Emulsions destabilization

In terms of measuring emulsion microstructure, ultrasonics is complementary to NMRI in that it is sensitive to droplet flocculation [54], which is the aggregation of droplets into clusters, or floes, without the occurrence of droplet fusion, or coalescence, as described earlier. Flocculation is an emulsion destabilization mechanism because it disrupts the uniform dispersion of discrete droplets. Furthermore, flocculation promotes creaming in the emulsion, as large clusters of droplets separate rapidly from the continuous phase, and also promotes coalescence, because droplets inside the clusters are in close contact for long periods of time. Ideally, a full characterization of an emulsion would include NMRI measurements of droplet size distributions, which only depend on the interior dimensions of the droplets and therefore are independent of flocculation, and also ultrasonic spectroscopy, which can characterize flocculation properties. 

Emulsions, destabilization, 173. See also Creams, Lotions Encapsulation, 175 Enfleurage, 20, 134 Enzymes, 169 Escape, 104,129, 269 Essential oils, 19 terpeneless, 21 Esters, 207... 

Many dairy emulsions destabilize by flocculation and networking. Hib-berd et al, (1997a, b) obtained the ultrasonic response to flocculation showing that floe size increased during the experiment. The experiment was repeated with a higher level of hydroxyethyl cellulose (0.1%, v/v) with the result that flocculation occurred more rapidly with the formation of a densely connected network of particulate material. The residual root-mean-square error associated with fitting the ECAH model to the ultrasonic data at various points in the flocculation reaction increased rapidly at the onset of network formation and could, in principle, be used to detect such phenomena in a process context. 

Relating Bulk-Fat Properties to Emulsified Systems Characterization of Emulsion Destabilization by Crystallizing Fats... 

Fig. 1. Emulsion destabilization of lard O, palm stearin/canola oil (PSCO) , and canola A emulsions monitored b y 3, solid fat content (SFC) and viscosity as a function of time at 25°C under quiescent conditions.

Crystallization of lard and PSCO emulsions with similar initial droplet size distributions led to partial coalescence under perikinetic and orthokinetic conditions. The application of shear accelerated the destabilization of the emulsions after the achievement of a critical SFC. The SFC was found not to be the sole contributing factor to emulsion destabilization. Crystal morphology and distribution within the droplet are important factors in the destabilization of these emulsified fats. The emulsions are relatively stable in the short term when crystals are small and form quickly in a consolidated mass in the bulk of the droplet. Polymorphic transitions were not detectable as a source of destabilization in this experiment. The observation of the microstructure of bulk and emulsified fats gave insight into the mechanisms of emulsion destabilization. 

Figure 3.19 Schematic representation of different forms of emulsion destabilization (modified from Mulder and Walstra, 1974),...

Emulsion Stability. An emulsion is defined as a macroscopic dispersion of two liquids, one of which forms the continuous phase of the system and the other forms the discrete phase. An emulsion of two liquids without a stabilizer will quickly break into two liquid layers. Emulsions destabilize by three distinct processes breaking, creaming, and flocculation (Figure 14). When emulsions break, the initial small droplets of the emulsion spontaneously join to form larger droplets. This process is termed coalescence , and it ultimately leads to two separate liquid layers. 

The second stage in ice cream production is foaming and emulsion destabilization. This is analogous to the foaming step in whipped cream [14, 48]. Air is incorporated by whipping or by air injection. Egg white acts as a foaming agent. 

CW Angle, HA Hamza. Evaluation of some biological surfactants as emulsion destabilizers. Proceedings of 59th International Siurface and Colloid and 5th Intemational Colloid Science Conference, Clarkson University, Potsdam, NY, 1985 CANMET Div. Rep. ERP/ERL 81— 99(CF), 1981. 

In the offshore produetion of petroleum, technical problems are sometimes eneountered with emulsions which are formed at different stages of the production and transportation processes. These have to be taken into consideration at an early stage of the planning and construction of a platform. Enough space must be reserved for emulsion destabilization equipment such as coalescers and separators. With effective methods of emulsion separation, based on reliable information about crude oil and its tendency to form emulsions, much of fliis space could be reserved for other more useful purposes. 

Direct emulsification Emulsion coalescence Emulsion destabilization Microfluidic emulsification Premix emulsification Spontaneous emulsification... 

Jones, T.J., Neustadter, E.L., and Whittingham, K.P., Water-in-crude oil emulsion stability and emulsion destabilization by chemical demulsifiers, J. Can. Petrol. Technol, 17, 100-108, 1978. 

Modulating light intensity as a function of time can influence and then control the rate of the (micro)emulsion destabilization, opening the avenue to potential applications in novel, controlled-release systems. 

Increasing the clove oil content and storage temperature resulted in an increase of emulsion destabilization, as traced by droplet size and analytical centrifugation (Fig. 10). 

Since Ostwald ripening is a diffusive process, it cannot be accelerated by centrifugation. Nevertheless, analytical centrifugation was able to trace emulsion destabilization... 

As part of the dispersed phase, lipids in a state of incipient or advanced crystallization may substantially increase emulsion destabilization. During processing and/or storage, intraglobular fat (e.g., in cream, margarines) may solidify, form-... 

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