breaks up into tiny, invisible droplets that disperse through the acidic liquid. The liquid turns

cloudy because the oil droplets no longer let the light through freely. You've just created an

emulsion, though this is only a temporary state. If you let the mixture sit for a few minutes, the

oil and vinegar separate again.

You can make the emulsion semi-permanent if you add a substance to slows the

separation, or you can make it permanent if you add an emulsifying agent that prevents

separation altogether. The simple French vinaigrette is a temporary emulsion. Add some dry

mustard and it becomes semi-permanent. Mayonnaise is a good example of a permanent

emulsion. The mixed ingredients in mayonnaise don't separate out, no matter how long they sit.

Egg yolks contain emulsifying agents that prevent separation. Some chemicals are also

emulsifying agents that food processors add to bottled salad dressings and other similar mixes to

prevent separation.

These were all examples of cold dressings. Cooked dressings thicken with heat. They

often also include eggs, and once cooked, they are permanently mixed. (These may not be

emulsions as chemists define the term.)

Oils

Salad oils range from simple, inexpensive, flavorless vegetable oils to slightly more

costly, more flavored olive oil, to more exotic peanut and sesame oils, extra virgin olive oil and

highly flavored and pricey almond, grape seed, walnut or hazelnut oils. Processors can make oil

from any grain, seed and nut if there are enough people to pay for them. You can jazz up any oil

yourself by infusing it with any aromatic herb or spice, and change basic vegetable oil to, say,

chili oil, thyme oil, fenugreek oil or cinnamon oil.

The acid part

Vinegars also range from the standard distilled white through the slightly more flavored

white or red wine and champagne varieties to malt and cider vinegars. The more exotic vinegars,

popular now because of their tastes and unique qualities, are mellow balsamic, fruit or herb-

infused vinegars, then rice and sherry vinegars.

Vinegars range from 4 to 12 percent acidity. Ordinary white distilled vinegar is the most

acidic, wine vinegars are milder and a few vinegars like rice and balsamic vinegars are the

mildest. But the acidity depends on the processing and how much they dilute them before

bottling, more than what the vinegar is made from. Today balsamic vinegars are in style,

tomorrow something else may be in the limelight. Balsamic vinegars are high-priced, and they

are aged for several years like good wines. The longer they are aged, the higher their price. Some

people are willing to pay the high price but their flavor is not for everyone. Many cooks are just

as happy to leave them on the shelf and pick a less exotic but good wine vinegar for their salads.

Nevertheless, several kinds of vinegar on your own shelf indicate a well-stocked kitchen.

It is the acetic acid in vinegar that gives the sour taste. To make vinegar, the processor

starts with a grain that yeast can ferment, converting the grain’s sugar into alcohol. Then bacteria

converts the alcohol into acetic acid and the processor dilutes the final product with water to the

desired acidity. Besides acetic acid, vinegars contain other organic acids and a group of organic

chemicals called esters which contribute to the flavor and aroma.

You can make your own vinegar from wine but you need to add a mother, which has the

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