By

Geethu S

2011-06-007

Emulsion is a type of colloid formed from a mixture of two or more immiscible liquid such as water and oil

Two phase- continuous phase and dispersed phase

Two type- water in oil and oil in water emulsion

Eg: egg ,cheese, milk, margarine

INTRODUCTION

Stirring equipment

Colloid mill

Homogenizers

Ultrasonics or microfluidizers

Methods of preparation of emulsion

It’s a novel techniques for producing single and multiple emulsions

Introduced by Nakashima and Shimizu in 1980s in Japan

The dispersed phase is forced through the pores of a microporous membrane directly into the continuous phase by using low pressure

Emulsified droplets are formed and detached at the end of the pores with a drop-by-drop mechanism

MEMBRANE EMULSIFICATION

Droplet detachment of the membrane surface dependant on four main forces

• Shear

• Interfacial tension between emulsified fluids

• Inertia/pressure from the flow through the membrane

• Buoyancy

Resulting droplet size is controlled primarily by the choice of the membrane

Contd….

Fig: Schematic diagram of ME process

Membrane parameters

Phase parameters

Process parameters

Parameter affecting the emulsion production

Pore size

Pore shape

Pore size distribution

Porosity

Wettability

Permeability

Thickness

Membrane parameters

Interfacial tension

Emulsifier type and concentration

Viscosity

Density

Phase parameters

Wall shear stress

Transmembrane pressure

Temperature

Process parameters

SPG membrane (.1-20µm)

Silicon membrane

silicon nitride microseive membrane

Ceramic aluminium oxide membrane

Polytetrafloroethylene membrane

Membrane materials

Dead end membrane emulsification

Cross flow membrane emulsification

Vibrated membrane emulsification

Rotating membrane emulsification

Types of membrane emulsification

Simplest form

This method employs applied pressure to force the dispersed phase through a porous membrane into the continuous phase

Droplets form at the pore and detach when they reach a specific size relative to the size of the pore

Surfactant is added to the continuous phase to stabilize the newly formed droplets and prevent droplet coalescence

PTFE is used as membrane

Dead end membrane emulsification

Continuous phase to provide shear by flowing it across the surface of the membrane

Droplets are detached before becoming large enough to spontaneously detach and smaller relative to the membrane pore size

Cross flow membrane emulsification

+

Uses vibration of the membrane (either sub sonic or ultrasonic) to detach droplets from the membrane

Improve the efficiency of emulsification in some circumstances

Vibrating membrane emulsification

Centrifugal force will work along with the shear at the membrane surface provided by the rotation to detach droplets

Rotating membrane emulsification

Simple emulsion

• Two main types of simple emulsion ,(o/w) emulsions and(w/o) emulsions

• ME is suitable for preparation of large scale w/o food emulsions

• Using SPG membranes, o/w emulsions with liquid butter fat or sunflower oil as the dispersed phase and a continuous phase containing milk proteins

Preparation of food materials

“Emulsion of emulsion”

The primary emulsion may be produced by means of a conventional method or by membrane emulsification

The mild conditions of membrane emulsification are especially useful for the second emulsification step in order to prevent rupture of the double emulsion droplets

Multiple emulsion

Microcapsules containing viable cells (Lactobacillus casei) were produced using the ME technique

Stability of encapsulated cells are high

Encapsulation

Food gels are soft solids containing a high amount of aqueous phase

Aerated food gels were produced recently by membrane foaming

Pressing the dispersed phase (gas) through the pores of a tubular membrane into the continuous phase

The bubbles formed are covered with surface-active substances of the continuous phase

Aerated gel

Suitable for large scale production, they are easy to scale-up, by adding more membranes to a device

Process can done in both batch and semi- continuous process

Product obtained from ME is very stable, for at least 6 months without the use of preservative,

Industrial applications

Lower energy input with respect to conventional emulsifier

No foaming, reduced coalescence phenomenon

Narrow droplet size distributions

Various configurations: premix emulsification, rotating device to reduce fouling and increase productivity

ADVANTAGES

Additional resistance to mass transfer created by the membrane

Relatively low membrane lifetime; high replacement cost

Low permeation rate associated to narrow droplet size distribution and reduced productivity

Fouling phenomenon on the membrane surface and/or in the pores

DRAWBACKS

CASE STUDY

Done by: Y. Asano and K. Sotoyama

Objective:

Evaluate the viscosity changes in o/w emulsion

Study the physical properties emulsions

TITILE :Viscosity change in oil/water food emulsions prepared using a membrane emulsification system

Membrane emulsification apparatus

Materials

• For the oil phase, corn oil was used. For the water phase, deionized water was used

• Emulsifier polyglycerol esters (PGE)

• Stabilizer carnageenan

Materials and methods

Preparation of emulsion

Before emulsification, the MPG tube was pre-soaked in the continuous phase in an ultrasonic bath for 30 min

The dispersion phase was delivered into the MPG tube

The continuous phase circulated in the vessel

The pressure of the dispersion phase was gradually increased

Methodology

Dispersion phase was emulsified into the continuous phase by passage through the membrane

Continued until dispersion phase concentration of 10 vol% at the emulsifying temperature of 25⁰C was reached

The dispersion phase volume was calculated by measuring the total weight of the vessel

Average droplet diameter and the droplet distribution were measured using an image analyser system

Viscosity by vibration viscometer

Contd…

Assessment of monodispersed emulsion

An index of monodispersion, a coefficient of dispersion (α )

α = Sd/Dp

Smaller the values, the more monodispersed the emulsions (<=.35)

Contd…

The value of α was 0.203, so it was evident that emulsion was monodispersed

From the micrographs obtained directly after emulsification and 1 month after emulsification there were no differences between these emulsions

Results and discussion

As the droplet size in the emulsion increased with decreasing viscosity

Contd..

Relation ship between droplet diameter and viscosity

Membrane emulsification should is a very interesting technique for the food processing industry.

Benefits of membrane emulsion for the food processing industry may arise from low shear properties, especially for the preparation of double emulsions

Another advantage of membrane emulsion is the scale-up ability of membrane devices

Main limitation is fouling phenomenon

And it solved by recent process called premix ME

CONCLUSION

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on the properties of foams produced by membrane foaming. J. Membrane Sci. 220,:5–11. Bals, A. and Kulozik, U., 2003b. Effect of pre-heating on the foaming properties of whey protein isolate using a

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Reference