Research

Jump to: Review

2023 KiB

Open AccessArticle

Characterization of Whey Protein Oil-In-Water Emulsions with Different Oil Concentrations Stabilized by Ultra-High Pressure Homogenization

by Essam Hebishy, Anna Zamora, Martin Buffa, Anabel Blasco-Moreno and Antonio-José Trujillo

Processes 2017, 5(1), 6; https://doi.org/10.3390/pr5010006 - 10 Feb 2017

Cited by 43 | Viewed by 8184

Abstract

In this study, the effect of ultra-high-pressure homogenization (UHPH: 100 or 200 MPa at 25 °C), in comparison to colloid mill (CM: 5000 rpm at 20 °C) and conventional homogenization (CH: 15 MPa at 60 °C), on the stability of oil-in-water emulsions with [...] Read more.

In this study, the effect of ultra-high-pressure homogenization (UHPH: 100 or 200 MPa at 25 °C), in comparison to colloid mill (CM: 5000 rpm at 20 °C) and conventional homogenization (CH: 15 MPa at 60 °C), on the stability of oil-in-water emulsions with different oil concentrations (10, 30 or 50 g/100 g) emulsified by whey protein isolate (4 g/100 g) was investigated. Emulsions were characterized for their microstructure, rheological properties, surface protein concentration (SPC), stability to creaming and oxidative stability under light (2000 lux/m²). UHPH produced emulsions containing lipid droplets in the sub-micron range (100–200 nm) and with low protein concentrations on droplet surfaces. Droplet size (d3.2, µm) was increased in CH and UHPH emulsions by increasing the oil concentration. CM emulsions exhibited Newtonian flow behaviour at all oil concentrations studied; however, the rheological behaviour of CH and UHPH emulsions varied from Newtonian flow (n ≈ 1) to shear-thinning (n ˂ 1) and thixotropic behaviour in emulsions containing 50% oil. This was confirmed by the non-significant differences in the d4.3 (µm) value between the top and bottom of emulsions in tubes left at room temperature for nine days and also by a low migration velocity measured with a Turbiscan LAB instrument. UHPH emulsions showed significantly lower oxidation rates during 10 days storage in comparison to CM and CH emulsions as confirmed by hydroperoxides and thiobarbituric acid-reactive substances (TBARS). UHPH emulsions treated at 100 MPa were less oxidized than those treated at 200 MPa. The results from this study suggest that UHPH treatment generates emulsions that have a higher stability to creaming and lipid oxidation compared to colloid mill and conventional treatments. Full article

(This article belongs to the Special Issue Emulsification Processes)

► Show Figures

Graphical abstract

7737 KiB

Open AccessArticle

Computational Fluid Dynamics (CFD)-Based Droplet Size Estimates in Emulsification Equipment

by Jo Janssen and Roy Mayer

Processes 2016, 4(4), 50; https://doi.org/10.3390/pr4040050 - 13 Dec 2016

Cited by 5 | Viewed by 7278

Abstract

While academic literature shows steady progress in combining multi-phase computational fluid dynamics (CFD) and population balance modelling (PBM) of emulsification processes, the computational burden of this approach is still too large for routine use in industry. The challenge, thus, is to link a [...] Read more.

While academic literature shows steady progress in combining multi-phase computational fluid dynamics (CFD) and population balance modelling (PBM) of emulsification processes, the computational burden of this approach is still too large for routine use in industry. The challenge, thus, is to link a sufficiently detailed flow analysis to the droplet behavior in a way that is both physically relevant and computationally manageable. In this research article we propose the use of single-phase CFD to map out the local maximum stable droplet diameter within a given device, based on well-known academic droplet break-up studies in quasi-steady 2D linear flows. The results of the latter are represented by analytical correlations for the critical capillary number, which are valid across a wide viscosity ratio range. Additionally, we suggest a parameter to assess how good the assumption of quasi-steady 2D flow is locally. The approach is demonstrated for a common lab-scale rotor-stator device (Ultra-Turrax, IKA-Werke GmbH, Staufen, Germany). It is found to provide useful insights with minimal additional user coding and little increase in computational effort compared to the single-phase CFD simulations of the flow field, as such. Some suggestions for further development are briefly discussed. Full article

(This article belongs to the Special Issue Emulsification Processes)

► Show Figures

Graphical abstract

5860 KiB

Open AccessFeature PaperArticle

From Single Microparticles to Microfluidic Emulsification: Fundamental Properties (Solubility, Density, Phase Separation) from Micropipette Manipulation of Solvent, Drug and Polymer Microspheres

by Koji Kinoshita, Elisa Parra, Abdirazak Hussein, Anders Utoft, Prasad Walke, Robin De Bruijn and David Needham

Processes 2016, 4(4), 49; https://doi.org/10.3390/pr4040049 - 30 Nov 2016

Cited by 11 | Viewed by 8381

Abstract

The micropipette manipulation technique is capable of making fundamental single particle measurements and analyses. This information is critical for establishing processing parameters in systems such as microfluidics and homogenization. To demonstrate what can be achieved at the single particle level, the micropipette technique [...] Read more.

The micropipette manipulation technique is capable of making fundamental single particle measurements and analyses. This information is critical for establishing processing parameters in systems such as microfluidics and homogenization. To demonstrate what can be achieved at the single particle level, the micropipette technique was used to form and characterize the encapsulation of Ibuprofen (Ibp) into poly(lactic-co-glycolic acid) (PLGA) microspheres from dichloromethane (DCM) solutions, measuring the loading capacity and solubility limits of Ibp in typical PLGA microspheres. Formed in phosphate buffered saline (PBS), pH 7.4, Ibp/PLGA/DCM microdroplets were uniformly solidified into Ibp/PLGA microparticles up to drug loadings (DL) of 41%. However, at DL 50 wt% and above, microparticles showed a phase separated pattern. Working with single microparticles, we also estimated the dissolution time of pure Ibp microspheres in the buffer or in detergent micelle solutions, as a function of the microsphere size and compare that to calculated dissolution times using the Epstein-Plesset (EP) model. Single, pure Ibp microparticles precipitated as liquid phase microdroplets that then gradually dissolved into the surrounding PBS medium. Analyzing the dissolution profiles of Ibp over time, a diffusion coefficient of 5.5 ± 0.2 × 10⁻⁶ cm²/s was obtained by using the EP model, which was in excellent agreement with the literature. Finally, solubilization of Ibp into sodium dodecyl sulfate (SDS) micelles was directly visualized microscopically for the first time by the micropipette technique, showing that such micellization could increase the solubility of Ibp from 4 to 80 mM at 100 mM SDS. We also introduce a particular microfluidic device that has recently been used to make PLGA microspheres, showing the importance of optimizing the flow parameters. Using this device, perfectly smooth and size-homogeneous microparticles were formed for flow rates of 0.167 mL/h for the dispersed phase (Q_d) and 1.67 mL/h for the water phase (Q_c), i.e., a flow rate ratio Q_d/Q_c of 10, based on parameters such as interfacial tension, dissolution rates and final concentrations. Thus, using the micropipette technique to observe the formation, and quantify solvent dissolution, solidification or precipitation of an active pharmaceutical ingredient (API) or excipient for single and individual microparticles, represents a very useful tool for understanding microsphere-processes and hence can help to establish process conditions without resorting to expensive and material-consuming bulk particle runs. Full article

(This article belongs to the Special Issue Emulsification Processes)

► Show Figures

Graphical abstract

1871 KiB

Open AccessArticle

The Influence of Viscosity on the Static and Dynamic Properties of PS-PEO Covered Emulsion Drops

by Damith P. Rozairo and Andrew B. Croll

Processes 2016, 4(4), 47; https://doi.org/10.3390/pr4040047 - 29 Nov 2016

Cited by 1 | Viewed by 5408

Abstract

Polymer stabilized emulsions are commonplace in industries ranging from cosmetics and foods to pharmaceuticals. Understanding the physical properties of emulsions is of critical importance to the rapid advancement of industrial applications. In this work, we use a sessile drop geometry to examine the [...] Read more.

Polymer stabilized emulsions are commonplace in industries ranging from cosmetics and foods to pharmaceuticals. Understanding the physical properties of emulsions is of critical importance to the rapid advancement of industrial applications. In this work, we use a sessile drop geometry to examine the effects of viscosity changes of the surrounding glycerine/water solution on polystyrene-b-polyethylene oxide (PS-PEO) covered toluene droplets. In the experiment, emulsion drops are driven by the buoyant force into a smooth mica surface. The drops buckle as they approach the mica, trapping some of the outer fluid which slowly drains out over time. The characteristic time of the drainage process as well as the surface tension was measured as a function of glycerine/water concentration. The surface tension is found to have a minimum at a glycerine concentration of approximately 50% (by weight to water) and the drainage rate is shown to be well described by a recent model. The simple experiment not only shows how critical features of emulsion stability can be easily and reliably measured, but also identifies important new features of the drainage process. Full article

(This article belongs to the Special Issue Emulsification Processes)

► Show Figures

Graphical abstract

3320 KiB

Open AccessArticle

Crystallization in Emulsions: A Thermo-Optical Method to Determine Single Crystallization Events in Droplet Clusters

by Serghei Abramov, Patrick Ruppik and Heike Petra Schuchmann

Processes 2016, 4(3), 25; https://doi.org/10.3390/pr4030025 - 11 Aug 2016

Cited by 18 | Viewed by 8314

Abstract

Delivery systems with a solid dispersed phase can be produced in a melt emulsification process. For this, dispersed particles are melted, disrupted, and crystallized in a liquid continuous phase (melt emulsification). Different to bulk crystallization, droplets in oil-in-water emulsions show individual crystallization behavior, [...] Read more.

Delivery systems with a solid dispersed phase can be produced in a melt emulsification process. For this, dispersed particles are melted, disrupted, and crystallized in a liquid continuous phase (melt emulsification). Different to bulk crystallization, droplets in oil-in-water emulsions show individual crystallization behavior, which differs from droplet to droplet. Therefore, emulsion droplets may form liquid, amorphous, and crystalline structures during the crystallization process. The resulting particle size, shape, and physical state influence the application properties of these colloidal systems and have to be known in formulation research. To characterize crystallization behavior of single droplets in micro emulsions (range 1 µm to several hundred µm), a direct thermo-optical method was developed. It allows simultaneous determination of size, size distribution, and morphology of single droplets within droplet clusters. As it is also possible to differentiate between liquid, amorphous, and crystalline structures, we introduce a crystallization index, CI_i, in dispersions with a crystalline dispersed phase. Application of the thermo-optical approach on hexadecane-in-water model emulsion showed the ability of the method to detect single crystallization events of droplets within emulsion clusters, providing detailed information about crystallization processes in dispersions. Full article

(This article belongs to the Special Issue Emulsification Processes)

► Show Figures

Graphical abstract

Review

Jump to: Research

1837 KiB

Open AccessFeature PaperReview

Extending Applications of High-Pressure Homogenization by Using Simultaneous Emulsification and Mixing (SEM)—An Overview

by Vanessa Gall, Marc Runde and Heike P. Schuchmann

Processes 2016, 4(4), 46; https://doi.org/10.3390/pr4040046 - 26 Nov 2016

Cited by 28 | Viewed by 11886

Abstract

Conventional high-pressure homogenization (HPH) is widely used in the pharmaceutical, chemical, and food industries among others. In general, its aim is to produce micron or sub-micron scale emulsions with excellent product characteristics. However, its energy consumption is still very high. Additionally, several limitations [...] Read more.

Conventional high-pressure homogenization (HPH) is widely used in the pharmaceutical, chemical, and food industries among others. In general, its aim is to produce micron or sub-micron scale emulsions with excellent product characteristics. However, its energy consumption is still very high. Additionally, several limitations and boundaries impede the usage of high-pressure homogenization for special products such as particle loaded or highly concentrated systems. This article gives an overview of approaches that have been used in order to improve the conventional high-pressure homogenization process. Emphasis is put on the ‘Simultaneous Emulsification and Mixing’ process that has been developed to broaden the application areas of high-pressure homogenization. Full article

(This article belongs to the Special Issue Emulsification Processes)

► Show Figures

Graphical abstract

2802 KiB

Open AccessFeature PaperReview

Optical Measuring Methods for the Investigation of High-Pressure Homogenisation

by Ariane Bisten and Heike P. Schuchmann

Processes 2016, 4(4), 41; https://doi.org/10.3390/pr4040041 - 15 Nov 2016

Cited by 23 | Viewed by 8459

Abstract

High-pressure homogenisation is a commonly used technique to produce emulsions with droplets in the micro to nano scale. Due to the flow field in the homogenizer, stresses are transferred to the interface between droplets and continuous phase. Cohesive forces within droplets interact with [...] Read more.

High-pressure homogenisation is a commonly used technique to produce emulsions with droplets in the micro to nano scale. Due to the flow field in the homogenizer, stresses are transferred to the interface between droplets and continuous phase. Cohesive forces within droplets interact with external stresses. To exceed the cohesive forces, high process pressures are necessary, which might cause a complex flow pattern and large flow velocities. Additionally, the pressure drop can induce cavitation. Inline measurements are a challenge, but necessary to understand droplet break-up in a high-pressure homogenizer. Recently, different optical methods have been used to investigate the flow conditions as well as the droplet deformation and break-up in high-pressure homogenisation, such as high speed imaging, particle and micro particle image velocimetry. In this review, those optical measuring methods are considered critically in their applications and limitations, achievable results and further developments. Full article

(This article belongs to the Special Issue Emulsification Processes)

► Show Figures

Graphical abstract

2151 KiB

Open AccessFeature PaperReview

Extending Emulsion Functionality: Post-Homogenization Modification of Droplet Properties

by Long Bai and David Julian McClements

Processes 2016, 4(2), 17; https://doi.org/10.3390/pr4020017 - 17 May 2016

Cited by 21 | Viewed by 17107

Abstract

Homogenizers are commonly used to produce oil-in-water emulsions that consist of emulsifier-coated oil droplets suspended within an aqueous phase. The functional attributes of emulsions are usually controlled by selecting appropriate ingredients (e.g., surfactants, co-surfactants, oils, solvents, and co-solvents) and processing conditions (e.g., homogenizer [...] Read more.

Homogenizers are commonly used to produce oil-in-water emulsions that consist of emulsifier-coated oil droplets suspended within an aqueous phase. The functional attributes of emulsions are usually controlled by selecting appropriate ingredients (e.g., surfactants, co-surfactants, oils, solvents, and co-solvents) and processing conditions (e.g., homogenizer type and operating conditions). However, the functional attributes of emulsions can also be tailored after homogenization by manipulating their composition, structure, or physical state. The interfacial properties of lipid droplets can be altered using competitive adsorption or coating methods (such as electrostatic deposition). The physical state of oil droplets can be altered by selecting an oil phase that crystallizes after the emulsion has been formed. The composition of the disperse phase can be altered by mixing different kinds of oil droplets together to induce inter-droplet exchange of oil molecules. The local environment of oil droplets can be altered by embedding them within hydrogel beads. The aggregation state of oil droplets can be controlled by promoting flocculation. These post-homogenization methods can be used to alter functional attributes such as physical stability, rheology, optical properties, chemical degradation, retention/release properties, and/or gastrointestinal fate. Full article

(This article belongs to the Special Issue Emulsification Processes)

► Show Figures

Graphical abstract

Journal Menu

Journal Browser

Emulsification Processes

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (8 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI