SIMULATION OF WATER TRANSFER IN SPRAY DRYING

A drying method by desorption in a water activity meter (Aw-meter) was used to simulate the conditions of spray drying and to determine the water transfer inside the dairy concentrate to the surface (first transfer) and from the surface to the drying air (second transfer). A limitation in the first transfer decreased the second transfer. The percentage of bound or unbound water was determined as a function of the nature of concentrates (milk concentrate, high protein milk concentrate, native casein suspension, caseinate dispersion, ) before drying. The water transfer in the different dairy concentrates during drying was shown as a function of the environment of their water content and the nature of the constituents. The percentage of bound or unbound water and the drying behavior of any dairy concentrate could be determined in 4 to 6 hours and might predict spray drying behavior in an industrial tower.     

MRI study of bread baking: experimental device and MRI signal analysis

An oven dedicated to a magnetic resonance imager (MRI) was designed and constructed for continuous monitoring of the entire baking process. The general aim was to test whether response variables conventionally measured on bread loaves, such as temperature, density, and water loss, were consistent with those reported for similar products baked in classical convection ovens. MRI images acquired during baking are presented and discussed, emphasising the need to develop quantitative MRI methods allowing conversion of the MRI signal into one variable of interest, such as local density or local water content.     

Signal decay due to susceptibility-induced intravoxel dephasing on multiple air-filled cylinders: MRI simulations and experiments

OBJECTIVE: Characterization of magnetic susceptibility artefacts with assessment of the gradient-echo signal decay function of echo time, pixel size, and object geometry in the case of air-filled cylinders embedded in water. MATERIALS AND METHODS: Experiments were performed with a 0.2 T magnet on a network of small interacting air-filled cylinders along with Magnetic resonance imaging (MRI) simulations integrating intravoxel dephasing. Signal decay over echo time was assessed at different pixel sizes on real and simulated images. The effects of radius, distance between cylinders and main magnetic field were studied using simulation. RESULTS: Signal loss was greater as echo time or pixel size increased. Voxel signal decay was not exponential but was weighted by sinus cardinalis functions integrating echo time, pixel size and field inhomogeneities which depended on main magnetic field strength and geometric configuration of the object. Simulation was able to model signal decay, even for a complex object constituted of several cylinders. The specific experimental signal modulation we observed was thus reproduced and explained by simulation. CONCLUSION: The quantitative signal decay approach at 0.2 T can be used in characterization studies in the case of locally regular air/water interfaces as the signal depends on object size relative to pixel size and is relevant to the geometric configuration. Moreover, the good concordance between simulation and experiments should lead to further studies of magnetic susceptibility effects with other objects such as networks of spheres. MRI simulation is thus a potential tool for molecular and porous media imaging.     

Encoding Information on the Excited State of a Molecular Spin Chain

The quantum states of nano-objects can drive electrical transport properties across lateral and local-probe junctions. This raises the prospect, in a solid-state device, of electrically encoding information at the quantum level using spin-flip excitations between electron spins. However, this electronic state has no defined magnetic orientation and is short-lived. Using a novel vertical nanojunction process, these limitations are overcome and this steady-state capability is experimentally demonstrated in solid-state spintronic devices. The excited quantum state of a spin chain formed by Co phthalocyanine molecules coupled to a ferromagnetic electrode constitutes a distinct magnetic unit endowed with a coercive field. This generates a specific steady-state magnetoresistance trace that is tied to the spin-flip conductance channel, and is opposite in sign to the ground state magnetoresistance term, as expected from spin excitation transition rules. The experimental 5.9 meV thermal energy barrier between the ground and excited spin states is confirmed by density functional theory, in line with macrospin phenomenological modeling of magnetotransport results. This low-voltage control over a spin chain's quantum state and spintronic contribution lay a path for transmitting spin wave-encoded information across molecular layers in devices. It should also stimulate quantum prospects for the antiferromagnetic spintronics and oxides electronics communities.     

Core/shell nanoparticles for multiple biological detection with enhanced sensitivity and kinetics

The paper shows the different methods to attach a molecule to detect streptavidin to a dielectric particle made of a rare-earth oxide core and a polysiloxane shell containing fluorescein. First, the detection of streptavidin binding on a biotinylated gold substrate can be achieved in three ways: the shift of the surface plasmon resonance of the substrate and the double luminescence (organic and inorganic) of the core/shell particle. Second, these detections are efficient even after elimination upon thermal annealing of all the undesired molecules that skew the assays. Finally, the particle that ballasts the protein enhances its binding kinetics and increases the localized surface plasmon resonance shift that detects the binding.     

Proton Transport in Electrospun Hybrid Organic–Inorganic Membranes: An Illuminating Paradox

Chemistry and processing have to be judiciously combined to structure the membranes at various length scales to achieve efficient properties for polymer electrolyte membrane fuel cell to make it competitive for transport. Characterizing the proton transport at various length and space scales and understanding the interplays between the nanostructuration, the confinement effect, the interactions, and connectivity are consequently needed. The goal here is to study the proton transport in multiscale, electrospun hybrid membranes (EHMs) at length scales ranging from molecular to macroscopic by using complementary techniques, i.e., electrochemical impedance spectroscopy, pulsed field gradient‐NMR spectroscopy, and quasielastic neutron scattering. Highly conductive hybrid membranes (EHMs) are produced and their performances are rationalized taken into account the balances existing between local interaction driven mobility and large‐scale connectivity effects. It is found that the water diffusion coefficient can be locally decreased (2 × 10^?6 cm² s^?1) due to weak interactions with the silica network, but the macroscopic diffusion coefficient is still high (9.6 × 10^?6 cm² s^?1). These results highlight that EHMs have slow dynamics at the local scale without being detrimental for long‐range proton transport. This is possible through the nanostructuration of the membranes, controlled via processing and chemistry.     

High-efficiency, solid-state, dye-sensitized solar cells using hierarchically structured TiO₂ nanofibers

High-performance, room-temperature (RT), solid-state dye-sensitized solar cells (DSSCs) were fabricated using hierarchically structured TiO? nanofiber (HS-NF) electrodes and plastic crystal (PC)-based solid-state electrolytes. The electrospun HS-NF photoelectrodes possessed a unique morphology in which submicrometer-scale core fibers are interconnected and the nanorods are dendrited onto the fibers. This nanorod-in-nanofiber morphology yielded porosity at both the mesopore and macropore level. The macropores, steming from the interfiber space, afforded high pore volumes to facilitate the infiltration of the PC electrolytes, whereas the mesoporous nanorod dendrites offered high surface area for enhanced dye loading. The solid-state DSSCs using HS-NFs (DSSC-NF) demonstrated improved power conversion efficiency (PCE) compared to conventional TiO? nanoparticle (NP) based DSSCs (DSSC-NP). The improved performance (>2-fold) of the DSSC-NFs was due to the reduced internal series resistance (R(s)) and the enhanced charge recombination lifetime (τ(r)) determined by electrochemical impedance spectroscopy and intensity modulated photocurrent/photovoltage spectroscopy. The easy penetration of the PC electrolytes into HS-NF layers via the macropores reduces R(s) significantly, improving the fill factor (FF) of the resulting DSSC-NFs. The τ(r) difference between the DSSC-NF and DSSC-NP in the PC electrolytes was extraordinary (~14 times) compared to reported results in conventional organic liquid electrolytes. The optimized PCE of DSSC-NF using the PC electrolytes was 6.54, 7.69, and 7.93% at the light intensity of 100, 50, and 30 mW cm?2, respectively, with increased charge collection efficiency (>40%). This is the best performing RT solid-state DSSC using a PC electrolyte. Considering the fact that most reported quasi-solid state or nonvolatile electrolytes require higher iodine contents for efficient ion transport, our HS-NFs are a promising morphology for such electrolytes that have limited ion mass transport.     

Determination of the lipid content in fish muscle by a self‐calibrated NMR relaxometry method: comparison with classical chemical extraction methods

A low‐cost, accurate NMR method was developed to determine the lipid content in fish flesh. The fish samples are dried before NMR measurements, and the method is self‐calibrated with an oil reference. The NMR technique gave an intermediate fat content value, 4.7% lower in relative value than those obtained by a chemical cold extraction method and 6.7% higher than those from a petroleum ether extraction method at high temperature. Taking into account this systematic bias, the prediction error was only 3 g kg^?1 fat content between NMR and Soxhlet method determinations (R² = 0.98). The NMR technique thus offers a promising alternative method for determining the lipid content in previously dried fish flesh, since it is rapid, easily usable and solvent‐free, unlike chemical extraction methods. Furthermore, this accurate NMR method should be valuable to calibrate the fast but less accurate NMR, NIR and microwave methods based on fresh samples and to estimate the fat content in other animal meats when the fat is maintained in an amorphous state. © 2001 Society of Chemical Industry     

Mass spectrometry-based detection and risk assessment of mycotoxin contamination of ‘kankankan’ used for roasted meat consumption in Abidjan,Côte d’Ivoire

ABSTRACT

‘Kankankan’ is a popular spice powder used to season roasted meat in Côte d’Ivoire. However, produced in a traditional way, the conditions of production and storage of kankankan favour the proliferation of mycotoxin-producing fungal strains. The aim of this study was to carry out an inventory of mycotoxin contamination of this spice powder and to assess risk exposure to consumers. In total, 75 samples of kankankan were collected from wholesalers (6), sellers of kankankan in the markets (35) and sellers of roasted meat (34) across three municipalities of Abidjan, the economic capital of Côte d’Ivoire. Ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was used to detect and quantify nine different mycotoxins. Dietary exposure was calculated by using estimated daily intake (EDI), whereas risk characterisation was assessed using the margin of exposure (MOE) approach. Aflatoxins and fumonisins were found in 99% of samples assessed, while contamination with beauvericin was proportionally lowest (28%). At all the three types of actors within the food production chain (wholesalers, kankankan sellers and roasted meat sellers) the mean concentrations of aflatoxin B₁ (AFB1) in samples exceeded the European standard for spice mixtures, with concentrations reaching up to 502 µg/kg. The estimated daily intakes of aflatoxins observed in the different populations were above the recommended level of 0.017 ng kg^?1 b.w. day^?1. The MOE_S values for adolescents and adults were 8.10 and 12.78, respectively, well below the safe margin of 10,000. The co-occurrence of mycotoxins in kankankan samples together with high aflatoxin exposure to consumers represent a potential risk to public health, calling for immediate risk management and education of kankankan producers and consumers.