Surface tension and foam stability of commercial calcium and sodium caseinates

The static and dynamic surface tension of sodium and calcium caseinates was compared with their foam behavior. The surface tension behavior of sodium and calcium caseinates was similar but the foaming properties differed. Caseinates presented moderate surface activity lowering the surface tension of water to 40 mN/m. The surface pressure vs. composition data were analyzed using a new surface equation of state and obtained 0.1% (w/v) critical concentration and the molecular surface area; in the case of calcium caseinate was larger compared to sodium caseinate. Caseinates were evaluated at the critical concentration by means of dynamic surface tension to compare their behavior; calcium caseinate took longer time to reach equilibrium conditions. Their foam behavior was transient type with maximum foamability around the critical concentration; sodium caseinate presented better foaming properties than calcium caseinate.     

Adsorption of β-Lactoglobulin variants A and B to the air–water interface

Summary The adsorption of proteins to interfaces is a vital and complex process for the formation and stabilization of multiphase food systems (emulsions and foams). The process of protein adsorption is generally understood only at the phenomenological level, as the complexity of protein unfolding during adsorption is very difficult to predict and model. By comparing proteins with very similar structures, it is possible to attribute observed changes in adsorption behaviour. The A and B genetic variants of β-lactoglobulin (β-lg) differ by only two amino acids (Asp-64, Val-118 in A, and Gly-64, Ala-118 in B), thus making them ideal candidates for this type of comparison. In this study we monitored the surface behaviour of β-lg A and B, measuring the surface tension and surface dilational modulus of adsorbed protein, and the compression behaviour of spread protein films. At pH 7, variant B lowered the surface tension and increased the surface dilational modulus more rapidly than variant A. Raising the pH to 7.8 should increase the level of dissociation into monomers. Indeed, this was confirmed by the rate of adsorption, which increased in both cases. Also, the surface tension of both variants was much lower than at pH7. Variant B was less sensitive to the change of pH than A. Regardless of pH, after 3 h adsorption the difference between the variants in surface tension or surface dilational modulus was negligible. The differences in surface behaviour between the variants are discussed in terms of interactions between monomers at and with the interface, and the dimer : monomer equilibrium in the bulk solution.     

Use and properties of perfluoropolymethyl-isopropylethers in skin and hair cleaning; system stabilization and interference with sebum redistribution on skin and hair

Perfluoro-polymethyl-isopropyl ethers (PPIE) are known for their low surface tension and spreading characteristics. Their use in detergent systems was difficult because of their insolubility in most fluids (except fluorinated ones), but microdispersions have been obtained with surfactant blends, the compositions of which minimize the interfacial tension. Thickeners have been tried in order to improve suspension stability during shelf life. Spreading of PPIE has been studied by using in vivo and in vitro evaluations, both on hair and on skin. Results are discussed, as these systems could improve greasy skin conditions and decrease the rebound effect.     

双短氟碳链非离子表面活性剂的合成及其应用

以聚乙二醇-600、异佛尔酮二异氰酸酯以及1H,1H,2H,2H-全氟己-1-醇为原料,一锅法合成了一类双短氟碳链非离子表面活性剂(F4-PEG600-F4),通过卡尔费休法,测得其含水量在0.1％以下(有效成分>99.9％).采用FT-IR、1H-NMR对产物结构进行了表征,并研究了其在水溶液中的表面活性.表面张力测...     

Chemical and mineralogical characterization of blast-furnace sludge from an abandoned landfill

Blast-furnace sludge is generated during the production of pig iron and is disposed of in the environment in large surface landfills. We investigated blast-furnace sludge samples of an abandoned landfill in order to determine its chemical and mineralogical nature and to evaluate some environmental hazards that may arise from this industrial waste. The mineralogical inventory, which was quantified by Rietveld refinement of XRD analyses using the fundamental-parameter approach, revealed that blast-furnace sludge is dominated by X-ray amorphous substances (with a mean of 590 g kg(-1)) including coke and (hydr)oxides of Fe, Si, Al, Zn, and Pb. Calcite (CaCO3) (136 g kg(-1)), dolomite (Ca,Mg[CO3]2) (14 g kg(-1)), quartz (SiO2) (55 g kg(-1)), kaolinite (Al2[OH]4Si2O5) (40 g kg(-1)), graphite (C) (27 g kg(-1)), and chemically not specified layered double hydroxides (28 g kg(-1)) were identified in almost all samples. Iron is present as magnetite (Fe3O4) (34 g kg(-1)), hematite (Fe2O3) (38 g kg(-1)), wuestite (FeO) (20 g kg(-1)) and alpha-iron (Fe0) (6 g kg(-1)). Chemically, blast-furnace sludge is dominated by C (190 g kg(-1)) and Fe (158 g kg(-1)) reflecting the process of pig-iron production. On the basis of total contents, environmentally problematic metals (including As) are Zn (32.6 g kg(-1)), Pb (10.3 g kg(-1)), Cd (81 mg kg(-1)), and As (129 mg kg(-1)). As the forested landfill is used by residents for leisure activities, the exposure assessment by pathway oral uptake of blast-furnace sludge particles by humans has to be critically evaluated, particularly as significant proportions of metals are acid-soluble. However, under the prevailing slightly alkaline pH values of the sludge (pH 7.6-9.2), the solubility of the metals is very low as indicated by low pore water concentrations. Currently, groundwater monitoring should be focused mainly on F- since the F- concentrations in the pore water of blast-furnace sludge are at high level (2.65-24.1 mg of F- L(-1)).     

Influence of pH on surface properties of aqueous egg albumen solutions in relation to foaming behaviour

The surface properties of aqueous egg albumen protein solutions (0.1 g litre⁻¹) were studied at pH values of 4.8, 7.0, 9.2 and 10.7 and related to foaming behaviour such as bubble size distribution, overrun and drainage. By measurements far from equilibrium of dynamic steady state surface dilation using the overflowing cylinder technique, egg albumen showed ability to slow down surface expansion and to lower the dynamic surface tension. The pH‐effect was small, but at pH 4.8 the film length, at which a motionless surface was created, was longer than at higher pH indicating a somewhat more rigid surface at low pH. Near equilibrium sinusoidal surface area deformation resulted in relatively high moduli of egg albumen, with a significant effect of pH. The surface modulus E showed at pH 4.8 an increase in the course of time, but at higher pH it was constant. Large deformation of egg albumen surface was not destructive, and for all pH values the surface behaved viscoelastic, with highest loss modulus E″ and tan θ values at pH 4.8. Surface deformation frequency sweeps revealed the relaxation processes to be relatively slow at pH 4.8 and faster at pH 7.0–10.7. Foamability measured as overrun of foam as a result of shaking and stirring was highest at pH 4.8 and lowest at pH 10.7. Foam stability against drainage was best at pH 7.0 after 30 min, but at a long‐term scale foam at pH 4.8 was most resistant to drainage. Foam samples were subjected to microscopy and image analysis. The smallest bubbles were found at pH 4.8 (mean diameter 142 µm) and the largest at pH 7.0 (mean diameter 328 µm). In conclusion, the foaming behaviour of an aqueous egg albumen solution at pH 4.8 can be related to dynamic surface properties as follows: the more rigid behaviour of the surface at this pH favours a small bubble size and slow drainage of liquid from the foam. The high overrun at this pH can be explained by a lower dynamic surface tension, but also here film stability during foam making can be promoted by a more rigid liquid surface. © 1999 Society of Chemical Industry     

吸附性白细胞滤材表面润湿性能的测试

以熔喷聚酯非织造布作为白细胞过滤器的滤材 ,根据不同纤维直径 ,不同等离子体处理条件和丙烯酸接枝改性条件的组合变化 ,得到在本实验条件下试样表面润湿性能改善的最佳组合以及处理前后试样表面润湿性的改善情况。通过对滤材表面润湿性能的分析 ,提出可能影响其临界润湿表面张力的因素     

氧化石墨烯分散体系的流变性能

利用扫描电子显微镜对氧化石墨烯(G O)微观结构进行表征,从黏度、表面张力等角度分析G O分散体系的流变性能,研究GO在多种胺类有机溶剂及水基中的分散行为及其湿法纺丝性能.结果表明,在相同用量下,小尺寸GO分散体系的黏度小于大尺寸GO分散体系;在相同体系浓度下施加不同剪切应力,分散体系出现剪切变稀现象,即剪切速率越高,...     

烷基糖苷水溶液的表面活性以及电解质的影响

烷基糖苷APGs作为新一代绿色表面活性剂,以其优异的表面特性在各个领域的应用开发受到了广泛的关注。文章深入研究了不同链长的烷基糖苷水溶液的表面张力、胶束化行为以及电解质的加入对其的影响。结果表明,APGs溶液的CMC主要取决于其分子疏水端的结构。随着疏水链的增长,APGs溶液的CMC随之减小。相对离子型表面活性剂而言,硫酸钠的加入对溶液的影响较小,主要是通过对疏水链的盐析作用来实现的。在强碱体系下,APGs分子亲水端部分去质子化使得所形成的胶束带负电性,从而导致氢氧化钠的盐析效应相对较弱。     

不同水分活度降低剂对大菱鲆即食制品的影响

为了降低大菱鲆即食制品水分活度,延长制品保藏期,选择丙三醇、乳酸钠、麦芽糖醇3种水分活度降低剂,在单因素试验基础上,根据Box-Behnken原理设计三因素三水平响应面试验,建立二次多项数学模型,并进行保藏实验。以水分活度为指标,得到大菱鲆即食制品水分活度降低剂的最佳配比为丙三醇添加量4.1 mL/100 g、乳酸钠添加量1.5 mL/100 g、麦芽糖醇添加量4.0 g/100 g,在此配比下含水量40%的大菱鲆即食制品水分活度为0.781。将产品在37℃贮藏7 d后其菌落总数为4.04(lg(CFU/g))、TVB-N值为12.47 mg/100 g、TBA值为1.48 mg/100 g,均在国家标准限量范围内。说明利用水分活度降低剂能有效提高产品的保藏性能,延长产品的保藏期。     

海水制浆黑液制备液体防尘涂料及性能研究

为了解决造纸行业水资源短缺、原料短缺以及秸秆制浆黑液难以回收利用等问题,以海水秸秆制浆黑液为介质,以微晶纤维素为填料制备了液体防尘涂料,应用于码头、港口的防尘处理。研究了涂料的组分对涂料粘度、抗水性以及表面张力的影响。结果表明:以海水制浆黑液制备的液体防尘涂料的粒径为461.7nm;添加了2%的瓜尔胶增稠后,粘度达到6107mPa*s;当AKD乳液用量为40%,制浆黑液用量为35%,纤维用量为1%,PAE用量为5%时,制备的液体防尘涂料的表面张力可达30.5mN/m,涂料具有较佳的稳定性以及成膜性。     

羧酸盐型有机硅嵌段聚醚的合成及性能

以有机硅嵌段聚醚、氯乙酸钠和NaOH为原料,合成了羧酸盐型有机硅嵌段聚醚。采用正交实验法对反应条件进行了优化,并利用红外光谱和核磁共振氢谱对其结构进行了表征。考察了产物溶液的表面张力和润湿性能。结果表明,较优的反应条件为:反应时间5 h,反应温度60℃,n(有机硅嵌段聚醚)∶n(氯乙酸钠)=1.0∶2.1,n(氯乙酸钠)∶n(NaOH)=1.0∶1.1。产物溶液的表面张力最低降至25 mN/m左右,具有良好的润湿性能。     

十二烷基硫酸钠的提纯

采用水重结晶、乙醇重结晶、乙醚抽提等方法提纯市售的十二烷基硫酸钠（SDS）。通过对几种纯化方法的讨论，提出了制备表面张力满足表面化学实验研究用SDS的纯化方法。     

Wettability of Chitosan Coating Solution on'Fuji' Apple Skin

Wettability of chitosan coating solutions on‘Fuji’ apple skin in different surfactant concentration (Tween 80: 0, 10, 100, 1000 ppm) was investigated using the Du Nouy ring method and the sessile‐drop method. The surface property of‘Fuji’ apple skin as a coated solid surface was characterized by the Zisman plot. The critical surface tension of‘Fuji’ apple skin was 18.7 dyne/cm. The surface tension of the chitosan coating solution was too high (61.5 dyne/cm) to wet the apple skin. Tween 80 as surfactant in water‐borne coatings reduced the surface tension of the coating solution and enhanced its wettability. Surface morphology of the coated film was observed by scanning electron microscope. Surfactant driven autophilicity improved the adhesive force between coating solution and associative apple skin, and decreased the contact angle of coating solution.     

Interfacial and emulsifying behaviour of rice protein concentrate

Interfacial and emulsifying properties of rice protein concentrate (RPC) have been studied in order to evaluate its potential application to stabilize O–W emulsions. The interfacial behaviour of adsorbed proteins films constituted with RPC has been studied at the air–water and oil–water interfaces at two pH values (2 and 8). The type and the amount of soluble proteins have been determined in aqueous dispersions and results put forward the presence of most frequent rice protein profile and a significant degree of protein denaturation with a very low solubility. Air–water and oil–water interfacial properties have been determined as a function of time, concentration and pH: air–water by surface pressure under compression–expansion cycles and oil–water by interfacial tension. Interfacial rheology has been studied under dilatational deformations, either at the initial step of film formation or once the interfacial tension was at equilibrium (the film was completely formed). RPC-stabilised O–W emulsions has been also analysed by Droplet Size Distribution (DSD) measurements and interfacial protein concentration. Both interfacial and bulk emulsion properties reveal that RPC showed an enhanced potential as emulsifier at low pH. Globally; results indicate clearly important differences in the structural characteristics of rice protein films between pH 2 and 8 that impact on emulsifying properties.     

超声波对复配加脂剂乳液的作用

试验将超声波作用于多组分加脂剂的复配过程,通过作用前后的试样乳液表面张力、粒径分布的测定,探索超声波对加脂剂复配的影响.结果表明,将超声波应用于多组分加脂剂的复配过程中,可以降低其乳液的表面张力,减小乳液粒径,提高加脂剂性能.     

新型表面活性剂的表面张力和电导率性能研究

合成了三种孪连型阳离子季铵盐表面活性剂16-4-16,2Br-1、14-4-14,2Br-1、18-2-18,2Br-1,对三者的性能进行评定,分别通过表面张力和电导率测得临界胶束浓度(CMC)、表面活性剂在气-液界面的吸附量、单个分子的面积和胶束电离度α。结果表明:首先,相对于单头基单尾链的表面活性剂,三种孪连表面活性剂的表面活性更强,CMC值更低;其次,三种表面活性剂都有其各自的特性,16-4-16,2Br-1的粘弹性能较好,而14-4-14,2Br-1、18-2-18,2Br-1表面张力很低。实验表明,通过调节孪连表面活性剂联结基和疏水链的长度会对产品的性能有很大的影响。     

Influence of the presence of monoglyceride on the interfacial properties of wheat gluten

BACKGROUND: The physical stability of several food systems depends strongly on their interfacial properties, which may be modified by adding proteins and low‐molecular‐weight surfactants to their formulation. This study deals with the possibility of using wheat gluten to alter the surface and interfacial properties of an aqueous system, considering the effects of protein concentration, pH and the presence of monostearin. RESULTS: It was generally found that the surface tension decreased as the protein concentration increased, reaching a minimum value at 0.5 g kg^?1. The influence of protein concentration on surface tension was much greater than the effect of pH owing to the low ionic character of wheat gluten protein. At acidic and alkaline pH values the interfacial viscosity of the protein system underwent a significant increase with time. The addition of monostearin either promoted the displacement of protein molecules at the interface or generated an interfacial mixed film with surface tension values lower than those of both single components, depending on the pH. CONCLUSION: The results obtained indicate that gluten can contribute to the stabilisation of air/water and oil/water interfaces in some food systems (emulsions, foams, etc.). Copyright © 2010 Society of Chemical Industry     

Influence of the presence of monoglyceride on the interfacial properties of soy protein isolate

BACKGROUND: This study focused on the contribution of soy protein isolate (SPI), in the absence or presence of monostearin (ME), to surface and interfacial properties as a function of protein concentration and pH, which is relevant to the physical stability of a variety of food systems. RESULTS: An increase in protein content always yielded a rapid decrease in surface tension followed by an evolution towards an asymptotic value. Addition of ME gave rise to mixed SPI/ME films, although the interface became dominated by SPI above the concentration for interfacial saturation. The relative interfacial shear viscosity of SPI films showed a marked dependence on: aging time, which may be attributed to a reorganisation of protein species at the interface with some penetration of hydrophobic parts into the oil phase; shear forces, which may partially reverse this reorganisation, leading to shear‐thickening behaviour; and pH, which is the key factor controlling which SPI species is predominant at the interface. The effect of adding ME also depends on pH, favouring a reinforcement of SPI/ME films only at low pH, at which 3S and 7S fractions are dominant. CONCLUSION: The results obtained indicate that SPI shows excellent potential to favour stabilisation of air/water and oil/water interfaces in food systems. Copyright © 2012 Society of Chemical Industry     

Hydroxypropylmethylcellulose surface activity at equilibrium and adsorption dynamics at the air–water and oil–water interfaces

The surface behaviour of hydroxypropylmethylcelluloses (HPMC) was studied at the air–water (A/W) and oil–water (O/W) interfaces. At the A/W interface, the π-C isotherms were sigmoidal and presented inflexions as the HPMC bulk concentration increases, related with different structural patterns adopted by the biopolymer segments. The behaviour of these biopolymers at the O/W interface resulted different. No inflections in the adsorption isotherm were observed, denoting the absence of any change in the structure of the adsorbed monolayer. The order in the interfacial activity was different at the two interfaces.The dynamics of adsorption showed that the surface pressure (π) values and the rate of adsorption/penetration were lower at the O/W interface.Analogously to π values, the surface dilatational modulus was smallest at the O/W interface, however at long-term adsorption strong viscoelastic films are formed at the O/W interface.