People who are fussy about the olive oil they dribble over a salad, or who will buy only fine sweet butter, sometimes choose a cheap vegetable oil for their Asian cooking. Asian cookbooks are partly to blame. Many of them, without discussion, call simply for "vegetable oil" as if it didn't matter. Oil is not just a cooking medium; it flavors food and should be chosen carefully, perhaps even blended occasionally as Japanese chefs do for tempura.
In the history of cooking, fats came before oils, and in China the first used were those of the pig and the dog, both domesticated by the late stone age. Obviously the pig has proved more useful in this regard. Dishes such as roasted dog liver wrapped in dog fat have lost favor over the years.
By the second century, the Chinese, according to a text of the period, knew that "you can get lard out of a soybean." Other early vegetable oils were crushed from the seeds of the mustard family and sesame seeds -- introduced to China from central Asia. Since the peanut's introduction four centuries ago, peanut oil has become a major cooking oil.
As oil is a major expense of Asian cooking, you can save by shopping in Asian markets and buying in quantity. Gallon or even five-gallon containers can be purchased. Contents of the latter could be divided among friends. As for the kind of oil, you get what you pay for. Cheaper, all-purpose oils such as Wesson vegetable oil, Crisco oil and others pick up odors and break down easily when heated, which means you can't re-use them, and they have a cheap taste and odor to begin with.
The way to choose an oil is to cook with a variety of types (and brands). You may want different oils for different purposes. Available oils include:
Peanut Oil -- As chefs from Paris to Guangzhou know, peanuts yield one of the world's great oils, especially for frying. Peanut oil burns only at high temperature -- around 500 degrees -- it doesn't pick up odors and tastes as readily as other oils, and thus can be strained and used again.
Aside from Planters brand, which is undistinguished, there are peanut oils available in Asian markets that are cold pressed and have the fragrance of freshly roasted peanuts. Were they olive oils, they might be classified "extra virgin." Lion and Globe comes from China in a red and gold can of about a gallon with absolutely no English on it except a small notation which reads "NET 2910 G." Panther brand, with a neutral flavor, is also good.
Corn Oil -- A healthful, mostly polyunsaturated oil, corn oil is good for deep-frying, and OK for stir-frying; but the taste although not that of a cheap oil, is heavy and distinct, and you have to like it. I prefer peanut oil in most instances except for deep-fried foods where the crispy corn flavor is an enhancement.
Coconut Oil -- Heavy, saturated for the most part, this oil used in Southeast Asia and sold in Filipino markets, is tough to digest. It's good for frying, however, as it heats to about 480 degrees before it burns.
Soybean Oil -- A healthful cheap oil relied on by many Chinese restaurants, the taste of this can best be described as neutral to sometimes slightly fishy. Mixed with other oils, such as in Kong Fong, a brand from Taiwan that's 55 percent peanut oil, it can be very good.
Safflower Oil -- Touted as the most healthful oil, this is a decent deep-frying oil but it has a tendency to pick up odors and deteriorate because of its extreme unsaturation. Like soy bean oil, it can develop a fishy taste.
Sesame Seed Oil -- the amber-colored sesame oil pressed from roasted seeds is mainly used as a flavoring; when it's heated for cooking it loses most of its flavor, and it's expensive. However, Japanese chefs blend it with other oils to fry tempura, and Koreans pan-fry with it. Cold-pressed sesame oil, for sale in health food stores, keeps well and is fine for cooking, but it's a little pricey. Perhaps worth trying is the deep golden sesame oil called Gingelly oil, used widely in Southern Indian cooking, and for sale in Indian food shops.
Olive Oil -- Because of its flavor, its low burning point (280 degrees), and if nothing else, its expense, olive oil is not appropriate for Asian cooking.
Vegetable Oil, Storage and Reuse:
Store oil in a tightly sealed container out of the light (or in an opaque container). Light and air turn oil rancid. Oil that is used for frying may be re-used -- in fact, slightly used oil browns better -- if it's strained and properly stored. A crock is a good choice for used oil. When using again, add about one-third fresh oil. It shouldn't sit more than a few days before it's used again, and should be discarded after two or three usings.
Oil for tempura and other batter-fried foods:
Any good oil such as peanut oil will do, but you may want to mix in 10 percent or more Chinese or Japanese sesame oil for a more authentic taste. Tempura oil from Japan, available occasionally in Japanese markets is expensive and unnecessary.