Colloid transport and deposition in water-saturated Yucca Mountain tuff as determined by ionic strength

Colloid mobility and deposition were determined in model systems consisting of quartz sand or crushed Yucca Mountain tuff, latex microspheres (colloidal particles), and simulated groundwater. Ionic strength (I) was manipulated as a first step in defining limiting conditions for colloid transport in a system modeled after geochemical conditions at the Yucca Mountain site. Solutions of deionized water (DI), 0.1x, 1x, and 10x (the ionic strength of simulated groundwater) (I = 0.0116 M) were used in saturated columns under steady-state flow conditions. Separate experiments with conservative tracers indicated stable hydrodynamic conditions that were independent of I. Colloids were completely mobile (no deposition) in the DI and 0.1x solutions; deposition increased to 11-13% for 1x and to 89-97% for 10x treatments with similar results for sand and tuff. Deposition was described as a pseudo-first-order process; however, a decreasing rate of deposition was apparent for colloid transport at the 10x condition through the tuff. A linear dependence of colloid removal (extent and deposition rate coefficient) on I is illustrated for the model Yucca Mountain system and for a glass-KCl system reported in the literature. This simple relationship for saturated systems may be useful for predicting deposition efficiencies under conditions of varying ionic strength.     

Removal of arsenic from high ionic strength solutions: effects of ionic strength, pH, and preformed versus in situ formed HFO

Arsenic sorption to hydrous ferric oxide (HFO) is an effective treatment method for removing dissolved arsenic from fresh drinking water sources. However, detailed information is limited regarding arsenic removal from solutions of high ionic strength such as brackish groundwater, seawater, or high-pressure membrane process residuals. Bench-scale treatment experiments were conducted exploring arsenic removal from simple solutions with ionic strengths ranging from 0.008 to 1.5 M by addition of ferric chloride followed by solid/liquid separation (microfiltration or ultrafiltration). Arsenic removal from these solutions during in situ iron precipitation was approximately 90% at Fe:As molar ratios of 10 to 15 and > 95% for Fe:As molar ratios greater than 20. Arsenic removal at iron doses of 10(-6) to 10(-4) mol-Fe/L improved when pH was lowered from 8 to less than 6.5 at ionic strength 0.2 M; this improvement was not as significant at ionic strength 0.7 M. Arsenic removal diminished when alkalinity was increased from 400 to 1,400 mg/L as calcium carbonate; however, arsenic removal at the higher alkalinity improved when pH was lowered from approximately 8 to less than 7. Arsenic removal with preformed HFO solids and subsequent microfiltration was significantly less than that observed with in situ HFO precipitation. Increased removal by in situ precipitation compared to that of preformed solids is explained by an increased number of adsorption sites due to uptake during iron oxy-hydroxide polymerization as well as an increase in surface area resulting in diminished surface charge effects. Model simulations of arsenic uptake by in situ precipitation adequately captured these effect by changing the model parameters used to model arsenic uptake by preformed HFO, specificallythe total number of surface sites and surface area.     

槲皮万寿菊素纳米乳液的制备和性质表征:乳化剂类型、pH、离子强度、热处理的影响

分别以α-乳白蛋白、β-乳球蛋白和乳铁蛋白为乳化剂,食品级中碳链脂肪酸甘油三酯为油相,以槲皮万寿菊素为芯材,采用二级高压均质法制备槲皮万寿菊素水包油型纳米乳液。通过测定乳液粒径大小、多分散指数、Zeta电位、浊度来对比三种乳化剂的乳化效果,研究不同pH、离子强度、热处理对乳液理化性质的影响,利用分光光度法测定纳米乳液对槲皮万寿菊素的包埋率,并采用Lu Mi Sizer稳定性分析仪对样品稳定性进行分析检测。结果表明,乳化剂种类对乳液粒径大小、分布情况有显著影响,以α-乳白蛋白为乳化剂稳定的槲皮万寿菊素纳米乳液平均粒径最小,为285.3±3.3 nm,多分散指数为0.19±0.03,包埋率约96.8%。在不同pH、离子强度和热处理条件下,以α-乳白蛋白为乳化剂稳定的槲皮万寿菊素纳米乳液具有最优的稳定性。     

Influence of ionic strength and cation charge on transport of colloidal particles in fractured shale saprolite

The role of solution chemistry (cation charge and concentration) and particle size on colloid transport was examined in an intact monolith of fractured shale saprolite (highly weathered rock). Recovery of the microsphere tracers consistently decreased with increasing ionic strength of either mono- (Na+) or divalent- (Ca2+) dominated solutions, but a much greater concentration of Na+ in the influent solution was required to result in a similar reduction in colloid recovery as compared to Ca2+. However, composition of the solution along the flow path, and hence the degree of microsphere retention, was also strongly influenced by cation exchange and diffusive exchange between pore water in the fractures and in the fine-grained, Ca- and Mg-rich matrix. The influence of "matrix diffusion" on solute transport is also evident in the 5-fold difference between the arrival of the center-of-mass of microspheres as compared to the much later arrival of a bromide tracer. Particle size affected the extent of microsphere transport, but the solution chemistry appears to be a more dominant control. While confirming the importance of ionic strength, counterion charge, and particle size on colloid migration, this study emphasizes the profound effect that pore structure and geochemical processes such as cation exchange have on solution chemistry and thus on colloid transport.     

Complexes of bovine serum albumin with sulphated polysaccharides: effects of pH,ionic strength and high pressure treatment

Solutions of bovine serum albumin (BSA) (5 mg ml⁻¹) subjected to high pressure processing (600 MPa for 20 min) at low ionic strength and neutral pH have shown a reduction in protein surface hydrophobicity. This decreases further in the presence of ι- or κ-carrageenan (2.5:1 weight ratio). The total calorimetric enthalpy (ΔH) for the pressure treated BSA is reduced by 50%. Addition of ι- or κ-carrageenan to BSA reduces both the denaturation temperature (T_m) and ΔH under the same treatment conditions. Size exclusion chromatography at low ionic strength has indicated a weak electrostatic interaction for BSA+ι- or κ-carrageenan at pH 7, which becomes stronger at pH 6.5. Complexation of BSA with the more highly sulphated ι-carrageenan gives a stronger electrostatic interaction than with κ-carrageenan under the same solution conditions. Replacement of ι-carrageenan with dextran sulphate (DS) gives an even stronger complex, which again suggests that the strength of complexation is dependent on the charge density on the polysaccharide. Complexation of BSA with polysaccharide at low ionic strength appears to protect the globular protein against pressure-induced aggregation. The addition of salt dissociates the protein–polysaccharide complex(es), and the protective effect of polysaccharide is then lost.     

Emulsifying properties of ovalbumin in mixtures with sulphated polysaccharides: effects of pH,ionic strength,heat and high‐pressure treatment

The influence of sulphated polysaccharides (dextran sulphate (DS), ι‐carrageenan (ι‐CAR) and κ‐carrageenan (κ‐CAR)) on the emulsifying properties of ovalbumin (OVA) has been investigated over a range of pressures and temperatures. Oil‐in‐water emulsions (10 g l⁻¹ protein, 200 ml l⁻¹ n‐tetradecane, pH 6.2) prepared with heat‐treated (80 °C for 10 min) mixtures of OVA + DS (1:0.25 by weight) had increased creaming stability but unchanged average droplet size compared to those made with untreated OVA and OVA + DS. Emulsions made with pressure‐processed (600 MPa for 20 min) OVA + DS (1:0.25 or 1:0.5 by weight) mixtures had the best emulsifying efficiency and stability. Under similar experimental conditions, replacement of DS with either ι‐ or κ‐CAR gave emulsions with larger droplets and more rapid serum separation, probably owing to depletion flocculation. High‐pressure treatment (600 MPa) of the OVA and mixed biopolymer solutions at pH 6.2 in the presence of salt (>0.04 M ) led to unstable emulsions, and so the protective effect of DS was lost. High‐pressure treatment (600 MPa) of emulsions prepared with native OVA or OVA + DS mixtures induced significant levels of flocculation, as indicated by changes in the average droplet size and creaming behaviour. © 2000 Society of Chemical Industry     

离子强度对菜籽分离蛋白气液界面行为及泡沫特性的影响

来源于菜籽油饼粕的蛋白质氨基酸平衡性好、生物效价高,具有较高的营养价值,是近年来受到普遍关注的优质蛋白资源.采用动态滴形分析和荧光光谱法,分析了在pH值为7时,不同的离子强度下,气液界面压力的变化情况以及蛋白质微环境的变化.实验表明:表面压力π小于10 mN/m时扩散控制吸附动力学,扩散速率随着离子强度的增大而加快;表...     

Chloride salt type/ionic strength, muscle site and refrigeration effects on antioxidant enzymes and lipid oxidation in pork

The effects of NaCl and KCl at varying ionic strengths on catalase and glutathione peroxidase (GSH-Px) activities and lipid oxidation in refrigerated ground pork muscles from different anatomical locations were studied. Catalase and GSH-Px activities were higher in boston butt (BB) than in longissimus dorsi (LD), whereas lipid oxidation measured by 2-thiobarbituric acid substances (TBARS) content was higher in LD. Catalase activity was stable in both BB and LD during 4-day storage; GSH-Px activity decreased in LD. GSH-Px activity decreased more with NaCl than KCl, whereas salt type had no consistent effect on catalase activity. TBARS content, however, increased more with NaCl than with KCl. NaCl at the highest ionic strength decreased GSH-Px activity by 19.2 and 18% in LD and BB, respectively, and increased TBARS content by 8- and 3.6-fold. Results indicated that pork samples with higher catalase and GSH-Px activities would undergo less lipid oxidation, and the accelerated lipid oxidation in salted pork may be partly related to a decrease in GSH-Px activity.     

离子强度和pH值对肌原纤维蛋白热诱导凝胶特性的影响

以肌原纤维热诱导凝胶的保水性和质构特性,包括硬度、弹性、内聚性、胶黏性、回复性为指标,考察离子强度和pH值对猪背最长肌肌原纤维热诱导凝胶特性的影响.结果表明,离子强度和pH对凝胶不同特性的影响存在差异,综合各种指标,离子强度为0.5,pH值在6.5和7.0之间有利于形成较好的凝胶.不同条件下凝胶形成的机制可能存在差异.凝胶的硬度与弹性、胶黏性和保水性相关性显著(P＜0.05),可以作为重点考察的指标.     

Chloride salt type/ionic strength and refrigeration effects on antioxidant enzymes and lipid oxidation in cattle,camel and chicken meat

The effects of NaCl and KCl at varying ionic strengths on catalase and glutathione peroxidase (GSH-Px) activities and lipid oxidation in ground Longissimus dorsi (LD) of cattle and camel and breast muscle of chicken during refrigerated storage were studied. NaCl and KCl significantly increased 2-thiobarbituric reactive substances (TBARS) and peroxide values. TBARS and peroxide values increased and GSH-Px activity decreased during 4 day storage in the 4 °C, but catalase activity was stable. Salt type had no consistent effect on GSH-Px and catalase activities. Chicken samples had lower enzyme activities and TBARS content than cattle and camel. Their peroxide values were lower than camel samples. Camel meat showed higher catalase activity and TBARS content than cattle meat. Results indicated that negative correlation between lipid oxidation and GSH-Px activity and the accelerated lipid oxidation in salted meat may be partly related to a decrease in GSH-Px activity.     

Dielectric barrier discharge plasma for microbial decontamination of dried laver: effects on physicochemical characteristics

Dielectric barrier discharge (DBD) plasma in atmospheric pressure air was used for microbial decontamination of thin sheets of dried laver, which are commonly used in kimbab preparation. Microbial contaminants namely aerobic bacteria, moulds and marine bacteria were found in sun‐dried laver sheets. DBD plasma was generated at an output voltage of 30 kV AC and a frequency of 30 kHz. Upon the plasma treatment of laver, 2.5‐log (99.68%), nearly 1.5‐log (96.84%) and above 1.0‐log (90%) unit reductions in viable counts of aerobic bacteria, marine bacteria and moulds were observed over a 10‐min period, respectively. The inactivation pattern fitted well to Singh–Heldman model or pseudo first‐order kinetics. Compared to control laver, no significant (P > 0.05) changes in the colour characteristics, total phenolic content and 2,2‐diphenyl‐1‐picrylhydrazyl radical scavenging activity were observed in plasma‐treated laver. Furthermore, DBD plasma‐treated laver sheets had exerted no negative impact on the sensory characteristics of kimbab and can extend the shelf life.     

The effects of mixing,transport and duration of lairage on carcass characteristics in commercial bacon weight pigs

On arrival at the factory commercial crossbred pigs were subjected to various treatments: (i) penned in producer lots; (ii) mixed with pigs from another producer and (iii) mixed and subjected to an additional transport of 1-1.5h duration. Groups of pigs were killed on the day of arrival or after overnight lairage. Carcass parameters including pH₁ (pH 45 min post mortem) and pH_u (pH 20 h post mortem) values of the Longissimus dorsi (LD) and adductor muscles were taken post mortem. Mixing and transport had no statistically significant effect on any of the carcass parameters measured, although overnight lairage resulted in significant decreases in hot carcass weight, killing-out percentage and liver weight. The incidence of carcasses classified as pale soft and exudative [PSE (muscles with a pH₁ of 5.9 or less)] or dark firm dry [DFD (muscles with a pH_u of 6.2 or greater)] was high after both normal and overnight lairage. pH₁ and pH_u values of the LD and adductor muscles were not significantly affected by mixing or transport. Statistically significant differences in the incidence of DFD between treatment groups were observed. In general the incidence of DFD increased more after overnight lairage in pigs penned in producer lots, than in pigs penned in mixed producer lots.     

Soy protein-polysaccharide complex coacervate under physical treatment: Effects of pH,ionic strength and polysaccharide type

The objective of this paper is to explore the effects of pH, ionic strength and polysaccharide type on the aqueous phase behaviors and rheological properties of soy protein isolate-chitosan (SPI-CS) and soy protein isolate-carboxymethyl cellulose (SPI-CMC) coacervates treated by vortex fluidic device (VFD) and shear homogenization. Characterization in terms of phase behavior and microstructures depicted that the VFD and shear homogenization treatments affected only the SPI-CS complex. According to the ζ-potential values at tested pHs (3.0–8.0), both physical processing had insignificant effect on charge stabilization of protein-polysaccharide complex. Both the SPI-CS coacervates (at pH 7.0) and SPI-CMC coacervates (at pH 3.0) showed gel-type rheological behaviors (G′ > 1000 Pa), suggesting that the SPI and polysaccharides did not form complex coacervate (liquid in nature) but interpolymeric complex (solid in nature). In the absence of salt ions, independent on the type of coacervate, VFD slightly decreased the modulus (G′ < 1000 Pa) while homogenization significantly decreased the modulus (G′ < 20 Pa). Alternatively, the addition of salt ions produced an electrostatic shielding and weakened the protein-polysaccharide electrostatic interaction, resulting in a decrease of coacervate modulus. Interestingly, under certain condition, VFD treatment probably promoted the interaction between protein molecules in protein-polysaccharide coacervate, resulting in another increase in the elastic modulus of the complex coacervate.     

Solubilization of myofibrillar proteins in water or low ionic strength media: Classical techniques,basic principles,and novel functionalities

The qualitative characteristics of meat products are closely related to the functionality of muscle proteins. Myofibrillar proteins (MPs), comprising approximately 50% of total muscle proteins, are generally considered to be insoluble in solutions of low ionic strength (< 0.2 M), requiring high concentrations of salt (> 0.3 M) for solubilization. These soluble proteins are the ones which determine many functional properties of meat products, including emulsification and thermal gelation. In order to increase the utilization of meat and meat products, many studies have investigated the solubilization of MPs in water or low ionic strength media and determining their functionality. However, there still remains a lack of systematic information on the functional properties of MPs solubilized in this manner. Hence, this review will explore some typical techniques that have been used. The main procedures used for their solubilization, the fundamental principles and their functionalities in water (low ionic strength medium) are comprehensively discussed. In addition, advantages and disadvantages of each technique are summarized. Finally, future considerations are presented to facilitate progress in this new area and to enable water soluble muscle MPs to be utilized as novel meat ingredients in the food industry.     

NaCl离子强度、Mg2+浓度、热变温和pH对云南地方黄牛肌肉盐溶蛋白凝胶保水性的影响

以肉牛的背最长肌(LD)和股二头肌(BF)为材料.研究了NaCl离子强度、Mg2+浓度、热变温度和pH对牛肉背最长肌和股二头肌盐溶蛋白凝胶保水性的影响.结果表明,在一定范围内,背最长肌和股二头肌盐溶蛋白热诱导凝胶的保水性与NaCl离子强度、热变温度呈正相关;Mg2+浓度对凝胶保水性的影响不明显;pH越高,偏离肉蛋白的等电点越远,保水性越好.     

Associative interactions between chitosan and soy protein fractions: Effects of pH,mixing ratio,heat treatment and ionic strength

The objective of this paper is to explore the complexation between the soy protein fractions (glycinin and β-conglycinin) and chitosan (CS) and to investigate the influence of pH, mixing ratio, heat treatment and ionic strength. Phase behavior and microstructure showed that soluble complex and coacervate were obtained in glycinin/CS and β-conglycinin/CS mixtures at specific pHs, following a nucleation and growth mechanism. Moreover, the coacervates showed higher thermal stability than protein alone. Specially, the glycinin/CS mixture displayed a gel-like network structure at pH 5.5 and 6.0, and this structure kept the mixture soluble at a long pH region. The turbidity versus ζ-potential pattern showed that, independent of protein, the self aggregation of soy protein fractions and the coacervation of glycinin/CS and β-conglycinin/CS mixtures were all obtained at charge neutralization pH, indicating that the ζ-potential is the most critical parameter to understand the stability of soy protein/chitosan mixture. This predictive parameter was less affected by mixing ratio and heating but was significantly affected by ionic strength because mixing ratio and heating only changed the equilibrium between repulsive and attractive forces in colloid system while sodium chloride destroyed the predictability of colloidal stability via shielding charged reactive sites on both biopolymers to disrupt electrostatic interactions.