Structural basis for the rheology of molten chocolate: a multi-technique approach

Chocolate comprises a dense suspension of solids, mainly sucrose with cocoa and milk solids, in a continuous fat phase of cocoa butter stabilised by surfactants, namely lecithin (mostly phospholipid), and sometimes polyglycerol polyricinoleate (PGPR). The surfactants favourably affect the rheology of molten chocolate reducing energy cost during production. Lecithin reduces viscosity, however, undesirably increases the yield stress at high concentrations, whereas, PGPR is primarily used to reduce the yield stress. When combined, the viscosity and yield stress are reduced further than with either surfactant individually. Whilst this implies a modified inter-particle interaction, the molecular mechanism by which these modifications occur were previously poorly understood. This work provides a mechanism on the basis of molecular scale structural information for this co-operative rheological effect, opening up the potential to rationally select or design alternative surfactants and improve manufacturing of chocolate at a lowered fat content. Small Angle Neutron (SANS) and X-rays (SAXS) Scattering show that lecithin and PGPR form micellar structures in triglyceride oil. Lecithin forms extended inverse cylindrical micelles that exhibit lamellar arrangements at high concentration or upon ageing. The addition of PGPR disrupts these ordered structures and decreases the aspect ratio of the cylindrical micelles. The adsorption of these micelles at the solid/fat interface leads to a modification of the inter-particle interactions which in turn changes the rheology. The solid/fat interface in chocolate has been investigated using two complimentary model systems: a dense suspension of sucrose in triglyceride oil stabilised by lecithin and PGPR and an analogous model system based on an extended planar sucrose film. The model suspensions, comprising 65% w/w of sucrose in Glyceryl Triocotanoate (GTO) and Glyceryl Trioleate (TO) with 0.8% w/w total surfactant, exhibit similar rheology to molten chocolate and have been used to characterize the adsorption and structure of the interfacial surfactant films using SANS and SAXS. Varying the PGPR content whilst keeping the total surfactant amount constant shows that the adsorbed surfactant interfacial film thickness increases with increasing PGPR fraction. In the lecithin rich suspensions the sucrose grains are in contact decorated by lecithin, giving rise to a fractal interface. On increasing the PGPR fraction the particles are pushed out of contact, resulting in a smooth particle interface. Spin Echo SANS studies show that sucrose-sucrose correlation length also increases, consistent with the picture in which the sucrose particles are pushed further apart for the surfactant compositions containing more PGPR. A planar model system comprising a sucrose film spin-coated onto a silicon/silicon oxide substrate mounted into a flow cell has been used for Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D) and X-ray and Neutron Reflectivity (XRR and NR, respectively) studies. Triglyceride oil containing lecithin and PGPR and their binary mixtures in the same molar concentration as chocolate has been flowed across the planar sucrose surface and the adsorption of the surfactants characterised using QCM-D. The adsorbed amount, found using the frequency shift, is comparable to the surfactant amount adsorbed in model suspensions found using small angle scattering. The dissipation shift increases with increasing PGPR fraction of the surfactant mixture, showing that the layers become more extended and diffuse. Structural details, investigated using NR and XRR, show that lecithin forms a compact phospholipid multilayer (5-7 monolayers) extending ~10 nm and PGPR forms a solvated polymer layer of ~30 nm. In binary mixtures the PGPR intercalates into the lecithin and the whole structure swells to ~50 nm. Using these calculated thicknesses, the viscoelastic properties of the adsorbed surfactant films have been modelled by co-fitting the frequency and dissipation shift observed in QCM-D to the Voigt model. The interfacial surfactant structure and the viscoelastic properties of the interfacial films are then used to explain the role of different surfactants in the rheology of molten chocolate suspensions. Based on this work we propose that lecithin layers reduce friction between sucrose grains, reducing the high-shear viscosity due to their high load bearing capacity whilst maintaining the fluid characteristic of the interfacial layer. The compact fractal interfacial layer implies that the sucrose grains are still sufficiently close in the suspension for Van der Waals adhesion to maintain a yield stress. PGPR incorporates into the lecithin layer, swelling it. This osmotically pushes the grains apart, decreasing Van der Waals interactions and reducing the yield stress giving the desired liquid-like flow

Nanostructure in Amphiphile-Based Deep Eutectic Solvents

Deep eutectic solvents (DESs) are an emerging class of modern, often “green” solvents with unique properties. Recently, a deep eutectic system based on amphiphilic surfactant N-alkyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (C12 & C14 sulfobetaine) and (1S)-(+)-10-camphor-sulfonic acid in the molar ratio 1:1.5 has been reported. Nanostructuring can be expected in this DES due to the nature of the components. In this work, we have investigated the native nanostructure in the DES comprising C12–C18 alkyl chain sulfobetaines with camphor sulfonic acid and how it interacts with polar and nonpolar species, water and dodecane, respectively, using small angle neutron scattering. By using contrast variation to highlight the relative position of the solvent components and additives, we can resolve the structure of the solvent and how it changes upon interaction with water and dodecane. Scattering from the neat DES shows structures corresponding to the self-assembly of sulfobetaines; the size of the structure increases as the alkyl chain length of the sulfobetaines increases. Water and dodecane interact, respectively, with the hydrophilic and hydrophobic moieties in the DES structure, primarily the sulfobetaine, thereby swelling and solvating the entire structure. The extent of the shift of the peak position, and the swelling, depend on concentration of the additive. The solution phase organization and the interaction of polar and nonpolar species as observed here, have the potential to affect the ordering of inorganic or polymeric materials grown in such solvents, paving new avenues for templating applications

Data set for "Surfactant Effects on the Synthesis of Porous Cerium Oxide from a Type IV Deep Eutectic Solvent"

This dataset relates to a novel, low temperature and green method for atom-efficient solvothermal synthesis of crystalline, micelle templated cerium IV oxide (ceria) from a type IV deep eutectic solvent (DES) comprising a hydrated cerium containing metal salt, cerium(iii) nitrate hexahydrate (Ce(NO₃)₃·6H₂O), and a hydrogen bond donor, urea, in a molar ratio of 1:3.5. We have used high concentration (20% w/w) solutions of C-12 and C-16 alkyl chain length cationic surfactants (CₙTAB and CₙTANO₃) and C-16 alkyl chain length non-ionic surfactant BrijC₁₀ in the DES to alter the porosity of the cerium oxide produced. The characterisation of the cerium oxide has been carried out using scanning and transmission electron microscopy (SEM/TEM), N₂ sorption, Small Angle X-ray Scattering (SAXS) and temperature programmed reduction (TPR) to understand and quantify the nature of the crystallinity, morphology and porosity along with CO oxidation for the catalytic activity of the material. Included in the dataset are the X-ray diffraction (XRD), SAXS, N₂ sorption, SEM Energy Dispersive X-Ray Analysis (EDX), X-ray photoelectron (XPS) and CO oxidation characterization data for these materials.Full details of the methodology can be found in the Materials and Methods section of the associated paper.Each ZIP file contains an MS Excel spreadsheet that provides details of the samples identified by number in the data file names. In "SAXS_paper.zip", the .dat files are comma-separated value (CSV) plain text files. In "XRD paper.zip", the .raw files are STOE RAW Powder X-ray diffraction files (from a STOE STADI P instrument) and the .xyd files are fixed-width field plain text files

Data supporting: Morphology modulation of ionic surfactant micelles in ternary deep eutectic solvents

This dataset contains raw and processed data in support of the named publication. This consists primarily of small-angle neutron scattering (SANS) data for mixtures of anionic and cationic surfactants in ternary deep eutectic solvents. Data files for differential scanning calorimetry (DSC) and viscosity measurements on the pure deep eutectic solvents are also included.Small-angle neutron scattering (SANS) measurements were carried out on the LOQ and Zoom instruments at ISIS Pulsed Neutron and Muon Source, UK. Mixtures either of sodium dodecyl sulfate (SDS), C12TAB and C16TAB (at concentrations of 25 mM and 130 mM) in choline chloride:urea:glycerol DES at different molar ratios were measured in various isotopic substitutions at 70 °C. The following measurements were carried out on pure choline chloride:urea:glycerol DES in molar ratios of 1:0.5:1.5, 1:1:1 and 1:1.5:0.5: - Differential scanning calorimetry: DSC measurements on the neat solvents were carried out on a TA Instruments DSC-Q20 differential scanning calorimeter. The sample was first equilibrated at 50 °C and held for 1 min, cooled to -75 °C at a ramp rate of 10 °C min-1 and held for 10 min, before heating to 30 °C at a ramp rate of 5 °C min-1 . - Viscosity: The viscosity of the solvents was measured using a TA Instruments HR-3 Discovery Hybrid Rheometer operating in flat plate geometry with Peltier temperature control. Viscosity data was obtained in a temperature range of 20 °C – 85 °C at a fixed shear rate of 1 s-1. The DES were measured as prepared, with a seal of mineral oil to prevent solvent interaction with the atmosphere during measurements.SANS data were reduced using the routines within Mantid (https://www.mantidproject.org/Main_Page) following the standard procedures on each instrument. The data were normalized to the sample transmission, calibrated to absolute units using a polymer standard and corrected for detector efficiencies, before scattering from the empty cell was subtracted. The resulting output was converted to absolute units of the scattering intensity (I(q), cm-1) vs. the momentum transfer (q, Å-1). Subtraction of the scattering from the pure solvents was performed afterwards using Igor Pro to account for the incoherent contribution to each sample.Output data from the SANS experiment consists of .txt files in the standard 1D format of I(q) vs. q (http://danse.chem.utk.edu/trac/wiki/NCNROutput1D_IQ). This data can be fitted using any available software capable of fitting SANS data. All other data is also given as .txt files and can be viewed and plotted using any suitable software.All data files relating to the same experimental technique are grouped together in sub-folders. Files relating to DSC and viscosity measurements on the pure DES. A PDF file is included in the sub-folder containing SANS data which provides a brief description of the contents of each data file

Role of the Deep Eutectic Solvent Reline in the Synthesis of Gold Nanoparticles.

This work presents a mechanistic understanding of the synthesis of small (<3 nm) gold nanoparticles in a nontoxic, eco-friendly, and biodegradable eutectic mixture of choline chloride and urea (reline) without the addition of external reducing or stabilization agents. Reline acts as a reducing agent by releasing ammonia (via urea hydrolysis), forming gold nanoparticles even at trace ammonia concentration levels. Reline also affects the speciation of the gold precursor forming gold chloro-complexes, stabilizing Au+ species, leading to an easier reduction and avoiding the otherwise fast disproportionation reaction. Such a capability is however lost in the presence of large amounts of water, where water replaces the chloride ligands in the precursor speciation. In addition, reline acts as a weak stabilizing agent, leading to small particles (<3 nm) and narrow distributions although agglomerates quickly form. Such properties are maintained in the presence of water, indicating that it is linked to the urea stabilization rather than the hydrogen-bonding network. This work has important implications in the field of green synthesis of nanoparticles with small sizes, especially for biomedical and health care applications, due to the nontoxic nature of the components of deep eutectic solvents in contrast to the conventional routes

Data set for "Self-assembly of ionic and non-ionic surfactants in type IV cerium nitrate and urea based deep eutectic solvent"

This is the dataset for cationic surfactants dodecyl trimethylammoniumnitrate/bromide (C12TANO3/C12TAB), anionic surfactant sodium dodecyl sulfate (SDS), and non-ionic surfactants hexaethylene glycol monododecyl ether (C12EO6) and octaethylene glycol monohexadecyl ether (C16EO8) in a Type IVDES comprising the metal salt cerium (III) nitrate hexahydrate and urea in the ratio 1:3.5. The folder contains data from the SANS measurements along with the fits, tensiometery measurements used to calculate the cmc and the characterization data including the DSC and viscosity measurements.Small Angle Neutron Scattering Measurements were carried out at room temperature on SANS2D instrument at the ISIS Pulsed Neutron and Muon Source, UK (RB1920676) Differential scanning calorimetry (DSC) measurements to determine the melting/transition temperature of the neat DES were carried out on a TA Instruments DSC-Q20 differential scanning calorimeter. The viscosity of the DES was measured using a TA Instruments HR-3 Discovery Hybrid Rheometer operating in flat plate geometry with Peltier temperature control. Room temperature viscosity data for the DES was obtained for applied shear rate ranging from 0.1−100 1/s at 25C the temperature sweep data was measured at shear rate of 1 1/s for temperature ranging from−10C to 40C.The SANS data was fitted using SasView software and plotted in Igor 6.

Morphology Modulation of Ionic Surfactant Micelles in Ternary Deep Eutectic Solvents

Deep eutectic solvents (DES) are potentially greener solvents obtained through the complexation of simple precursors which, among other applications, have been investigated in recent years for their ability to support the self-assembly of amphiphilic molecules. It is crucial to understand the factors which influence surfactant solubility and self-assembly with respect to the interaction of the surfactant molecule with the DES components. In this work, small-angle neutron scattering (SANS) has been used to investigate the micellization of cationic (CnTAB) and anionic (SDS) surfactants in a ternary DES comprising choline chloride, urea, and glycerol, where the hydrogen bond donors are mixed in varying molar ratios. The results show that in each case either globular or rodlike micelles are formed with the degree of elongation being directly dependent on the composition of the DES. It is hypothesized that this composition dependence arises largely from the poor solubility of the counterions in the DES, especially at low glycerol content, leading to a tighter binding of the counterion to the micelle surface and giving rise to micelles with a high aspect ratio. This potential for accurate control over micelle morphology presents unique opportunities for rheology control or to develop templated syntheses of porous materials in DES, utilizing the solvent composition to tailor micelle shape and size, and hence the pore structure of the resulting material

Data supporting: Morphology modulation of ionic surfactant micelles in ternary deep eutectic solvents

This dataset contains raw and processed data in support of the named publication. This consists primarily of small-angle neutron scattering (SANS) data for mixtures of anionic and cationic surfactants in ternary deep eutectic solvents. Data files for differential scanning calorimetry (DSC) and viscosity measurements on the pure deep eutectic solvents are also included

Data supporting: Morphology modulation of ionic surfactant micelles in ternary deep eutectic solvents

This dataset contains raw and processed data in support of the named publication. This consists primarily of small-angle neutron scattering (SANS) data for mixtures of anionic and cationic surfactants in ternary deep eutectic solvents. Data files for differential scanning calorimetry (DSC) and viscosity measurements on the pure deep eutectic solvents are also included

Data set for "Surfactant Effects on the Synthesis of Porous Cerium Oxide from a Type IV Deep Eutectic Solvent"

This dataset relates to a novel, low temperature and green method for atom-efficient solvothermal synthesis of crystalline, micelle templated cerium IV oxide (ceria) from a type IV deep eutectic solvent (DES) comprising a hydrated cerium containing metal salt, cerium(iii) nitrate hexahydrate (Ce(NO₃)₃·6H₂O), and a hydrogen bond donor, urea, in a molar ratio of 1:3.5. We have used high concentration (20% w/w) solutions of C-12 and C-16 alkyl chain length cationic surfactants (CₙTAB and CₙTANO₃) and C-16 alkyl chain length non-ionic surfactant BrijC₁₀ in the DES to alter the porosity of the cerium oxide produced. The characterisation of the cerium oxide has been carried out using scanning and transmission electron microscopy (SEM/TEM), N₂ sorption, Small Angle X-ray Scattering (SAXS) and temperature programmed reduction (TPR) to understand and quantify the nature of the crystallinity, morphology and porosity along with CO oxidation for the catalytic activity of the material. Included in the dataset are the X-ray diffraction (XRD), SAXS, N₂ sorption, SEM Energy Dispersive X-Ray Analysis (EDX), X-ray photoelectron (XPS) and CO oxidation characterization data for these materials