Protein-stabilised emulsions

Monahan, F.R., McClements, D.J., and Kinsella, J.E. 1993. Polymerisation of whey protein-stabilised emulsions. J. Agric. Food Chem. 41, 1826-1829. 

Tobias, J., Tracy, P.H. 1958. Observation on low fat dairy spreads. J. Dairy Sci. 41, 1117-1120. Tornberg, E., Ediriweera, N. 1987. Coalescence stability of protein-stabilised emulsions. In Food Emulsions and Foams (E. Dickinson, ed.), pp. 52-63, Royal Society of Chemistry, London. 

Kiokias, S. and Bot, A., Temperature cycling stability of pre-heated acidified whey protein-stabilised o/w emulsion gels in relation to the internal surface area of the emulsion. Food Hydro colloids, 20, 246,... 

Gharsallaoui A, Saurel R, Chambin O et al. (2010) Utilisation of pectin coating to enhance spray-dry stability of pea protein-stabilised oil-in-water emulsions. Food Chemistry 122 447-454. 

Khouryieh H, Puli G, Williams K, Aramouni F. Effects of xanthan-locust bean gum mixtures on the physicochemical properties and oxidative stability of whey protein stabilised oil-in-water emulsions. Food Chem. 167 340-348,2015. 

In the spray-dried particles, microencapsulation efficiency was increased in bilayer emulsions (Fig. 2.23) and when using low-methoxylated pectin, oxidative stability of the encapsulated bioactive ingredient was decreased (Fig. 2.24). The process-induced shift in the oil droplet size was more pronounced in bilayer emulsions based on high methoxylated pectin than in bilayer emulsions based on low-methoxlyated pectin (Fig. 2.25). However, both emulsions were more stable than the protein-stabilised emulsions. Data from dilatational rheology show an... 

Flocculation by a bridging mechanism is well known for particle suspensions, where it is straightforward to adsorb polymers onto surfactant-free interfaces, but it is less commonly observed in emulsions. An exception is a protein-stabilised emulsion where the protein acts as a surfactant, but can cause bridging when there is incomplete surface coverage. 

A strain of Acinetobacter calcoaceticus produces an unusual polysaccharide called emulsan. It is a complex polymer comprising about 15% fatty acyl esters and 20% protein. This structure enables it to act as an emulsifying agent, stabilising hydrocarbon/water emulsions at very low concentrations (0.1-1.0%). This property,... 

A stable foam is likely to have ingredients that are in a low energy state at the air-liquid interface. Substances that fit this description include proteins, emulsifiers some fats and fat components such as diglycerides monoglycerides and fatty acids. Food law uses the term emulsifier and stabiliser to cover the situation where the ingredient is stabilising an emulsion rather than helping to form it. 

Dickinson, E., Galazka, V.B. (1992). Emulsion stabilization by protein-polysaccharide complexes. In Phillips, G.O., Wedlock, D.J., Williams, P.A. (Eds). Gums and Stabilisers for the Food Industry 6, Oxford IRL Press, pp. 351-362. 

The stability of emulsions stabilised by proteins arises from the mechanical protection given by the adsorbed films around the droplets rather than from a reduction of interfacial tension. 

Abstract. Surface pressure/area isotherms of monolayers of micro- and nanoparticles at fluid/liquid interfaces can be used to obtain information about particle properties (dimensions, interfacial contact angles), the structure of interfacial particle layers, interparticle interactions as well as relaxation processes within layers. Such information is important for understanding the stabilisation/destabilisation effects of particles for emulsions and foams. For a correct description of II-A isotherms of nanoparticle monolayers, the significant differences in particle size and solvent molecule size should be taken into account. The corresponding equations are derived by using the thermodynamic model of a two-dimensional solution. The equations not only provide satisfactory agreement with experimental data for the surface pressure of monolayers in a wide range of particle sizes from 75 pm to 7.5 nm, but also predict the areas per particle and per solvent molecule close to the experimental values. Similar equations can also be applied to protein molecule monolayers at liquid interfaces. 

Radford, S.J., and Diekinson, E. (2004). Depletion floeeulation of easeinate-stabilised emulsions what is the optimum size of the nonadsorbed protein Colloids Sutf. A. 238, 71-81. 

Mayonnaise is a very concentrated emulsion of oil droplets in water, stabilised by proteins from egg yolk. The emulsion is so concentrated (70-80 vol.%) that the oil droplets are squeezed together. This squeezing together causes the nice consistency of mayonnaise. 

The chapter has dealt with the stability and stabilisation of colloidal systems and covered topics such as their formation and aggregation. If the particle size of a colloidal particle determines its properties (such as viscosity or fate in the body), then maintenance of that particle size throughout the lifetime of the product is important. The emphasis in the section on stability is understandable. Various forms of emulsions, microemulsions and multiple emulsions have also been discussed, while other chapters deal with other important colloidal systems, such as protein and polymer micro- and nanospheres and phospholipid and surfactant vesicles. 

The ability of some macromolecules to adsorb at interfaces is made use of in suspension and emulsion stabilisation (see Chapter 7). Gelatin, acacia, poly(vinyl alcohol) and proteins adsorb at interfaces. Sometimes such adsorption is unwanted, as in the case of insulin adsorption onto glass infusion bottles and poly(vinyl chloride) infusion containers and tubing used in giving sets. Adsorption of insulin to glass bottles and plastic i.v. tubing at slow rates of infusion is well documented. It... 

Though useful for classifying emulsifiers the HLB concept is of little practical value in food formulations since emulsions are for the most part stabilised by proteins or polysaccharides and there is always an interaction between the emulsion and the other food ingredients. 

Long-term stability of emulsified systems is usually provided by proteins or polysaccharides. The role of a good emulsion stabiliser is to keep the droplets apart once they have been formed. This protects the emulsion against processes such as creaming, flocculation and coalescence during long-term storage. 

Soy proteins are applied in a wide range of food products. In this context most attention has been paid to the ability of soy proteins to form a gel upon heating. Heat denaturation and subsequent gel formation of soy proteins in bulk solutions have been extensively studied.1-5 Besides this, studies have been performed on the interfacial tension and adsorbed amount of soy proteins and on their suitability for formation and stabilisation of emulsions and foams.6-10 A question that, to our knowledge, has not been discussed is how far these different functional properties are mutually related. 

Let us now discuss mixtures of proteins with low-molecular weight surfactants. These mixtures are of great practical importance for the stabilisation of emulsions and foams, and play an important role in biological systems. Let us consider equilibrium ideal (with respect to the enthalpy) solutions of proteins and surfactants. If such a solution contains i different surfactants (or proteins) which exist in j different states at the interface, the following system of equations from (2.26) and (2.27) may be formulated [24,25] ... 

Many food items contain emulsions and foams, which are often stabilised by proteins forming a protective membrane at the interface. By preparing the food, adsorption of the available proteins, - by virtue of their surface activity -, is performed at the liquid/air (foams) and/or at the liquid/liquid (emulsions) interface. One way to study the interfacial behaviour of food proteins at those interfaces is to follow the interfacial tension decay accomplished by the adsorption of the proteins. 

Proteins and proteoglycans are important stabilisers of emulsions and foams in many food and non-food applications [3]. The interactions between protein molecules, either when adsorbed at interfaces or when present in the bulk, are very complex and are connected with changes in the conformation of the folded polypeptide chains. These changes have a wide range of characteristic time-scales [4]. When these particular features of proteins are superimposed on the above picture of a deformed interfacial film it is seen that the task of understanding the mechanism of action of proteins as surfactants is a daunting task. 

---