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Chapter 8: Problem 16

Mayonnaise is mostly vegetable oil and vinegar. So what's the essential difference between oil and vinegar salad dressing and mayonnaise? Learn for yourself: Combine a half cup of pure vegetable oil (olive oil will work) with two tablespoons of vinegar in a bottle, cap it securely, and shake the mixture vigorously. What do you see? Now let the mixture sit undisturbed for an hour. What do you see now? Add one egg yolk to the mixture, and shake vigorously again. Let the mixture stand as before. What do you see after an hour? After two hours? Egg yolk is rich in phosphatidylcholine. Explain why the egg yolk caused the effect you observed.

Short Answer

Expert verified
The egg yolk introduces an emulsifier, phosphatidylcholine, into the mixture of oil and vinegar. With the reduced surface tension between the oil and vinegar created by the phosphatidylcholine, a stable emulsion is maintained and the ingredients don't separate.

Step by step solution

01

Observation of Oil and Vinegar Mixture

Combine a half cup of pure vegetable oil with two tablespoons of vinegar, shake the mixture vigorously and observe. A temporary emulsion will be formed, but as there is no emulsifying agent present, the oil and vinegar would begin to separate shortly after being mixed.
02

Observing the Separation Over Time

Allow the combination from Step 1 to rest undisturbed for an hour. The oil and vinegar will separate into two distinct layers because they are immiscible fluids, meaning they are not mixable.
03

Introduction of the Egg Yolk

Introduce one egg yolk into the mixture and shake vigorously again. The purpose of this step is to add an emulsifier, found in the egg yolk, to the mix.
04

Observing the change after egg yolk is introduced

Allow the mixture to stand as before. You'll observe after an hour or two that the mixture doesn't separate like it did in Step 2. The egg yolk contains phosphatidylcholine, an effective emulsifier, which prevents the oil and vinegar from separating.
05

Explaining the Observation

Phosphatidylcholine, found in egg yolk, acts as an emulsifier. An emulsifier is a substance that allows water and oil to stay mixed together instead of separating. It functions by reducing the surface tension between the oil and vinegar, thus stabilizing the emulsion.

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Most popular questions from this chapter

If most plant-derived food products contain plant sterols and stanols, would it be as effective (for cholesterol-lowering purposes) to simply incorporate plant fats in one's diet as to use a sterol- or stanol-fortified spread like Benecol? Consult a suitable reference (for example, http://lpi.oregonstate.edu/infocenter/phytochemicals/sterols/ #sources at the Linus Pauling Institute) to compose your answer.

Describe in your own words the structural features of a. a ceramide and how it differs from a cerebroside. b. a phosphatidylethanolamine and how it differs from a phosphatidylcholine. c. an ether glycerophospholipid and how it differs from a plasmalogen. d. a ganglioside and how it differs from a cerebroside. e. testosterone and how it differs from estradiol.

Describe all of the structural differences between cholesterol and stigmasterol.

Compare and contrast two individuals, one whose diet consists largely of meats containing high levels of cholesterol and the other whose diet is rich in plant sterols. Are their risks of cardiovascular disease likely to be similar or different? Explain your reasoning.

Tetrahydrogestrinone is an anabolic steroid. It was banned by the U.S. Food and Drug Administration in \(2003,\) but it has been used illegally since then by athletes to increase muscle mass and strength. Nicknamed "The Clear," it has received considerable attention in high-profile steroid-abuse cases among athletes such as baseball player Barry Bonds and track star Marion Jones. Use your favorite Web search engine to learn more about this illicit drug. How is it synthesized? Who is "the father of prohormones" who first synthesized it? Why did so many prominent athletes use The Clear (and its relative, "The Cream") when less expensive and more commonly available anabolic steroids are in common use? (Hint: There are at least two answers to this last question.)
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