|MadSci Network: Chemistry|
What factors prohibit the use of a cold-pressed vegetable oil, e.g. olive oil, for the creation of edible oil products such as whipped topping?
This is an interesting question, which can be answered in two ways. But first, it is important to point out that producing vegetable oil by cold pressing is not as important to its composition as what source is used. In this case, olive oil is unique in its high content of monounsaturated fatty acids, which are thought to have health benefits and lower blood cholesterol.
An emulsion of oil and water is really just water with microscopic oil droplets floating in it (this is called a colloidal suspension). To get the oil to form these droplets, called micelles, the molecules of fatty acid have to pack together as closely as possible to minimize the volume of the micelle. Fatty acids have two parts (as their name suggests): an acidic "head", and a long hydrocarbon "tail" (the fatty part). To form a micelle, the heads of the molecules, which are soluble, form the outside of the drop, while the tails fill the inside. The defining characteristic of unsaturated fats is that their tails have kinks in them. These kinks prevent the molecules from packing close together, so they tend to disrupt the micelles - the more unsaturated fats, the fewer and larger the micelles. Without good micelles, the emulsion will separate into its two phases (oil and water), and without a good emulsion, you can't whip the suspension into a dessert topping.
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