Impact of effervescent atomization on oil drop size distribution of atomized oil-in-water emulsions (original) (raw)
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Food and Bioprocess Technology, 2021
The goal of this study was to investigate the changes in oil droplet size in whey protein–stabilized emulsions during the atomization and the subsequent drying step of a spray drying process. For this purpose, experiments were performed in an atomization rig and a pilot spray dryer with two commercial pressure swirl atomizers. By comparing the oil droplet size before atomization, after atomization, and after spray drying, the changes in oil droplet size during each process step were quantified. The effect of oil droplet breakup during atomization was isolated by atomizing emulsions with 1 wt.% oil content and a protein to oil concentration ratio of 0.1. At 100 bar, the Sauter mean diameter of oil droplet size was reduced from 3.13 to 0.61 μm. Directly after breakup, coalescence of the oil droplets was observed for emulsions with a high oil content of 30 wt.%, leading to a droplet size after atomization of 1.15 μm. Increasing the protein to oil concentration ratio to 0.2 reduced coal...
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The goal of this study was to investigate oil droplet breakup in food emulsions during atomization with pressure swirl (PS), internal mixing (IM), and external mixing (EM) twin-fluid atomizers. By this, new knowledge is provided that facilitates the design of atomization processes, taking into account atomization performance as well as product characteristics (oil droplet size). Atomization experiments were performed in pilot plant scale at liquid volume flow rates of 21.8, 28.0, and 33.3 L/h. Corresponding liquid pressures in the range of 50–200 bar and air-to-liquid ratios in the range of 0.03–0.5 were applied. Two approaches were followed: oil droplet breakup was initially compared for conditions by which the same spray droplet sizes were achieved at constant liquid throughput. For all volume flow rates, the strongest oil droplet breakup was obtained with the PS nozzle, followed by the IM and the EM twin-fluid atomizer. In a second approach, the concept of energy density EV was u...
Physicochemical parameters influencing the emulsion drop size
Colloid & Polymer Science, 1996
The stirring-mixing energy is the most obvious factor in the drop size reduction process, but it is not necessarily the most important one. Both the physicochemical formulation and the composition variables are shown to play a determinant role, at constant stirring condition. The generalized formulation versus water/oil ratio diagram allows to map emulsion properties such as emulsion type, stability and viscosity. It is used to discuss the combined effect of the formulation and composition upon the emulsion drop size, through their influences on the interfacial tension, and the emulsion viscosity and stability.
Applied Sciences, 2019
In this work, the evolution of dispersed droplets in a water-in-oil (W/O) emulsion during formation, storage, and destabilization was observed using a calorimetry technique. The emulsion was prepared by dispersing drop by drop an aqueous phase into an oil continuous phase at room temperature using a rotor-stator homogenizer. The evolution of droplets during (1) preparation; (2) storage; and (3) destabilization was observed using differential scanning calorimetry (DSC). The samples were gently cooled-down below its solid-liquid equilibrium temperature then heated back above the melting point to determine its freezing temperature. The energy released during the process was recorded in order to get information about the water droplet dispersion state. The mean droplet size distribution of the sample emulsion was correlated to its freezing temperature and the morphology was followed by optical microscopy. The results indicated that the calorimetry technique is so far a very good techniq...
Breakup of Water-in-Oil Emulsions in Liquid Jets and Conical Sheets
2010
The breakup process is investigated experimentally for water/oil emulsions. The effects of the dispersed liquid phase and stabilizers on breakup behavior of emulsions are studied at ambient conditions. The results are utilized to explain the breakup process in pressure atomization experiments at fuel flow conditions typical in large-scale gas turbine applications. Unstable emulsions are generated with a static screen filter. Stabilized water and diesel fuel #2 (DF2) are well mixed with corresponding surface stabilizing agents (surfactants) prior to emulsion formation. Stabilized components are flowed through a controlled shear device to generate size distributions with established droplet statistics. The presence of the discrete phase in volume fractions below 0.5 are studied, which are governed by Newtonian fluid behavior. To better understand the initial breakup of these types of emulsions, a simplified experiment utilizing a mono-disperse droplet stream generator is used to isolate the ligament and droplet formation in an emulsion stream. The shear forces in these scenarios are used to relate the performance with the addition of shearing from pressure atomization. Laser diffraction and high speed cinematography are utilized to measure spray drop size statistics for these fuel emulsions. Spray results for both unstable and stabilized emulsions show that DF2 droplet size can decrease 10 microns with minor concentrations of water addition when compared to those from neat DF2. A monodisperse droplet stream at this optimum water/oil concentration produces a random breakup behavior not observed for neat liquids or emulsions of higher or lower dispersed phase concentrations.
Affect Of Viscosity And Droplet Diameter On Water-In-Oil (W/O) Emulsions: An Experimental Study
2010
The influence of viscosity on droplet diameter for water-in-crude oil (w/o) emulsion with two different ratios; 20-80 % and 50-50 % w/o emulsion was examined in the Brookfield Rotational Digital Rheometer. The emulsion was prepared with sorbitan sesquiolate (Span 83) act as emulsifier at varied temperature and stirring speed in rotation per minute (rpm). Results showed that the viscosity of w/o emulsion was strongly augmented by increasing volume of water and decreased the temperature. The changing of viscosity also altered the droplet size distribution. Changing of droplet diameter was depends on the viscosity and the behavior of emulsion either Newtonian or non-Newtonian.
Drying behavior and locking point of single droplets containing functional oil
Advanced Powder Technology, 2016
Inception of the second drying stage called locking point plays a crucial role in the microencapsulation process of functional oils by spray drying. The transition between the first and the second drying periods can directly affect encapsulation efficiency and lipid oxidation by modifying the mechanism of globules migration to the surface of droplet/particles. In this study, the locking point of a single emulsion droplet prepared by incorporating walnut oil into skim milk powder solution was determined using a droplet suspension device. The effects of drying air temperature (80-140°C), total solid content (12-33% w/ w), and oil/wall material mass fraction (0.25-1.00 w/w) were assessed on the droplet/particle drying behavior, shrinkage, and locking point. The latter was achieved by plotting the variation of drying rate against moisture content of the droplet/particle. Moreover, confocal laser scanning microscopy (CLSM) was applied in order to investigate the morphology of the produced particles. Finally, a regression function for estimating the locking point from experimental variables was developed. Overall, such research can pave the way towards increasing the encapsulation efficiency and mitigating the lipid oxidation in industrial-scale spray dryers applied for microencapsulation of functional oils.
Transfer of Oil between Emulsion Droplets
Journal of Colloid and Interface Science, 1996
tion, liquid flow may cause encounters and coalescence of A contrast matching technique was used to determine the exdroplets; hence, process (b) may make it impossible to obchange of oils between emulsion droplets having different refractain sufficiently fine emulsions. At a later stage, during stortive indexes. Emulsions of tetradecane and 1-bromo tetradecane age of the emulsion, oil molecules may transfer spontanein water were made separately in a high-pressure homogenizer, ously from smaller droplets to larger ones; hence, process (a) then mixed and equilibrated at rest. It was found that droplets may make it impossible to keep sufficiently fine emulsions. exchanged oil molecules through the continuous phase, in a pro-Finally, if the emulsion is a mixture of drops containing cess similar to Ostwald ripening. Emulsions of hexadecane and 1different reactants, the same process (a) would cause mixing bromo hexadecane were also mixed; at rest, no exchange of oil of the reactants, premature reaction, and loss of reactivity took place. These mixtures were subsequently recirculated in the high-pressure homogenizer. Exchange of oil occurred as a result of for subsequent applications. droplet coalescence in the homogenizer. Two regimes were found, In order to study these processes, it is necessary to track ''surfactant-poor'' and ''surfactant-rich.'' In the ''surfactantthe oil from some droplets and measure its transfer to other poor'' regime, recoalescence took place at all values of the pressure droplets. Hence, the basic principle is to use a mixture of used in the homogenizer. In the ''surfactant-rich'' regime, recoalesdroplets containing oils of a different nature and measure cence took place only if the pressure was at least equal to that the exchange of oils between these droplets as they evolve used originally to make the emulsion. These results demonstrate toward an average composition. that the size of the emulsion droplets made in a high-pressure This principle has been applied by McClements et al. (1, homogenizer results from a succession of fragmentation and reco-2) to mixtures of oils with different crystallization temperaalescence processes. Possible mechanisms preventing recoalestures. In this case, the exchange of oil between droplets cence are discussed.