School of Chemistry - Research Publications
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ItemNo Preview AvailableIncorporating whey protein aggregates produced with heat and ultrasound treatment into rennet gels and model non-fat cheese systems(Elsevier, 2020-12-01)Native whey proteins (WP) are expulsed from cheese coagulation during syneresis. Although incorporating denatured WP aggregates into cheese gels has been previously proposed to improve the overall cheese yield, the effects of WP aggregate properties on gelation kinetics and protein retention are not yet fully understood. In this study, heat and power ultrasound were used to produce denatured whey protein aggregates with a wide range of sizes. The effects of size and hydrophobicity differences in WP aggregates produced by heat and heat coupled with ultrasound were investigated in relation to the kinetics of rennet gelation and protein retention in model non-fat cheddar cheeses. Rheological measurements showed that sufficiently large, denatured WP aggregates could avoid impairment of rennet gelation caused by native WP, irrespective of changes in the soluble calcium concentration or the surface hydrophobicity of the aggregates. WP aggregates formed by the combined heat and ultrasound treatment were more hydrophobic than the larger heat-treated aggregates and were better retained in the cheese. However, inclusion of sufficiently large aggregates in cheese milk conferred an openness to the cheese microstructure and showed promise in improving the otherwise rigid non-fat cheese.
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ItemFe(III)-catalyzed degradation of persistent textile dyes by chlorine at slightly acidic conditions: the crucial role of Cl(2)(BLACK CIRCLE-)radical in the degradation process and impacts of mineral and organic competitors(WILEY, 2020-08-02)Abstract In this work, we have explored for the first time the potential application of trace‐Fe(III)/chlorine system as an innovative oxidation technology for the degradation of persistent textile dyes. Fe(III)/chlorine combination improved the dye removal by ~40% within 30 s, as compared with chlorination alone, mainly through a radical pathway induced by the catalytic activation of chlorine in the presence of Fe(III). A chemical probe method was used for identifying the main reactive species. Cl2●− was found to be the key species responsible of huge abatement of dyes in the Fe(III)/chlorine system, whereas ●OH and Cl● can participate with only ~5% in the overall removal efficiency. At pH 3, 77% of reactive green 12 (RG12) was removed after 30 s, and then the removal efficiency diminished to 60% at pH 4, 20% at pH 5, and ~10% at pH 6 and 7. However, the best implication of free radicals was achieved at pH 4, at which the degradation rate was 3.3 time higher than that of chlorination alone. The dye removal efficiency increased with an increase in chlorine and iron loads up to certain optimums, but detrimental effect was observed at higher dosage levels. An increase in the solution temperature notably accelerated the removal yield (i.e., 81% of RG12 was removed at 50°C against 67% at 30°C and 57% at 10°C). NO2− and HSO3− as well as the cationic surfactant Adogen 464 showed strongest inhibiting effect on the performance of the process. Based on these findings, the Fe(III)/chlorine process is highly efficient in removing dyes from wastewaters.
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ItemNo Preview AvailableEffect of solid surface in vicinity of multi-bubble array in cryogenic environment(IOP PUBLISHING LTD, 2020-01-01)Abstract Multiple bubble interactions in initially quiescent liquid are often accompanied by generation of jets, shockwaves and light. At cryogenic temperature (< 123 K) when certain materials (particularly bcc-type) become brittle, such afore-mentioned physical effects can be effective in disintegrating them to smaller fragments. CFD techniques based on direct numerical simulations can help to understand this phenomenon that may benefit nanotechnology-based industries and oil-gas exploration-firms working with air-gun arrays. In this paper, multiple bubble-pairs are simulated in a co-centric manner around a centrally located solid target (5 mm radius). The ambient fluid is liquid nitrogen (77 K) and the bubbles are gaseous nitrogen (87 K). 2D numerical simulation using the VOF method in compressible domain is carried out neglecting the effect of phase change and gravity. The stand-off distance between the solid target and bubble-pairs are varied systematically and its influence on the fluid-dynamic effects (e.g. pressure shockwave & jets) are compared. Initial calculations suggest that for stand-off distance of 0.93 mm, shockwaves measure above 10 times the ambient pressure and liquid jet speeds around 30 m/s in cryogenic environment, at multiple locations very close to the solid target. These consecutive physical impacts can foster ample liquid-hammer pressures, making it promising for solid wear at 77 K when juxtaposed against room-temperature cases.
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ItemSono-Assembly of the [Arg-Phe]4 Octapeptide into Biofunctional Nanoparticles.(MDPI AG, 2020-09-08)High-frequency ultrasound treatment is found to be a one-pot green technique to produce peptide-based nanostructures by ultrasound assisted self-assembly of oligopeptides. [Arg-Phe]4 octapeptides, consisting of alternating arginine (Arg/R) and phenylalanine (Phe/F) sequences, were subjected to 430 kHz ultrasound in aqueous solution in the absence of any external agents, to form [RF]4 nanoparticles ([RF]4-NPs), ~220 nm in diameter. A comprehensive analysis of the obtained nanoparticles demonstrated that the aromatic moieties of the oligopeptides can undergo oxidative coupling to form multiple oligomeric species, which then self-assemble into well-defined fluorescent nanoparticles. [RF]4-NPs were functionalized with polyethylene glycol (PEGylated) to improve their colloidal stability. Unlike the parent peptide, the PEGylated [RF]4-NPs showed limited cytotoxicity towards MDA-MB-231 cells. Furthermore, the intracellular trafficking of PEGylated [RF]4-NPs was investigated after incubation with MDA-MB-231 cells to demonstrate their efficient endo-lysosomal escape. This work highlights that the combined use of ultrasonic technologies and peptides enables easy fabrication of nanoparticles, with potential application in drug delivery.
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ItemEffect of Bulk Viscosity and Emulsion Droplet Size on the Separation Efficiency of Model Mineral Oil-in-Water (O/W) Emulsions under Ultrasonic Standing Wave Fields: A Theoretical and Experimental Investigation(American Chemical Society (ACS), 2020-04-22)Ultrasound standing waves can be used to separate emulsions. So far, they have been applied to oil-in-water emulsions with low continuous phase viscosity. This technique has the potential to be used for novel applications such as separating lipids from algal biomass; however, this requires the methodology to be optimized to process viscous emulsions. We have addressed this issue by studying the effects of bulk phase viscosity (1–23 mPa·s), emulsion droplet size (4.5–20 μm), power (10–54 W/L), and frequency (1 and 2 MHz) of ultrasound on the separation efficiency of model mineral oil-in-water–glycerol-mixture emulsions. For the small droplet size (4.5 μm) emulsion in water, the maximum separation achieved increased from 36 to 79% when ultrasound power increased from 10 to 54 W/L. However, for the large droplet size (11 μm) emulsion, the maximum separation was greater than 95% and was independent of ultrasound power. The maximum separation efficiency for small droplet size (4.5–6 μm) emulsions decreased from 80 to 14% when the viscosity increased from 1 to 23 mPa·s. However, for the large droplet size (11–20 μm) emulsion, the maximum separation efficiency decreased from 98 to 62% when the viscosity of the bulk phase was increased from 1 to 23 mPa·s. The experimental results were then interpreted using analytical and numerical simulations by calculating the time required for the emulsion droplets to migrate to the nearest pressure antinodal plane under the influence of ultrasound standing waves. Further experiments showed that increasing the ultrasound frequency from 1 to 2 MHz increased the maximum separation from 36 to 86% for fine emulsions and water as the continuous phase.
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ItemSound-driven dissipative self-assembly of aromatic biomolecules into functional nanoparticles(Royal Society of Chemistry, 2020-03-01)Dissipative self-assembly processes were recently exploited to assemble synthetic materials into supramolecular structures. In most cases, chemical fuel or light driven self-assembly of synthetic molecules was reported. Herein, experimental and computational approaches were used to unveil the role of acoustic cavitation in the formation of supramolecular nanoaggregates by dissipative self-assembly. Acoustic cavitation bubbles were employed as an energy source and a transient interface to fuel and refuel the dissipative self-assembly of simple aromatic biomolecules into uniform nanoparticles. Molecular dynamics simulations were applied to predict the formation of metastable aggregates and the dynamic exchange of the interacting molecules in the nanoaggregates. The intracellular trafficking and dissipative dissolution of the nanoparticles were tracked by microscopy imaging.
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ItemFormation of Cheddar cheese analogues using canola oil and ultrasonication – a comparison between single and double emulsion systems(Elsevier BV, 2020-06)Cheddar cheese analogues were produced from skim milk in which canola oil was emulsified using ultrasound to form either single (O/W) or double emulsions (W1/O/W2). The double emulsion cheese analogues (DECH) had a distinct microstructure and retained small skim milk droplets, dispersed in the fat phase, for more than 7 months of aging at 4 °C. The single emulsion cheese analogues (SECH), prepared with the same fat content as control cheeses, produced comparable yields of cheese and whey, with similar composition, although the fat droplets were more spherical and showed greater coalescence. The DECH cheese with skim milk encapsulated in the oil droplets was harder, melted less and showed more free fatty acid development over 7 months of aging than the control cheeses. The SECH cheeses were softer than the control and also melted less effectively but did not show greater free fatty acid development.