Production of fat-based emulsion powder by prilling process using twin-fluid atomizer for controlled release of iron

Encapsulation of iron is necessary to supply bioavailable iron to large number of population possess iron deficiency. In the present study, we dispersed the iron solution in a fat matrix of palm stearin, and prepared the simple emulsion (water-in-oil) at 60 ◦C, where fat was a continuous phase. Using that emulsion, we produced fat based emulsion particles through prilling (spray + chilling) process using twin fluid atomizers (internal mixing). We characterized the particle in terms of size and size distribution, and investigated the internal structure of the fatparticles by cryogenic scanning electron microscopy (cryo-SEM) for observing the distribution or homogeneity of dispersed phase. Present study includes mainly the iron release kinetics through the fat matrix of the emulsion particle in an in-vitro gastric system (pH ≈ 2.0 ) as a function of (a) particle size of prills, (b) thickener concentration (polyethylene glycol, PEG) in dispersed phase, (c) droplet size of dispersed phase, (d) mixing properties (Reynolds number, Re), and (e) shelf-life of particles. The release kinetics was explained by the second order kinetics, where we estimated the release kinetic constant, and co-related with the viscosity ratio of dispersed phase to continuous phase, mean particle size of emulsion, and shelf-life of particles. The result showed that the control of the release properties can be obtained by choosing particle size and thickener concentration

Modification of the CAB Model for Air-Assist Atomization of Food Sprays

The Cascade Atomization and Drop Breakup (CAB) model has been originally developed for pressure atomizers. In this study, the CAB model is modified to accommodate the atomization of low-pressure, air-assist atomizers. The modifications include the first breakup which is modeled by estimating theWeber number due to the increased liquid-gas relative velocity caused by the air flow. This breakup depends on whether the Weber number is in the catastrophic, stripping or bag breakup regime. The second modification includes a change in the product drop distributions, namely, instead of a uniform distribution, as used in the original CAB model, a X-squared distribution with the same average drop size is assumed. The model changes are validated with experimental data obtained by means of two different air-assist atomizers using an oil-in-water emulsion. The simulations are performed with a modified version of the KIVA-3 CFD code; they show good agreement with the experiments

Parameters influencing cocrystallization and polymorphism in milk fat

Dry fractionation of milk fat is a common technique used to produce fat fractions with physical properties that are suitable for a variety of food and pharmaceutical products. During milk fat fractionation, the partial crystallization of triacylglycerols from the melt is the most important step. The efficiency of the separation of the crystals from the suspension is also important, but the crystallization itself influences the chemical composition and thereby determines the properties of the crystal fraction. At low supercooling, the crystallization kinetics are slow, and thus process time is increased. With increased kinetics due to a strong supersaturation, the chemical composition of the crystals is changed compared to crystals formed under slow kinetic conditions. This study shows to what extent controlled temperature and supercooling during milk fat crystallization influence crystal amount and the physical properties of the resulting fractions. Differences of the thermal characteristics of the crystal suspensions are directly detected by differential scanning calorimetry and nuclear magnetic resonance. At slow crystallization kinetics, the melting temperature range of the crystals in the suspensions is broader, and the resolution of the melting peak is higher. It is shown that compound crystals are formed when supercooling is performed, even if the supercooling takes place only for a short period of time. Controlled temperature conditions during crystallization govern larger differences in the fatty acid and triacylglycerol composition of the liquid and of the crystalline phases, compared to fractions crystallized under supercooling conditions, which contain a high amount of compound crystal

Crystallization Kinetics of Cocoa Fat Systems: Experiments and Modeling

Isothermal crystallization kinetics of unseeded and seeded cocoa butter and milk chocolate is experimentally investigated under quiescent conditions at different temperatures in terms of the temporal increase in the solid fat content. The theoretical equations of Avrami based on one-, two- and three-dimensional crystal growth are tested with the experimental data. The equation for one-dimensional crystal growth represents well the kinetics of unseeded cocoa butter crystallization of form α and β′. This is also true for cocoa butter crystal seeded milk chocolate. The sterical hindrance due to high solids content in chocolate restricts crystallization to lineal growth. In contrast, the equation for two-dimensional crystal growth fits best the seeded cocoa butter crystallization kinetics. However, a transition from three- to one-dimensional growth kinetics seems to occur. Published data on crystallization of a single component involving spherulite crystals are represented well by Avrami's three-dimensional theoretical equation. The theoretical equations enable the determination of the fundamental crystallization parameters such as the probability of nucleation and the number density of nuclei based on the measured crystal growth rate. This is not possible with Avrami's approximate equation although it fits the experimental data well. The crystallization can be reasonably well defined for single component systems. However, there is no model which fits the multicomponent crystallization processes as observed in fat system

Viscosity of a Newtonian fluid calculated from the deformation of droplets covered with a surfactant under a linear shear flow

The viscosity of small fluid droplets covered with a surfactant is determined using drop deformation techniques. This method, proposed by Hu and Lips, is here extended to the case of the presence of a surface-active adsorpted at the liquid-liquid interface, to consider more general scenarios. In these experiments, a droplet is sheared by another immiscible fluid of known viscosity, both Newtonian liquids. From the steady-state deformation and retraction mechanisms, the droplet viscosity is calculated using an equation derived from the theories of Taylor and Rallison. Although these theories were expressed for surfactant-free interfaces, they can be applied when a surfactant is present in the system if the sheared droplet reaches reliable steady-state deformations and the surfactant attains its equilibrium adsorption concentration. These determinations are compared to bulk viscosities measured in a rheometer for systems with different viscosity ratios and surfactant concentrations. Very good agreement between both determinations is found for drops more viscous than the continuous phas

In-line measurement of tempered cocoa butter and chocolate by means of near-infrared spectroscopy

In the present work cocoa butter and chocolate were precrystallized by means of a newly developed shear crystallizer. The shear crystallizer was integrated into a circular loop. The handling of precrystallized cocoa butter showed a high dependency on the timing of applied analysis. Differential scanning calorimetry, calorimetry, rheometry, and in-line near-infrared (NIR) were all directly influenced by the fat crystal structure. Nevertheless, for cocoa butter it was shown that mechanical energy input (rpm) had a significant influence on viscosity, melting enthalpy, and slope at the second point of inflection of a temper curve. Experiments with cocoa butter at constant exit temperature showed a linear increase of viscosity between 0.1 and 0.8 Pa·s in the range of 300 to 1300 rpm. Melting enthalpy increased in the same rpm interval from 0.02 to 2.5 J/g. Solidification time (from 4.5 to 0.5 min) and slope (from 0.82 to 0.15, second point of inflection of temper curve) consequently decreased (both with exponential approximation). For cocoa butter, slope and solidification time correlated linearly whereas solidification time and viscosity followed a power law fit. This proved that defined relationships exist between rheological data and data from temper curve measurements. Viscosity was linearly dependent on crystal content. By means of NIR spectroscopy good correlation models for cocoa butter viscosity, enthalpy (crystal content), and slope values were found. For precrystallized chocolate, analytical values such as viscosity and slope values were detected off-line and used for calibration of NIR spectroscop

Rheology of concentrated suspensions containing mixtures of spheres and fibres

Optimising flow properties of concentrated suspensions is an important issue common for many industries. The rheology of concentrated suspensions has therefore been studied intensively both experimentally and theoretically. Most studies have focused on monodisperse and polydisperse suspensions of either spheres or fibres. In practice, most suspensions contain particles that are polydisperse both in size and shape. A mixing rule for such systems is expected to be a powerful tool for engineers and product designers. Therefore in this work, suspensions of spheres, fibres and mixtures thereof were characterised using rotational shear rheometry and in-line image analyses. Thereby, total solids volume concentration and fibre fraction was varied. Results from transient and steady-state shear rheometry are discussed with respect to concentration, fibre fraction, and shear induced microstructure. Experimentally obtained viscosity data were accurately fitted using the model proposed by Farris (T Soc Rheol 12:281, 1968) for mixtures of monodisperse non-interacting spheres of different size

Protein adsorption and interfacial rheology interfering in dilatational experiment

The static and dilatational response of β-lactoglobulin fibrils and native β-lactoglobulin (monomers) at water-air and water-oil interfaces (pH 2) was measured using the pendant drop method. The resulting adsorption behavior and viscoelasticity is dependent of concentration and adsorption time. The interfacial pressure of the β-lactoglobulin fibrils obtained in static measurements was 16-18 mN/m (against air) and 7 mN/m (against oil) for all concentrations. With higher concentrations, faster adsorption kinetics and slightly higher interfacial and surface pressure is achieved but did not lead to higher viscoelastic moduli. The transient saturation of the interface is similar for both the fibril solution and the monomers, however the fibril solution forms a strong viscoelastic network. To evaluate the superimposed adsorption behavior and rheological properties, the formed interfacial layer was subjected to dilatational experiments, which were performed by oscillating the surface area of the drop in sinusoidal and sawtooth (diagonal) deformation manner. The sinusoidal oscillations (time depended area deformation rate) result in a complex interfacial tension behavior against air and oil interfaces and show remarkable differences during compression and expansion as emphasized by Lissajous figures. For diagonal (constant area deformation rate) experiments, a slight bending of the interfacial tension response was observed at low frequencies emphasizing the influence of protein adsorption during rheological measurement

Rheometry for large-particulated fluids: analysis of the ball measuring system and comparison to debris flow rheometry

For large-particulated fluids encountered in natural debris flow, building materials, and sewage treatment, only a few rheometers exist that allow the determination of yield stress and viscosity. In the present investigation, we focus on the rheometrical analysis of the ball measuring system as a suitable tool to measure the rheology of particulated fluids up to grain sizes of 10mm. The ball measuring system consists of a sphere that is dragged through a sample volume of approximately 0.5l. Implemented in a standard rheometer, torques exerted on the sphere and the corresponding rotational speeds are recorded within a wide measuring range. In the second part of this investigation, six rheometric devices to determine flow curve and yield stress of fluids containing large particles with maximum grain sizes of 1 to 25mm are compared, considering both rheological data and application in practical use. The large-scale rheometer of Coussot and Piau, the building material learning viscometer of Wallevik and Gjorv, and the ball measuring system were used for the flow curve determination and a capillary rheometer, the inclined plane test, and the slump test were used for the yield stress determination. For different coarse and concentrated sediment-water mixtures, the flow curves and the yield stresses agree well, except for the capillary rheometer, which exhibits much larger yield stress values. Differences are also noted in the measuring range of the different devices, as well as for the required sample volume that is crucial for applicatio

Single bubble deformation and breakup in simple shear flow

Experiments in a parallel band apparatus and a transparent concentric cylinder device allow the observation of bubble deformation (shape and orientation) and breakup as a function of the viscosity ratio λ and the Capillary number Ca. For viscosity ratios between 3.1×10−7 and 6.7×10−8, critical Capillary numbers Ca c for bubble breakup between 29 and 45 are found. It is furthermore shown that in the given parameter space no clear distinction between tip breakup and fracture can be made for bubble