Function of Emulsifiers
The use of food emulsifier began with adding monoglyceride and lecithin to margarine. Originally, these substances were only known as emulsifiers. However, as studies progressed, more functions were found and they began to be used in various fields, such as bread, ice cream and cake. Nowadays, emulsifiers are applied to Japanese foods like tofu and minced fish products.
Why do bread and tofu need emulsifiers? Generally speaking, an emulsifier is well known for its emulsifying effects, however, actually it has various functions and followings are just some examples:
Modifies oil crystal and prevents water spattering in cooking;
Destroys emulsion to stabilize foam and to make smooth texture in ice cream, and keeps its shape;
Reacts with proteins to make a smooth easy-rising dough in bread;
Acts on starch to make bread soft.
|Functions of Emulsifiers||Application Examples|
|Surface Active Ability||Emulsification||W/O||Margarine, Butter, Butter Cream|
|O/W||Ice cream, Cream, Milk Drink|
|Dispersion||Chocolate, Cocoa, Peanut Butter|
|Anti-foaming/Defoaming||Tofu, Fermentation Industry, Jam|
|Wetting||Powdered Foods, Chewing Gum|
|Cleaning||Cleaning Agent for Food Industry|
|Starch Complex Forming Ability||Protection of Starch Granule||Instant Mashed Potato|
|Anti staling||Bread, Cakes|
|Prevention of Sticking||Pasta, Noodles, Rice|
|Prevention of Gelatinization||Flour Paste, Desserts|
|Modifying Ability for Oils and Fats||Crystal Modification||Margarine, Shortening, Chocolate|
|Creaming Ability||Margarine, Shortening|
|Water-Holding Ability||Margarine, Shortening|
|Others||Coating Agent, Lubricant Agent|
|Protein Modifying Ability||Gluten Modification||Dough Conditioner|
|Others||Tofu, Frozen Surimi|
|Others||Antibacterial and Anti-Fungal|
Oil and water produce emulsion by stirring, however, the emulsion starts to break down immediately after stirring is stopped. The purpose of emulsification is to stabilize emulsion state by preventing break down which occurs due to creaming aggregation and coalescence. To solve these issues, decreasing size of dispersed particles, reducing the density different of dispersion and protecting the surface of oil droplets are effective.
There are two types of emulsion, O/W emulsion or oil droplets in water, which can be found in ice cream and or milk, and W/O emulsion or water droplets in oil, found in butter and margarine.
Recently, developments of W/O/W type emulsion or water dispersed within
oil droplets of O/W type emulsion and O/W/O type, an opposite type emulsion
have been progressing.
These multiple type emulsions not only make low calorie items such as cream which contain less oil, but also stabilize the emulsion by dissolving the unstable substance present in the deepest region of water droplets. Taste can also be enhanced by injecting seasonings and flavors into the water droplets.
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.
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.
For example, chewing gum is apt to stick to teeth.
Adhesion to natural teeth does not occur easily because the enamel is hydrophilic and always wet, whereas the adhesion to artificial teeth, occurs easily. We can prevent adhesion by wetting the surface of chewing gum by adding emulsifier.
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.
Action on Starch
Fresh bread is soft, but it becomes elastic and hardens over time.
Starch particles consist of spherical shaped amylopectine and amylose. Raw starch called beta-starch is insoluble in water.
But when heated to a certain temperature, the starch absorbs water and
changes into the crystalline form of alpha-starch.
Amylose gets hard easily with cooling and amylopectin becomes hard gradually with time. The immediate hardening of bread by cooling is mainly due to the change of amylose.
Amylose changes to a helix structure, a kind of spiral structure by heating. If
monoglycerides are introduced, they can be anchored into the helix structure. Since
the anchoring does not change even after cooling, softness is maintained.
This function is also utilized for instant mashed potatoes, noodles and rice.
Action on Protein
Wheat flour contains protein called gluten which takes the shape of a
mesh-like structured when mixed with water.
This wheat flour and water based dough is filled with carbon dioxide produced by fermentation and steam generated during baking, which produces raised bread.
When the gluten content is small, the dough only rises a little.
An emulsifier modifies gluten molecules and enhances its film-forming power resulting in good spreadability and improvement of working efficiency. Thus, easy-rising bread can be obtained.
Action on Oils and Fats
When fats and oils form into crystal, an emulsifier promotes and inhibits the growth which prevents the formation of abnormal crystal.
This function is utilized for margarine, shortening and chocolate.