RESUMEN
Salar de Uyuni (SdU), with a geological history that reflects 50 000 years of climate change, is the largest hypersaline salt flat on Earth and is estimated to be the biggest lithium reservoir in the world. Its salinity reaches saturation levels for NaCl, a kosmotropic salt, and high concentrations of MgCL2 and LiCl, both salts considered important chaotrophic stressors. In addition, extreme temperatures, anoxic conditions, high UV irradiance, high albedo and extremely low concentrations of phosphorous, make SdU a unique natural extreme environment in which to contrast hypotheses about limiting factors of life diversification. Geophysical studies of brines from different sampling stations show that water activity is rather constant along SdU. Geochemical measurements show significant differences in magnesium concentration, ranging from 0.2 to 2M. This work analyses the prokaryotic diversity and community structure at four SdU sampling stations, selected according to their location and ionic composition. Prokaryotic communities were composed of both Archaea (with members of the classes Halobacteria, Thermoplasmata and Nanohaloarchaea, from the Euryarchaeota and Nanohaloarcheota phyla respectively) and Bacteria (mainly belonging to Bacteroidetes and Proteobacteria phyla). The important differences in composition of microbial communities inversely correlate with Mg2+ concentration, suggesting that prokaryotic diversity at SdU is chaotropic dependent.
Asunto(s)
Archaea/clasificación , Archaea/aislamiento & purificación , Bacterias/clasificación , Bacterias/aislamiento & purificación , Ambientes Extremos , Archaea/genética , Bacterias/genética , Biodiversidad , Bolivia , Cloruro de Litio/análisis , Cloruro de Magnesio/análisis , ARN Ribosómico 16S/genética , Salinidad , Sales (Química)/análisis , Cloruro de Sodio/análisisRESUMEN
This paper reports a novel and very simple method for measuring the zeta potential of electrolyte solution-air interface. When a measuring electrode contacts the electrolyte solution-air interface, an electrical current will be generated due to the potential difference between the electrode-air surface and the electrolyte solution-air interface. The amplitude of the measured electric signal is linearly proportional to this potential difference; and depends only on the zeta potential at the electrolyte solution-air interface, regardless of the types and concentrations of the electrolyte. A correlation between the zeta potential and the measured voltage signal is obtained based on the experimental data. Using this equation, the zeta potential of any electrolyte solution-air interface can be evaluated quickly and easily by inserting an electrode through the electrolyte solution-air interface and measuring the electrical signal amplitude. This method was verified by comparing the obtained results of NaCl, MgCl2 and CaCl2 solutions of different pH values and concentrations with the zeta potential data reported in the published journal papers.
Asunto(s)
Cloruro de Calcio/análisis , Técnicas Electroquímicas , Electrólitos/química , Cloruro de Magnesio/análisis , Cloruro de Sodio/análisis , Aire , Electricidad , Electrodos , Soluciones , AguaRESUMEN
Our objective was to examine the physico-chemical and sensory attributes of low-sodium restructured caiman steaks containing microbial transglutaminase (MTG) and salt replacers (KCl and MgCl2). Trimmings from caiman carcasses were processed into restructured steaks with or without MTG and salt replacers; the five treatments were CON (1.5% NaCl), T-1 (1.5% NaCl+1% MTG), T-2 (0.75% NaCl+1% MTG+0.75% KCl), T-3 (0.75% NaCl+1% MTG+0.75% MgCl2), and T-4 (0.75% NaCl+1% MTG+0.375% KCl+0.375% MgCl2). T-4 demonstrated the greatest (P<0.05) succulence and the lowest (P<0.05) values for cooked hardness, springiness, and cohesiveness. The greatest (P<0.05) purchase intention was for T-3. Furthermore, T-3 and T-4 were similar (P>0.05) to controls in salty flavor. Our findings suggest that the combination of MTG, KCl, and MgCl2 can be employed as a suitable salt reduction strategy in restructured caiman steaks without compromising sensory attributes and consumer acceptance.
Asunto(s)
Fenómenos Químicos , Carne/análisis , Sodio/análisis , Gusto , Transglutaminasas/química , Adolescente , Adulto , Caimanes y Cocodrilos , Animales , Color , Comportamiento del Consumidor , Culinaria , Femenino , Manipulación de Alimentos , Humanos , Concentración de Iones de Hidrógeno , Cloruro de Magnesio/análisis , Masculino , Persona de Mediana Edad , Cloruro de Potasio/análisis , Análisis de Componente Principal , Sales (Química)/análisis , Adulto JovenRESUMEN
We report a fatal case of hypermagnesemia caused by oral ingestion of milk containing magnesium chloride as a folk remedy. The autopsy of the 75-year-old woman showed no injury or illness as the cause of death. Neither alcohol nor controlled drugs were found by the toxicological analysis. Her posthumous serum magnesium concentration was 10.2 mg/dL. The concentration of magnesium in serum was higher than that of the previous reports. Therefore, the cause of death was considered to be hypermagnesemia. Recently, the prescription drugs, over-the-counter drugs, and health foods containing magnesium are consumed as supplements in the world, and their potential toxicity should be recognized.
Asunto(s)
Cloruro de Magnesio/envenenamiento , Magnesio/sangre , Medicina Tradicional/efectos adversos , Anciano , Animales , Femenino , Toxicología Forense , Humanos , Cloruro de Magnesio/análisis , Leche/químicaRESUMEN
The use of mineral salt replacers to reduce the sodium content in cheese has been investigated as a method to maintain both the salty flavor and the preservative effects of salt. The majority of studies of sodium reduction have used mineral salt replacers at levels too low to produce equal water activity (a(w)) in the finished cheese compared with the full-sodium control. Higher a(w) can result in differences in cheese quality due to differences in the effective salt-to-moisture ratio. This creates differences in biochemical and microbial reactions during aging. We hypothesized that by targeting replacer concentrations to produce the same a(w) as full sodium cheese, changes in cheese quality would be minimized. Stirred-curd Cheddar-style cheese was manufactured and curd was salted with NaCl or naturally reduced sodium sea salt. Reduced-sodium cheeses were created by blends of NaCl or sea salt with KCl, modified KCl, MgCl2, or CaCl2 before pressing. Sodium levels in reduced-sodium cheeses ranged from 298 to 388 mg of sodium/100g, whereas the control full-sodium cheese had 665 mg/100g. At 1 wk of age, a(w) of reduced-sodium cheeses were not significantly different from control, which had an a(w) of 0.96. The pH values of all reduced-sodium cheeses, excluding the treatment that combined sea salt and MgCl2, were lower than those of full-sodium cheese, indicating that the starter culture was possibly less inhibited at the salting step by the replacers than by NaCl. Instrumental hardness values of the treatments with sea salt were higher than in cheeses containing NaCl, with the exception of the NaCl/CaCl2 treatment, which was the hardest. Treatments with MgCl2 and modified KCl were generally less hard than other treatments. In-hand and first-bite firmness values correlated with the instrumental texture profile analysis results. Both CaCl2 and MgCl2 produced considerable off-flavors in the cheese (bitter, metallic, unclean, and soapy), as measured by descriptive sensory analysis with a trained panel. Bitterness ratings for cheese with KCl and modified KCl were not significantly different from the full-sodium control. Potassium chloride can be used successfully to achieve large reductions in sodium when replacing a portion of the NaCl in Cheddar cheese.
Asunto(s)
Queso , Tecnología de Alimentos/métodos , Cloruro de Calcio/análisis , Queso/análisis , Queso/normas , Dieta Hiposódica , Cloruro de Magnesio/análisis , Cloruro de Potasio/análisis , Sodio en la Dieta/análisisRESUMEN
The reduction of the content of sodium chloride in dry-cured ham was studied in to prevent the problems related to high sodium intake (i.e. the hypertension). One of the possibilities to reduce the sodium content is the partial replacement of sodium chloride by mixtures of potassium, magnesium and calcium chloride salts. The effect of two salting formulations (formulation II: 50% NaCl-50% KCl and formulation III: 55% NaCl, 25% KCl, 15 CaCl(2) and 5 MgCl(2)) on the protease activity through the dry-curing process and on the sensory characteristics of the final product was evaluated and compared to those of control hams (formulation I, 100% NaCl). Sensory attributes were all affected in the hams containing CaCl(2) and MgCl(2) while hams containing 50% KCl and NaCl (formulation II) were better valued, except for the attribute taste probably due to the potassium contribution to bitter taste.
Asunto(s)
Manipulación de Alimentos/métodos , Productos de la Carne/análisis , Cloruro de Sodio Dietético/análisis , Gusto , Animales , Cloruro de Calcio/análisis , Fenómenos Químicos , Conservación de Alimentos/métodos , Cloruro de Magnesio/análisis , Cloruro de Potasio/análisis , Proteolisis , PorcinosRESUMEN
The range of sodium chloride (salt)-to-moisture ratio is critical in producing high-quality cheese products. The salt-to-moisture ratio has numerous effects on cheese quality, including controlling water activity (a(w)). Therefore, when attempting to decrease the sodium content of natural cheese it is important to calculate the amount of replacement salts necessary to create the same a(w) as the full-sodium target (when using the same cheese making procedure). Most attempts to decrease sodium using replacement salts have used concentrations too low to create the equivalent a(w) due to the differences in the molecular weight of the replacers compared with salt. This could be because of the desire to minimize off-flavors inherent in the replacement salts, but it complicates the ability to conclude that the replacement salts are the cause of off-flavors such as bitter. The objective of this study was to develop a model system that could be used to measure a(w) directly, without manufacturing cheese, to allow cheese makers to determine the salt and salt replacer concentrations needed to achieve the equivalent a(w) for their existing full-sodium control formulas. All-purpose flour, salt, and salt replacers (potassium chloride, modified potassium chloride, magnesium chloride, and calcium chloride) were blended with butter and water at concentrations that approximated the solids, fat, and moisture contents of typical Cheddar cheese. Salt and salt replacers were applied to the model systems at concentrations predicted by Raoult's law. The a(w) of the model samples was measured on a water activity meter, and concentrations were adjusted using Raoult's law if they differed from those of the full-sodium model. Based on the results determined using the model system, stirred-curd pilot-scale batches of reduced- and full-sodium Cheddar cheese were manufactured in duplicate. Water activity, pH, and gross composition were measured and evaluated statistically by linear mixed model. The model system method accurately determined the concentrations of salt and salt replacer necessary to achieve the same a(w) as the full-sodium control in pilot-scale cheese using different replacement salts.
Asunto(s)
Queso/análisis , Cloruro de Sodio/análisis , Cloruro de Calcio/análisis , Manipulación de Alimentos/métodos , Cloruro de Magnesio/análisis , Modelos Teóricos , Cloruro de Potasio/análisis , Sodio en la Dieta , Agua/análisisRESUMEN
Blends of calcium, magnesium and potassium chloride were used to partially replace sodium chloride (50-75%) in reduced-fat mortadella formulations. The presence of calcium chloride reduced the emulsion stability, cooking yield, elasticity and cohesiveness and increased hardness; however, it yielded the best sensory acceptance when 50% NaCl was replaced by 25% CaCl(2) and 25% KCl. There was no effect of the salt substitutes on mortadella color, appearance and aroma. All salt combinations studied showed stable lipid oxidation during its shelf life. The use of a blend with 1% NaCl, 0.5% KCl and 0.5% MgCl(2) resulted in the best emulsion stability, but the worst scores for flavor. This study suggests that it is possible to reduce the sodium chloride concentration by 50% in reduced-fat mortadella using the studied salt combinations with necessary adjustments to optimize the sensory properties (MgCl(2) 25%; KCl 25%) or emulsion stability (CaCl(2) 25%; KCl 25%).
Asunto(s)
Fenómenos Químicos , Productos de la Carne/análisis , Cloruro de Potasio/análisis , Cloruro de Sodio Dietético/análisis , Gusto , Animales , Cloruro de Calcio/análisis , Color , Grasas/análisis , Manipulación de Alimentos/métodos , Conservantes de Alimentos/química , Metabolismo de los Lípidos , Cloruro de Magnesio/análisis , Sustancias Reactivas al Ácido Tiobarbitúrico/análisisRESUMEN
Sodium intake above nutritional recommendations may involve harmful consequences to health such as the increased risk of cardiovascular diseases. Dry-cured ham constitutes a product with a relatively large amount of sodium. Thus, to obtain a healthier product for consumers with reduced sodium content, two formulations containing KCl alone (formulation II) or mixed with CaCl2 and MgCl2 (formulation III) have been proposed to partially replace NaCl. Lipolysis and lipid oxidation occurring in hams processed with these formulations have been studied since they have direct influence on the final flavor. No significant differences in acid lipase activity or lipid oxidation were found at the end of the process between the alternative formulations and formulation I (control with 100% NaCl). Differences in some free fatty acids, generated along the processing, were detected among treatments and at the end of dry-curing. Data suggests a slight trend towards a major lipolysis during treatment III.
Asunto(s)
Conservación de Alimentos/métodos , Lipólisis/efectos de los fármacos , Productos de la Carne/análisis , Sales (Química)/química , Animales , Cloruro de Calcio/análisis , Manipulación de Alimentos/métodos , Conservantes de Alimentos/análisis , Lipasa/metabolismo , Cloruro de Magnesio/análisis , Oxidación-Reducción , Cloruro de Potasio/análisis , Porcinos , GustoRESUMEN
Application of chemical road deicers has a negative impact on roadside vegetation. Every year, the trees in cities suffer from direct and indirect effects of salt application for winter road maintenance. To elucidate this problem in the city of Kielce, the chemistry of snow, soil, tree bark, and leaf samples has been investigated together with an assessment of the health status of the trees. Twelve investigation sites were selected along the roads with different traffic intensity. Snow samples were collected twice during the winter and analyzed for pH, EC, Na(+), Ca(2+), Mg(2+), and Cl(-). In soil (collected from two depth intervals), tree bark, and leaf samples, the concentrations of B, Ca, Fe, K, Mg, Mn, N, Na, P, S, and Zn were determined. The contents of total organic carbon (TOC) in soils, as well as the pH of soil and tree bark samples were also measured. Negative symptoms revealed by roadside trees included the loss of assimilative apparatus and decreased vitality. The results of chemical analyses indicated that the snowmelt might be a substantial source of chloride ions and alkalizing substances that influenced higher pH of soils. The soil samples displayed elevated concentrations of S and Zn and lower than typical for soil contents of B, Mg, and TOC. The pH of alkaline soils favored greater bioavailability of B and reduced bioavailability of Na and Zn by the trees examined.
Asunto(s)
Nieve/química , Suelo/química , Árboles/química , Árboles/metabolismo , Cloruro de Calcio/análisis , Ciudades , Monitoreo del Ambiente , Cloruro de Magnesio/análisis , Corteza de la Planta/química , Hojas de la Planta/química , Polonia , Cloruro de Sodio/análisisRESUMEN
In 2008 the European Commission developed an EU framework for dietary sodium chloride (NaCl) reduction in order to achieve the World Health Organization recommendations for no more than 5 g/day/person. This initiative is based on four elements: investigate the national data available on NaCl consumption and current NaCl levels of foods, develop actions to raise public awareness, develop reformulation actions with industry/catering, monitor and evaluate actions and reformulations. The initiative is working towards a reduction in NaCl of 16% over 4 years against the 2008 levels and is concentrated on meat products, bread, cheese, and ready meals. In this context, NaCl content and mineral composition of commercial Italian salami were investigated to provide information on their current mineral levels. Moreover, a technological intervention based on NaCl partial replacement by other chloride salts was investigated on Cacciatore salami, a typical Italian dry fermented sausage, as a strategy to decrease the sodium (Na) content of cured meat products. The effect of NaCl partial replacement by KCl, MgCl2, and CaCl2 in some compositional, physicochemical, and sensory properties of Cacciatore salami was evaluated. A 50% reduction of NaCl used for salami manufacture and its replacement by a mixture of KCl, CaCl2, and MgCl2 allowed a 40% lowering of Na content with limited detrimental effects on sensory attributes. Although no effects were observed on pH, water activity, proximate, and free fatty acid composition in reduced sodium Cacciatore salami formulation compared to the traditional one, the NaCl partial replacement induced a significant increase of lipid oxidation.
Asunto(s)
Productos de la Carne/análisis , Sales (Química)/análisis , Cloruro de Sodio Dietético/análisis , Animales , Cloruro de Calcio/análisis , Peroxidación de Lípido , Cloruro de Magnesio/análisis , Cloruro de Potasio/análisis , Sodio/análisis , PorcinosRESUMEN
The reduction of added sodium chloride in dry-cured ham has been proposed to reduce dietary sodium intake in Mediterranean countries. The effect of substituting sodium chloride with potassium chloride, calcium chloride and magnesium chloride on some physicochemical characteristics of dry-cured ham during processing was evaluated. The results showed that hams salted with a mixture of sodium and potassium chloride registered higher salt concentrations and lower water contents and thus, needed less time to reach the required weight loss at the end of the process. The opposite effect was observed when calcium and magnesium chloride were added to the salt mixture. The observed differences in the texture and colour parameters were mainly due to differences in water and salt content.
Asunto(s)
Cloruro de Calcio/farmacología , Cloruro de Magnesio/farmacología , Carne/análisis , Cloruro de Potasio/farmacología , Cloruro de Sodio Dietético/farmacología , Animales , Cloruro de Calcio/análisis , Bovinos , Cloruro de Magnesio/análisis , Cloruro de Potasio/análisis , Cloruro de Sodio Dietético/análisis , PorcinosRESUMEN
This study reports an investigation of the effect of the anode surface area on the performance of a single chamber microbial fuel cell (SCMFC) based biosensor for measuring the organic content of wastewater. A packed bed of graphite granules was used as the anode. The surface area of the anode was changed by altering the granule bed thickness (0.3 cm and 1 cm). The anode surface area was found to play a role in the dynamic response of the system. For a granule bed thickness of 1 cm and with an external resistance of 500 Omega, the response time (defined as the time required to achieve 95% of the steady-state current) was reduced by approximately 65% in comparison to a SCMFC biosensor with a carbon cloth anode.
Asunto(s)
Compuestos Orgánicos/análisis , Eliminación de Residuos Líquidos/métodos , Microbiología del Agua/normas , Cloruro de Amonio/análisis , Técnicas Biosensibles , Cloruro de Calcio/análisis , Cloruros/análisis , Sulfato de Cobre/análisis , Electrodos , Diseño de Equipo , Cloruro de Magnesio/análisis , Compuestos de Manganeso/análisis , Sulfatos/análisis , Eliminación de Residuos Líquidos/estadística & datos numéricos , Agua/análisis , Compuestos de Zinc/análisisRESUMEN
Magnesium chloride (MgCl2)-based dust suppression products are commonly used throughout western United States on nonpaved roads for dust suppression and road stabilization by federal, state, and county transportation agencies. The environmental implications of annually applying these products throughout spring and summer months on adjacent stream chemistry are not known. Sixteen streams were monitored biweekly for 1 to 2 yr in two Colorado counties for a suite of water quality variables up and downstream of nonpaved roads treated with MgCl2-based dust suppression products. Eight of 16 streams had significantly higher downstream than upstream concentrations of chloride or magnesium over the entire monitoring period (pAsunto(s)
Agua Dulce/química
, Cloruro de Magnesio/análisis
, Animales
, Colorado
, Polvo/prevención & control
, Conductividad Eléctrica
, Monitoreo del Ambiente
RESUMEN
The effects of Ca, Mg and pH on the toxicity of Ni to juvenile rainbow trout (Oncorhynchus mykiss) were examined during 17-26-day exposures to Ni in 15 synthetic test solutions. Higher chemical activities of Ca2+, Mg2+ and H+ reduced Ni toxicity, as demonstrated by increased 17-day median lethal concentrations expressed as Ni2+ activity (17-d LC50(Ni2+)). A non-linear increase of the 17-d LC50(Ni2+) with increasing H+ suggested that the effect of pH could not be appropriately described by single-site competition between Ni(2+) and H+ for sensitive sites on the fish gill. Instead, a linear increase of pNi2+ (=-log 17-d LC50(Ni2+)) with increasing pH was observed with a slope of 0.32. This slope was used as the basis for modelling the effect of pH. The effects of Ca and Mg were modelled according to single-site competition with logK(CaBL)=logK(MgBL)=3.6, both assumed to be independent of pH. The effect of pH was superimposed on this competition effect and was also assumed to be independent of Ca and Mg concentrations. The model was able to predict 17-d LC50s (expressed as dissolved Ni) in most synthetic test waters within a factor 2 deviation from observed toxicity. The model's predictive capacity was also evaluated using results of similar laboratory toxicity tests with juvenile rainbow trout in Ni-spiked European natural surface waters. For most of these waters, predicted 17-d LC50s did not deviate more than a factor 2 from observed toxicity. The same model, calibrated to account for sensitivity differences between species, life stages and/or exposure durations, was able to accurately predict 96-h LC50s for larval and juvenile fathead minnow (Pimephales promelas) and juvenile rainbow trout, based on data taken from literature. Although the developed model seems very promising, the uncertainty around the role of alkalinity and the exact mechanisms by which Ca, Mg and pH modify Ni toxicity need to be further explored.
Asunto(s)
Cyprinidae/crecimiento & desarrollo , Agua Dulce/química , Níquel/farmacocinética , Níquel/toxicidad , Oncorhynchus mykiss/crecimiento & desarrollo , Contaminantes Químicos del Agua/farmacocinética , Contaminantes Químicos del Agua/toxicidad , Factores de Edad , Animales , Disponibilidad Biológica , Cloruro de Calcio/análisis , Cloruro de Calcio/farmacología , Cyprinidae/metabolismo , Relación Dosis-Respuesta a Droga , Europa (Continente) , Crecimiento y Desarrollo/efectos de los fármacos , Concentración de Iones de Hidrógeno , Dosificación Letal Mediana , Cloruro de Magnesio/análisis , Cloruro de Magnesio/farmacología , Modelos Biológicos , Níquel/análisis , Oncorhynchus mykiss/metabolismo , Valor Predictivo de las Pruebas , Reproducibilidad de los Resultados , Factores de Tiempo , Contaminantes Químicos del Agua/análisisRESUMEN
Contents of minerals (Mg, Ca, Na and K), anions (SO4(2-), Br- and Cl) and heavy metals (Pb, Cd, Zn, Hg and As) were determined in 17 commercial samples of Nigari, 15 samples of crude magnesium chloride (sea water) products as a food additive and 2 magnesium-containing foods. Obtained values were compared with the specifications proposed in a draft of the eighth edition of Japan's Specifications and Standards for Food Additives. Out of 15 food additive samples, only 5 samples satisfied the specification. Since the Joint FAO/WHO Expert Committee on Food Additives (JECFA) proposed to lower the limits of heavy metals in food additives, a simple method was developed for the determination of low levels of Pb and Cd by extracting chelates of these metals with organic solvents. The quantification limits for Pb and Cd were 0.5 microg/g and 0.05 microg/g, respectively. It was estimated from the SO4(2-)/Ca ratios that 15 samples were sea water evaporation products, and the remaining 2 were ion-exchange membrane process products. No pollution with heavy metals was found in any of the samples.
Asunto(s)
Aditivos Alimentarios/análisis , Análisis de los Alimentos , Cloruro de Magnesio/análisis , Agua de Mar/análisis , Metales Pesados/análisis , Espectrofotometría Atómica , Contaminantes Químicos del Agua/análisisRESUMEN
Deep hypersaline anoxic basins in the Mediterranean Sea are a legacy of dissolution of ancient subterranean salt deposits from the Miocene period. Our study revealed that these hypersaline basins are not biogeochemical dead ends, but support in situ sulfate reduction, methanogenesis, and heterotrophic activity. A wide diversity of prokaryotes was observed, including a new, abundant, deeply branching order within the Euryarchaeota. Furthermore, we demonstrated the presence of a unique, metabolically active microbial community in the Discovery basin, which is one of the most extreme terrestrial saline environments known, as it is almost saturated with MgCl2 (5 M).
Asunto(s)
Archaea/fisiología , Fenómenos Fisiológicos Bacterianos , Ecosistema , Agua de Mar/microbiología , Cloruro de Sodio , Anaerobiosis , Archaea/clasificación , Archaea/aislamiento & purificación , Bacterias/clasificación , Bacterias/aislamiento & purificación , Biodiversidad , Análisis por Conglomerados , Euryarchaeota/clasificación , Euryarchaeota/aislamiento & purificación , Euryarchaeota/fisiología , Genes Arqueales , Genes Bacterianos , Genes de ARNr , Cloruro de Magnesio/análisis , Mar Mediterráneo , Metano/metabolismo , Datos de Secuencia Molecular , Oxidación-Reducción , Filogenia , ARN Ribosómico 16S/genética , Agua de Mar/química , Sulfatos/metabolismoRESUMEN
Subsurface bacteria often have to travel significant distances through tortuous porous media for purposes of groundwater remediation. In modeling such processes, motile bacteria are often represented as suspended colloids, ignoring their individual swimming or diffusive properties. In fact, bacterial migration is much more profoundly affected by the presence of porous media than is that of a chemical contaminant. In this study, we use magnetic resonance imaging (MRI) to perform noninvasive measurements of changes in bacterial concentration distributions across a packed column at a spatial resolution of 330 microm as a function of time. We analyze the diffusive behavior of Pseudomonas putida F1 under static conditions and compare that behavior to the diffusion of a chemical solute and of Escherichia coli NR50. Results indicate that P. putida cells experience a column tortuosity 50 times higher than that predicted from solute diffusion experiments. E. coli cells, which display shorter swimming run lengths in bulk solution than P. putida, seem to be less affected by the constricted pore space. Knudsen diffusion, or reductions in run length because of interactions between the diffusing bacteria and the porous media, may help to explain some of this discrepancy.
Asunto(s)
Monitoreo del Ambiente/métodos , Cloruro de Magnesio/química , Pseudomonas putida , Microbiología del Agua , Difusión , Escherichia coli , Cloruro de Magnesio/análisis , Imagen por Resonancia Magnética , PorosidadRESUMEN
The amount of coagulant added to soy milk is a critical factor for tofu-making; particularly it affects the textural properties of tofu. Earlier research indicated that the critical point of coagulant concentration (CPCC) is a characteristic parameter of soy milk and could be used as an effective indicator of optimal coagulant concentration (OCC) for making filled tofu. The objective of this study was to investigate the possible correlations between CPCC and the characteristics of soy milk made from various soybean samples and the effect of soy milk cooking and dilution conditions on CPCC. CPCC was determined by a titration method. Calcium chloride and magnesium chloride were used as coagulants. Soy milk characteristics including solid, protein, phytate, pH, titratable acidity, mineral content, and 11S/7S protein and these characteristics as affected by heating rate, heating time, and sequence of dilution and heating were studied. The results showed that the CPCC was significantly (p < 0.05) positively correlated with phytate content (grams per gram of protein), pH, and 7S protein content but negatively correlated with protein content, 11S protein content, 11S/7S ratio, titratable acidity, and original calcium content. Within the same soybean material, more proteins required more coagulant, but higher protein concentration during cooking resulted in less coagulant required by each gram of protein during coagulation. The CPCC decreased with increasing soy milk heating time or decreasing heating rate. The sequence of heating and diluting for preparing soy milk also had an effect on CPCC.
Asunto(s)
Manipulación de Alimentos/métodos , Calor , Alimentos de Soja/análisis , Leche de Soja/química , Cloruro de Calcio/análisis , Cloruro de Calcio/química , Fenómenos Químicos , Química Física , Concentración de Iones de Hidrógeno , Cloruro de Magnesio/análisis , Cloruro de Magnesio/química , Proteínas de Plantas/análisisRESUMEN
The migration of organic de-icers in the shallow aquifers typical in Finland is not well known and we need to find solutions to minimise the negative impacts of de-icing on groundwater quality. The objective of the MIDAS project is to find de-icers which have the least harmful impacts on groundwater quality. Migration of sodium chloride as a tracer and five alternative de-icers in aquifers was studied. The alternative de-icers were calcium chloride, magnesium chloride, calcium-magnesium-acetate, potassium acetate and potassium formate. The research consists of leaching of heavy metals from roadsides in the area of Highway 1 in southern Finland; an in vitro study, which represented the full length of winter at low temperatures; and the subsequent on-going field research in south-eastern Finland. So far, in our studies potassium formate caused fewer changes to the quality of the infiltrated water than the chlorides and acetates. After finishing the on-going research the results will be used to choose a preferred de-icer from the existing chemicals and for the development of new less harmful de-icers. The information will be used mainly in Scandinavia and North America where the hydrogeological conditions are similar to those in Finland.