Membrane emulsification method

In the early 1990s, Nakashima et al. [2] introduced membrane technology in emulsions preparation by a direct emulsification method, whereas, in the late 1990s, Suzuki et al. used premix membrane emulsification to obtain production rates higher than other membrane emulsification methods [11]. 

Suzuki, K., Shuto, I., and Hagura, Y. (1996). Characteristics of the membrane emulsification method combined with preliminary emulsification for preparing com oil-in-water emulsions. FoodSci. Technol. Int. 2, 43-47. 

Figure 7.2 Illustration of some approaches to making fine emulsions using membrane emulsification methods. Two approaches to making fine O/W emulsions are shown by passing oil through a microporous hydrophilic membrane (a) and passing a...

The above emulsification methods (perhaps except the Couette flow technique) have as a common feature that the final DSD is primarily determined by the interaction of turbulent eddies with interfaces. Note, however, that turbulence is hard to control and to maintain consistently throughout the whole reactor volume. From a practical point of view, it is almost impossible to predict the DSD after a scale-up based on laboratory-scale experiments. Emulsification techniques based on other principles are necessary to overcome these drawbacks. An alternative technique is the so-called membrane emulsification method where the liquid forming the disperse phase is pressed through a porous membrane. The other side of the membrane where the droplets are formed is in contact with the continuous phase. This concept is simple and it is assumed to be superior to the above techniques (35). The basic relationship of membrane emulsification (equation (8.10)) correlates the trans-membrane pressure required to start the drop-wise flow through the pores (ft) with the average pore diameter of the membrane (Dm) with being the contact angle of the mixture with the wall of the pore ... 

A membrane emulsification method has been applied for the preparation of glutaraldehyde-cross-linked CS particles loaded with BSA as a model dmg. The diameter of the particles depended on the membrane pore size and was in the range of 0.65-26.06pm. ... 

Recent research has explored various chitosan based microencapsulated nanoparticles for circumventing various problems of conventional delivery systems. One beautiful example of chitosan-alginate PEC microcapsules by membrane emulsification method is mentioned in Fig. 3.10. 

Fig. 3.10 Plan representation of chitosan-alginate PEC microcapsules by membrane emulsification method...

Figure 6.1 Membrane emulsification methods (a) Direct ME (Nakashima et al., 1991a) (b) premix ME (Suzuki et al., 1996) (c) premix ME with phase inversion (Suzuki et al., 1999).

You JO, Park SB, Park HY, HaamS, Chung CH, Kim WS. 2001. Preparation of regular sized Ca-alginate microspheres using membrane emulsification method. J Microen-capsul 18 521-532. 

Membrane emulsification is an appropriate technology for production of single and multiple emulsions and suspension. It was proposed for the first time at the 1988 Autumn Conference ofthe Society of Chemical Engineering, Japan. Since then, the method has continued to attract attention in particular in Japan, but also in Europe [1-10]. 

A peculiar advantage of membrane emulsification is that both droplet sizes and size distributions may be carefully and easily controlled by choosing suitable membranes and focusing on some fundamental process parameters reported below. Membrane emulsification is also an efficient process, since the energy-density requirement (energy input per cubic meter of emulsion produced, in the range of 104-106 J m-3) is low with respect to other conventional mechanical methods (106-108 J m-3), especially for emulsions with droplet diameters smaller than 1 (4m [1]. The lower energy density requirement also improves the quality and functionality... 

The global balance models are less accurate than the other methods, however, they are easier to handle and more instructive. The latter feature is crucial to acquire the necessary understanding of the physical causes at the basis of the droplet formation and detachment. The balance methods are versatile and permit analysis of the influence of many membrane emulsification parameters with limited computational time, useful in process optimizations. Starting from these considerations, in this section more attention will be paid to the proposed torque and force balances. 

Although the premix membrane emulsification can yield larger fluxes with respect to direct membrane emulsification neither methods using surface-energy minimization nor microfluid dynamics approaches have been until now reported on the theoretical treatment of the premix membrane emulsification. 

Nakajima et al. referred to membrane emulsification as a method to make functional ethanol-in-oil-in-water (e/o/w) emulsions. These e/o/w emulsions are suitable to encapsulate functional components that have a low water and oil solubility... 

An emerging class of emulsification methods is not based on imposing an overall flow field, but rather by making individual droplets on the mouths of membrane pores or micro-engineered channels. Characteristic is that the flow fields applied are much milder energy consumption is much lower, while the droplet sizes are strongly dependent on the shape and dimensions of the pores or micro-channels. A number of processes belong to this class ... 

A few food products have been on the market using cross-flow membrane emulsification. The method can make emulsions that have small droplets with a narrow size distribution. Thus, it is possible to make sauces with lower oil content than with conventional emulsification techniques. The technique of cross-flow emulsification is clearly the best developed process for small-scale, high-value applications it is an attractive process. 

Liu, R., Ma, G.H., Meng, F.-T., and Su, Z.-G., Preparation of uniform-sized PLA microcapsules by combining Shirasu Porous Glass membrane emulsification technique and multiple emulsion-solvent evaporation method, J. Contrail. Ret, 103, 31, 2005. 

Higashi et al. (22), described a new method of producing W/O/W multiple emulsions by a membrane emulsification technique. This method permits the formation of monodis-persed liquid microdroplets containing aqueous micro-... 

FIGURE 16.22 Influence of emulsification method on droplet size distribution (disperse phase content (p Ri 1 vol% emulsion formulation as in Figure 16.15. MF, microfluidization ME, membrane emulsification MC, microchannel emulsification. (From Vladisavljevic, G.T., Lambrich, U., Nakajima, M., and Schubert, H., Colloid Surface A, 232 (2-3), 199-207, 2004. With permission.)... 

Considering the above, different groups have attempted to develop methods which would reduce the polydispersity of the emulsion droplets. One of these methods is called membrane emulsification [16]. In membrane emulsification, the dispersed phase is pressurized to pass through a microporous membrane into a continuous phase to form emulsion droplets the droplet size is determined by the membrane pore size. Employing this method, both OAV emulsions (hydrophilic membranes) and W/O emulsions (hydrophobic membranes) can be prepared. What is most important about the process is that the coefficient of variation of droplet size comes down to about 10 %. However, the method may not be suitable for all size ranges. 

Figure 20.16 Influence of emulsification method on droplet size distribution (dispersed phase content 1 vol.%) [73]. MF high pressure homogenization (Microfluidizer) in comparison with SPG membrane, microchannel and a-Al203 membrane emulsification. The span value is a measure of the width of the droplet size distribution. It decreases when distributions become narrower.

H. Okochi, M. Nakano, Comparative study of two preparation methods of W/O/W emulsions stirring and membrane emulsification, Chem. Pharm. Bull. 1997, 45, 1323. 

Schuchmann HP (2008) Membrane emulsification processes and characterisation methods. In Gilell C, Ferrando M, Lopez F (eds) Monitoring and visualizing membrane-based processes. Wiley-VHC, Weinheim (in press) (ISBN 3-527-32006-7)... 

Membrane emulsification processes can be directly visualized by microscope as vell as by the use of high-speed cameras. In this case, information can be obtained about droplet disruption [10, 11] and fouling of the membrane. An indirect characterization method is the (inline) measurement of the emulsion characteristics. The emulsion is mainly characterized by its droplet size and droplet size distribution [2]. These infiuence important product characteristics like structure, mouthfeel, color and appearance, texture and viscosity [12, 13]. 

This chapter gives some information about membrane emulsification technology. Moreover, as the main topic of this work, specific membrane and microporous emulsification processes and methods for their characterization are presented. 

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