scholarly journals Changes of pH inβ-Lactoglobulin andβ-Casein Solutions during High Pressure Treatment

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Karsten Olsen ◽  
Bo B. Jespersen ◽  
Vibeke Orlien
Keyword(s):  
Tertiary Structure ◽  
Additive Model ◽  
Pressure Treatment ◽  
Ph Change ◽  
Pressure Dependency ◽  
Casein Solution ◽  
Initial Decrease ◽  
Initial Ph ◽  
Ph Decrease

The pH changes in the milk systems,β-lactoglobulin B,β-casein, and mixture ofβ-lactoglobulin andβ-casein (pH 7 and ionic strength 0.08 M) were measuredin situduring increasing pressure up to 500 MPa. An initial decrease to pH 6.7 was observed from 0.1 to 150 MPa forβ-lactoglobulin, followed by an increase to pH 7.3 at 500 MPa. The initial decrease is suggested to be caused by the deprotonation of histidine, while the increase is suggested to result from an increase of hydroxide ions due to the loss of tertiary structure. The change in pH of theβ-casein solution displayed an almost linear increasing pressure dependency up to a pH of 7.7 at 500 MPa. The limited tertiary structure ofβ-casein could allow exposure of all amino acids; thus the increase of pH can be caused by binding of water protons resulting in an increase of hydroxide ions. Addition ofβ-casein toβ-lactoglobulin (1:1) was found to suppress the initial pH decrease found for theβ-lactoglobulin solution. The pH change of the mixture did not suggest any intermolecular interaction, and a simple additive model is proposed to calculate the pH change of the mixture from the corresponding individual samples.

scholarly journals A Theoretical and Experimental Study of Electrochemical pH Control at Gold Interdigitated Microband Arrays

2021 ◽  
Author(s):  
Bernardo Patella ◽  
Robert Daly ◽  
Ian Seymour ◽  
Pierre Lovera ◽  
James Rohan ◽  
...  
Keyword(s):  
Electrode Array ◽  
Ph Control ◽  
Reduction Peak ◽  
Solution Ph ◽  
Ph Indicator ◽  
Ph Change ◽  
Initial Ph ◽  
The Impact ◽  
Strong Acids

In electroanalysis, solution pH is a critical parameter that often needs to be adjusted and controlled for the detection of particular analytes. This is most commonly performed by the addition of chemicals, such as strong acids or bases. Electrochemical in-situ pH control offers the possibility for the local adjustment of pH at the point of detection, without additional reagents. FEA simulations have been performed to guide experimental design for both electroanalysis and in-situ control of solution pH. No previous model exists that describes the generation of protons at an interdigitated electrode array in buffered solution with one comb acting as a protonator, and the other as the sensor. In this work, FEA models are developed to provide insight into the optimum conditions necessary for electrochemical pH control. The magnitude of applied galvanostatic current has a direct relation to the flux of protons generated and subsequent change in pH. Increasing the separation between the electrodes increases the time taken for protons to diffuse across the gap. The final pH achieved at both, protonators and sensor electrodes, after 1 second, was shown to be largely uninfluenced by the initial pH of the solution. The impact of buffer concentration was modelled and investigated. In practice, the pH at the electrode surface was probed by means of cyclic voltammetry, i.e., by cycling a gold electrode in solution and identifying the potential of the gold oxide reduction peak. A pH indicator, methyl red, was used to visualise the solution pH change at the electrodes, comparing well with the model’s prediction

The influence of milk composition on pH and calcium activity measured in situ during heat treatment of reconstituted skim milk

2010 ◽  
Vol 77 (3) ◽  
pp. 257-264 ◽  
Author(s):  
Jayani Chandrapala ◽  
Ian McKinnon ◽  
Mary Ann Augustin ◽  
Punsandani Udabage
Keyword(s):  
Heat Treatment ◽  
High Temperatures ◽  
Skim Milk ◽  
Milk Composition ◽  
Complexing Agents ◽  
Calcium Activity ◽  
Initial Ph ◽  
Ph Decrease ◽  
Milk Solids

The pH and calcium activity of reconstituted skim milk solutions (9–21% w/w milk solids non-fat) on heating and after cooling were studied as a function of milk pH prior to heating (pH 6·2–7·2 at 25°C) and added calcium complexing agents (phosphate or EDTA). The pH decreased as the temperature was raised from 25 to 90°C and the magnitude of the pH decrease was greater with increase in initial pH at 25°C before heating or milk concentration. The pH decrease on heating from 25 to 90°C in skim milk solutions with added calcium complexing agents was lower than that of milk without the addition of these salts. The calcium activity decreased on heating from 25 to 60°C. The magnitude of the change decreased with increase in initial pH at 25°C before heating and milk concentration. The decrease in calcium activity on heating from 25 to 60°C for skim milk solutions with added calcium complexing agents was lower than that of milk solutions without the addition of calcium complexing agents. The changes in pH and calcium activity on heating milk were largely reversible after cooling the milk. The results suggested that the pH and calcium activity at high temperatures are a function of the milk composition. Knowledge of the initial pH prior to heating alone is not sufficient for predicting the changes that occur during heating.

scholarly journals A Theoretical and Experimental Study of Electrochemical pH Control at Gold Interdigitated Microband Arrays

2021 ◽  
Author(s):  
Bernardo Patella ◽  
Robert Daly ◽  
Ian Seymour ◽  
Pierre Lovera ◽  
James Rohan ◽  
...  
Keyword(s):  
Electrode Array ◽  
Ph Control ◽  
Reduction Peak ◽  
Solution Ph ◽  
Ph Indicator ◽  
Ph Change ◽  
Initial Ph ◽  
The Impact ◽  
Strong Acids

In electroanalysis, solution pH is a critical parameter that often needs to be adjusted and controlled for the detection of particular analytes. This is most commonly performed by the addition of chemicals, such as strong acids or bases. Electrochemical in-situ pH control offers the possibility for the local adjustment of pH at the point of detection, without additional reagents. FEA simulations have been performed to guide experimental design for both electroanalysis and in-situ control of solution pH. No previous model exists that describes the generation of protons at an interdigitated electrode array in buffered solution with one comb acting as a protonator, and the other as the sensor. In this work, FEA models are developed to provide insight into the optimum conditions necessary for electrochemical pH control. The magnitude of applied galvanostatic current has a direct relation to the flux of protons generated and subsequent change in pH. Increasing the separation between the electrodes increases the time taken for protons to diffuse across the gap. The final pH achieved at both, protonators and sensor electrodes, after 1 second, was shown to be largely uninfluenced by the initial pH of the solution. The impact of buffer concentration was modelled and investigated. In practice, the pH at the electrode surface was probed by means of cyclic voltammetry, i.e., by cycling a gold electrode in solution and identifying the potential of the gold oxide reduction peak. A pH indicator, methyl red, was used to visualise the solution pH change at the electrodes, comparing well with the model’s prediction

In situ AFM and XPS Investigation of U6+ Reduction by Fe2+ on Hematite and Pyrite

2012 ◽  
Vol 1444 ◽  
Author(s):  
Jingjie Niu ◽  
Udo Becker ◽  
Rodney Ewing
Keyword(s):  
Charge Transfer ◽  
Co Adsorption ◽  
Reduction Rate ◽  
Mulliken Charge ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Initial Ph ◽  
Adsorption Reduction ◽  
Tapping Mode Afm

ABSTRACTUranyl adsorption/reduction by Fe2+ on hematite and pyrite has been studied at neutral pH under anoxic and CO2-free conditions. XPS results confirm that more U3O8 precipitates on hematite than on pyrite reacted for 24 h in 160 μM uranyl nitrate and 160 μM Fe2+ solution at initial pH 7.3. These results are explained in terms of co-adsorption energy and U atom Mulliken charge transfer by quantum mechanical calculations. Moreover, in situ fluid tapping-mode AFM experiments on hematite indicate a deceleration of the U reduction rate within 24 h due to the passivation of the surface caused by the formation of orthorhombic U3O8 crystals. In addition, crystals observed using AFM show morphologies of orthorhombic schoepite appearing on hematite after 5 h.

scholarly journals Technical note: Stability of tris pH buffer in artificial seawater stored in bags

Ocean Science ◽  
2021 ◽  
Vol 17 (3) ◽  
pp. 819-831
Author(s):  
Wiley H. Wolfe ◽  
Kenisha M. Shipley ◽  
Philip J. Bresnahan ◽  
Yuichiro Takeshita ◽  
Taylor Wirth ◽  
...  
Keyword(s):  
Dissolved Inorganic Carbon ◽  
Technical Note ◽  
Artificial Seawater ◽  
Upper And Lower Bounds ◽  
Sensor Calibration ◽  
Time Data ◽  
Ph Change ◽  
Ph Measurements ◽  
Experimental Conditions ◽  
Initial Ph

Abstract. Equimolal tris (2-amino-2-hydroxymethyl-propane-1,3-diol) buffer in artificial seawater is a well characterized and commonly used standard for oceanographic pH measurements. We evaluated the stability of tris pH when stored in purportedly gas-impermeable bags across a variety of experimental conditions, including bag type and storage in air vs. seawater over 300 d. Bench-top spectrophotometric pH analysis revealed that the pH of tris stored in bags decreased at a rate of 0.0058±0.0011 yr−1 (mean slope ±95 % confidence interval of slope). The upper and lower bounds of expected pH change at t=365 d, calculated using the averages and confidence intervals of slope and intercept of measured pH change vs. time data, were −0.0042 and −0.0076 from initial pH. Analyses of total dissolved inorganic carbon confirmed that a combination of CO2 infiltration and/or microbial respiration led to the observed decrease in pH. Eliminating the change in pH of bagged tris remains a goal, yet the rate of pH change is lower than many processes of interest and demonstrates the potential of bagged tris for sensor calibration and validation of autonomous in situ pH measurements.

Superior transport J c obtained in in-situ MgB 2 wires by tailoring the starting materials and using a combined cold high pressure densification and hot isostatic pressure treatment

2017 ◽  
Vol 129 ◽  
pp. 79-83 ◽  
Author(s):  
Hyunseock Jie ◽  
Wenbin Qiu ◽  
Motasim Billah ◽  
Mislav Mustapic ◽  
Dipak Patel ◽  
...  
Keyword(s):  
High Pressure ◽  
Pressure Treatment

scholarly journals A Study on the Mechanism and Kinetic of Nitrate Reduction by the nZVI-g-C3N4/TiO2  Composite Under the Simulated Sunlight

2021 ◽  
Author(s):  
Linyu Wei ◽  
Jing Tian ◽  
Qing Wang ◽  
Yuanyuan Liu ◽  
Yi Yu ◽  
...  
Keyword(s):  
Nitrate Reduction ◽  
Reduction Method ◽  
Nitrate Removal ◽  
Simulated Sunlight ◽  
Photoelectric Properties ◽  
Phase Reduction ◽  
Reduction Efficiency ◽  
Initial Ph ◽  
Lamp System

Abstract g-C3N4/TiO2 composite has excellent photoelectric properties and is considered as a good carrier of nanoparticles. A novel composite of nZVI-g-C3N4/TiO2 was successfully synthesized through in-situ growth nZVI on the surface of g-C3N4/TiO2 with liquid phase reduction method. The composite was characterized by TEM, XRD, EDS and evaluated its nitrate removal efficiency. The effects of composite dosage, solution initial pH and HCOOH concentration on nitrate reduction were investigated. The results showed that nitrate was rapidly reduced by nZVI-g-C3N4/TiO2 composite. The dosage of 4 g/L nZVI-g-C3N4/TiO2 composite and 3.0 mM of HCOOH concentration was more suitable for nitrate reduction. Solution initial pH had little impact on the nitrate reduction efficiency, but affected the proportion of the nitrate reduction products. The mechanism of nitrate reduction in the nZVI-gC3N4/TiO2/HCOOH-Xe-lamp system was proposed. The nZVI-gC3N4/TiO2 composite could be considered as a viable and promising technology for water pollution remediation.

A FRET-based two-photon probe for in vivo tracking of pH during a traumatic brain injury process

2019 ◽  
Vol 43 (43) ◽  
pp. 17018-17022
Author(s):  
Baoping Zhai ◽  
Shuyang Zhai ◽  
Ruilin Hao ◽  
Jianjun Xu ◽  
Zhihong Liu
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Neurodegenerative Diseases ◽  
Intracellular Ph ◽  
Ph Change ◽  
Ph Probe ◽  
Two Photon ◽  
Ph Decrease

Traumatic brain injury (TBI) is a cause of neurodegenerative diseases accompanied by intracellular pH decrease. Herein, a FRET-based ratiometric two-photon fluorescent pH probe is designed to monitor pH change and understand TBI process.

Histamine and Tyramine Production by a Lactobacillus Strain Subjected to External pH Decrease

1994 ◽  
Vol 57 (3) ◽  
pp. 259-262 ◽  
Author(s):  
RIITTA MAIJALA
Keyword(s):  
Lactic Acid ◽  
Room Temperature ◽  
Lactobacillus Strain ◽  
Ph Values ◽  
Initial Ph ◽  
Ph Decrease ◽  
In The Beginning ◽  
Influence Of Ph ◽  
External Ph ◽  
Made In

The preservative effect of fermentation is based on the pH decrease during processing. However, most studies conceming the influence of pH on the formation of biogenic amines have been made in broths with different initial pH values. A histamine- and tyramine-positive Lactobacillus strain isolated from dry sausage was added at an initial level of 3.9- to 4.4-logl0 CFU/ml and incubated on a shaker at room temperature (20.0°C) for 6 days. The pH was decreased in histidine- or tyrosine-fortified MRS broth by adding glucono-delta-lactone (GDL) or lactic acid during the incubation. The external acidification decreased the growth and the production of histamine and tyramine by the strain. GDL was more effective as a preventative than lactic acid. According to these results, a rapid pH decrease resulting in decreased growth of amine-positive lactic acid bacteria in the beginning of fermentation may be a means of preventing the formation of high levels of amines in foods.

scholarly journals In situ observation of pH change during water splitting in neutral pH conditions: impact of natural convection driven by buoyancy effects

2020 ◽  
Vol 13 (12) ◽  
pp. 5104-5116
Author(s):  
Keisuke Obata ◽  
Roel van de Krol ◽  
Michael Schwarze ◽  
Reinhard Schomäcker ◽  
Fatwa F. Abdi
Keyword(s):  
Natural Convection ◽  
Water Splitting ◽  
In Situ Observation ◽  
Ph Change ◽  
Neutral Ph ◽  
Ph Conditions

Buoyancy-driven natural convection stabilizes the pH and reduces overpotentials during water splitting, both in near-neutral pH unbuffered and buffered solutions.

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