Food Lipids: Chemistry, Nutrition, and Biotechnology

3
Lipid-Based Emulsions
and Emulsifiers
D. JULIAN MCCLEMENTS
University of Massachusetts, Amherst, Massachusetts
I. INTRODUCTION
Many natural and processed foods exist either partly or wholly as emulsions, or have
been in an emulsified state at some time during their existence [1–5]. Milk is the
most common example of a naturally occurring food emulsion [6]. Mayonnaise, salad
dressing, cream, ice cream, butter, and margarine are all examples of manufactured
food emulsions. Powdered coffee whiteners, sauces, and many desserts are examples
of foods that were emulsions at one stage during their production but subsequently
were converted into another form. The bulk physicochemical properties of food
emulsions, such as appearance, texture, and stability, depend ultimately on the type
of molecules the food contains and their interactions with one another. Food emulsions
contain a variety of ingredients, including water, lipids, proteins, carbohydrates,
minerals, sugars, and small-molecule surfactants [3]. By a combination of covalent
and physical interactions, these ingredients form the individual phases and structural
components that give the final product its characteristic physicochemical properties
[7]. It is the role of food scientists to untangle the complex relationship between the
molecular, structural, and bulk properties of foods, so that foods with improved
properties can be created in a more systematic fashion.
II. EMULSIONS
An emulsion is a dispersion of droplets of one liquid in another liquid with which
it is incompletely miscible [1,8]. In foods, the two immiscible liquids are oil and
water. The diameter of the droplets in food emulsions are typically within the range
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