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.     

蒜油蛋黄酱稳定性及其流变学特性研究

对蛋黄酱稳定性的影响因素及其流变学特性进行了研究，确定了最佳生产工艺流程、配方组合及品质指标。     

Droplet characterization and stability of soybean oil/palm kernel olein O/W emulsions with the presence of selected polysaccharides

Droplet characteristics, flow properties and stability of egg yolk-stabilized oil-in-water (O/W) emulsions as affected by the presence of xanthan gum (XG), carboxymethyl cellulose (CMC), guar gum (GG), locust bean gum (LBG) and gum Arabic (AG) were studied. The dispersed phase (40%) of the emulsions was based on soybean oil/palm kernel olein blend (70:30) that partially crystallized during extended storage at 5 °C. In freshly prepared emulsions, the presence of XG, CMC, GG and LBG had significantly decreased the droplet mean diameters. XG, LBG, GG and CMC emulsions exhibited a shear-thinning behavior but AG emulsion exhibited a Bingham plastic behavior and control (without gum) emulsion almost exhibited a Newtonian behavior. Both control and AG emulsions exhibited a severe phase separation after storage (30 days, 5 °C). The microstructure of stored XG emulsion showed the presence of partially coalesced droplets, explaining a large increase in its droplet mean diameters. Increases in droplet mean diameters and decreases in flow properties found for stored GG and LBG emulsions were attributed to droplet coalescence. Nevertheless, the occurrence of droplet coalescence in these emulsions was considered to be small as no free oil could be separated under centrifugation force. Increases in flow properties and excellent stability towards phase separation found for stored CMC emulsion suggested that CMC could retard partial coalescence. Thus, the results support the ability of CMC, GG and LBG in reducing partial coalescence either by providing a sufficiently thick continuous phase or by acting as a protective coating for oil droplets.     

Rheology of spray-dried egg yolk-stabilized emulsions

This paper deals with the influences that concentrations of oil fraction (65–77.5% w/w) and egg yolk (1–5% w/w), as well as temperature (5–35 °C), exerted on the droplet size distribution and rheological functions of concentrated oil-in-water food emulsions that were stabilized by a spray-dried egg yolk product. This work must be considered as a preliminary study concerning the use of low-in-cholesterol egg yolk as emulsifier. In order to achieve this aim, steady-state flow and dynamic viscoelasticity tests were done with emulsions processed with a rotor-stator turbine. The same processing conditions were always maintained. All of the emulsions prepared showed a high stability. An increase in oil fraction yielded higher values for the rheological functions, and larger droplet diameters. The influence of processed egg yolk concentration was more complex. Thus, an increase in egg yolk content yielded lower values for the rheological functions, but, after a particular concentration, a further increase in emulsifier content yielded higher values for the rheological functions. The experimental results have been discussed taking into account the close relationship between rheology and emulsion structural parameters.     

An improved high-pressure homogenizer for making fine emulsions on a small scale

A reliable high-pressure laboratory homogenizer is described for the small-scale production of emulsions with highly reproducible droplet-size distribution. A key feature of the design of this 'jet homogenizer' is the inclusion of separate chambers for oil and aqueous phases, thereby eliminating the necessity for premixing prior to homogenization, with its associated problems of air incorporation. To illustrate the performance characteristics of the jet homogenizer, data are presented for the effect of homogenization pressure and equipment dimensions on the droplet size of n-tetradecane-in-water emulsions stabilized by sodium caseinate.     

紫苏籽油双层乳状液的制备及其物理化学稳定性评价

采用紫苏籽油为芯材,大豆多糖和壳聚糖为壁材,分别制备紫苏籽油单层与双层乳状液,并且对乳状液的粒径、Zeta电位、物理稳定性以及化学稳定性进行评价。结果显示,单层乳状液粒径随着芯壁比（质量比）的升高而增大,物理稳定性变差,最适的芯壁比（质量比）为2∶1;随着壳聚糖质量分数的增加,双层乳状液的Zeta电位逐渐增大,并且由负值变为正值,壳聚糖质量分数为0.2%时电位绝对值最小为3.6 mV,当壳聚糖质量分数为0.4%时电位为43 mV,电位增加速率变小;随着壳聚糖质量分数的增加,乳状液粒径呈先减小、再增大、再减小的变化,壳聚糖质量分数为0.2%时达到最大粒径为5.21 μm,0.4%时达到最小粒径为1.185 μm;随着壳聚糖质量分数的增加乳状液物理稳定逐渐增强。壳聚糖质量分数对乳状液化学稳定性影响显著（p＜0.05）,抗氧化效果依次为0.4%＞0.6%＞0.2%。     

Emulsifying properties of β-lactoglobulin and Quillaja bark saponin mixtures: Effects of number of homogenization passes,pH, and NaCl concentration

The effects of number of homogenization passes, pH, and NaCl concentration on the formation and stability of oil-in-water emulsions comprising a mixture of a biosurfactant (Quillaja bark saponin) and a globular protein (β-lactoglobulin) were investigated. The emulsions were characterized as to visual appearance, droplet size, droplet surface charge, and rheology. The emulsions obtained by different conditions (4, 6, or 8 passes; pH 7, 8, or 9; and 0, 100, or 200 mmol L^?1 of NaCl) were polydisperse, presented relatively small average droplet sizes (z-average < 323 nm) as well as negative droplet charge (between –20 and –79.6 mV) in all evaluated conditions. Regardless of the number of homogenization passes, the emulsions exhibited low apparent viscosity and pseudoplastic behavior with small yield stress. Viscoelastic behavior was also observed, thus the emulsions were characterized as weak gels. Four homogenization passes were enough to obtain small droplets in the evaluated conditions. Droplet size was not significantly affected by NaCl concentration and pH (p > 0.05). On the other hand, the absolute ζ-potential values significantly decreased and increased upon increased NaCl content and pH, respectively. Regardless of the tested conditions, all emulsions had good stability against phase separation and droplet aggregation, since no significant changes in average droplet size were observed throughout storage (p > 0.05). In the presence of NaCl, in which droplet charge significantly decreased, emulsion was also stable. Thus, we can conclude that electrostatic repulsion as well as steric repulsion was responsible for stabilization.     

水溶性米糠多糖的溶液流变学性能研究

以脱脂米糠为原料,提取、分离水溶性米糠多糖,以动态流变仪为主要实验仪器,研究了水溶性米糠多糖的流体力学性能和相关影响因素.研究结果表明,水溶性米糠多糖溶液是典型的非牛顿流体,表现为剪切稀化的流体性能,多糖浓度越高,溶液剪切稀化现象越严重.同时其多糖溶液的流体性能还受体系温度、剪切速率和pH值等因素的影响.     

大豆水溶性多糖的提取及其对酸性乳饮料的稳定作用

为了提高油菜籽油体乳液在不同环境条件下的稳定性。本文以带负电荷的可溶性大豆多糖（SSPS）和不带电荷的魔芋葡甘聚糖（KGM）为原料形成油菜籽油体乳液。利用激光粒度分析仪和显微镜分别对两种不同多糖的油菜籽油体乳液进行了粒度分析和微观结构观察,考察了两种含不同多糖的油菜籽油体乳液在不同环境应力（pH、离子浓度和热处理）下的稳定性,以不含多糖的油菜籽油体乳液作为对照。实验结果表明：油菜籽油体乳液的粒径随着SSPS和KGM浓度的增加逐渐减小。除了pH2.0,不含多糖的油菜籽油体乳液在不同pH的粒径都显著高于（P<0.05）含KGM和SSPS的油菜籽油体乳液的粒径,此外,除了pH10.0外,含SSPS的油菜籽油体乳液在不同pH的粒径显著低于（P<0.05）含KGM的油菜籽油体乳液的粒径,而且含SSPS的油菜籽油体乳液的粒径受pH的影响较小。不含多糖的油菜籽油体乳液在不同盐离子浓度时的粒径变化不显著（P>0.05）,但都显著高于（P<0.05）含KGM和SSPS的油菜籽油体乳液的粒径。微观结构图也显示了含KGM和SSPS的油菜籽油体乳液在不同盐离子浓度下其油滴的分散性要好于不含多糖的油菜籽油体乳液。不含多糖的油菜籽油体乳液的粒径随着温度的升高而逐渐增加,且都显著高于（P<0.05）含KGM和SSPS的油菜籽油体乳液的粒径,而含SSPS的油菜籽油体乳液的粒径受温度的影响不显著（P>0.05）。综合以上结果,KGM和SSPS都能显著提高油菜籽油体乳液的稳定性,且SSPS效果更好。

     

橄榄油与椰子油混油基对类蛋黄酱乳液流变及冻融稳定性的影响

以类蛋黄酱体系为研究对象,运用Turbiscan、流变仪、粒度仪、显微镜研究在pH 3条件下橄榄油与椰子油不同比例复配(10:0、9:1、8:2、7:3)的混油基对于乳清分离蛋白-蛋黄卵磷脂稳定的乳液体系流变性质及冻融稳定性的影响.结果表明:随着椰子油比例增加,乳液黏度增加,弹性模量增加,橄榄油与椰子油质量比7:3复配...     

乳清蛋白-多糖的制备及功能特性的研究

通过美拉德反应将壳寡糖引入乳清蛋白,形成乳清蛋白-壳寡糖共价复合物,对其溶解性、乳化性、乳化稳定性及热稳定性进行研究。结果表明,乳清蛋白-壳寡糖共价复合物可以较好的改善乳清蛋白的热稳定性,对乳清蛋白在等电点附近的溶解性,乳化性,乳化稳定性有一定的调节作用。采用三因素二次通用旋转组合设计对乳清蛋白-壳寡糖的制备条件(糖比例,温度,时间)进行优化,建立了以乳化性及乳化稳定性为响应值的回归方程。以乳化性为响应值,优化结果为:糖比例28%,温度45℃,时间17 h,此时乳清蛋白-壳寡糖乳化性为0.55,以乳化稳定性为响应值,优化结果为:糖比例34%,温度45℃,时间17 h,此时乳化稳定性为1.25 min。