Emulsifiers offer options: the type of emulsifier used can impact clarity, stability, and texture in the foods and beverages in which it is used

Prepared Foods, Feb, 2005 by Richard F. Stier

Growing up, we learn that certain things tend not to mix: cats and dogs, gasoline and fire, liberals and conservatives and oil and water. Yet, when the need arises, these disparate entities can and are mixed. In food product development, oil and water often are mixed in formulations. Both are integral parts of most food systems and, as much as health-conscious individuals do not wish to acknowledge it, fats and oils are dietary necessities.

However, oil and water cannot mix without help. The enabler generally occurs in the form of emulsifier ingredients that assist in getting two immiscible liquids to mix and stay mixed. According to the Lipid Glossary 2 (2000, eds. Gunstone, FD and Herslof, BG, The Oily Press), an emulsifier is defined as "a surface-active compound which promotes the formation of emulsions between water and fatty or oily compounds. Important in cleaning processes and also in many foods."

The glossary goes further: "a variety of emulsions exist in food. Examples include margarine, butter, and mayonnaise (semi-solid; water-in-oil emulsions), milk and dressings (liquid; oil-in-water emulsions) and ice cream (mixture)."

To better understand how to use emulsifiers, it is important to explore the chemistry behind these ingredients and how that chemistry may be manipulated in foods and ingredients.

Immersing in Emulsifiers

When a food processor sets out to produce an emulsion, the primary goal is to create small droplets--often through mixing and shearing--which then must be stabilized. To ensure the desired emulsion is properly stabilized, an emulsifier is employed. Emulsifiers have components in their molecular structure that are soluble in oil (lipophilic or fat-loving) and in water (hydrophilic or water-loving). Different emulsifiers are categorized as being ionic or non-ionic. Ionic compounds may be cationic, anionic or amphoteric. Ionic emulsifiers have a problem; however, they can react with various ions to form complexes that adversely affect performance. Non-ionic emulsifiers tend not to react with ions and are used most extensively in the food industry.

Perhaps the easiest way to envision how an emulsifier works is to think of hand washing. If salad oil or beef fat gets on one's hands, experience shows that simply rinsing them with water does not get them clean. Running cold water over them after handling animal fats causes the fat to congeal, which is not a pleasant experience. Hot or warm water partially melts the fat, but does not remove it. Soap, acting as an emulsifying agent, promotes the formation of an emulsion between the oil and water so that hands are cleaned.

Emulsions can take several forms. In an oil-in-water (O/W) emulsion, the water surrounds the fat globules, which are dispersed throughout the oil; the emulsifier acts to form a micelle as concentrations of emulsifier increase. The fat-soluble portions of the molecule are in the fat and the water-soluble parts in the water. The water-in-oil emulsion (W/O) is the opposite, with water dispersed throughout the fat matrix. Micelles may be spherical, rod-shaped or lamellar. Proper use of emulsifiers allows manufacturers of salad dressings, which generally have high levels of fats, to reduce the fat content and, hence, calories. Processors can further manipulate emulsion systems to create water-oil-water (W/O/W) type emulsions. In these systems, water is dispersed within O/W emulsions. And, of course, if there are W/O emulsions, it also is possible to make oil-water-oil products. However, most of the emulsions that are used in foods are of the first two types.

Since so many different types of emulsifiers are available to the food processor, the industry has developed a system to determine what kind of system should be employed to create the desired products quickly, efficiently and, most important, economically. The system, called the HLB Method, which stands for "Hydrophile-Lipophile Balance," is defined as the ratio of the weight percentages of the hydrophilic and hydrophobic groups in an emulsifier. Emulsifiers with HLB values below 9 are lipophilic, those with values between 11 and 20 are hydrophilic and those with values between 8 and 11 are intermediates. The solubility of an emulsifier in water will, therefore, increase as its HLB value increases. (See chart "Helpful HLB Values.") As the HLB value increases, the dispersability of that compound in water will increase along with the clarity of the solution that is formed. For example, the use of an intermediate level product, that is an emulsifier with an HLB value of between 8 and 10, will yield a stable solution that appears milky. Using a product that has an HLB value of greater than 13 will give the user clear solutions.

Functions in Foods

Emulsifiers perform many functions in foods. The type of emulsifier that is used in a particular application depends upon the desired end product and the processing system that is being used. The use of emulsifiers in spreads and dairy desserts has been noted, but they also are used in breads, tofu, instant mashed potatoes, chewing gums, flavors, noodles, powdered products, beverages, chocolates and even in deep-fat frying. When producing emulsifiers, manufacturers look for certain characteristics. These include: