An emulsifier is generally known as a substance that stably emulsifies liquids that are not blended with each other, such as oil and water. However, a food emulsifier has a number of functions that include not only emulsification but also dispersion, infiltration, foaming, defoaming, mold-release, bacterio-statics, and mutual actions between starch and protein. Food is a complicated mixture of carbohydrates, proteins, oils and fats, water, and air. Food emulsifiers are used to help these properties in a variety of mutual actions that improve the quality of food.
Many processed foods such as margarines, non-dairy creamers, beverages and cake batters are emulsions where one phase is dispersed in another. For example, a non-dairy creamer is an emulsion where a fat or oil is dispersed throughout an aqueous protein phase.
During the process, mechanical shear is facilitated by impellers or by homogenization and provides energy to disperse the fat phase. Emulsifiers can initially aid in the formation of the emulsion by reducing the surface tension for a given amount of energy, allowing a greater interfacial surface (smaller droplet size).
In certain cases, emulsifiers can also provide stabilization of the emulsion by various mechanisms such as particulate and electrostatic stabilization. These mechanisms are determined by the molecular structure and ionic nature of the emulsifier.
Water-insoluble fine powder like cocoa is difficult to disperse because small lumps tend to form on the surface of interface. Powders gradually aggregate and precipitate even after dispersing by shaking. Maintaining suspension of water-insoluble fine powder is called dispersion. When the dispersing material is liquid, we call it emulsion.Cocoa is produced by dispersing cocoa powders in water (O/W type emulsion), while chocolate is made by dispersing them in oil (W/O type emulsion).
Emulsifier adsorbed on the surface of insoluble fine powder changes the particle surface to be hydrophilic or lipophilic. This results in producing water or fats and oils at the outer layer and stabilizing of suspension by an increase in the affinity to water or oil in the outer phase.
Foaming ability is one of the major characteristics of emulsifiers. When a solution containing an emulsifier is stirred, the emulsifier is adsorbed on the surface of the produced foam to make a mono-molecular layer and the foam outside of the solution makes a bimolecular layer of the emulsifier.
The film coating a bubble is about 100 times thicker than a bimolecular layer, but a bubble breaks off as soon as migration of liquid trapped between bimolecular films occurs. The addition of emulsifier enables foaming and stabilizes emulsion state of products, thus, smooth texture and expanded volume can be obtained. Typically, emulsifier for ability above is used for cakes, ice cream, moose, whipped topping, etc.
–Anti-foaming / Defoaming
Emulsifier also has anti-foaming and defoaming ability. Anti-foaming or defoaming agents are used in food production where undesirable foaming may occur in the presence of protein, starch etc.
Anti-Foaming/Defoaming Agents Characteristics:
• water insoluble
• floatable on the surface because of its small specific gravity
• small surface tension and easy spreading on liquid surface
These characteristics lower the surface tension, and the foam will get thinner. As these agents spread on the liquid surface, all foam will be diminished.
Wetting effects of emulsifier moisten the solid surfaces. If a solid material is mixed with an emulsifier or its surface spreads with an emulsifier, the surface then becomes hydrophilic.
Monoglycerides of middle chain fatty acid and some polyglycerol esters have specific bacteriostatic effects, and are used as bacteriostatic agents. They are typically used in hot vendor drinks, flour paste, and canned soup.
–Interaction with starch
Emulsifiers with a long fatty acid chain form complexes with starch; the fatty acid chain penetrates the amylose helix and prevents starch retrogradation. Retrogradation is the mechanism responsible for staling of bread, so the use of emulsifiers can extend the shelf life. Another attribute of the use of emulsifiers in starch based products is the reduction of stickiness in reconstituted products such as pasta and instant mashed potatoes.
–Interaction with protein
Emulsifiers with an ionic structure can interact with proteins, particularly wheat gluten. This interaction strengthens the gluten network in yeast raised dough, making it more stable against mechanical stress, resulting in increased volume and improved crumb structure.
–Interaction with fat
Emulsifiers are fat-like substances and they influence fat in several ways. Emulsifiers can promote or inhibit crystallization, influence the crystal shape of the fat, and improve the dispersion of fat crystals inside the food product.