Influence of EDTA and citrate on physicochemical properties of whey protein-stabilized oil-in-water emulsions containing CaCl2

The influence of chelating agents (disodium ethylenediaminetetraacetate (EDTA) and sodium citrate) on the physicochemical properties of whey protein isolate (WPI)-stabilized oil-in-water emulsions containing calcium chloride was determined. The calcium-binding characteristics of EDTA and citrate at 30 degrees C were characterized in aqueous solutions (20 mM Tris buffer, pH 7.0) by isothermal titration calorimetry (ITC). EDTA and citrate both bound calcium ions in a 1:1 ratio, but EDTA had a much higher binding constant. Oil-in-water emulsions (pH 7.0) were prepared containing 6.94% (w/v) soybean oil, 0.35% (w/v) WPI, 0.02% (w/v) sodium azide, 20 mM Tris buffer, 10 mM CaCl(2), and 0-40 mM chelating agent. The particle size, apparent viscosity, creaming stability, free calcium concentration, and particle surface potential of the emulsions were measured. The chelating agents reduced or prevented droplet aggregation in the emulsions. When they were present above a certain concentration (>3.5 mM EDTA or >5 mM citrate), droplet aggregation was prevented. The reduction of aggregation was indicated by decreases in particle size, shear-thinning behavior, apparent viscosity, and creaming. Emulsions containing chelating agents had lower free calcium concentrations and more negatively charged droplets, indicating that the chelating agents improved emulsion stability by binding calcium ions. EDTA could be used at lower concentrations than citrate because of its higher calcium ion binding constant.     

Effect of salts on the gelatinization and rheological properties of sago starch.

The effects of various salts on the gelatinization and rheological properties of sago starch have been studied using differential scanning calorimetry, small deformation oscillation, and large deformation techniques. The presence of salts affected the gelatinization peak temperature, T(p), gelatinization enthalpy, DeltaH, swelling properties, storage modulus, G', gel strength, GS, and gelation rate constants, k, depending on the type of salt and the concentration. Their influence followed the Hofmeister series, and the effect of anions was more pronounced than that of cations. Sulfate ions increased T(p), G', GS, and k and reduced the swelling properties, whereas iodide and thiocyanate ions reduced T(p), G', GS, and k but increased the swelling properties. For all of the salts studied except for Na(2)SO(4), T(p) increased to a maximum and then decreased again at higher salt concentrations while DeltaH reduced with concentration. In the presence of MgCl(2), CaCl(2), and LiCl complex behavior was observed such that at approximately 3.5 M MgCl(2) and CaCl(2) and 8 M LiCl the starch samples were gelatinized at room temperature, whereas at much higher concentration T(p) increased again and the transition became exothermic.     

Effects of lipase, lipoxygenase, peroxidase, and rutin on quality deteriorations in buckwheat flour

To investigate the effects of changes in lipase, lipoxygenase, peroxidase (POX), and rutin concentrations on the quality of buckwheat flour, 14 buckwheat varieties were stored for 0, 4, 10, and 30 days at 5 or 20 degrees C. During the storage period, lipase activity correlated to pH (significantly negative) and water-soluble acid (WSA) (significantly positive). The lipoxygenase 1 protein concentration had a negative correlation to WSA (significant at 0 and 4 storage days at 5 degrees C and at 0 and 10 storage days at 20 degrees C). POX had significant correlation to pH and peroxide value (POV) at 5 degrees C, whereas it was not significant at 20 degrees C. The rutin concentration had negative correlations to WSA (significant at 30 days of storage at 5 degrees C and at 4 days of storage at 20 degrees C). Thus, lipase activity plays an important role that relates to lipid degradation in quality deterioration of buckwheat flour.     

CaCl_2和SrCl_2提取土壤氮钾的比较

为了探讨0.01mol L-1 CaCl2和0.02mol L-1 SrCl2提取土壤氮、钾能力的差异,用0.01mol L-1 CaCl2和0.02mol L-1 SrCl2提取14个土壤样品,再分别用流动分析和火焰光度法测定提取液中的硝态氮和亚硝态氮之和和钾的含量,以1mol L-1 KCl和1mol L-1中性醋酸铵提取液作为无机氮和钾的对照提取剂,同时选择部分土壤样品用盆栽试验测定提取数量与土壤氮、钾有效性的关系。结果表明,两种方法和对照方法提取氮和钾数量的相关性均达到p<0.01水平,对照提取剂、0.01mol L-1 CaCl2和0.02mol L-1 SrCl2对于14个土壤的硝态氮和亚硝态氮之和提取含量平均值分别为13.36、15.33和26.62mgkg-1,14个土样的提取钾含量的平均值分别为120.4、33.58和54.24mgkg-1。盆栽试验结果表明,对照提取剂和0.01molL-1CaCl2和0.02molL-1SrCl2提取氮的数量与植物吸氮量的相关性达到p<0.05显著水平,钾的相关性达到p<0.01显著水平。与对照提取剂的氮、钾分别提取相比,SrCl2和CaCl2提取剂均可大大降低样品提取中试剂费用。以上结果表明,0.01mol L-1 CaCl2和0.02mol L-1 SrCl2提取对土壤氮和钾的提取能力均可反映土壤硝态氮和亚硝态氮、有效钾的含量和供应能力,而提取能力以0.02mol L-1 SrCl2为高。     

Influence of CaCl(2) on the foliar biomass and quality of tobacco leaves

The aim of the present work was to determine the influence of different CaCl(2) dosages on foliar biomass and quality of tobacco plants (Nicotiana tabacum L. var. Tennesse 86). Plants were grown under controlled conditions and submitted to regular fertilization with macro- and micronutrients. The CaCl(2) was applied to the nutrient solution at 1.25 mM (T1), 2.5 mM (T2), and 5 mM (T3). The results indicated that, under the experimental conditions of this work, the application of 1.25 mM of CaCl(2) favored the growth and development of the leaves, this leading to improved biomass production in tobacco leaves. The increase in foliar biomass in treatment T1 could largely be a result of the stimulation of NO(3)(-) assimilation. However, this situation has negative consequences for tobacco quality, given that the T1 treatment augmented the NO(3)(-) concentration and the foliar concentration of nicotine (both effects being harmful for human consumption) and decreased the concentration of reducing sugars in leaves of tobacco plants compared with those of T2 and T3. Finally, a close and directly proportional relationship was found in our experiment between the parameters of foliar-biomass production, total N concentration, chlorophyll concentration, and decline in quality.     

Catalytic characteristics of peroxidase from wheat grass

The crude enzyme extract of wheat grass was heated at 60 degrees C for 30 min, followed by ammonium sulfate fractionation and isoelectric chromatofocusing on Polybuffer exchanger (PBE 94) for purification. The purified peroxidase was then characterized for its catalytic characteristics. It was found that AgNO3 at a concentration of 0.25 mM and MnSO4 and EDTA at concentrations of 5 mM significantly inhibited the activity of wheat grass peroxidase. However, KCl, NaCl, CuCl2, CaCl2, ZnCl2, and MgCl2 at concentrations of 5.0 mM and HgCl2 at a concentration of 0.25 mM enhanced enzyme activity. Chemical modification significantly influenced the activity of wheat grass peroxidase. Particularly, N-bromosuccinimide (5 mM) inhibited 16% of the enzyme activity, whereas N-acetylimidazole (2.5 mM), diethyl pyrocarbonate (2.5 mM), and phenylmethanesulfonyl fluoride (2.5 mM) enhanced by 18-29% of the enzyme activity. Such results implied that tryptophan, histidine, tyrosine, and serine residues are related to enzyme activity. The pH optima for wheat grass peroxidase to catalyze the oxidation of o-phenylenediamine (OPD), catechol, pyrogallol, and guaiacol were 5.0, 4.5, 6.5, and 5.0, respectively. The apparent Km values for OPD, catechol, pyrogallol, and guaiacol were 2.9, 18.2, 2.5, and 3.8 mM, respectively. Under optimal reaction conditions, wheat grass peroxidase catalyzed the oxidation of OPD (an aromatic amine substrate) 3-11 times more rapidly than guaiacol, catechol, and pyrogallol (phenolic substrates containing one to three hydroxy groups in the benzene ring).     

Maltodextrin-anionic surfactant interactions: isothermal titration calorimetry and surface tension study

Interactions between maltodextrin (DE = 10) and an anionic surfactant (sodium dodecyl sulfate, SDS) were studied in a buffer solution (pH 7.0, 10 mM NaCl, 20 mM Trizma, 30.0 degrees C) using isothermal titration calorimetry (ITC), surface tension, differential scanning calorimetry (DSC), and turbidity techniques. ITC measurements indicated that the binding of SDS to maltodextrin was exothermic and that, on average, one SDS monomer bound per 24 glucose units of maltodextrin at saturation. Surface tension measurements indicated that there was a critical surfactant concentration ( approximately 0.05 mM SDS) below which surfactant and maltodextrin did not interact and that the amount of surfactant bound to the maltodextrin above this concentration increased with increasing maltodextrin concentration. Turbidity measurements indicated that the solutions remained transparent at all maltodextrin (0-1 wt %) and SDS (0-20 mM) concentrations studied, which suggested that phase separation did not occur. DSC measurements indicated that no phase transitions occurred between 10 and 110 degrees C for maltodextrin solutions (0.5 wt %) in the presence or absence of surfactant. A phase diagram was developed to describe the interactions between SDS and maltodextrin.     

1H nuclear magnetic resonance relaxometry study of water state in milk protein mixtures

1H NMR signal was used to characterize highly hydrated milk protein dispersions (3-20% dry matter) with various micellar casein concentrations (3-15%), whey protein concentrations (0-3%), lactose concentrations (0-7.5%), CaCl(2) concentrations (0-2 mM), and pH (6.2-6.6). The results showed the predominant effect of micellar casein concentration on water state and were consistent with the three-site relaxation model in the absence of lactose. The relaxation rates observed for these dispersions were explained by the free water relaxation rate, the hydration water relaxation rate, and the exchangeable proton relaxation rate. Hydration water was found to be mainly influenced by casein micelle concentration and structure. The variations in hydration with pH were consistent with those observed for classical measurement of voluminosity observed at this range of pH. The effects of lactose and whey protein content are discussed.     

The application of polyamines by pressure or immersion as a tool to maintain functional properties in stored pomegranate arils

Pomegranate fruits were treated with putrescine (Put) or spermidine (Spd) at 1 mM either by pressure infiltration or by immersion and then were stored at 2 degrees C for 60 days. Samples were taken biweekly and were further stored 3 days at 20 degrees C for shelf life study. The treatments were effective on maintaining the concentration of ascorbic acid, total phenolic compounds, and total anthocyanins in arils at higher levels than in control samples. In addition, the two ways of polyamine application increased the levels of total antioxidant activity (TAA) during storage, especially when polyamines were applied by pressure infiltration. Moreover, Spd showed the best results on increasing TAA through maintenance of total phenolic compounds.     

A DSC study on the gel-sol transition of a starch and hsian-tsao leaf gum mixed system

Differential scanning calorimetric analysis was performed on the admixture of 4% hsian-tsao leaf gum and 8% wheat starch as a function of salt types and concentrations. The salt concentrations (C(s)) studied were 5-100 mM for sodium and potassium chloride, and 3.4-34 mM for calcium and magnesium chloride. It was found that hsian-tsao leaf gum or starch alone did not present a readily recognizable exothermic peak or endothermic peak during cooling or heating in DSC. However, mixing these two polymers promoted the intermolecular binding and subsequent gelation of the mixtures as evidenced by the DSC exothermic and endothermic peaks during cooling and heating, respectively. The setting and melting temperatures of such a mixed system shifted progressively to higher temperatures with increasing concentrations of added salts. It was considered that the aggregated mixed polymers formed thermally stable junction zones with higher binding energies. The thermal behavior change was more remarkable by the addition of K(+) than by Na(+), and by Ca(2+) than by Mg(2+). For monovalent cations, the DSC heating and cooling curves showed a single endothermic and exothermic peak. For divalent cations at low concentration, the DSC curves showed a single peak. However, with sufficient divalent cations, the DSC curves eventually developed a bimodal character. A mixed system with sufficient Ca(2+) could form firm gel that was difficult to remelt completely upon heating to 130 degrees C, indicating the possibility of the formation of ionic bonds through cross-links with the carboxyl groups in hsian-tsao leaf gum.     

Influence of environmental conditions on the stability of oil in water emulsions containing droplets stabilized by lecithin-chitosan membranes

Oil-in-water emulsions containing cationic droplets stabilized by lecithin-chitosan membranes were produced using a two-stage process. A primary emulsion containing anionic lecithin-coated droplets was prepared by homogenizing oil and emulsifier solution using a high-pressure valve homogenizer (5 wt % corn oil, 1 wt % lecithin, 100 mM acetic acid, pH 3.0). A secondary emulsion containing cationic lecithin-chitosan-coated droplets was formed by diluting the primary emulsion with an aqueous chitosan solution (1 wt % corn oil, 0.2 wt % lecithin, 100 mM acetic acid, and 0.036 wt % chitosan). The stabilities of the primary and secondary emulsions with the same oil concentration to thermal processing, freeze-thaw cycling, high calcium chloride concentrations, and lipid oxidation were determined. The results showed that the secondary emulsions had better stability to droplet aggregation during thermal processing (30-90 degrees C for 30 min), freeze-thaw cycling (-10 degrees C for 22 h/30 degrees C for 2 h), and high calcium chloride contents (相似文献   

Orthokinetic flocculation of caseinate-stabilized emulsions: influence of calcium concentration, shear rate, and protein content

Calcium-induced flocculation of caseinate-stabilized soybean oil-in-water emulsions in conditions of Couette flow was studied. A concentrated emulsion (20% oil, 0.5-2.0% sodium caseinate in 20 mM imidazole, pH 7) was diluted 20 times in buffer containing concentrations of CaCl(2) between 9 and 17 mM and sheared at rates between 335 and 1340 s(-)(1). The average particle size (d(43)), measured by integrated light scattering, increased in a sigmoidal manner with shearing time. An increased shear rate resulted in an increased flocculation rate, because of the increased number of collisions between particles, but a decreased value of the maximum d(43), because higher shear rates increasingly disrupted the flocs. The flocculation rate was increased by increasing the calcium concentration, indicating an increased collision efficiency. The orthokinetic stability of the emulsions was increased with increased protein content, and it is postulated that the increased surface coverage and hydrodynamic thickness of the adsorbed protein layer increased steric repulsion between droplets, so that higher calcium concentrations were necessary to induce sufficient conformational change of the proteins to allow flocculation. At high caseinate concentrations, calcium may also induce precipitation of unadsorbed caseins from the serum to the oil-water interface, thereby increasing steric repulsion and hence increasing orthokinetic stability.     

Effect of calcium and magnesium on 65zinc absorption and translocation in rice seedlings

Effect of calcium and magnesium on zinc absorption by 21‐day‐old rice seedlings and its translocation within the plants was studied in the nutrient solution culture using radioactive zinc. The concentrations of the elements in the nutrient solution were 0.5, 1.0 and 2.0 μM zinc and 0, 10 and 20 mM calcium and magnesium. Absorption of ⁶⁵zinc was studied for 30, 60 and 90 minutes and translocation for 24 hours. Zinc absorption increased with time and increased zinc concentration in the nutrient solutions. Addition of calcium and magnesium reduced zinc absorption by rice seedlings by about 60 and 90% respectively at a concentration of 20 mM. The nature of inhibition of both calcium and magnesium on zinc was non‐competitive as indicated by Michaelis constants. A large fraction of zinc absorbed remained in roots and only 5.3% was translocated to shoots even at 2.0 #GMM zinc concentrations in solution. The effect of cations on translocation of ⁶⁵zinc within rice seedlings was more at lower( 0.5 μM zinc) than at higher (2.0 μM zinc) concentrations.     

ADSORPTION OF PHOSPHATE BY GIBBSITE

The effects of the salts were studied using I per cent suspensions of gibbsite at pH 5.5 and 26°C. At 480μM phosphate and I mM calcium, the kinetic pattern was an initial rapid adsorption reaction, which approached equilibrium in 24 h, revealing a slower reaction. Adsorption isotherms determined at 24 h, with a range of final phosphate concentrations from 0.1 to 1000 μ in solution, were not affected by 20 mM sodium or potassium chloride or 10 mM magnesium chloride. Increasing calcium chloride from o to 20 TIM increased the adsorption of phosphate over the range from 1 to 100 μM final phosphate concentration. At lower (0.1 μM) and higher (1000 μM) phosphate, the effect of calcium was smaller. These results help to explain several effects of the various cations on the adsorption of phosphate by clays and soils, when effects of neutral salts on pH are also considered.     

Synthesis of morphiceptin (Tyr-Pro-Phe-Pro-NH(2)) by dipeptidyl aminopeptidase IV derived from Aspergillus oryzae

Morphiceptin (Tyr-Pro-Phe-Pro-NH(2)), tetrapeptide, was synthesized using dipeptidyl aminopeptidase IV (DP IV, EC 3.4.14.5) derived from Aspergillus oryzae RIB 915 as a catalyst. Tyr-Pro-OEt was incubated with Phe-Pro-NH(2) in the presence of DP IV under various conditions of temperature, concentrations of ethylene glycol, pH, reaction time, and others. Morphiceptin was obtained at 40% yield under the optimal reaction conditions: substrate, 4 mM Tyr-Pro-OEt.HCl and 20 mM Phe-Pro-NH(2).HCl; enzyme, DP IV, 0.275 nkat; solvent, 60% ethylene glycol containing 20 mM phosphate buffer at pH 7.0; amine, 4.2 mM diisopropylamine at 4 degrees C for 24 h. Amino group protection was unnecessary for synthesis of morphiceptin by DP IV.     

Levan fructotransferase from Arthrobacter oxydans J17-21 catalyzes the formation of the di-D-fructose dianhydride IV from levan

A new levan fructotransferase (LFTase) isolated from Arthrobacter oxydans J17-21 was characterized for the production of difructose dianhydride IV (DFA IV). LFTase was purified to apparent homogeneity by Q-Sepharose ion exchange chromatography, Mono-Q HR 5/5 column chromatography, and gel permeation chromatography. The enzyme had an apparent molecular mass of 54000 Da. The optimum pH for the enzyme-catalyzed reaction was pH 6.5, and the optimum temperature was observed at 45 degrees C. The LFTase was activated by the presence of CaCl(2) and EDTA-2Na but inhibited strongly by MnCl(2) and CuSO(4) at 1 mM and completely by FeSO(4) and Ag(2)SO(4) at 1 mM. A bacterial levan from Zymomonas mobilis was incubated with an LFTase; final conversion yield from the levan to DFA IV was 35%. Neither inulin, levanbiose, sucrose, dextran, nor starch was hydrolyzed by LFTase. DFA IV was very stable at acidic pH and high temperature, thus indicating that DFA IV may be suitable for the food industry and related areas.     

Effect of temperature and/or pressure on tomato pectinesterase activity

The activity of tomato pectinesterase (PE) was studied as a function of pressure (0.1-900 MPa) and temperature (20-75 degrees C). Tomato PE was rather heat labile at atmospheric pressure (inactivation in the temperature domain 57-65 degrees C), but it was very pressure resistant. Even at 900 MPa and 60 degrees C the inactivation was slower as compared to the same treatment at atmospheric pressure. At atmospheric pressure, optimal catalytic activity of PE was found at neutral pH and a temperature of 55 degrees C. Increasing pressure up to 300 MPa increased the enzyme activity as compared to atmospheric pressure. A maximal enzyme activity was found at 100-200 MPa combined with a temperature of 60-65 degrees C. The presence of Ca(2+) ions (60 mM) decreased the enzyme activity at atmospheric pressure in the temperature range 45-60 degrees C but increased enzyme activity at elevated pressure (up to 300 MPa). Maximal enzyme activity in the presence of Ca(2+) ions was noted at 200-300 MPa in combination with a temperature of 65-70 degrees C.     

Influence of heating on oil-in-water emulsions prepared with soybean soluble polysaccharide

The effect of heating on the physicochemical properties of emulsions prepared with soybean soluble polysaccharide (SSPS) was investigated. The emulsions were stable after heating at 90 degrees C for up to 30 min. Heating at different pH values or in the presence of CaCl2 (<10 mM) did not affect the stability; however, at higher concentrations of calcium ions, the emulsion particle size increased. Two fractions, a high molecular weight (HMF) and a low molecular weight (LMF) fraction, were separated from the crude SSPS preparation by gel fitration. Emulsions prepared with SSPS/HMF (MW = 310-420 kDa) showed little change in size with heating, while the protein impurities of the SSPS/LMF fraction formed aggregates by heating at pH 7. Analysis of the heat-induced aggregation of the two fractions of SSPS suggested that the changes in SSPS functionality with heating can be attributed to the protein impurities (LMF) present in the SSPS.     

Production, purification, and properties of an endoglucanase produced by the hyphomycete Chalara (Syn. Thielaviopsis) paradoxa CH32

The hyphomycete Chalara (syn. Thielaviopsis) paradoxa produces endoglucanase activity during the late trophophase. The low molecular mass (35 kDa) endoglucanase purified from cultured broths works optimally at 37 degrees C and pH 5.0. The enzyme inactivates at pH below 3.0 and also at temperatures of 50 degrees C or higher, but it is stable at lower temperatures, including refrigeration temperature and freezing. The enzyme is inhibited by detergents, by EDTA, and by the divalent cations Hg(2+) and Ag(2+). It is also inhibited to some extent by 10 mM Zn(2+), Fe(2+), and Mg(2+), but it is stimulated by Mn(2+). Enzyme activity is not affected by reducing agents. In the presence of low concentrations of water miscible organic solvents (20%) endoglucanase activity is inhibited by 7% (for methanol) to 50% (for acetonitrile), and it is totally inhibited at higher solvent concentrations (50%). Enzyme activity is not affected by the water immiscible solvent ethyl acetate. Carboxymethylcellulose is the preferred substrate (K(m(app)) = 8.3 g/L; V(max(app)) = 1.1 microM/min). Hydrolysis of crystalline cellulosic substrates is very limited, but it is greatly enhanced by phosphoric acid swelling. The purified enzyme shows no activity toward disaccharides or aryl-glucosides. Its activity is inhibited by cellobiose.     

Examination into the Accuracy of Exchangeable Cation Measurement in Saline Soils

Abstract

Despite the increasing prevalence of salinity worldwide, the measurement of exchangeable cation concentrations in saline soils remains problematic. Two soil types (Mollisol and Vertisol) were equilibrated with a range of sodium adsorption ratio (SAR) solutions at various ionic strengths. The concentrations of exchangeable cations were then determined using several different types of methods, and the measured exchangeable cation concentrations were compared to reference values. At low ionic strength (low salinity), the concentration of exchangeable cations can be accurately estimated from the total soil extractable cations. In saline soils, however, the presence of soluble salts in the soil solution precludes the use of this method. Leaching of the soil with a prewash solution (such as alcohol) was found to effectively remove the soluble salts from the soil, thus allowing the accurate measurement of the effective cation exchange capacity (ECEC). However, the dilution associated with this prewashing increased the exchangeable calcium (Ca) concentrations while simultaneously decreasing exchangeable sodium (Na). In contrast, when calculated as the difference between the total extractable cations and the soil solution cations, good correlations were found between the calculated exchangeable cation concentrations and the reference values for both Na (Mollisol: y=0.873x and Vertisol: y=0.960x) and Ca (Mollisol: y=0.901x and Vertisol: y=1.05x). Therefore, for soils with a soil solution ionic strength greater than 50 mM (electrical conductivity of 4 dS/m) (in which exchangeable cation concentrations are overestimated by the assumption they can be estimated as the total extractable cations), concentrations can be calculated as the difference between total extractable cations and soluble cations.