Food emulsions protein-stabilized

Most food emulsions are stabilized by proteins and/or emulsifiers, which slow down or prevent separation of the oil and the water. Proteins are built from amino acids, some of which are hydrophilic and some of which are hydrophobic. Thus certain proteins, such as casein from milk, have hydrophilic and hydrophobic regions, which makes them surface active. Emulsifiers, for example, mono- and diglycerides, also contain hydrophilic and hydrophobic regions. 

Many food emulsions are stabilized by surface-active polymers that adsorb to droplet surfaces and form protective membranes. Some of these functional polymers are integral components of more complex food ingredients used in food manufacture (e.g. milk, eggs, meat, fish, and flour), whereas others have been isolated from their normal environments and possibly modified before being sold as specialty ingredients (e.g. protein concentrates or isolates, hydrocolloid emulsifiers). In this section, we will focus primarily on those surface-active polymers that are sold as functional ingredients specifically designed for use as emulsifiers in foods. 

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Benichou, A., Aserin, A., Garti, N. (2002). Protein-polysaccharide interactions for stabilization of food emulsions. Journal of Dispersion Science and Technology, 23, 93-123. 

Dickinson, E. (2008). Interfacial structure and stability of food emulsions as affected by protein-polysaccharide interactions. Soft Matter, 4, 932-942. 

Damodaran, S. (2005). Protein stabilization of emulsions and foams. Journal of Food... 

Dickinson, E., Euston, S.R. (1991). Stability of food emulsions containing both protein and polysaccharide. In Dickinson E. (Ed.). Food Polymers, Gels and Colloids, Cambridge, UK Royal Society of Chemistry, pp.132-146. 

Dickinson, E., Pawlowsky, K. (1997) Effect of i-carrageenan on flocculation, creaming, and rheology of a protein-stabilized emulsion. Journal of Agricultural and Food Chemistry, 45, 3799-3806. 

Gancz, K., Alexander, M., Corredig, M. (2006). In situ study of flocculation of whey protein-stabilized emulsions caused by addition of high-methoxy 1 pectin. Food Hydro-colloids, 20, 293-298. 

Khalloufi, S., Corredig, M., Goff, H.D., Alexander, M. (2009). Flaxseed gums and their adsorption on whey protein-stabilized oil-in-water emulsions. Food Hydrocolloids, 23, 616-618. 

Lucassen-Reynders, E.H., Benjamins, J. (1999). Dilational rheology of proteins adsorbed at fluid interfaces. In Dickinson, E., Rodriguez Patino, J.M. (Eds). Food Emulsions and Foams Interfaces, Interactions and Stability, Cambridge, UK Royal Society of Chemistry, pp. 195-206. 

Many food colloids are stabilized from proteins from milk or eggs [817]. Milk and cream, for example, are stabilized by milk proteins, such as casein micelles, which form a membrane around the oil (fat) droplets [817]. Mayonnaise, hollandaise, and bearnaise, for example, are O/W emulsions mainly stabilized by egg-yolk protein, which is a mixture of lipids (including lecithin), proteins, and lipoproteins [811,817]. The protein-covered oil (fat) droplets are stabilized by a combination of electrostatic and steric stabilization [817]. Alcohols may also be added, such as glycerol, propylene glycol, sorbitol, or sucrose sometimes these are modified by esterification or by... 

Casein or egg-yolk proteins are used as emulsifiers in a number of food products, such as O/W food emulsions (Table 13.1) [78,824]. A key difference here is that in caseinate-stabilized oil emulsions, the casein forms essentially monolayers and there are no casein micelles nor any calcium phosphate. Such emulsions are thought to be stabilized more by electrostatic repulsive forces and less by steric stabilization, in contrast to the situation in homogenized milk products [824]. 

Some products, like butter and margarine are stabilized by fat crystals. Salad dressings and beverage emulsions are stabilized by other emulsifiers. The stability of non-protein stabilized food emulsions, involving lower molar mass type molecules, tend to be better described by the DLVO theory than are protein-stabilized emulsions. An example of an O/W emulsifier whose emulsions are fairly well described by DLVO theory is sodium stearoyl lactylate [812],... 

Damodaran, S. Protein-Stabilized Foams and Emulsions in Food Proteins and Their Applications, Damodaran, S. Paraf, A. (Eds.), Dekker, New York, 1997, pp. 57-110. 

Proteins, which are also surface active, can be used to prepare food emulsions. The protein molecules adsorb at the O/W interface and they may remain in their native state (forming a rigid layer of unfolded molecules) or undergo unfolding, forming loops, tails, and trains. These protein molecules stabilize the emulsion droplets, either by a steric stabilization mechanism or by producing a mechanical barrier at the O/W interface. 

Das, K.P. and Kinsella, J.E. 1990. Stability of food emulsions physicochemical role of protein and non-protein emulsions. Adv. Food Nutr. Res. 34, 81-201. 

Dalgleish, D.G. 1989. Protein-stabilized emulsions and their properties. In Water and Food Quality (T.M. Hardman, ed.), pp. 211-250, Elsevier Applied Science, London. 

Hailing, P.J. 1981. Protein-stabilized foams and emulsions. CRC Crit. Rev. Food Sci. Nutr. 15,155-203. 

Klemaszewski, J.L., Haque, Z., Kinsella, J.E. 1989. An electronic imaging system for determining droplet size and dynamic breakdown of protein-stabilized emulsions. J. Food Sci. 54, 440-445. 

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. 

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