间的氧化稳定性。添加AE浓度为100μg/mL时,乳状液在储藏期间最为稳定,但是AE的添加量超过100μg/mL会与PPH形成竞争吸附,影响PPH在界面上的分布,导致稳定性下降。     

紫苏油乳液的制备及其稳定性影响因素研究

本研究针对紫苏油不饱和脂肪酸含量高,在储存过程中易氧化等特点,采用高压均质法制备紫苏油乳液,通过激光粒度仪分析乳液粒径大小与分布,通过TURBISCAN浓缩体系稳定性分析仪监测乳液稳定性的变化趋势,探究乳化剂用量、油水比例、高压均质的压力和循环次数及HLB值对紫苏油乳液稳定性的影响,以提供一种紫苏油缓释方法,拓宽紫苏油在食品中的应用范围。试验结果表明,紫苏油乳液粒径主要分布在300~670nm;乳化剂浓度由0.2%增加至1.2%,乳液粒径下降,稳定性提高;浓度为1.2%时,乳液平均粒径(d=513nm)最小。随着油水比增加,紫苏油乳液稳定性下降;高压均质过程对乳液的稳定性有显著影响,压力越大,循环次数越高,乳液越稳定。与单一乳化剂(HLB=15)相比,复配乳化剂(HLB=8~14)可制得更为稳定的乳液,且当HLB值为11时,紫苏油乳液的平均粒径(d=374nm)最小,乳液稳定性最佳。     

共轭亚油酸多重乳状液的制备及稳定性研究

以多重乳状液相对体积为衡量标准,借助显微镜直接观察,探讨油水相质量比、亲油亲水乳化剂质量比、乳化剂的HLB值、乳化剂的含量等因素对共轭亚油酸多重乳状液体系稳定性的影响.结果表明,单一乳化剂体系中,以Tween80作亲水乳化剂制备的多重乳状液稳定性较好.当m(内水相):m(油相):m(外水相)=1:5:1.3,m(Span80):m(Tween80)=9,乳化剂的含量为9.7%时,多重乳液相对体积达到93%.复合乳化剂体系中,在第一相的HLB值为7.4,m(复合乳化剂):m(Tween80)=9,乳化剂质量分数为6.67%时,稳定性最好.     

复配乳化剂HLB值对壳聚糖精油复合膜物理和结构性能的影响

通过复配吐温和司盘获得不同亲水亲油平衡(hydrophile lipophilic balance,HLB)值的复配乳化剂,探究乳化剂HLB值对壳聚糖精油复合膜的物理和结构性能的影响。结果表明,HLB值在9~15之间,单独乳化剂与精油体积比1∶5和1∶10均可获得较小的精油粒径。乳化剂加入壳聚糖精油复合膜中,随着乳化剂HLB值的升高,膜乳液的粒度逐渐减小。与加入精油的对照膜相比,乳化剂的添加可以提高膜的L*值,降低膜的厚度、膨胀度和水溶性,但乳化剂HLB值对膜的抗拉强度和断裂伸长率影响较小。在乳化剂HLB值11~15之间时,可获得较高的DPPH自由基清除率。从扫描电镜结果来看,乳化剂能显著降低复合膜中精油的粒径。综合来看,HLB值为13时,能获得性能较好的复合膜。     

乳化体系中花生油氧化稳定性的研究

主要探讨花生油乳化体系中乳化剂类型、用量、pH值、EDTA、温度等对花生油氧化稳定性的影响,结果显示:乳化剂种类和pH对于乳状液体系的氧化稳定性有显著影响,阴离子乳化剂SDS稳定的乳化液,pH4.0的氧化速率最快;非离子乳化剂Tween20稳定的乳化液,pH的影响不是很显著;阳离子乳化剂CTAB稳定的乳化液,随着pH的升高,氧化速率变快。乳化液体系中微量金属离子对于体系也有相当大的影响,随着金属离子螯合剂EDTA浓度的增加,其乳化体系中花生油的氧化速率显著降低。乳化剂用量也会影响体系的氧化稳定性,随着乳化剂用量的增加,乳化乳化体系中花生油的氧化稳定性降低。     

Process-Induced Changes in Molecular Structure that Alter Adsorbed Layer Properties in Oil-in-Water Emulsions Stabilised by β-Casein/Tween20 Mixtures

Competitive adsorption of purified β-casein and the non-ionic surfactant Tween20 has been investigated in model oil-in-water emulsions. The emulsions were characterised by measurement of droplet size distribution and specific surface area as a function of surfactant content. The distributions of β-casein and Tween20 between the subnatant and the adsorbed layer were measured. The results revealed subtle but important differences that are dependent upon the processing history of the components. Further studies examining the effect of Tween20 on the extent of interactions formed between β-casein molecules adsorbed at the interfaces of oil–water thin films using the fluorescence recovery after photobleaching technique have provided evidence of a homogenisation-induced structural change in Tween20 resulting in a major reduction in its hydrophobic–lipophilic balance (HLB) value. Analytical evidence supporting these observations was provided by thin layer chromatography. The process-induced change in emulsifier structure has important implications for the formulation of food and non-food emulsions. In particular, emulsion formulations based on the HLB method may fail due to homogenisation-induced changes in the emulsifier's HLB during homogenisation. In addition, our findings resolve apparent contradictions arising from a number of competitive adsorption studies reported in the literature.     

A novel improvement in whey protein isolate emulsion stability: Generation of an enzymatically cross-linked beet pectin layer using horseradish peroxidase

Extensive research has indicated that the electrostatic attraction between polysaccharides and proteins on the oil-water interface can improve the stability of emulsions. However, this electrostatic effect will be weakened or even eliminated as the solution pH or ionic strength of emulsions change, resulting in the shedding of the polysaccharide layer. We prepared primary oil-in-water emulsions at pH 7.0 using whey protein isolate (WPI) as an emulsifier and then beet pectin was added to form secondary emulsions. After the pH of emulsions was adjusted to 4.0 to promote electrostatic attraction between the beet pectin molecules and the protein-coated droplets, horseradish peroxidase was added to generate a cross-linked beet pectin coating. Results show that stable emulsions coated with WPI and cross-linked beet pectin interfaces could be formed. The sensitivity of the emulsions to the environmental stresses of pH changes, ions addition, thermal processing and freezing was also characterized in this work. Our results support the view that cross-linked beet pectin improves the stability of emulsions and is superior to simple deposition on the surface of lipid droplets. The interfacial engineering technology used in this study could be used to create food emulsions with improved stability to environmental stresses.     

Interfacial and emulsifying properties of sucrose ester in coconut milk emulsions in comparison with Tween

In this study, sucrose esters were presented as a promising alternative to petrochemically synthesized Tweens for application in coconut milk emulsions. The interfacial and emulsifier properties of sucrose ester (SE), mainly sucrose monostearate, had been investigated in comparison with Tween 60 (TW), an ethoxylate surfactant. The interfacial tension measurement showed that SE had a slightly better ability to lower the interfacial tension at coconut oil–water interface. These surfactants (0.25 wt%) were applied in coconut milk emulsions with 5 wt% fat content. The effects of changes in pH, salt concentration, and temperature on emulsion stability were analyzed from visual appearance, optical micrograph, droplet charges, particle size distributions, and creaming index. Oil droplets in both SE and TW coconut milk emulsions extensively flocculated at pH 4, or around the pI of the coconut proteins. Salt addition induced flocculation in both emulsions. The pH and salt dependence indicated polyelectrolyte nature of proteins, suggesting that the proteins on the surface of oil droplets were not completely displaced by either added nonionic SE or TW. TW coconut milk emulsions appeared to be thermally unstable with some coalesced oil drops after heating and some oil layers separated on top after freeze thawing. The change in temperature had much lesser influence on stability of SE coconut milk emulsions and, especially, it was found that SE emulsions were remarkably stable after the freeze thawing.     

Influence of chitosan and NaCl on physicochemical properties of low-acid tuna oil-in-water emulsions stabilized by non-ionic surfactant

An influence of low molecular weight (LMW) chitosan on physicochemical properties and stability of low-acid (pH 6) tuna oil-in-water emulsion stabilized by non-ionic surfactant (Tween 80) was studied. The mean droplet diameter, droplet charge (ζ-potential), creaming stability and microstructure of emulsions (5 wt% oil) were evaluated. The added chitosan was adsorbed on the surface of oil droplets stabilized by Tween 80 through electrostatic interactions. Such addition of chitosan at different concentrations (0–10 wt%) to emulsions showed slight effect on the mean droplet diameter. However, the degree of flocculation was a function of chitosan concentration assessed by emulsions' microstructure and creaming index. The impact of chitosan on the strength of the colloidal interaction between the emulsion droplets increased with increasing chitosan concentration. The mean diameter of droplet in emulsions increased with increasing NaCl because of the electrostatic screening effect. The addition of LMW chitosan could be performed to create tuna oil emulsions with low-acid to neutral character, as well as various physicochemical and stability properties suitable for health food products.     

加脂剂乳化稳定性的探讨

本文从表面化学的角度讨论了维持及影响加脂剂乳液稳定性的因素。界面张力、油水之间的界面有蓦 及乳液颗粒所速 电荷是维持加脂剂乳液稳定性的主要因素;而加脂剂的乳化成分及其复配、水的硬度、pH值、中性盐和温度则会影响乳液的稳定.     

DHA油乳状液制备研究

采用高压均质法制备DHA乳液,选择经典的亲水亲油平衡(HLB)法作为乳化剂选择的依据,首先确定体系乳化需要的HLB值为11.3,然后选择几种常见的乳化剂进行复配,确定出较好复配乳化剂为:分子蒸馏单甘酯(42%)+Tween20(58%)。乳化剂最适添加量为1.2%。通过正交实验和单因素实验对乳状液制备最佳工艺条件进行优化,结论为:初乳制备的最佳工艺条件是乳化温度为60℃,搅拌强度为13000r/min,乳化时间为20min,选择均质压力为60MPa。